ganesh

cd 4017 running light ic

2009-02-12T18:30:00.000-08:00

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uc 3842 ic

2009-02-12T18:21:00.000-08:00

UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
Current Mode PWM Controller
FEATURES
• Optimized For Off-line And DC
To DC Converters
• Low Start Up Current (<1mA)
• Automatic Feed Forward
Compensation
• Pulse-by-pulse Current Limiting
• Enhanced Load Response
Characteristics
• Under-voltage Lockout With
Hysteresis
• Double Pulse Suppression
• High Current Totem Pole
Output
• Internally Trimmed Bandgap
Reference
• 500khz Operation
• Low RO Error Amp
DESCRIPTION
The UC1842/3/4/5 family of control ICs provides the necessary features to
implement off-line or DC to DC fixed frequency current mode control schemes
with a minimal external parts count. Internally implemented circuits include
under-voltage lockout featuring start up current less than 1mA, a precision
reference trimmed for accuracy at the error amp input, logic to insure latched
operation, a PWM comparator which also provides current limit control, and a
totem pole output stage designed to source or sink high peak current. The
output stage, suitable for driving N Channel MOSFETs, is low in the off state.
Differences between members of this family are the under-voltage lockout
thresholds and maximum duty cycle ranges. The UC1842 and UC1844 have
UVLO thresholds of 16V (on) and 10V (off), ideally suited to off-line
applications. The corresponding thresholds for the UC1843 and UC1845 are
8.4V and 7.6V. The UC1842 and UC1843 can operate to duty cycles
approaching 100%. A range of zero to 50% is obtained by the UC1844 and
UC1845 by the addition of an internal toggle flip flop which blanks the output
off every other clock cycle.
BLOCK DIAGRAM
Note 1: A/B A = DIL-8 Pin Number. B = SO-14 and CFP-14 Pin Number.
Note 2: Toggle flip flop used only in 1844 and 1845.
SLUS223A - APRIL 1997 - REVISED MAY 2002
application
INFO
available
2
UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
ABSOLUTE MAXIMUM RATINGS (Note 1)
Supply Voltage (Low Impedance Source) . . . . . . . . . . . . . . 30V
Supply Voltage (ICC < 30mA) . . . . . . . . . . . . . . . . . Self Limiting
Output Current. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±1A
Output Energy (Capacitive Load). . . . . . . . . . . . . . . . . . . . . 5μJ
Analog Inputs (Pins 2, 3). . . . . . . . . . . . . . . . . . . -0.3V to +6.3V
Error Amp Output Sink Current . . . . . . . . . . . . . . . . . . . . 10mA
Power Dissipation at TA ≤ 25°Χ (DIL−8) . . . . . . . . . . . . . . . . . . 1Ω
Power Dissipation at TA ≤ 25°C (SOIC-14) . . . . . . . . . . 725mW
Storage Temperature Range. . . . . . . . . . . . . . -65°C to +150°C
Lead Temperature (Soldering, 10 Seconds) . . . . . . . . . . 300°C
Note 1: All voltages are with respect to Pin 5.
All currents are positive into the specified terminal.
Consult Packaging Section of Databook for thermal
limitations and considerations of packages.
CONNECTION DIAGRAMS
DIL-8, SOIC-8 (TOP VIEW)
N or J Package, D8 Package
PLCC-20 (TOP VIEW)
Q Package
SOIC-14, CFP-14. (TOP VIEW)
D or W Package
PACKAGE PIN FUNCTION
FUNCTION PIN
N/C 1
COMP 2
N/C 3
N/C 4
VFB 5
N/C 6
ISENSE 7
N/C 8
N/C 9
RT/CT 10
N/C 11
PWR GND 12
GROUND 13
N/C 14
OUTPUT 15
N/C 16
VC 17
VCC 18
N/C 19
VREF 20
Package TA ≤ 25°C
Power Rating
Derating Factor
Above TA ≤ 25°C
TA ≤ 70°C
Power Rating
TA ≤ 85°C
Power Rating
TA ≤ 125°C
Power Rating
W 700 mW 5.5 mW/°C 452 mW 370 mW 150 mW
DISSIPATION RATING TABLE
3
PARAMETER TEST CONDITIONS
UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5 UNITS
MIN TYP MAX MIN TYP MAX
Reference Section
Output Voltage TJ = 25°C, IO = 1mA 4.95 5.00 5.05 4.90 5.00 5.10 V
Line Regulation 12 ≤ VIN ≤ 25V 6 20 6 20 mV
Load Regulation 1 ≤ I0 ≤ 20mA 6 25 6 25 mV
Temp. Stability (Note 2) (Note 7) 0.2 0.4 0.2 0.4 mV/°C
Total Output Variation Line, Load, Temp. (Note 2) 4.9 5.1 4.82 5.18 V
Output Noise Voltage 10Hz ≤ f ≤ 10kHz, TJ = 25°C (Note2) 50 50 μV
Long Term Stability TA = 125°C, 1000Hrs. (Note 2) 5 25 5 25 mV
Output Short Circuit -30 -100 -180 -30 -100 -180 mA
Oscillator Section
Initial Accuracy TJ = 25°C (Note 6) 47 52 57 47 52 57 kHz
Voltage Stability 12 ≤ VCC ≤ 25V 0.2 1 0.2 1 %
Temp. Stability TMIN ≤ TA ≤ TMAX (Note 2) 5 5 %
Amplitude VPIN 4 peak to peak (Note 2) 1.7 1.7 V
Error Amp Section
Input Voltage VPIN 1 = 2.5V 2.45 2.50 2.55 2.42 2.50 2.58 V
Input Bias Current -0.3 -1 -0.3 -2 μA
AVOL 2 ≤ VO ≤ 4V 65 90 65 90 dB
Unity Gain Bandwidth (Note 2) TJ = 25°C 0.7 1 0.7 1 MHz
PSRR 12 ≤ VCC ≤ 25V 60 70 60 70 dB
Output Sink Current VPIN 2 = 2.7V, VPIN 1 = 1.1V 2 6 2 6 mA
Output Source Current VPIN 2 = 2.3V, VPIN 1 = 5V -0.5 -0.8 -0.5 -0.8 mA
VOUT High VPIN 2 = 2.3V, RL = 15k to ground 5 6 5 6 V
VOUT Low VPIN 2 = 2.7V, RL = 15k to Pin 8 0.7 1.1 0.7 1.1 V
Current Sense Section
Gain (Notes 3 and 4) 2.85 3 3.15 2.85 3 3.15 V/V
Maximum Input Signal VPIN 1 = 5V (Note 3) 0.9 1 1.1 0.9 1 1.1 V
PSRR 12 ≤ VCC ≤ 25V (Note 3) (Note 2) 70 70 dB
Input Bias Current -2 -10 -2 -10 μA
Delay to Output VPIN 3 = 0 to 2V (Note 2) 150 300 150 300 ns
UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for -55°C ≤ TA ≤ 125°C for the
UC184X; -40°C ≤ TA ≤ 85°C for the UC284X; 0°C ≤ TA ≤ 70°C for the 384X; VCC = 15V
(Note 5); RT = 10k; CT = 3.3nF, TA=TJ.
Note 2: These parameters, although guaranteed, are not 100% tested in production.
Note 3: Parameter measured at trip point of latch with VPIN 2 = 0.
Note 4: Gain defined as
A
VPIN
VPIN
= Δ ≤VPIN ≤ V
Δ
1
3
,0 3 0.8
Note 5: Adjust VCC above the start threshold before setting at 15V.
Note 6: Output frequency equals oscillator frequency for the UC1842 and UC1843.
Output frequency is one half oscillator frequency for the UC1844 and UC1845.
Note 7: Temperature stability, sometimes referred to as average temperature coefficient, is described by the equation:
Temp Stability
V max VREF min
TJ max TJ min
= REF −
−
( ) ( )
( ) ( )
VREF (max) and VREF (min) are the maximum and minimum reference voltages measured over the appropriate
temperature range. Note that the extremes in voltage do not necessarily occur at the extremes in temperature.
4
PARAMETER TEST CONDITION
UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5 UNITS
MIN TYP MAX MIN TYP MAX
Output Section
Output Low Level ISINK = 20mA 0.1 0.4 0.1 0.4 V
ISINK = 200mA 1.5 2.2 1.5 2.2 V
Output High Level ISOURCE = 20mA 13 13.5 13 13.5 V
ISOURCE = 200mA 12 13.5 12 13.5 V
Rise Time TJ = 25°C, CL = 1nF (Note 2) 50 150 50 150 ns
Fall Time TJ = 25°C, CL = 1nF (Note 2) 50 150 50 150 ns
Under-voltage Lockout Section
Start Threshold X842/4 15 16 17 14.5 16 17.5 V
X843/5 7.8 8.4 9.0 7.8 8.4 9.0 V
Min. Operating Voltage
After Turn On
X842/4 9 10 11 8.5 10 11.5 V
X843/5 7.0 7.6 8.2 7.0 7.6 8.2 V
PWM Section
Maximum Duty Cycle X842/3 95 97 100 95 97 100 %
X844/5 46 48 50 47 48 50 %
Minimum Duty Cycle 0 0 %
Total Standby Current
Start-Up Current 0.5 1 0.5 1 mA
Operating Supply Current VPIN 2 = VPIN 3 = 0V 11 17 11 17 mA
VCC Zener Voltage ICC = 25mA 30 34 30 34 V
Note 2: These parameters, although guaranteed, are not 100% tested in production.
Note 3: Parameter measured at trip point of latch with VPIN 2 = 0
.
Note 4: Gain defined as: A
VPIN
VPIN
= Δ ≤VPIN ≤ V
Δ
1
3
;0 3 0.8 .
Note 5: Adjust VCC above the start threshold before setting at 15V.
Note 6: Output frequency equals oscillator frequency for the UC1842 and UC1843.
Output frequency is one half oscillator frequency for the UC1844 and UC1845.
UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for −55°C ≤ TA ≤ 125°C for the
UC184X; −40°C ≤ TA ≤ 85°C for the UC284X; 0°C ≤ TA ≤ 70°C for the 384X; VCC =
15V (Note 5); RT = 10k; CT = 3.3nF, TA=TJ.
ERROR AMP CONFIGURATION
Error Amp can Source or Sink up to 0.5mA
5
UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
UNDER-VOLTAGE LOCKOUT
CURRENT SENSE CIRCUIT
OSCILLATOR SECTION
During under-voltage lock-out, the output driver is
biased to sink minor amounts of current. Pin 6 should be
shunted to ground with a bleeder resistor to prevent
activating the power switch with extraneous leakage
currents.
A small RC filter may be required to suppress switch transients.
Peak Current (IS) is Determined By The Formula
ISMAX ′
RS
6
High peak currents associated with capacitive loads necessitate
careful grounding techniques. Timing and bypass
capacitors should be connected close to pin 5 in a
single point ground. The transistor and 5k potentiometer
are used to sample the oscillator waveform and apply
an adjustable ramp to pin 3.
Shutdown of the UC1842 can be accomplished by two
methods; either raise pin 3 above 1V or pull pin 1 below
a voltage two diode drops above ground. Either method
causes the output of the PWM comparator to be high
(refer to block diagram). The PWM latch is reset dominant
so that the output will remain low until the next
clock cycle after the shutdown condition at pin 1 and/or
3 is removed. In one example, an externally latched
shutdown may be accomplished by adding an SCR
which will be reset by cycling VCC below the lower
UVLO threshold. At this point the reference turns off, allowing
the SCR to reset.
UC1842/3/4/5
UC2842/3/4/5
OUTPUT SATURATION CHARACTERISTICS
ERROR AMPLIFIER OPEN-LOOP
FREQUENCY RESPONSE
OPEN-LOOP LABORATORY FIXTURE
SHUT DOWN TECHNIQUES
7
UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
OFFLINE FLYBACK REGULATOR
SLOPE COMPENSATION
A fraction of the oscillator ramp can be resistively
summed with the current sense signal to provide
slope compensation for converters requiring duty
cycles over 50%.
Power Supply Specifications
1. Input Voltages 5VAC to 130VA
(50 Hz/60Hz)
2. Line Isolation 3750V
3. Switching Frequency 40kHz
4. Efficiency at Full Load 70%
5. Output Voltage:
A. +5V, ±5%; 1A to 4A load
Ripple voltage: 50mV P-P Max
B. +12V, ±3%; 0.1A to 0.3A load
Ripple voltage: 100mV P-P Max
C. -12V ,±3%; 0.1A to 0.3A load
Ripple voltage: 100mV P-P Max
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to discontinue
any product or service without notice. Customers should obtain the latest relevant information before placing
orders and should verify that such information is current and complete. All products are sold subject to TI’s terms
and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI
deems necessary to support this warranty. Except where mandated by government requirements, testing of all
parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for
their products and applications using TI components. To minimize the risks associated with customer products
and applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,
copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process
in which TI products or services are used. Information published by TI regarding third–party products or services
does not constitute a license from TI to use such products or services or a warranty or endorsement thereof.
Use of such information may require a license from a third party under the patents or other intellectual property
of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is without
alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction
of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for
such altered documentation.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that
product or service voids all express and any implied warranties for the associated TI product or service and
is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Mailing Address:
Texas Instruments
Post Office Box 655303
Dallas, Texas 75265
Copyright  2002, Texas Instruments Incorporated
This datasheet has been download from:
www.datasheetcatalog.com
Datasheets for electronics components.
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la4440 amplifier ic with circuit diagram

