Introduction
An electronic code lock system is widely used in mechanical and electronic devices to make them secure. An electronic combination lock is also used for the same purpose, having an IC 7220 used in the circuit. If you are a beginner in digital electronics, this would help you understand and learn about digital circuitry, and for all electronic engineers, it is necessary to learn about digital electronics.
This Electronic Combination Lock using IC LS7220 uses a relay that can drive any load or circuitry, keypads are used to press or enter the combination of four digits of digital code, the right combination of code would cause the relay to open.
Hardware Required
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Breadboard | – | 1 |
| 2. | Capacitor | 1uf/25V, 220uf/25V | 1 |
| 3. | Resistor | 2.2K | 1 |
| 4. | Transistor | 2N222 | 1 |
| 5. | Diode | 1N4148 | 1 |
| 6. | SPDT Relay | 12V | 1 |
| 7. | Push Buttons | – | 12 |
| 8. | Position Header | – | 1 |
| 9. | IC | LS7220 | 1 |
| 10. | Battery | 12V | 1 |
Circuit Diagram
Working Explanation of Electronic Combination Lock
To establish the combination connect the appropriate switches to pins 3, 4, 5, and 6 of the IC through the header. As an instance, if S1 is connected to pin 3, S2 is connected to pin 4, S3 is wired to pin 5, and S4 is to pin 6 of the IC the combination will be 1234. And this is how any 4-digit combinations can be created. Connect the rest of the switches to pin 2 of the IC. This will cause the IC to reset if any ineffective key is pressed, and the whole key code has to be re-entered again. The relay gets active after pressing the right key and the capacitor determines time. Therefore, increase C1 to increase on time.
Application and Uses Electronic Combination Lock
- It can be utilized in home and office automation for security
- It can be used in any circuit or device that needs a lock
