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
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
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