2009-02-12T18:17:00.000-08:00

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lm324

2009-02-12T18:15:00.000-08:00

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upa1436ah

2009-02-12T18:12:00.000-08:00

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bu2508af

2009-02-11T11:36:00.000-08:00

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7554 ic data sheet

2009-02-03T05:08:00.000-08:00

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Clap Activated Remote

2009-01-20T03:13:00.001-08:00

An infra-red or wireless remote control has the disadvantage that the small, handy, remote transmitter is often misplaced. The sound operated switch has the advantage that the transmitter is always with you. This project offers a way to control up to four latching switches with two claps of your hand. These switches may be used to control lights or fans – or anything else that does not produce too loud a sound. To prevent an occasional loud sound from causing malfunction, the circuit is normally quiescent. The first clap takes it out of standby state and starts a scan of eight panel-mounted LEDs. Each of the four switches are accompanied with two LEDs – one for indicating the ‘on’ and the other for indicating the ‘off’ state. A second clap, while the appropriate LED is lit, activates that function. For example, if you clap while LED10 used in conjunction with Lamp 1 is lit then the lamp turns on. (If it is already on, nothing happens and it remains on.) A condenser microphone, as used in tape recorders, is used here to pick up the sound of the claps. The signal is then amplified and shaped into a pulse by three inverters (N1 through N3) contained in CMOS hex inverter IC CD4069. A clock generator built from two of the inverter gates (N5 and N6) supplies clock pulses to a decade counter CD4017 (IC2). Eight outputs of this IC drive LEDs (1 through 8). These outputs also go to the J and K inputs of four flip-flops in two type CD4027 ICs (IC3 and IC4). The clock inputs of these flip-flops are connected to the pulse shaped sound signal (available at the output of gate N3). Additional circuitry around the CD4017 counter ensures that it is in the reset state, after reaching count 9, and that the reset is removed when a sound signal is received. Outputs of the four flip-flops are buffered by transistors and fed via LEDs to the gates of four triacs. These triacs switch the mains supply to four loads, usually lamps. If small lamps are to be controlled, these may be directly driven by the transistors. If this circuit is to be active, i.e. scanning all the time, some components around CD4017 IC could be omitted and some connections changed. But then it would no longer be immune to an occasional, spurious loud sound. The condenser microphone usually available in the market has two terminals. It has to be supplied with power for it to function. Any interference on this supply line will be passed on to the output. So the supply for the microphone is smoothed by resistor-capacitor combination of R2, C1 and fed to it via resistor R1. CD4069, a hex unbuffered inverter, contains six similar inverters. When the output and input of such an inverter is bridged by a resistor, it functions as an inverting amplifier. Capacitor C2 couples the signal developed by the microphone to N1 inverter in this IC, which is configured as an amplifier. The output of gate N1 is directly connected to the input of next gate N2. Capacitor C3 couples the output of this inverter to N3 inverter, which is connected as an adjustable level comparator. Inverter N4 is connected as an LED (9) driver to help in setting the sensitivity. Preset VR1 supplies a variable bias to U3. If the wiper of VR1 is set towards the negative supply end, the circuit becomes relatively insensitive (i.e. requires a thunderous clap to operate). As the wiper is turned towards resistor R4, the circuit becomes progressively more sensitive. The sound signal supplied by gate N2 is added to the voltage set by preset VR1 and applied to the input of gate N3. When this voltage crosses half supply voltage, the output of gate N3 goes low. This output is normally high since the input is held low by adjustment of preset VR1. This output is used for two things: First, it releases the reset state of IC2 via diode D1. Second, it feeds the clock inputs to the four flip-flops contained in IC3 and IC4. In the quiescent state, IC2 is reset and its ‘Q0’ output is high. Capacitor C4 is charged positively and it holds this charge due to the connection from R5 to this output (Q0). IC2 is a decade counter with fully decoded outputs. It has ten outputs labelled Q0 to Q9 which go successively high, one at a time, when the clock in put is fed with pulses. IC3 and IC4 are dual JK flip-flops. In this circuit they store (latch) the state of the four switches and control the output through transistors and triacs. At the first clap, the output of gate N3 goes low. Diode D1 is forward biased and it conducts, discharging capacitor C4. The reset input of IC2 goes low, releasing its reset state. All the J and K inputs of the four flip-flops are low and so these do not change state, even though their clock inputs receive pulses. When the reset input of IC2 is low, each clock pulse causes IC2 to advance by one count and its outputs go high successively, lighting up the corresponding LEDs and pulling high the J and K inputs of the four flip-flops, one after the other. Resistor R8 limits the current through LEDs 1 through 8 to about 2 mA. Larger current might cause malfunction due to the outputs of IC2 being pulled down below the logic 1 state input voltage. If a second clap is detected while the J input of a particular flip-flop is high, its Q output will go high, regardless of what state it was in previously. Similarly, if its K input was high, the output will go low. (If both J and K are high, the output will change state at each clock pulse.) Thus although all flip-flops receive the clap signal at their clock inputs, only the one selected by the active output of IC2 will change state. Resistor R9 and capacitor C6 ensure that the flip-flops start in the off state when power to the circuit is switched on, by providing a positive power-on-reset pulse to the reset input pins when power is applied. The preset input pins are not used and are therefore connected directly to ground. When, after eight clock pulses, output Q8 of IC2 becomes high, diode D2 conducts, charging capacitor C4, thereby resetting IC2 and making its Q0 output high. And there it stays, awaiting the next clap. The four Q outputs of IC3 and IC4 are buffered by npn transistors, fed through current limiting resistors and LEDs (to indicate the on/off state of the loads) to the gates of four triacs. Four lamps operating on the mains may thus be controlled. For demonstrations, it might be better to drive small lamps (drawing less than 100 mA at 12V) directly from the emitters of the transistors. In this case the triacs, LEDs and their associated current limiting resistors may be omitted. It has to be noted that one side of the mains has to be connected to the negative supply line of this circuit when mains loads are to be controlled. This necessitates safe construction of the circuit such that no part of it is liable to be touched. The advantage is that it may be mounted out of reach of curious hands since it does not need to be handled during normal operation. It is advisable to start with the low voltage version and then upgrade to mains operation, once you are sure everything else is working satisfactorily. CMOS ICs are used in this circuit for implementing the amplifying and logic functions. Use of a dedicated supply is recommended because the integrated circuits will be damaged if the supply voltage is too high, or is of wrong polarity. An external power supply may get connected up the wrong way around, or be inadvertently set to too high a voltage. Therefore it is a good idea to start by constructing the power supply section and then add the other components of the circuit. If the clock is working, you may turn your attention to the amplifier. LED9 should be off, and should flash when the terminals of capacitor C2 are touched with a wet finger (the classic wet finger test). Preset VR1 may need to be adjusted until LED9 just turns off. The output of gate N2 will be at about half the supply voltage. The output of gate N3 would normally be high. The voltage at the input of gate N3 should vary when preset VR1 is varied. High-efficiency LEDs should preferably be used in this circuit. The microphone has two terminals, one of which is connected to its body. This terminal has to be connected to circuit ground, and the other to the junction of resistor R2 and capacitor C2. These wires are preferably kept short (one or two centimetres) to avoid noise pickup. With the microphone connected, a loud sound (a clap) should result in LED9 blinking. Adjust preset VR1 so that LED9 stays off on the loudest of background noises but starts glowing when you clap. If the clap-to-start feature is not required, it may be disabled by omitting components D1, D2, R5, C4 and connecting a wire link in place of diode D2. Then IC2 will be alive and kicking all the time.

Power supply failure alarm

2009-01-07T11:18:00.000-08:00

Most of the power supply failure indicator circuits need a separate power supply for themselves. But the alarm circuit presented here needs no additional supply source. It employs an electrolytic capacitor to store adequate charge, to feed power to the alarm circuit which sounds an alarm for a reasonable duration when the supply fails.This circuit can be used as an alarm for power supplies in the range of 5V to 15V. To calibrate the circuit, first connect the power supply (5 to 15V) then vary the potentiometer VR1 until the buzzer goes from on to off.Whenever the supply fails, resistor R2 pulls the base of transistor low and saturates it, turning the buzzer ON.

Water Level Indicator with alarm

2009-01-07T11:17:00.000-08:00

This circuit not only indicates the amount of water present in the overhead tank but also gives an alarm when the tank is full.The circuit uses the widely available CD4066, bilateral switch CMOS IC to indicate the water level through LEDs.When the water is empty the wires in the tank are open circuited and the 180K resistors pulls the switch low hence opening the switch and LEDs are OFF. As the water starts filling up, first the wire in the tank connected to S1 and the + supply are shorted by water. This closes the switch S1 and turns the LED1 ON. As the water continues to fill the tank, the LEDs2 , 3 and 4 light up gradually.The no. of levels of indication can be increased to 8 if 2 CD4066 ICs are used in a similar fashion.
When the water is full, the base of the transistor BC148 is pulled high by the water and this saturates the transistor, turning the buzzer ON. The SPST switch has to be opened to turn the buzzer OFF.Remember to turn the switch ON while pumping water otherwise the buzzer will not sound!

Fire Alarm

2009-01-07T11:16:00.001-08:00

This circuit warns the user against fire accidents. It relies on the smoke that is produced in the event of a fire. When this smoke passes between a bulb and an LDR, the amount of light falling on the LDR decreases. This causes the resistance of LDR to increase and the voltage at the base of the transistor is pulled high due to which the supply to the COB (chip-on-board) is completed. Different COBs are available in the market to generate different sounds. The choice of the COB depends on the user. The signal generated by COB is amplified by an audio amplifier. In this circuit, the audio power amplifier is wired around IC TDA 2002. The sensitivity of the circuit depends on the distance between bulb and LDR as well as setting of preset VR1. Thus by placing the bulb and the LDR at appropriate distances, one may vary preset VR1 to get optimum sensitivity. An ON/OFF switch is suggested to turn the circuit on and off as desirable.

DayLight Alarm

2009-01-07T11:14:00.000-08:00

The circuit presented here wakes you up with a loud alarm at the break of the daylight. Once again the 555 timer is used here. It is working as an astable multivibrator at a frequency of about 1kHz.The circuit's operation can be explained as follows:When no light falls on the LDR, the transistor is pulled high by the variable resistor. Hence the transistor is OFF and the reset pin of the 555 is pulled low. Due the this the 555 is reset.When light falls on the LDR, its resistance decreases and pulls the base of the transistor low hence turning it ON. This pulls the reset pin 4 of the 555 high and hence enables the 555 oscillator and a sound is produced by the speaker.The variable 100K resistor has to be adjusted to set the light intensity that triggers the alarm.

4 in 1 Burglar Alarm

2009-01-07T11:12:00.000-08:00

I n this circuit, the alarm will be switched on under the following four different conditions: 1. When light falls on LDR1 (at the entry to the premises). 2. When light falling on LDR2 is obstructed. 3. When door switches are opened or a wire is broken. 4. When a handle is touched. The light dependent resistor LDR1 should be placed in darkness near the door lock or handle etc. If an intruder flashes his torch, its light will fall on LDR1, reducing the voltage drop across it and so also the voltage applied to trigger 1 (pin 6) of IC1. Thus transistor T2 will get forward biased and relay RL1 energise and operate the alarm. Sensitivity of LDR1 can be adjusted by varying preset VR1. LDR2 may be placed on one side of a corridor such that the beam of light from a light source always falls on it. When an intruder passes through the corridor, his shadow falls on LDR2. As a result voltage drop across LDR2 increases and pin 8 of IC1 goes low while output pin 9 of IC1 goes high. Transistor T2 gets switched on and the relay operates to set the alarm. The sensitivity of LDR2 can be adjusted by varying potentiometer VR2. A long but very thin wire may be connected between the points A and B or C and D across a window or a door. This long wire may even be used to lock or tie something. If anyone cuts or breaks this wire, the alarm will be switched on as pin 8 or 6 will go low. In place of the wire between points A and B or C and D door switches can be connected. These switches should be fixed on the door in such a way that when the door is closed the switch gets closed and when the door is open the switch remains open. If the switches or wire, are not used between these points, the points should be shorted. With the help of a wire, connect the touch point (P) with the handle of a door or some other suitable object made of conducting material. When one touches this handle or the other connected object, pin 6 of IC1 goes ‘low’. So the alarm and the relay gets switched on. Remember that the object connected to this touch point should be well insulated from ground. For good touch action, potentiometer VR3 should be properly adjusted. If potentiometer VR3 tapping is held more towards ground, the alarm will get switched on even without touching. In such a situation, the tapping should be raised. But the tapping point should not be raised too much as the touch action would then vanish. When you vary potentiometer VR1, re-adjust the sensitivity of the touch point with the help of potentiometer VR3 properly. If the alarm has a voltage rating of other than 6V (more than 6V), or if it draws a high current (more than 150 mA), connect it through the relay points as shown by the dotted lines. As a burglar alarm, battery backup is necessary for this circuit. Note: Electric sparking in the vicinity of this circuit may cause false triggering of the circuit. To avoid this adjust potentiometer VR3 properly.

