Security plays a very important role in todays world, therefore electronic code locks are very useful.
This Digital Code Lock Circuit using IC 4017 is a simple.
It uses push buttons, diodes, resistors, capacitor and IC CD 4017 .
Moreover, it is low cost and easy to build and it works on 9V power supply.
Also, it is good for students and beginners.
Circuit Working:
Parts List:
| Components | Value | Quantity |
|---|---|---|
| Resistors | 100k | 2 |
| 10k, 1k | 1 each | |
| Capacitor | Electrolytic 100uF 25V | 1 |
| Transistor BC547 | 1 | |
| IC CD 4017 | 1 | |
| Diodes 1N4007 | 6 | |
| LED any color | 1 | |
| Push Button Switch | 10 | |
| Relay 9V DC | 1 | |
| Battery 9V | 1 |
This circuit uses IC CD 4017 and it is a decade counter IC.
There are 10 push buttons with some buttons are correct keys and some buttons are wrong keys.
A relay is used as output switch and a transistor drives the relay.
Diodes are used for logic isolation and an LED shows output status.
At first, the power is applied, so CD 4017 resets to Q0.
Then correct keys must be pressed in order and each correct key sends a clock pulse.
Therefore, output shifts step by step.
Wrong keys are connected to reset and so if wrong key is pressed then IC resets.
After last correct key the output goes high and thus transistor turns ON.
Relay gets energized and the load is switched ON.
LED also glows and so user knows lock is opened.
When power is removed the system resets again.
Code Explanation:
If my code is ABCD then:
After RESET:
Pin 3 (Q0) is HIGH then B is the start state
Press Key A:
Clock pulse applied
Output moves from Pin 3 to Pin 2
So, A = Pin 2 becomes HIGH
Press Key B:
Next, clock pulse
Output moves from Pin 2 to Pin 4
So, B = Pin 4 becomes HIGH
Press Key C:
Next, clock pulse
Output moves from Pin 4 to Pin 7
So, C = Pin 7 becomes HIGH
Press Key D:
Next, clock pulse
Output moves from Pin 7 to Pin 10
So, D = Pin 10 becomes HIGH (Relay ON)
How to Build:
To build a Digital Code Lock Circuit using IC 4017 follow the below steps:
- First, start to collect all the parts as shown in circuit diagram.
- CD 4017 pin 16 connect to +9V supply.
- Pin 8 goes to ground.
- Pin 14 is clock input and correct switches connect to pin 14 through diodes.
- Pin 13 is enable pin and it is connected to ground.
- Pin 15 is reset pin and all wrong switches connect to pin 15.
- Output pin 3 is Q0 connects from diode D2 and switch S1.
- Pin 2 is Q1 connects from diode D3 and switch S2.
- Pin 4 is Q2 connects from diode D4 and switch S3.
- Pin 7 is Q3 connects from diode D5 and switch S4.
- Pin 10 is Q4 connects from diode D1 to base of transistor Q1 through resistor R3.
- Transistor Q1 base is connected to R3 resistor.
- Emitter goes to ground and collector goes to relay coil.
- Relay one side goes of coil to +9V.
- Other side to transistor collector.
- Diode 1N4002 across relay for protection.
- LED connect in series with R4 1k resistor and is connected parallel to relay coil.
- After that resistor R2 is connected to pin 14 of IC and GND.
- Then, push buttons 1 to 6 one end is connected to positive supply and other end is connected to pin 15 of IC through resistor R1 and GND.
- At last, capacitor C1 positive end is connected to 9V battery positive and negative end to battery negative.
Conclusion:
To conclude, this Digital Code Lock Circuit using IC 4017 is very useful.
It is simple and reliable and it provides good security.
Moreover, it is easy to build at home and students can learn digital logic from this project.
Finally, this circuit is perfect for basic electronic security systems.