Here is an interesting project of a smart and efficient electronic combination code lock circuit. The circuit will provide a code lock device that is using a few 555 timer ICs and CD4017 decade counter ICs. There is also a feature of completely locking the device if the user has not put the right code in a few attempts. There are a few options like two, three, or four attempts to choose anyone according to your preference.
Hardware Components
The following components are required to make Smart Combination Lock Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Decade Counter IC | CD4017 | 5 |
| 2. | IC | NE555 Timer | 3 |
| 3. | Resistor | 10KΩ, 1KΩ, 470RΩ, 390RΩ | 6, 2, 4, 3 |
| 4. | Switch | Push-button | 3 |
| 5. | Transistor | 2N3904 | 3 |
| 6. | Relay | – | 1 |
| 7. | LED | – | 32 |
| 8. | Capacitor | 0.1µF, 4.7µF | 3, 1 |
| 9. | Photocoupler | PC817 | 3 |
| 10. | Diode | 1N4148 | 4 |
| 11. | DC Supply | 9-12 V |
CD4017 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of CD4017
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
Smart Combination Lock Circuit
Working Explanation
This circuit is based on three digits code lock. These three digits of the code can be inserted by push switches S1, S2, and S3. We have used 10 LEDs in the circuit for the visual representation of the number selected by the user. Mark 1 to 10 numbers on the LEDs it will be convenient for the user to understand which number is pressed.
The desired code for the lock is selected by code selectors 1,2 and 3. The code selection points and code selectors are marked with red. If you want to select code 982 then connect the code selector point marked 1 (code selector 1) with pin 9 of the IC2, connect code selector 2 with pin 6 of IC4, and code selector 3 with pin 2 of IC6. The passcode will be set as 982. Now if you want to put the password 982 to open the lock, then you have to press S1 9 times, press S2 8 times, and press S3 2 times. Now the passcode will be inserted as 982 and the lock will open and the circuit will activate the relay.
Applications and Uses
Locking doors and security purposes.