THE 555 IC

2009-01-06T02:58:00.000-08:00

CHIP PRICES

The 555 IC is one of the simplest and most rugged IC's on the market. It has been used in thousands of applications and is extremely popular. This discussion will cover its numerous modes of operation and present a number of circuits for these applications. However I must point out one thing. The 555 is not suited for battery applications and it is not really suited for combining with some types of CMOS circuitry. The 555 is a very noisy chip and has a very nasty internal feature called "crow-bar effect" that can put a lot of noise on the power rails of a circuit. Its operation as an oscillator can be done by other chips and we have provided some alternatives in the notes. The 555 has a number of derivatives that offer improvements (such as low-power, low voltage, high speed operation) and these will also be covered. This is the first time a number of comparisons and alternatives have been provided in a discussion and this is needed for you to get a complete picture of its suitability for a particular project. There are cheaper and better chips to carry out identical operations to a 555 and we will leave it to you to decide. THE 555 TIMER IC The 555 is commonly called a TIMER IC. It is an 8-pin chip and has a number of different identifications: LM555CN from National and SE555/NE555 from Signetics are just two manufacturers. These numbers all refer to the most common and cheapest version, we will call the 555. The 555 contains more than 28 transistors and it is basically a chip containing a number of building blocks that end up very similar to an oscillator without the TIMING COMPONENTS. It needs two or three external components to produce an oscillator capable of operating at a frequency from 1Hz to 500kHz. When it oscillates at a frequency less than 1Hz, the circuit is called a Timer or Delay. The chip also has a pin (pin 2) that prevents the chip from starting the Timing cycle until it is taken LOW. Another pin (pin 4) stops the chip from oscillating (or continuing with a delay-time) when it is taken LOW and a pin (pin 5) that can adjust the mark-space ratio of the waveform. The diagrams below show the names of each pin and a simplified block diagram of the internal workings.
The 555

THE FUNCTION OF EACH PIN Pin 1 Ground The ground (or common) pin is connected to the 0v rail - commonly called the negative rail or EARTH rail. Pin 2 Trigger This pin connects to the lower comparator and is used to set the control flip flop. When it is taken LOW, it causes the output to go HIGH. This is the beginning of the timing sequence for a monostable operation. Triggering is accomplished by taking the pin below 1/3 of rail voltage - in digital terms, this is called a LOW. The action of the trigger input is level-sensitive, allowing slow rate-of-change waveforms, (as well as pulses), to be used as trigger sources. The trigger pulse must be of shorter duration than the time interval determined by external R and C. If this pin is held low for a longer period of time, the output will remain high until the trigger input is high again.If the trigger input remains lower than 1/3 rail voltage for longer than the timing cycle, the timer will re-trigger upon termination of the first output pulse. When the timer is used in monostable mode with trigger pulses longer than the output pulse, the trigger duration must be shortened by external circuitry.The minimum pulse-width for reliable triggering is about 10uS.Pin 3 Output The output of the 555 comes from a high-current totem-pole stage. This provides both sinking and sourcing current. The high-state output voltage is about 1.7 volts less than the supply. At 15 volt supply, the chip can sink 200mA with an output-low voltage level of 2 volts. High-state level is 13.3 volts. Both rise and fall times of the output waveform are quite fast, typical switching being 100nS.To make the output HIGH, the TRIGGER PIN (pin 2) is momentarily taken from a HIGH to a LOW. This causes the output to go HIGH. This is the only way the output can be made to go high. The output can be returned to a LOW by making the THRESHOLD PIN (Pin 6) go from a LOW to a HIGH.The output can also be made to go LOW by taking the RESET PIN to a LOW state.Pin 4 Reset This pin is used to make the OUTPUT PIN (Pin 3) LOW. The reset pin must go below 0.7 volt and it needs 0.1mA to reset the chip. The RESET PIN is an overriding function. It will force the OUTPUT PIN to go LOW regardless of the state of the TRIGGER PIN (Pin 2). It can be used to terminate an output pulse prematurely, to gate oscillations from "on" to "off." The pin is active when a voltage level between 0v and 0.4 volt is applied to it. When not used, it is recommended that the RESET PIN be tied to the positive rail to avoid the possibility of false resetting.Pin 5 Control Voltage This pin allows direct access to the 2/3 voltage-divider point. This is the reference level for the upper comparator. When the 555 timer is used in a voltage-controlled mode, the voltage-controlled operation ranges from about 1 volt below rail-voltage to 2 volts above ground (0v). Voltages can be safely applied outside these limits, but they should be confined to between 0v and rail voltage. By applying a voltage to this pin, it is possible to vary the timing of the chip independently of the RC network. The control voltage may be varied from 45 to 90% of the Vcc in the monostable mode, making it possible to control the width of the output pulse independently of RC. When used in the astable mode, the control voltage can be varied from 1.7v to the full Vcc. Varying the voltage in the astable mode will produce a frequency modulated (FM) output.If the control-voltage pin is not used, it should be bypassed to ground, with a 10n capacitor to prevent noise entering the chip. Pin 6 Threshold Pin 6 is one input to the upper comparator (the other is pin 5). It makes the OUTPUT PIN go LOW. To make the output go LOW, the Threshold pin is taken from a LOW to a level above 2/3 of rail voltage. This pin is level-sensitive, allowing slow rate-of-change waveforms to be detected.A dc current, termed the threshold current, must also flow into this pin from the external circuit. This current is typically 0.1µA, and will determine the upper limit of total resistance allowable from pin 6 to rail. For 5v operation the resistance is 16M. For 15v operation, the maximum resistance is 20M.Pin 7 Discharge This pin is connected to the open collector of an NPN transistor. The emitter goes to ground. When the transistor is turned "on,'" pin 7 is effectively shorted to ground. The timing capacitor is connected between pin 7 and ground and is discharged when the transistor turns "on". The conduction state of this transistor is identical in timing to that of the output stage. It is "on" (low resistance to ground) when the output is LOW and "off" (high resistance to ground) when the output is HIGH.Maximum collector current is internally limited by design, so that any size capacitor can be used without damage to the chip. In certain applications, this open collector output can be used as an auxiliary output terminal, with current-sinking capability similar to the OUTPUT (pin 3).Pin 8 Rail This pin (also referred to as Vcc) is the positive supply voltage pin for the 555. Supply-voltage operating range is +4.5 volts to +16 volts. The chip will operate over this voltage range without change in timing period. The only change is the output drive capability, which increases in current as the supply voltage is increased.
USING THE 555A 555 can be wired:1. As a TIMER (monostable operation - also called a DELAY), 2. As an OSCILLATOR (also called a MULTIVIBRATOR - or astable operation) 3. As a ONE-SHOT (also called monostable operation). The 555 IC is an extremely popular IC. It is simple to use and very rugged. It comes in a single, dual or quad package with part numbers such as LM555, NE555, LM556, NE556. It is ideal for astable (free-running) oscillators as well as the one-shot monostable mode.The 555 can be triggered and reset on falling waveforms and the output can source or sink up to 200mA. The HIGH output is about 1.7v less than supply. The NE555 operates 3v - 16v DC.Maximum operating frequency is 500kHz.
THE 75557555 is a CMOS version of the 555. It is exactly the same as the 555 but consumes less power. The 555 consumes 10mA, while the 7555 consumes 80uA (1/120th). The CMOS version comes with different identifications according to the manufacturer.LMC555 or LM555CN is made by National Semiconductors, TLC555 is made by Texas Instruments, ICM7555 is supplied by Philips, ZSCT1555 comes from Zetex and ICM7555 is made by Maxim. The main feature to note is the inclusion of the number "7" or the letter "C" to identify the CMOS version. They use less power than the older (555, NE555, LM555) versions and don't require a capacitor on the control pin. Although pin and functionally compatible, the component values differ between the low-power CMOS and older versions.The Exar XR-L555 timer is a micro-power version of the standard 555 offering a direct, pin-for-pin substitute with the advantage of lower power operation. It is capable of operation from 2.7v to 18v. At 5v, the L555 will consume about 900 microwatts, making it ideally suitable for battery operated circuits. The internal schematic of the L555 is similar to the standard 555 but with current-spiking filtering, lower output drive capability, higher nodal impedances, and better noise reduction system.USING THE 7555 The ICM7555 is a CMOS timer providing significantly improved performance over the standard NE/SE555 timer, while at the same time being a direct replacement in most applications. Improved parameters include low supply current, wide operating supply voltage range, low THRESHOLD, TRIGGER, and RESET currents, no crow-barring of the supply current during output transitions, higher frequency performance and no requirement to decouple CONTROL VOLTAGE for stable operation.The ICM7555 is a stable controller capable of producing accurate time delays or frequencies.In the one-shot mode, the pulse width of each duration is precisely controlled by one external resistor and capacitor. For astable operation as an oscillator, the free-running frequency and the duty cycle are both accurately controlled by two external resistors and one capacitor. Unlike the bipolar 555 device, the CONTROL VOLTAGE pin does not have to be decoupled with a capacitor. The output can source or sink currents large enough to drive TTL loads or provide minimal offsets to drive CMOS loads. Maximum output current 50 - 80mA.
Exact equivalent in most applications for NE/SE555
Low supply current: 80µA (typical)
Extremely low trigger, threshold, and reset currents: 20pA (typical)
High-speed operation: 500kHz guaranteed
Wide operating supply voltage: 3v to 16v
Normal reset function. No crow-barring of supply during output transition
Can be used with higher-impedance timing elements than the bipolar 555 for longer time constants
Timing from microseconds to hours
Operates in both astable and monostable modes
Adjustable duty cycle
Output source/sink driver can drive TTL/CMOS. Maximum output current 50 - 80mA.
Typical temperature stability of 0.005%/°C at 25°C
Rail-to-rail outputs
An improvement on the CMOS 7555 is the ZSCT1555 from Zetex. It is guaranteed to work down to to 0.9 volts with bipolar technology. It has been designed for portable applications, by offering single battery cell operation. (See end of P3 for a technician's difficulty with getting this chip to oscillate.)It provides the same precision timing capabilities as its predecessors, (the 555 and 7555) it has the same 8 legged pin-out. With the simple adjustment of external passive components to set the frequency, the device's function is just the same, whether it be generating accurate time delays or oscillations.Assuming a 5v supply, a typical CMOS part draws 170uA while the new timer pulls 140uA, and at 1.5v just 75uA.
555 Vs 7555The choice between the standard 555 and CMOS version (7555) or ZSCT1555 will depend on cost, availability, load current required and frequency of operation. It will mainly come down to battery or mains operation for the project. Normally, when we change from a TTL chip to a CMOS chip, the component values change by a factor of 10x or 100x. This is because the TTL chips are very low impedance and CMOS is very high impedance. But if a 555 is substituted for a CMOS version, the timing components remain the SAME! This is very convenient. Chips can be substituted without having to alter the surrounding circuitry. The only change will be the current consumption of the chip. In general, the consumption will reduce from about 10mA to approx 0.5mA. (A LED Voltmeter circuit made the following circuit-current comparison: using 555 = 7mA, using 7555 = 0.35mA). This is typical of the current-saving of a CMOS version. This article covers most types and provides a number of comparisons and substitutions. A typical 7555 circuit is shown below:

Note the need for the driver transistor in the circuit above, as the 7555 has an output capability of about 50mA. DRAWING 555 "BLOCKS"One of the most important points when drawing a 555 "block" is maintaining a standard layout. Diagrammatic blocks on a circuit diagram are not supposed to show the pins in the same order as the legs on a chip. The wiring to the chip should be placed in positions to represent their function. The power is placed at the top, ground at he bottom, input at the left and output at the right. The other lines are also placed in appropriate positions.The layout should be positioned to aid in the interpretation of a diagram. The end result should be to provide the maximum information and make it easy to interpret the symbol.Many of the 555 circuit diagrams place the lines to the 555 block so you have to interpret every diagram individually. This makes reading a circuit diagram very slow. The first thing you need to know is the function of each pin. See the animation below:

The 555 can be used for a number of applications.It can be wired as an OSCILLATOR or a MONOSTABLE or DELAY and many different circuits can be produced with these modes of operation.
THE 555 AS AN OSCILLATOR The 555 can be wired as an OSCILLATOR. It needs 2 external components - a resistor R and a capacitor C. These are called TIMING COMPONENTS. The diagram below shows these two components:

The capacitor charges via R and when it reaches 2/3 of rail voltage, pin 7 shorts the capacitor to ground. This means the capacitor charges slowly but discharges very quickly. An improved layout is shown below:

The capacitor charges via R (plus the top resistor) and discharges via R (only). If the top resistor is small compared with R, we can neglect it, so that C charges via R and discharges via R at about the same rate. The top resistor simply separates pin 7 from the positive rail as pin 7 shorts to ground to discharge the capacitor during part of the cycle.
HOW THE 555 OSCILLATES The capacitor charges via the timing resistor R and when the voltage across it reaches 2/3 of the supply voltage, the output of the 555 goes LOW. The timing resistor is taken to the 0v rail via pin 7 and the capacitor discharges. When the voltage across the capacitor reaches 1/3 of rail voltage the output of the 555 goes HIGH. The timing resistor is taken to the positive rail via the top resistor (pin7 effectively comes out of circuit) and the cycle repeats. Don't worry about pins 4 or 5 at the moment.The animation below shows how the 555 oscillates:

These are the three points to note:1. Pin 2 detect the low voltage on the capacitor, and makes pin 7 and the output go HIGH2. Pin 6 detects the high voltage on the capacitor and makes pin 7 and the output go LOW3. Pin 7 is "in-phase" with the output. (both are low at the same time)An improved oscillator is shown in the diagram below. It uses only one resistor to charge and discharge the capacitor and the circuit does not have the wasteful top resistor. The circuit draws less current than the circuit above but the only difference is the frequency of operation will be lower for the same value of components because the voltage delivered by the output line is 1.7v less than the supply rail. The output can deliver up to 200mA but if it is delivering a high current, the output voltage may be reduced and this will affect the frequency of operation. If a reliable frequency is needed, this is not the circuit to choose.

