July 02, 2009

Simple Electronic Lock


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!

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

Stripboard Layout

Stripboard layout for simple electronic lock

Circuit diagram

Circuit diagram for simple electronic lock


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Electronics is the study and use of electrical that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves. and semiconductors. The pure study of such devices is considered as a branch of physics, while the design and construction electronic circuits to solve practical problems is called electronic engineering.

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