The circuit is a three digit code lock. These three number can be selected by push switch S1, S2 and S3. The LEDs used in the circuit will provide the visual indication of the number selected by the user. For best performance marked 1 to 10 number on the LEDs due to which you will easily understand which number you have pressed. For example if you want to select the number "658" for lock, then for opening the lock you have to 6 time press the push switch S1, five time push switch S2 and eight times push switch S3. If all the three number are selected right then the output relay switch will become activated.
The desired code for lock can be easily selected with code selector 1, 2 and 3. The code selector and code selection points are marked with red. The selection of code is easy for example you want to select code "982" then connect the code selector point marked 1 (code selector 1) with pin 9 of the IC2, connect the code selector 2 with the pin 6 of the IC4 and connect the code selector 3 with the pin 2 of the IC6.
Here is a project of a very smart and efficient electronic combination code lock circuit using few NE555 Timers and 4017 CMOS decade counter ICs. The circuit also has a few wrong attempt OFF function which will completely switch off the circuit if the user has not selected the right code in
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