THE ACTION OF PIN 4 Pin 4 is called the RESET PIN. It is called an ACTIVE LOW pin. When pin 4 is HIGH, the chip operates normally. When pin 4 is taken LOW, the output of the chip is INHIBITED - it remains LOW. Pin 7 is also taken low and the chip is prevented from oscillating. Mouseover the following animation to see the action of pin 4:
Mouse-over to INHIBIT the 555
THE 555 AS A MONOSTABLE The 555 can be wired as a monostable. A monostable has one stable state and that is the OFF state. The unstable state is called the ON or HIGH state. When it is triggered by an input pulse, the monostable switches to its temporary or ON state. It remains in that state for a period of time determined by an RC network and returns to its stable state. In other words, the monostable circuit generates a single pulse of a fixed time duration each time it receives and input trigger pulse. The monostable circuit can also be called a ONE-SHOT due to the single-pulse it creates. This type of circuit can be used for activating an external device for a specific length of time. They can also be used to generate delays. Another use for this type of circuit is to take the brief pulse of a push-button and activate a device. This is called a PULSE-EXTENDER. It can also be used to clean-up the noisy output of a push-button and this is called SWITCH DEBOUNCING. The diagram below shows a push-button connected to a 555. When the button is pressed, the relay operates for 5 seconds. The button must be released before the time-interval has expired otherwise the time is extended. This is the only limitation of this circuit.

In the next circuit, the "button-press" is detected via "AC-means." In other words, the button is "AC-coupled." This allows the button to be pressed for any length of time and the output pulse will be determined by the value of the 47k resistor and 1u electrolytic. The "trigger pulse" from the switch involves a capacitor (10n) to detect the low. The second 100k and 10n capacitor have a "charge-rate" of about about 1/100th second and this means the circuit will not detect a "single-shot" above 100 pulses per second. (The first 100k is used to discharge the capacitor, in conjunction with the second 100k resistor). This means you can make the output pulse as short as 1mS but you will not be able to get a "pulse-rate" above 100 pulses per second, as the capacitor has to discharge through both 100k's (equal to 200k).

In the next circuit, the switch can be pressed for any length of time and the circuit will only produce a 5 second output. The circuit is prevented from re-triggering by the addition of a 470k and 100n capacitor. When the switch is pressed, the uncharged capacitor takes pin 2 low and triggers the circuit. If the button is kept pressed the 100n charges and takes pin 2 high. The potential across the voltage divider formed by the 47k and 470k resistors is insufficient to re-trigger the monostable. The circuit "times-out" and the output goes low. When the button is released, the 100n discharges through the 470k and is ready for the next press. Alternatively, you can use the "front-end" of the pervious circuit (two 100k's and 10n) for detecting the press of the button.
A monostable (one-shot) can be connected to an astable (free-running oscillator) so that it gates (or inhibits) the oscillator to produce an output tone for a short duration. The circuit below can be used for an application such as doorbell. It is not suitable for battery operation as the 555 IC's are connected to the supply and draw current at all times.
This circuit can be used for a doorbell..
Pin 2 of the first 555 is HIGH and thus it is "non-operational" as it detects a LOW. Pin 6 is detecting a HIGH and thus the output of the IC is LOW. The output of the first 555 goes to the INHIBIT pin of the second 555. When pin 4 is LOW, the output of the chip is kept LOW.

PCB Design Guidelines

2008-12-27T20:29:00.000-08:00

http://www.mediafire.com/?pbckzmyrlxd

Simple Security Wire Loop Alarm Circuit

2008-12-27T20:28:00.001-08:00

A wire loop is used to protect valuable objects in this simple alarm circuit. The electronic hobby circuit is powered by a 9v battery. The alarm beeper is activated if the wire loop is severed. The standby current is so low that the 9v battery should last for many years.

Light to Frequency Converter

2008-12-27T20:22:00.000-08:00

This circuit uses a CMOS version of the classic 555 timer, to form a light intensity to frequency converter. A small PIN photo diode is used as the light detector. The pulses produced are short, so in some applications you may want to stretch them or feed them through a flip/flop to produce a square wave signal. Although the circuit shown is designed for a 5v supply, it could operate from almost any voltage from 3v to 15v.

The 555 timer circuit is configured as a free running oscillator. When a PIN photodiode is reversed biased, it leaks current proportional to the light intensity hitting lt. The photodiode leakage current charges the 0.01uF capacitor. When the voltage of the capacitor reaches about 2/3 of the supply voltage, the pin 3 output of the 555 timer swings low. This state quickly discharges the capacitor through the photo diode, until the capacitor voltage is less than 1/3 of the supply voltage. This causes the pin 3 output of the 555 to swing high again, for another charge cycle. With the component value chosen, the frequency of the oscillator will range from about 1Hz in total darkness to about 25KHz in sunlight. Other frequencies are possible by changing the value of the 0.01uF capacitor.

Click on Schematic below to view PDF version of this Circuit

3v Low Battery Voltage Flasher Circuit

2008-12-27T20:20:00.000-08:00

Many battery powered devices use two AA alkaline cells. Often you will not know when it is time to replace the batteries until the device powered by them actually stops operating. The hobby circuit below can be connected to a 3v battery, to give you some warning when the battery is nearing its end of life. It will flash a LED when the battery voltage drops to about 2.4 volts. The electronic circuit draws only 1ua of current in standby mode and jumps to only 20ua when flashing, so it can safely be included without depleting the battery energy. A voltage detector IC from Panasonic (Microchip also makes similar devices) is used to monitor the battery voltage. The device’s open drain output swings low, when the battery voltage is below 2.4 to 2.5 volts. This action turns on the two transistor oscillator circuit, which drives the LED with short current pulses lasting only 2ms. I published this Flasher circuit in the January 2 issue of EDN magazine in 1997.

Remote LED Indicator Light

2008-12-27T20:15:00.000-08:00

There are times when you would like to transmit a signal from one LED indicator light to second LED at another location. The circuit below works well for this application. It takes advantage of the fact that the internal infrared LED inside an opto-isolator has a lower voltage drop than the visible LED being tapped into. Using a darlington type opto-isolator also means very little current needs to be diverted to the isolator. The photodarlington side of the isolator can be used to turn on the remote LED using any convenient DC source. In automotive applications, this is often 12v. You can also use the output of the opto-isolator to drive a low power beeper. This might be handy for something like a “check engine” or a “windshield washer fluid” light.

Click on Schematic to view PDF

PCB Design with TINA

2008-12-27T19:48:00.000-08:00

Create single, double-sided or multilayer PCBs of your circuits with a single mouse click, using automatically-placed and routed components. All components in TINA are "PCB-ready" and have associated footprints. If necessary, you can review and edit a component's footprint using the components' spreadsheet. TINA's unique 3D capability displays a schematic with the physical parts in place of their electronic symbols. You can also view the PCB in 3D from any angle to see how it will look after manufacture.

The fully integrated layout module of TINA 7 has all the features you need for advanced PCB design, including powerful autoplacement & autorouting, flexible PCBs, manual and "follow-me" trace placement, DRC, forward/back annotation, pin/gate swapping, keep-in/out areas, thermal relief, fanout, plane layers, Gerber file output and much more.

Single layer SMD circuit

Schemaric diagram

Schematic with 3D view of parts

Single sided layout

3D view of the circuit

Double layer through-hole circuit

Schematic diagram of a double-sided design

3D part preview on the schematic

PCB layout with Top (red) layer selected

PCB layout with Bottom (green) layer selected

3D view of the top side

Looking at the bottom layer

4-layer SMD circuit

Schematic diagram of the 4-layer SMD design

PCB layout of the 4-layer SMD design

3D view of the top side

3D view of the bottom side

Flexible PCB Layout (Flex PCB)

Flex PCBs are PCBs whose electronic devices are mounted on flexible plastic substrates. They are widely used in modern electronics where space is a critical factor e.g., cameras, mobile phones, etc. TINA supports Flex PCB design, which we will introduce by way of an example. Our example will consist of a conventional rigid PCB with two flexible extensions.

Example file „PIC Flasher DIP4SW flex top.TSC” from the Examples\PCB folder of TINA.

TINA can present a 3D view of the circuit board. Press the rightmost button (3D View) in the TINA PCB Designer program see the PCB as presented in the next figure.

.Pict.Collage.Maker.203.1976.CRD

2008-12-22T11:44:00.000-08:00

http://www.mediafire.com/?sharekey=cec59dfde689398ed2db6fb9a8902bda

Simple Electronic Lock Project

2008-12-22T11:28:00.000-08:00

A kit for this project is available from RSH Electronics.
Download PDF version of this page
There are six (or more) push switches. To 'unlock' you must press all the correct ones at the same time, but not press any of the cancel switches. Pressing just one cancel switch will prevent the circuit unlocking. When the circuit unlocks it actually just turns on an LED for about one second, but it is intended to be adapted to turn on a relay which could be used to switch on another circuit.
Please Note: This circuit just turns on an LED for about one second when the correct switches are pressed. It does not actually lock or unlock anything!
This project uses a 555 monostable circuit.
Parts Required
resistors: 470, 100k ×2, 1M
capacitors: 0.1µF, 1µF 16V radial
red LED
555 timer IC
8-pin DIL socket for IC
on/off switch
push-switch ×6 (or more)
battery clip for 9V PP3
stripboard 12 rows × 25 holes

12V to 120V Inverter

2008-12-22T11:26:00.001-08:00

Have you ever wanted to run a TV, stereo or other appliance while on the road or camping? Well, this inverter should solve that problem. It takes 12 VDC and steps it up to 120 VAC. The wattage depends on which tansistors you use for Q1 and Q2, as well as how "big" a transformer you use for T1. The inverter can be constructed to supply anywhere from 1 to 1000 (1 KW) watts.
Important: If you have any questions or problems with the circuit, see the forum topic linked to in the Notes section. It will answer all your questions and provide links to many other (and better) inverter circuits.

Q1 and Q2, as well as T1, determine how much wattage the inverter can supply. With Q1,Q2=2N3055 and T1= 15 A, the inverter can supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power.
The easiest and least expensive way to get a large T1 is to re-wind an old microwave transformer. These transformers are rated at about 1KW and are perfect. Go to a local TV repair shop and dig through the dumpster until you get the largest microwave you can find. The bigger the microwave the bigger transformer. Remove the transformer, being careful not to touch the large high voltage capacitor that might still be charged. If you want, you can test the transformer, but they are usually still good. Now, remove the old 2000 V secondary, being careful not to damage the primary. Leave the primary in tact. Now, wind on 12 turns of wire, twist a loop (center tap), and wind on 12 more turns. The guage of the wire will depend on how much current you plan to have the transformer supply. Enamel covered magnet wire works great for this. Now secure the windings with tape. Thats all there is to it. Remember to use high current transistors for Q1 and Q2. The 2N3055's in the parts list can only handle 15 amps each.
Remember, when operating at high wattages, this circuit draws huge amounts of current. Don't let your battery go dead :-).
Since this project produces 120 VAC, you must include a fuse and build the project in a case.
You must use tantalum capacitors for C1 and C2. Regular electrolytics will overheat and explode. And yes, 68uF is the correct value. There are no substitutions.
This circuit can be tricky to get going. Differences in transformers, transistors, parts substitutions or anything else not on this page may cause it to not function.
If you want to make 220/240 VAC instead of 120 VAC, you need a transformer with a 220/240 primary (used as the secondary in this circuit as the transformer is backwards) instead of the 120V unit specified here. The rest of the circuit stays the same. But it takes twice the current at 12V to produce 240V as it does 120V.
Check out this forum topic to answer many of the most commonly asked questions about this circuit: 12 - 120V Inverter Again. It covers the most common problems encountered and has some helpful suggestions.
Related Circuits

Part
Total Qty.
Description
Substitutions
C1, C2
2
68 uf, 25 V Tantalum Capacitor
R1, R2
2
10 Ohm, 5 Watt Resistor
R3, R4
2
180 Ohm, 1 Watt Resistor
D1, D2
2
HEP 154 Silicon Diode
Q1, Q2
2
2N3055 NPN Transistor (see "Notes")
T1
1
24V, Center Tapped Transformer (see "Notes")
MISC
1
Wire, Case, Receptical (For Output)

Automatic Room Lights

2008-12-22T11:14:00.000-08:00

An ordinary automatic room power control circuit has only one light sensor. So when a person enters the room it gets one pulse and the lights come ‘on.’ When the person goes out it gets another pulse and the lights go ‘off.’ But what happens when two persons enter the room, one after the other? It gets two pulses and the lights remain in ‘off’ state. The circuit described here overcomes the above-mentioned problem. It has a small memory which enables it to automatically switch ‘on’ and switch ‘off’ the lights in a desired fashion. The circuit uses two LDRs which are placed one after another (separated by a distance of say half a metre) so that they may separately sense a person going into the room or coming out of the room. Outputs of the two LDR sensors, after processing, are used in conjunction with a bicolour LED in such a fashion that when a person gets into the room it emits green light and when a person goes out of the room it emits red light, and vice versa. These outputs are simultaneously applied to two counters. One of the counters will count as +1, +2, +3 etc when persons are getting into the room and the other will count as -1, -2, -3 etc when persons are getting out of the room. These counters make use of Johnson decade counter CD4017 ICs. The next stage comprises two logic ICs which can combine the outputs of the two counters and determine if there is any person still left in the room or not. Since in the circuit LDRs have been used, care should be taken to protect them from ambient light. If desired, one may use readily available IR sensor modules to replace the LDRs. The sensors are installed in such a way that when a person enters or leaves the room, he intercepts the light falling on them sequentially—one after the other. When a person enters the room, first he would obstruct the light falling on LDR1, followed by that falling on LDR2. When a person leaves the room it will be the other way round. In the normal case light keeps falling on both the LDRs, and as such their resistance is low (about 5 kilo-ohms). As a result, pin 2 of both timers (IC1 and IC2), which have been configured as monostable flip-flops, are held near the supply voltage (+9V). When the light falling on the LDRs is obstructed, their resistance becomes very high and pin 2 voltages drop to near ground potential, thereby triggering the flip-flops. Capacitors across pin 2 and ground have been added to avoid false triggering due to electrical noise. When a person enters the room, LDR1 is triggered first and it results in triggering of monostable IC1. The short output pulse immediately charges up capacitor C5, forward biasing transistor pair T1-T2. But at this instant the collectors of transistors T1 and T2 are in high impedance state as IC2 pin 3 is at low potential and diode D4 is not conducting. But when the same person passes LDR2, IC2 monostable flip-flop is triggered. Its pin 3 goes high and this potential is coupled to transistor pair T1-T2 via diode D4. As a result transistor pair T1-T2 conducts because capacitor C5 retains the charge for some time as its discharge time is controlled by resistor R5 (and R7 to an extent). Thus green LED portion of bi-colour LED is lit momentarily. The same output is also coupled to IC3 for which it acts as a clock. With entry of each person IC3 output (high state) keeps advancing. At this stage transistor pair T3-T4 cannot conduct because output pin 3 of IC1 is no longer positive as its output pulse duration is quite short and hence transistor collectors are in high impedance state. When persons leave the room, LDR2 is triggered first followed by LDR1. Since the bottom half portion of circuit is identical to top half, this time with the departure of each person red portion of bi-colour LED is lit momentarily and output of IC4 advances in the same fashion as in case of IC3. The outputs of IC3 and those of IC4 (after inversion by inverter gates N1 through N4) are ANDed by AND gates (A1 through A4) are then wire ORed (using diodes D5 through D8). The net effect is that when persons are entering, the output of at least one of the AND gates is high, causing transistor T5 to conduct and energise relay RL1. The bulb connected to the supply via N/O contact of relay RL1 also lights up. When persons are leaving the room, and till all the persons who entered the room have left, the wired OR output continues to remain high, i.e. the bulb continues to remains ‘on,’ until all persons who entered the room have left. The maximum number of persons that this circuit can handle is limited to four since on receipt of fifth clock pulse the counters are reset. The capacity of the circuit can be easily extended for up to nine persons by removing the connection of pin 1 from reset pin (15) and utilising Q1 to Q9 outputs of CD4017 counters. Additional inverters, AND gates and diodes will, however, be required

5 band graphic equalizer using a single IC/chip

2008-12-22T11:09:00.000-08:00

This circuit uses a single chip, IC BA3812L for realizing a 5 band graphic equalizer for use in hi-fi audio systems.The BA3812L is a five-point graphic equalizer that has all the required functions integrated onto one IC. The IC is comprised of the five tone control circuits and input and output buffer amplifiers. The BA3812L features low distortion, low noise, and wide dynamic range, and is an ideal choice for Hi-Fi stereo applica-tions. It also has a wide operating voltage range (3.5V to 16V), which means that it can be adapted for use with most types of stereo equipment.
The five center frequencies are independently set using external capacitors, and as the output stage buffer amplifier and tone control section are independent circuits, fine control over a part of the frequency bandwidth is possible, By using two BA3812Ls, it is possible to construct a 10-point graphic equalizer. The amount of boost and cut can be set by external components.
The recommended power supply is 8V, but the circuit should work for a supply of 9V also. The maximum voltage limit is 16V.
The circuit given in the diagram operates around the five frequency bands:
100Hz
300Hz
1kHz
3kHz
10kHz

Digital Volume Control

2008-12-22T11:06:00.000-08:00

This circuit could be used for replacing your manual volume control in a stereo amplifier. In this circuit, push-to-on switch S1 controls the forward (volume increase) operation of both channels while a similar switch S2 controls reverse (volume decrease) operation of both channels.
A readily available IC from Dallas semiconductor, DS1669 is used here.
FEATURES:
Replaces mechanical variable resistors
Electronic interface provided for digital as well as manual control
Wide differential input voltage range between 4.5 and 8 volts
Wiper position is maintained in the absence of power
Low-cost alternative to mechanical controls
Applications include volume, tone, contrast,brightness, and dimmer control
The circuit is extremely simple and compact requiring very few external components.
The power supply can vary from 4.5V to 8V.

Discrete component motor direction controller

2008-12-22T11:04:00.000-08:00

This circuit can control a small DC motor, like the one in a tape recorder. When both the points A & B are "HIGH" Q1 and Q2 are in saturation. Hence the bases of Q3 to Q6 are grounded. Hence Q3,Q5 are OFF and Q4,Q6 are ON . The voltages at both the motor terminals is the same and hence the motor is OFF. Similarly when both A and B are "LOW" the motor is OFF.When A is HIGH and B is LOW, Q1 saturates ,Q2 is OFF. The bases of Q3 and Q4 are grounded and that of Q4 and Q5 are HIGH. Hence Q4 and Q5 conduct making the right terminal of the motor more positive than the left and the motor is ON. When A is LOW and B is HIGH ,the left terminal of the motor is more positive than the right and the motor rotates in the reverse direction. I could have used only the SL/SK100s ,but the ones I used had a very low hFE ~70 and they would enter the active region for 3V(2.9V was what I got from the computer for a HIGH),so I had to use the BC148s . You can ditch the BC148 if you have a SL/SK100 with a decent value of hFE ( like 150).The diodes protect the transistors from surge produced due to the sudden reversal of the motor. The approx. cost of the circuit without the motor is around Rs.40.Note: You can change the supply voltage depending on the motor, only thing is that it should be a 2 or 3V more than the rated motor voltage( upto a max. of 35V).

555 Timing for a stepper motor

2008-12-22T11:03:00.000-08:00

In the circuit a 555 drives a UCN 5804 stepper motor chip. My problem is with the speed switch set to slow the motor is driven too slow, and with the switch set to fast the motor is driven too fast.
I have changed the pot to 1M but the slowest speed (with the switch set to fast) is the fastest speed I require. At the slowest speed I would like to pulse the motor every 1-2 seconds.
I understand that the capacitor and resistors adjust the timing, but I dont understand the relationship between them.
Could somebody help me with this?

Ashampoo_Photo_Optimizer_3.02_www.softarchive.net_2

2008-12-22T10:46:00.000-08:00

http://www.mediafire.com/?sharekey=cec59dfde689398ed2db6fb9a8902bda

viralnuniyil thirukkural

2008-12-22T10:09:00.000-08:00

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Dancing Lights

2008-12-21T04:58:00.000-08:00

Here is a simple circuit which can be used for decoration purposes or as an indicator. Flashing or dancing speed of LEDs can be adjusted and various dancing patterns of lights can be formed.The circuit consists of two astable multivibrators. One multivibrator is formed by transistors T1 and T2 while the other astable multivibrator is formed by T3 and T4. Duty cycle of each multivibrator can be varied by changing RC time constant. This can be done through potentiometers VR1 and VR2 to produce different dancing pattern of LEDs. Total cost of this circuit is of the order of Rs 30 only. Potentiometers can be replaced by light dependent resistors so that dancing of LEDs will depend upon the surrounding light intensity. The colour LEDs may be arranged as shown in the Figure

Serial Data Link Kits

2008-12-21T04:43:00.000-08:00

This Transmitter Receiver kit can receive up to 64 characters via its serial port. The serial port baud rate is selectable from 300, 1200, 2400 and 9600. The data format is fixed at 8N1(8 data bits, no parity, 1 stop bit). Two input modes are available as well as input echo if required. An optional destination address can be automatically inserted into the message before transmitting.
Specifications:
Transmitter L: 2-3/8" W: 2" H: 7/8"
Receiver L: 2-3/8" W: 1-7/8" H: 7/8:
Power Requirement: 12 VDC(Need a Power Supply?)
Operates at 433.92 MHz. (uses amplitude modulation)
Up to 16 Receivers can be used in a Network
See the following documents for complete details, including schematic and theory of operation. Requires Adobe Acrobat Reader available at http://www.adobe.com/ for FREE!

http://www.mediafire.com/?g1yjzam0qzo

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Parallel Data Link Kits

2008-12-21T04:40:00.001-08:00

K175 monitors 8 digital inputs for change. If change is detected on any input the state of all the inputs is transmitted. An optional destination address can be added to the message before transmitting. The pinout of the input connector allows direct connection to a PC printer port.
Specifications:
Transmitter L: 2-3/8" W: 1-7/8" H: 7/8"
Receiver L: 2-3/8" W: 2-3/8" H: 7/8:
Power Requirement: 12 VDC(Need a Power Supply?)
Operates at 433.92 MHz. (uses amplitude modulation)
Up to 16 Receivers can be used in a Network
See the following documents for complete details, including schematic and theory of operation. Requires Adobe Acrobat Reader available at http://www.adobe.com/ for FREE!

http://www.mediafire.com/?ejyg3mmmoxn

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Audio Video Transmitter Kit

2008-12-21T04:21:00.000-08:00

If it is desired to connect a video signal originating from a camera or other video source to a normal TV set, you will need this modulator. The audio and video signal is converted into a UHF TV signal so that the signal can be received through the TV antenna input. In certain countries (find out from your national telecommunications authority) it is permitted to use this modulator as a mini-transmitter by connecting a small antenna to it. With this facility it is possible to receive the signal from the video recorder or camera elsewhere within your home (range ~100'). The kit comes complete with housing and antenna connector. Specifications:
Input: rca style audio and video jacks
Output: UHF channel 21 (450 - 500MHz adjustable)
Power supply: 12 to 15V DC / 100mA(Need a Power Supply?)
Dimensions: 2.8" x 4.1" x 1.2"

http://www.mediafire.com/?39pmt0omlkw

Digital Clock With Timer Kit

2008-12-21T04:18:00.000-08:00

This circuit is a digital clock with a built-in 24-hour timer. It includes a one-piece LED display which provides a 4-digit display of hours and minutes, AM/PM and timer-on indicators. The timer includes a relay output which be connected to any external electrical device of up to 3A / 110V AC or 24V DC (1.5A / 220V AC).
Specifications:
Supply voltage: 12V AC C.T. (2 x 6V AC) / 300mA transformer
Output relay handles up to 3A / 110V AC or 24V DC (1.5A / 220V AC)
Display height: 15.2mm
50/60 Hz operation
Snooze function
PC board dimensions: 3.6" x 1.9" (93mm x 49mm)

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Outgoing Phone Number Logger

2008-12-21T04:09:00.000-08:00

The logger records the start and stop time of ALL outgoing calls along with the number dialed (plus any other digits pressed during the call). There is no limit to the number of key presses it will log. It operates “stand alone” – no need for any connection to a PC. Telephone call data is output in a format that can be easily imported into Microsoft Excel. Various Excel functions can then be used to analyze and sort the data and produce formatted printouts. Data is stored in non-volatile EEPROM memory, so there is no loss of data in the event of a power failure - DIY KIT 164.
Specifications:
L: 5" W: 3-3/4" H: 1"
Requires 9 - 12 VDC Power Supply.(Need a Power Supply?)
3 Volt Lithium Back Up Battery (not included).
Stores up to 700 strings of (10 digit) numbers.(It will store as many digits that are pushed, there is no limit)
Download data to PC via Serial Port.
Use any terminal emulator program to get data.
Includes plastic case and all parts.

http://www.mediafire.com/?v0ytwobgyzt

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Electronic Combination Lock Kit

2008-12-21T04:05:00.000-08:00

This really is an excellent introduction to security devices. Set your own four digit code; any wrong key-in sequence resets the lock; correct sequence activates the relay (up to 240VAC contacts). A 9-digit key pad circuit board is separate and connects via ribbon cable, 30" supplied. Requires 12 VDC battery or supply - DIY Kit 29.
Specifications:
Main Board: L: 3" W: 2-3/8" H: 3/4".
Key Pad Board: L: 2-5/8" W: 1-1/4" H: 1/2".
Requires 12 Volt DC power supply.(Need a Power Supply?)
Relay contacts rated for 240VAC @ 12Amps.

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AM/FM Radio Kit and Training Course

2008-12-21T04:01:00.000-08:00

"Superheterodyne" receiver of standard AM (amplitude modulation) FM (frequency modulated) broadcast frequencies. (PC board 11 5/8" x 5 1/4")
The unique design of this kit allows you to place the parts over its corresponding symbol in the schematic drawing on the surface of the printed circuit board. This technique maximizes the learning process while keeping the chances for an assembly error at a minimum.
This kit includes an assembly, lesson and theory of operation manual. The actual assembly is broken into simple sections. Each section should be completely tested before moving on. This reduces difficult trouble-shooting associated with many similar kits. Also included are practical hi-tech blue PC board with the schematic printed on the surface, and battery and solder included. The manual is easy to understand, no previous knowledge of electronics is necessary. This radio kit PC board has been designed so that no cabinet is necessary. A special bracket provides the necessary support to use the radio in any location, displaying the work achievement of the student.
Specifications:
Uses 14 Transistors and 5 Diodes.
PC Board Dimensions 11-5/8" x 5-1/4".
Operates on 9Volt battery (not included).(or Use this Power Supply instead of a Battery)
Includes complete course study guide.
Excellent for classroom trainer.

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PIC Programmer & Experiment Board

2008-12-21T03:54:00.000-08:00

This electronic kit is a multifunctional Microchip PIC Flash Micro controller programmer with built in test circuit. You can create your programs and use the built in LED's and Push buttons to test and debug.
The code to program PIC's is written in standard ASCII and can be edited in any text editor or Microchip's MPLAB. We have also included a PIC16F627 so you can start programming and testing immediately.
Specifications:
Requires 12-15 Volt DC power supply.(Need a Power Supply?)
L: 5-3/4" W: 4" H: 3/4".
Supports 4 different 300 mil. PICs: 8p, 14p, 18p and 28p
Test buttons and LED indicators to carry out educational experiments, such as the enclosed programming examples.
PC connection through serial port.
Includes In Circuit Serial Programming (ICSP) connector.
Includes one Flash Microcontroller (PIC16F627) that can be reprogrammed up to 1000 times for experimenting at will.
CDROM Software to compile and program your source code is included minimum system requirements: IBM Compatible PC, Pentium or betterWindows™ 95/98/ME/NT/2000/XP
Rev 2.5 supports the following microcontrollers: PIC12F629, PIC12F675, PIC16C83, PIC16CR83, PIC16F83, PIC16C84, PIC16CR84,PIC16F84, PIC16F84A, PIC16F870, PIC16F871, PIC16F872, PIC16F873, PIC16F873A, PIC16F874, PIC16F874A, PIC16F876, PIC16F876A, PIC16F877(A)(ICSP only), PIC16F627, PIC16F627A, PIC16F628, PIC16F628A, PIC16F648A, PICF630, PIC16F676, PIC16F818, PIC16F819

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EEPROM Programmer Kit

2008-12-21T03:51:00.000-08:00

Serial eeproms are finding more and more use in electronic devices. These small 8 pin devices offer non-volatile data storage and require minimal I/O lines to connect them. The programmer connects to the Parallel PC Port. The software runs under DOS, Win95, Win3.1, and WinNT (service pack 5).
Programs the following devices:2401, 2402, 2404, 2408, 24162432, 2464, 24128, 242569346, 9356, 9366, 9376, 9386
Specifications: L: 2-1/2" W: 2-1/4" H: 5/8" Requires external 9- 12 volt dc @ 50 mA power supply (Need a Power Supply?) Requires parallel port PC cable Link to download software provided Supports 8 bit eeproms only

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Bi-directional DC Motor Speed Controller (Kit or Assembled)

2008-12-21T03:48:00.000-08:00

This DC motor controller kit allows controlling the speed of a DC motor in both the forward and reverse direction using pulse-width modulation (PWM). The range of DC motor control is from fully OFF to fully ON in both directions. Turning the pot in the other direction causes the DC motor to spin in the opposite direction. The center position on the pot is OFF, forcing the motor to slow and stop before changing direction. See our one direction DC Motor Controller.
Specifications:
L: 3-3/4" W: 1-5/8" H: 1".
Motor Speed Controlled via a potentiometer.
For DC motors 12 to 32 Volts DC @ 5 Amps as constructed. The IRFZ44 Mosfets can handle up to a maximum 49Amps, but PCB trace capacity would have to be beefed up with some hookup wire (underneath the PCB) soldered between the MOFSET pins and the screw terminal blocks. If you are running beyond 5 Amps and the MOFSETS are getting hot, bigger heatsinks should be used. You can also dissipate heat with a cooling fan directed over the heat sinks.
Requires operating voltage of 6 - 32 VDC.(Need a Power Supply?)
This PWM DC motor controller circuit can be used for generating hydrogen, build your own fuel cell station. More common uses include controlling DC motors in golf carts, buggies, RC cars, robotics, DC hobby motors, toy DC motors, etc.

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Three Digit Counter Module Kit

2008-12-21T03:45:00.000-08:00

This electronic kit is a basic low cost counter module (DIY Kit1). Two or more may be plugged together with 6-pin sockets and harness provided. Excellent use as event counter. Has a single 3-digit display. Uses the 14553 and 14551 chips. Has count and reset switches with debounce built in to eliminate problems from noisy switches. Two or more may be joined to make 6 or 9 digit unit. Display may be located remotely. Plastic case included, 9 volt battery operation.
Specifications:
Main Board: L: 2-1/8" W: 3-1/4" H: 1-1/2"
Input Board: L: 1-1/4" W: 1-1/2" H: 1/2"
Requires 9 volt battery.(or Use this Power Supply instead of a Battery)

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Metal Detector Kit

2008-12-21T03:42:00.000-08:00

To come up against an electric cable while drilling a hole in a wall can have catastrophic consequences. Likewise, drilling into gas, water pipes or central heating pipes can be extremely hazardous. With a handy metal detector it can now be determined beforehand whether there are metal objects to be found in a wall, ceiling or floor. An LED indicates if a metal object is in the vicinity.
Specifications:
Metal detecting distance adjustable: up to 3.15"
Power supply: 9V battery (not included)
LED and buzzer indication
Dimensions: L: 2.2" x W: 2.5" x H 1.5"

http://www.mediafire.com/?zlyno2jptnu

Cell Phone Remote Control Kit

2008-12-21T03:29:00.000-08:00

Use this light activated circuit to turn equipment on and off at any location via GSM mobile phone. Applications include turning on lighting, heating, opening your gate, simulating presence, controlling animal feeders, activating car alarms, etc... Ring detection circuit avoids phone charges and there is no need to open or modify phone, no physical connection to mobile phone. Works with most GSM mobile phones.
Specifications:
L: 4" W: 1.7" H: 1"
Power supply: 12Vdc / 100mA(Need a Power Supply?)
Dual operation mode: on/off toggle or on with auto turn-off timer
Timer settings: 0.5s, 2s, 30s, 1 min, 5 min, 15 min, 30min or 1 hour
Relay has Normally Open and Normally Closed Contact.
Relay Contact Max Current 3Amp @ 120VAC.(more info on how relays work)

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Sound Activated Relay Switch

2008-12-21T03:21:00.000-08:00

This mini-VOX - voice operated relay - is based on a circuit published in Silicon Chip, 9/1994, p31. We have improved it by putting an on-board Koa potentiometer in order to adjust the sensitivity. The idea behind a VOX is that instead of the user pressing a switch to activate a relay, the sound of the users voice itself activates the relay. This gives hands-free control over devices like lights and tape recorders. Relay stays on for 1 or 5 seconds (depending on components used) then shuts off. Different time values can be realized by using different value components (read k126.pdf for more information).
Specifications:
L: 2-1/4" W: 1-1/4" H: 5/8"
Requires 12 VDC Power Supply(Need a Power Supply?)
Current drain when off is 5-7mA and 35mA when activated
Relay output rated at 12/24VDC/1A (more info on how relays work)
Microphone can be connected on leads up to 2 feet away from the PCB.
Off time delay adjustable by changing component values.

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Digital Clock With 24 Hour Timer - Kit and Assembled Circuit Available

2008-12-20T10:00:00.000-08:00

This digital clock with timer kit is an ideal option for use in homes and offices. The circuit is based on the LM8560 chip which is one of the most popular clock chips and incorporates a wide range of features such as alarm, snooze, and 24 hour timer (a relay can be connected to the PCB). The clock display is made up of a discrete array of 87 LEDs with digits measuring 2“ high.

Specifications:

Supply voltage: 18V AC C.T. (2 x 9V AC) / 300mA (not included)
4-digit display
Number of LEDs: 87 bright 4mm LEDs
Digit height: 2" (50mm)
Single board design
Includes alarm melody generator
Includes output circuit for external relay
PC board dimensions: 8.84"L x 3.48"W x 1/2"H
Speaker not included

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Headlight Warning Kit

2008-12-20T09:54:00.000-08:00

This head light indicator may be set for one or two functions. To indicate that the head lights (or the side lights) should be switched off after switching off the ignition contact (battery protection). Or to indicate that the head lights should be on once ignition contact is switched on (obligatory in some countries).

Specifications:

continuously repeated alarm tone for lights ON (may be disabled)
repeated alarm tone for lights OUT
only 3 wires are required for hook-up
supply voltage: 12V DC
PCB dimensions: 1.9" x 2.2"

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Learn To Solder Kit - Our Best Seller!

2008-12-20T09:43:00.000-08:00

Why not introduce someone to the Exciting world of Electronics. This is a great introduction to a hobby that could lead to a career in the High Tech Industry. The kit includes a 30W soldering iron, diagonal cutters, solder, solder iron stand, printed circuit board, all components needed to build a flashing siren, and complete lesson plan. Complete with speaker and light emitting diodes. Finished circuit has an adjustable European Siren and flashing diodes.

We have sold thousands of these! Great for Schools, Clubs, Boy Scouts, Summer Programs etc. Fun for ages 10 through Adult.

Specifications:

Includes all the tools needed to learn soldering.
Includes a Printed Circuit Board and all components to build a working electronic siren.
Includes a complete 10 page lesson plan and instruction booklet for easy integration into any electronics program.
Requires 9 volt battery.
Recommended for ages 10 and up (adult supervision required).

http://www.mediafire.com/?sharekey=cec59dfde689398ed2db6fb9a8902bda

2008-12-20T07:36:00.000-08:00

This is a newer version of the original CK1616 which includes resets on the board so you can use a switch to reset the relay when using toggle mode. This is handy for applications like a garage door where you would want the motor to stop when the door is closed or open all the way.
This 4 channel remote control relay board is available as a kit or assembled unit. The relay board uses "Rolling Code" so it is nearly impossible to crack. Features pre assembled and aligned RF modules, pre assembled key-chain transmitter that only requires you to solder battery clips and case. Receiver requires component mounting & soldering. Receiver can "learn" up to 16 transmitters. Transmitters can be used with multiple receivers. 4 channel output with Single Pole Double Throw (SPDT) relays rated 10A @ 28VDC. Each output can independently be made latching (Push-on/Push-off) or momentary. Range exceeds 50meters. Transmitter uses 12V cell (included). Ideal for higher security garage doors, auto gates, electric locks etc.
Specifications:
Range is over 50 Meters (~150 feet).
Transmits on 433.9 MHz
Transmitter comes fully assembled and includes battery.
Receiver Power 12 VDC (power supply not included).(Need a Power Supply?)
Circuit draws 8mA in idle state, 1 relay energized 44mA, 2 relays 78mA, 3 relays 111mA, and 4 relays 144mA.
Relays have a Common, Normally Closed (NC), and Normally Open (NO).
Each Individual Relay is jumper selectable latching or momentary.
Relay Contact Ratings: 240VAC 7Amps, 125VAC 10Amps, 28VDC 10Amps, (more info on how relays work)
Has 4 resets for each relay.
Includes transmitter and receiver.
Transmitter Dimensions 2-1/4" L x 1-1/2" W x 1/2" H
Receiver Dimensions 3-3/8" L x 3" W x 1" H

This is a practical power supply for all your projects. Converts AC to DC power. It provides 6 different outputs between 6 and 20VDC @ 500mA. There are also 6 different size jacks to accommodate most projects and two alligator clips just in case there isn't a jack.
Note: This is not a kit, no assembly required.
Specifications:
L: 3-3/4" W: 2-1/2" H: 2-1/2".
Output Voltage: 6, 9, 12, 15, 18 or 20 VDC.
Output Current: Up to 500 mA.
Includes 6 different size jack connectors.
Jack can be reversed from center positive to negative.
Includes alligator clips for projects without power jack.
Includes 9 volt snap type connector
Input: 110VAC

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10 Channel Auto Roll RF Remote Control Relay Board

2008-12-20T07:28:00.000-08:00

This ten channel Auto Roll RF Remote Control is virtually impossible to 'crack'. Ten channels that are selectable as either latching or momentary. Each relay has led indicators. Receiver can support up to 15 transmitters. This kit makes remote control very affordable for you next project.
Note: Transmitter has only 4 buttons, button combinations are used to control all 10 channels, see pdf file below for details.
Specifications:
Range is over 30 yards (120 feet).
Transmits on 433.9 MHz
Transmitter comes fully assembled and includes battery.
Receiver Power 12 VDC (Need a Power Supply?)
Relays are Individually latching or momentary selectable.
Relay Contact Max Current 1Amp, Max Voltage 60VDC or 120VAC. (more info on how relays work)
Relay has Normally Open and Normally Closed Contacts
Includes transmitter and receiver.
Transmitter Dimensions 2-1/4" L x 1-1/2" W x 1/2" D
Receiver Board Dimensions 4- 7/16" L x 3-5/16" W x 5/8" D

http://www.mediafire.com/?sharekey=cec59dfde689398ed2db6fb9a8902bda

60 SECOND DIGITAL VOICE RECORDER

2008-12-20T07:23:00.000-08:00

With this advanced digital audio recorder/player, you can record up to 60 seconds of speech or any other audio with the built-in microphone and later play it back anytime. This unique design is made possible through the ISD25xx series of Integrated Circuits which store voice and audio signals directly, in their analog form, into a 480K Cell Nonvolatile Analog Storage EEPROM requiring neither analog-to-digital nor digital-to-analog converter. Recordings stored in this non-volatile memory cell last up to 100 years and therefore even if the supply voltage is disconnected, the recording will not be lost. Another unique feature of this circuit is a message looping mode of operation which continuously plays back the recorded message automatically. The circuit also incorporates a built-in audio amplifier so it can be directly connected to a speaker or connected to a power amplifier for greater output power.

Doorbell or entrance message. Greet your guests or customers with a welcome message.
"Watchdog" burglar alarm system. Record the barking of a dog and connect this circuit to a alarm system to deter burglars.
Toys applications where you need speech or audio effects.
Talking picture frames for personal or museum use. Add it to the back of a picture frame of a friend or relative to have his or her voice be played back at any time.
With the looping mode of operation, you can connect the circuit to one of our FM Transmitters in order to build a FM Announcement System or talking sign which is ideal for real estate applications.

http://www.mediafire.com/?sharekey=cec59dfde689398ed2db6fb9a8902bda

10 WATT x 10 WATT STERE0 AMPLIFIER

2008-12-20T07:20:00.000-08:00

This class AB stereo audio power amplifier is designed for quality hi-fi applications using a TDA2009A module. It is easy to construct and has a minimum of external components. The module has output current and thermal protection. This is the data book circuit which outputs excellent sound. The supply voltage for this kit is 8 - 24V DC at 1 to 2 Amps. Maximum output power will only be obtained with a power supply of at least 20V and greater than 1.5 A, and using 4 ohm speakers. Powerful enough to power a stereo for a mid-sized room and more than enough for use in an automobile.
Specifications:
L: 3" W: 1-3/4" H: 1-1/2"
Requires external 8-24 VDC Power Supply(Need a Power Supply?)
Output up to 10 watts per channel

http://www.mediafire.com/?sharekey=cec59dfde689398ed2db6fb9a8902bda

Karaoke Kit

2008-12-20T07:03:00.000-08:00

This neat little circuit will remove the vocals from most songs so you can add your own lyrics. Hooks up between your CD-player, MP3-player or any other line-level source and your amplifier RCA input and output jacks and a 1/4" ( 6.3mm) microphone jack, fits most microphones
Specifications:
Dimensions: L: 3.9" W: 3.3" H: 1"
Power: Requires 9 Volt Battery (not included)
Low power consumption (16mA typical)
Adjustable microphone level
Vocal remove on/off switch
LED power indicator light
See VEMK140.pdf for complete details, including schematic and theory of operation. Requires Adobe Acrobat Reader available at http://www.adobe.com/ for FREE!

Audio Light Modulator

2008-12-19T21:00:00.000-08:00

Audio light modulations add to the enjoyment of music during functions organised at home or outdoors. Presented here is one such simple circuit in which light is modulated using a small fraction of the audio output from the speaker terminals of the audio amplifier. The output from the speaker terminals of audio amplifier is connected to a transformer (output transformer used in transistor radios) through a non-polarised capacitor. The use of transformer is essential for isolating the audio source from the circuit in The sensitivity control potentiometer VR1 provided in the input to transistor T1 may be adjusted to ensure that conduction takes place only after the AF exceeds certain amplitude. This control has to be adjusted as per audio source level. The audio signal Proper earthing of the circuit is quite essential. The diode bridge provides pulsating DC output and acts as a guard circuit between the mains input and pulsating DC output. Extreme care is necessary to avoid any electric shock

Running Message Display

2008-12-19T20:58:00.000-08:00

Light emitting diodes are advan- tageous due to their smaller size, low current consumption and catchy colours they emit. Here is a running message display circuit wherein the letters formed by LED arrangement light up progressively. Once all the letters of the message have been lit up, the circuit gets reset. The circuit is built around Johnson decade counter CD4017BC (IC2). One of the IC CD4017BE’s features is its provision of ten fully decoded outputs, making the IC ideal for use in a whole range of sequencing operations. In the circuit only one of the outputs remains high and the other outputs switch to high state successively on the arrival of each clock pulse. The timer NE555 (IC1) is wired as a 1Hz astable multivibrator which clocks the IC2 for sequencing operations. On reset, output pin 3 goes high and drives transistor T7 to ‘on’ state. The output of transistor T7 is connected to letter ‘W’ of the LED word array (all LEDs of letter array are connected in parallel) and thus letter ‘W’ is illuminated. On arrival of first clock pulse, pin 3 goes low and pin 2 goes high. Transistor T6 conducts and letter ‘E’ lights up. The preceding letter ‘W’ also remains lighted because of forward biasing of transistor T7 via diode D21. In a similar fashion, on the arrival of each successive pulse, the other letters of the display are also illuminated and finally the complete word becomes visible. On the following clock pulse, pin 6 goes to logic 1 and resets the circuit, and the sequence repeats itself. The frequency of sequencing operations is controlled with the help of potmeter VR1.The display can be fixed on a veroboard of suitable size and connected to ground of a common supply (of 6V to 9V) while the anodes of LEDs are to be connected to emitters of transistors T1 through T7 as shown in the circuit. The above circuit is very versatile and can be wired with a large number of LEDs to make an LED fashion jewellery of any design. With two circuits connected in a similar fashion, multiplexing of LEDs can be done to give a moving display effect
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Super simple stepper motor controller

2008-12-19T20:56:00.000-08:00

The circuit shown above can be used to control a unipolar stepper motor which has FOUR coils (I've swiped it off an old fax machine). The above circuit can be for a motor current of up to about 500mA per winding with suitable heat sinks for the SL100. For higher currents power transistors like 2N3055 can be used as darlington pair along with SL100. The diodes are used to protect the transistor from transients.Activating sequence:-
Inputs

Coils Energised
D0
D1
0
0
A,B
0
1
B,C
1
0
C,D
1
1
D,A
To reverse the motor just reverse the above sequence viz. 11,10,01,00.
Alternately a 2bit UP/DOWN counter can also be used to control the direction , and a 555 multi-vibrator can be used to control the speed

Automatic Speed Controller for fans & Coolers

2008-12-19T20:53:00.000-08:00

During summer nights, the temperature is initially quite high. As time passes, the temperature starts dropping. Also, after a person falls asleep, the metabolic rate of one’s body decreases. Thus, initially the fan/cooler needs to be run at full speed. As time passes, one has to get up again and again to adjust the speed of the fan or the cooler.The device presented here makes the fan run at full speed for a predetermined time. The speed is decreased to medium after some time, and to slow later on. After a period of about eight hours, the fan/cooler is switched off.Fig. 1 shows the circuit diagram of the system. IC1 (555) is used as an astable multivibrator to generate clock pulses. The pulses are fed to decade dividers/counters formed by IC2 and IC3. These ICs act as divide-by-10 and divide-by-9 counters, respectively. The values of capacitor C1 and resistors R1 and R2 are so adjusted that the final output of IC3 goes high after about eight hours.The first two outputs of IC3 (Q0 and Q1) are connected (ORed) via diodes D1 and D2 to the base of transistor T1. Initially output Q0 is high and therefore relay RL1 is energised. It remains energised when Q1 becomes high. The method of connecting the gadget to the fan/cooler is given in Figs 3 and 4.

It can be seen that initially the fan shall get AC supply directly, and so it shall run at top speed. When output Q2 becomes high and Q1 becomes low, relay RL1 is turned ‘off’ and relay RL2 is switched ‘on’. The fan gets AC through a resistance and its speed drops to medium. This continues until output Q4 is high. When Q4 goes low and Q5 goes high, relay RL2 is switched ‘off’ and relay RL3 is activated. The fan now runs at low speed.Throughout the process, pin 11 of the IC is low, so T4 is cut off, thus keeping T5 in saturation and RL4 ‘on’. At the end of the cycle, when pin 11 (Q9) becomes high, T4 gets saturated and T5 is cut off. RL4 is switched ‘off’, thus switching ‘off’ the fan/cooler.Using the circuit described above, the fan shall run at high speed for a comparatively lesser time when either of Q0 or Q1 output is high. At medium speed, it will run for a moderate time period when any of three outputs Q2 through Q4 is high, while at low speed, it will run for a much longer time period when any of the four outputs Q5 through Q8 is high.If one wishes, one can make the fan run at the three speeds for an equal amount of time by connecting three decimal decoded outputs of IC3 to each of the transistors T1 to T3. One can also get more than three speeds by using an additional relay, transistor, and associated components, and connecting one or more outputs of IC3 to it.In the motors used in certain coolers there are separate windings for separate speeds. Such coolers do not use a rheostat type speed regulator. The method of connection of this device to such coolers is given in Fig. 4.The resistors in Figs 2 and 3 are the tapped resistors, similar to those used in manually controlled fan-speed regulators. Alternatively, wire-wound resistors of suitable wattage and resistance can be used.

Remote Control Circuits

2008-12-19T20:51:00.000-08:00

Radio Remote Control using DTMF Click here for the circuit diagram
H ere is a circuit of a remote control unit which makes use of the radio frequency signals to control various electrical appliances. This remote control unit has 4 channels which can be easily extended to 12. This circuit differs from similar circuits in view of its simplicity and a totally different concept of generating the control signals. Usually remote control circuits make use of infrared light to transmit control signals. Their use is thus limited to a very confined area and line-of-sight. However, this circuit makes use of radio frequency to transmit the control signals and hence it can be used for control from almost anywhere in the house. Here we make use of DTMF (dual-tone multi frequency) signals (used in telephones to dial the digits) as the control codes. The DTMF tones are used for frequency modulation of the carrier. At the receiver unit, these frequency modulated signals are intercepted to obtain DTMF tones at the speaker terminals. This DTMF signal is connected to a DTMF-to-BCD converter whose BCD output is used to switch-on and switch-off various electrical applicances (4 in this case). The remote control transmitter consists of DTMF generator and an FM transmitter circuit. For generating the DTMF frequencies, a dedicated IC UM91214B (which is used as a dialler IC in telephone instruments) is used here. This IC requires 3 volts for its operation. This is provided by a simple zener diode voltage regulator which converts 9 volts into 3 volts for use by this IC. For its time base, it requires a quartz crystal of 3.58 MHz which is easily available from electronic component shops. Pins 1 and 2 are used as chip select and DTMF mode select pins respectively. When the row and column pins (12 and 15) are shorted to each other, DTMF tones corresponding to digit 1 are output from its pin 7. Similarly, pins 13, 16 and 17 are additionally required to dial digits 2, 4 and 8. Rest of the pins of this IC may be left as they are. The output of IC1 is given to the input of this transmitter circuit which effectively frequency modulates the carrier and transmits it in the air. The carrier frequency is determined by coil L1 and trimmer capacitor VC1 (which may be adjusted for around 100MHz operation). An antenna of 10 to 15 cms (4 to 6 inches) length will be sufficient to provide adequate range. The antenna is also necessary because the transmitter unit has to be housed in a metallic cabinet to protect the frequency drift caused due to stray EM fields. Four key switches (DPST push-to-on spring loaded) are required to transmit the desired DTMF tones. The switches when pressed generate the specific tone pairs as well as provide power to the transmitter circuit simultaneously. This way when the transmitter unit is not in use it consumes no power at all and the battery lasts much longer. The receiver unit consists of an FM receiver (these days simple and inexpensive FM kits are readily available in the market which work exceptionally well), a DTMF-to-BCD converter and a flip-flop toggling latch section. The frequency modulated DTMF signals are received by the FM receiver and the output (DTMF tones) are fed to the dedicated IC KT3170 which is a DTMF-to-BCD converter. This IC when fed with the DTMF tones gives corresponding BCD output; for example, when digit 1 is pressed, the output is 0001 and when digit 4 is pressed the output is 0100. This IC also requires a 3.58MHz crystal for its operation. The tone input is connected to its pin 2 and the BCD outputs are taken from pins 11 to 14 respectively. These outputs are fed to 4 individual ‘D’ flip-flop latches which have been converted into toggle flip-flops built around two CD4013B ICs. Whenever a digit is pressed, the receiver decodes it and gives a clock pulse which is used to toggle the corresponding flip-flop to the alternate state. The flip-flop output is used to drive a relay which in turn can latch or unlatch any electrical appliance. We can upgrade the circuit to control as many as 12 channels since IC UM91214B can generates 12 DTMF tones. For this purpose some modification has to be done in receiver unit and also in between IC2 and toggle flip-flop section in the receiver. A 4-to-16 lines demultiplexer (IC 74154) has to be used and the number of toggle flip-flops have also to be increased to 12 from the existing 4

Remote Control Circuits

2008-12-19T20:47:00.001-08:00

Remote control using telephone Click here for the circuit diagram
Here is a teleremote circuit which enables switching ‘on’ and ‘off’ of appliances through telephone lines. It can be used to switch appliances from any distance, overcoming the limited range of infrared and radio remote controls.The circuit described here can be used to switch up to nine appliances (corresponding to the digits 1 through 9 of the telephone key-pad). The DTMF signals on telephone instrument are used as control signals. The digit ‘0’ in DTMF mode is used to toggle between the appliance mode and normal telephone operation mode. Thus the telephone can be used to switch on or switch off the appliances also while being used for normal conversation.The circuit uses IC KT3170 (DTMF-to-BCD converter), 74154 (4-to-16-line demult-iplexer), and five CD4013 (D flip-flop) ICs. The working of the circuit is as follows.Once a call is established (after hearing ring-back tone), dial ‘0’ in DTMF mode. IC1 decodes this as ‘1010,’ which is further demultiplexed by IC2 as output O10 (at pin 11) of IC2 (74154). The active low output of IC2, after inversion by an inverter gate of IC3 (CD4049), becomes logic 1. This is used to toggle flip-flop-1 (F/F-1) and relay RL1 is energised. Relay RL1 has two changeover contacts, RL1(a) and RL1(b). The energised RL1(a) contacts provide a 220-ohm loop across the telephone line while RL1(b) contacts inject a 10kHz tone on the line, which indicates to the caller that appliance mode has been selected. The 220-ohm loop on telephone line disconnects the ringer from the telephone line in the exchange. The line is now connected for appliance mode of operation.If digit ‘0’ is not dialed (in DTMF) after establishing the call, the ring continues and the telephone can be used for normal conversation. After selection of the appliance mode of operation, if digit ‘1’ is dialed, it is decoded by IC1 and its output is ‘0001’. This BCD code is then demultiplexed by 4-to-16-line demultiplexer IC2 whose corresponding output, after inversion by a CD4049 inverter gate, goes to logic 1 state. This pulse toggles the corresponding flip-flop to alternate state. The flip-flop output is used to drive a relay (RL2) which can switch on or switch off the appliance connected through its contacts. By dialing other digits in a similar way, other appliances can also be switched ‘on’ or ‘off.’Once the switching operation is over, the 220-ohm loop resistance and 10kHz tone needs to be removed from the telephone line. To achieve this, digit ‘0’ (in DTMF mode) is dialed again to toggle flip-flop-1 to de-energise relay RL1, which terminates the loop on line and the 10kHz tone is also disconnected. The telephone line is thus again set free to receive normal calls.This circuit is to be connected in parallel to the telephone instrument

Lights & LED Circuits

2008-12-19T20:45:00.000-08:00

Flashy Christmas Lights Click here for the circuit diagram
This simple and inexpensive circuit built around a popular CMOS hex inverter IC CD4069UB offers four sequential switching outputs that may be used to control 200 LEDs (50 LEDs per channel), driven directly from mains supply. Input supply of 230V AC is rectified by the bridge rectifiers D1 to D4. After fullwave rectification, the average output voltage of about 6 volts is obtained across the filter comprising capacitor C1 and resistor R5. This supply energises IC CD4069UB.All gates (N1-N6) of the inverter have been utilised here. Gates N1 to N4 have been used to control four high voltage transistors T1 to T4 (2N3440 or 2N3439) which in turn drive four channels of 50 LEDs each through current limiting resistors of 10-kilo-o Base drive of transistors can be adjusted with the help of 10-kilo-ohm pots provided in their paths. Remaining two gates (N5 and N6) form a low frequency oscillator. The frequency of this oscillator can be changed through pot VR1. When pot VR1 is adjusted To get the best results, a low leakage, good quality capacitor must be used for the timing capacitor C2

Fun/Games Circuits

2008-12-19T20:43:00.000-08:00

Electronic Scoring Game Click here for the circuit diagram
You can play this game alone or with your friends. The circuit comprises a timer IC, two decade counters and a display driver along with a 7-segment display. The game is simple. As stated above, it is a scoring game and the competitor who scores 100 points rapidly (in short steps) is the winner. For scoring, one has the option of pressing either switch S2 or S3. Switch S2, when pressed, makes the counter count in the forward direction, while switch S3 helps to count downwards. Before starting a fresh game, and for that matter even a fresh move, you must press switch S1 to reset the circuit. Thereafter, press any of the two switches, i.e. S2 or S3. On pressing switch S2 or S3, the counter’s BCD outputs change very rapidly and when you release the switch, the last number remains latched at the output of IC2. The latched BCD number is input to BCD to 7-segment decoder/driver IC3 which drives a common-anode display DIS1. However, you can read this number only when you press switch S4. The sequence of operations for playing the game between, say two players ‘X’ and ‘Y’, is summarised below:1. Player ‘X’ starts by momentary pressing of reset switch S1 followed by pressing and releasing of either switch S2 or S3. Thereafter he presses switch S4 to read the display (score) and notes down this number (say X1) manually.2. Player ‘Y’ also starts by momentary pressing of switch S1 followed by pressing of switch S2 or S3 and then notes down his score (say Y1), after pressing switch S4, exactly in the same fashion as done by the first player.3. Player ‘X’ again presses switch S1 and repeats the steps shown in step 1 above and notes down his new score (say, X2). He adds up this score to his previous score. The same procedure is repeated by player ‘Y’ in his turn.4. The game carries on until the score attained by one of the two players totals up to or exceeds 100, to be declared as the winner.Several players can participate in this game, with each getting a chance to score during his own turn. The assembly can be done using a multipurpose board. Fix the display (LEDs and 7-segment display) on top of the cabinet along with the three switches. The supply voltage for the circuit is 5V

Remote Control Circuits

2008-12-19T20:40:00.000-08:00

Remote control using VHF modules Click here for the circuit diagram
A few designs for remote control switches, using VG40T and VG40R remote control pair, are shown here.The miniature transmitter module shown in Fig. 1, which just measures 34 mm x 29 mm x 10 mm, can be used to operate all remote control receiver-cum-switch combinations described in this project. A compact 9-volt PP3 battery can be used with the transmitter. It can transmit signals up to 15 metres without any aerial. The operating frequency of the transmitter is 300 MHz. The following circuits, using VG40R remote control receiver module measuring 45 mm x 21 mm x 13 mm, can be used to:(a) activate a relay momentarily,(b) activate a relay for a preset period,(c) switch on and switch off a load.To activate a relay momentarily (see Fig. 2), the switch on the transmitter unit is pressed, and so a positive voltage is obtained at output pin of VG40R module. This voltage is given to bias the relay driver transistor. The relay gets activated by just pressing push-to-on micro switch on the transmitter unit. The relay remains energised as long as the switch remains pressed. When the switch is released, the relay gets deactivated. Any electrical/electronic load can be connected via N/O contacts of the relay.To activate a relay for a preset period (refer Fig. 3), the switch on the transmitter unit is pressed momentarily. The transistor gets base bias from VG40R module. As a result the transistor conducts and applies a trigger pulse to IC 555, which is wired as a monostable multivibrator. The relay remains activated till the preset time is over. Time delay can be varied from a few seconds to a few minutes by adjusting timing components.To switch on and switch off a load (refer Fig. 4), a 555 IC and a decade counter 4017 IC are used. Here the 4017 IC is wired as a flip-flop for toggle action. This is achieved by connecting Q2 output to reset terminal while Q1 output is unused. Q0 output is used for energising the relay. The relay is activated and deactivated by pressing the transmitter switch alternately. So, to activate the load, just press the transmitter switch once, momentarily. The relay will remain activated. To switch off the relay, press the transmitter switch again. This process can be repeated. Time delay of monostable multivibrator is set for about one second.Note: Short length of shielded wire should be used between VG40R receiver module output and the rest of the circuit. The transmitter with 9V battery must be housed inside a nonmetallic (say, plastic) cabinet for maximum range of operation.

Lights & LED Circuits

2008-12-19T19:44:00.000-08:00

Automatic Room Lights Click here for the circuit diagram
An ordinary automatic room power control circuit has only one light sensor. So when a person enters the room it gets one pulse and the lights come ‘on.’ When the person goes out it gets another pulse and the lights go ‘off.’ But what happens when two persons enter the room, one after the other? It gets two pulses and the lights remain in ‘off’ state. The circuit described here overcomes the above-mentioned problem. It has a small memory which enables it to automatically switch ‘on’ and switch ‘off’ the lights in a desired fashion. The circuit uses two LDRs which are placed one after another (separated by a distance of say half a metre) so that they may separately sense a person going into the room or coming out of the room. Outputs of the two LDR sensors, after processing, are used in conjunction with a bicolour LED in such a fashion that when a person gets into the room it emits green light and when a person goes out of the room it emits red light, and vice versa. These outputs are simultaneously applied to two counters. One of the counters will count as +1, +2, +3 etc when persons are getting into the room and the other will count as -1, -2, -3 etc when persons are getting out of the room. These counters make use of Johnson decade counter CD4017 ICs. The next stage comprises two logic ICs which can combine the outputs of the two counters and determine if there is any person still left in the room or not. Since in the circuit LDRs have been used, care should be taken to protect them from ambient light. If desired, one may use readily available IR sensor modules to replace the LDRs. The sensors are installed in such a way that when a person enters or leaves the room, he intercepts the light falling on them sequentially—one after the other. When a person enters the room, first he would obstruct the light falling on LDR1, followed by that falling on LDR2. When a person leaves the room it will be the other way round. In the normal case light keeps falling on both the LDRs, and as such their resistance is low (about 5 kilo-ohms). As a result, pin 2 of both timers (IC1 and IC2), which have been configured as monostable flip-flops, are held near the supply voltage (+9V). When the light falling on the LDRs is obstructed, their resistance becomes very high and pin 2 voltages drop to near ground potential, thereby triggering the flip-flops. Capacitors across pin 2 and ground have been added to avoid false triggering due to electrical noise. When a person enters the room, LDR1 is triggered first and it results in triggering of monostable IC1. The short output pulse immediately charges up capacitor C5, forward biasing transistor pair T1-T2. But at this instant the collectors of transistors T1 and T2 are in high impedance state as IC2 pin 3 is at low potential and diode D4 is not conducting. But when the same person passes LDR2, IC2 monostable flip-flop is triggered. Its pin 3 goes high and this potential is coupled to transistor pair T1-T2 via diode D4. As a result transistor pair T1-T2 conducts because capacitor C5 retains the charge for some time as its discharge time is controlled by resistor R5 (and R7 to an extent). Thus green LED portion of bi-colour LED is lit momentarily. The same output is also coupled to IC3 for which it acts as a clock. With entry of each person IC3 output (high state) keeps advancing. At this stage transistor pair T3-T4 cannot conduct because output pin 3 of IC1 is no longer positive as its output pulse duration is quite short and hence transistor collectors are in high impedance state. When persons leave the room, LDR2 is triggered first followed by LDR1. Since the bottom half portion of circuit is identical to top half, this time with the departure of each person red portion of bi-colour LED is lit momentarily and output of IC4 advances in the same fashion as in case of IC3. The outputs of IC3 and those of IC4 (after inversion by inverter gates N1 through N4) are ANDed by AND gates (A1 through A4) are then wire ORed (using diodes D5 through D8). The net effect is that when persons are entering, the output of at least one of the AND gates is high, causing transistor T5 to conduct and energise relay RL1. The bulb connected to the supply via N/O contact of relay RL1 also lights up. When persons are leaving the room, and till all the persons who entered the room have left, the wired OR output continues to remain high, i.e. the bulb continues to remains ‘on,’ until all persons who entered the room have left. The maximum number of persons that this circuit can handle is limited to four since on receipt of fifth clock pulse the counters are reset. The capacity of the circuit can be easily extended for up to nine persons by removing the connection of pin 1 from reset pin (15) and utilising Q1 to Q9 outputs of CD4017 counters. Additional inverters, AND gates and diodes will, however, be required

This tip For older XP builds

2008-12-19T10:04:00.001-08:00

Edit or remove the "Comments" link in window title bars

During the Windows XP beta, Microsoft has added a "Comments?" hyperlink to the title bar of each window in the system so that beta testers can more easily send in a problem report about the user interface. But for most of us, this isn't an issue, and the Comments link is simply a visual distraction. And for many programs that alter the title bar, the Comments link renders the Minimize, Maximize, and Close window buttons unusable, so it's actually a problem.
Let's get rid of it. Or, if you're into this kind of thing, you can edit it too.

Open the Registry Editor and navigate to the following keys:
My Computer \ HKEY_CURRENT_USER \ Control Panel \ Desktop \ LameButtonEnabled
My Computer \ HKEY_CURRENT_USER \ Control Panel \ Desktop \ LameButtonText

The first key determines whether the link appears at all; change its value to 0 to turn it off. The second key lets you have a little fun with the hyperlink; you can change the text to anything you'd like, such as "Paul Thurrott" or whatever.

Editing either value requires a restart before the changes take effect.

Before: An unnecessary hyperlink. Have some fun with it! Or just remove it entirely. It's up to you.

Speed up the Start Menu

2008-12-19T10:01:00.000-08:00

The default speed of the Start Menu is pretty slow, but you can fix that by editing a Registry Key. Fire up the Registry Editor and navigate to the following key:
HKEY_CURRENT_USER \ Control Panel \ Desktop \ MenuShowDelay

By default, the value is 400. Change this to a smaller value, such as 0, to speed it up.