Security System Laser Alarm Circuit | Using 555 Timer IC and Relay.

How are you all? I hope you are well. By the grace of God, I am also well. Today I will show you how to make a laser alarm circuit.

Edited with Canva.

This is basically a security circuit, where the alarm sounds when the laser light is turned off. In the circuit, I have used a 555 timer IC and will detect the cutting of the laser line through the LDR sensor. This circuit can be used in the door of the house, a table drawer or any small secure place. I have drawn the circuit by myself step by step so that even beginners can understand it easily.

Function of the components used.

555 Timer IC:

Edited with Canva.

Used to generate timing signals.

LDR:

The signal changes when the light decreases.

Relay:

Transfers the low-voltage signal to the high-voltage device.

Diode:

Blocks the reverse current coming from the relay.

Resistor:

Controls voltage and current.

Polar Capacitor 1000 µF:

Keeps the signal stable and fixes the timing.

Non-Polar Capacitor 0.22 µF, 10 nF:

Helps filter small spikes.

Step 1: Use notebook and colored pen.

I used coloured colouring pens to clearly explain the diagram of this circuit on a white paper so that each connection can be clearly seen.

Step 2: IC connection.

I gave a positive line to pin number 8 and took pin number 1 to ground. Then I placed a 10 nF capacitor on pin number 5 so that the circuit works stably.

Step 3: Timing part connection.

I connected 1 megaohm resistor to pin number 6 and 2. Then I placed 20K and 10K resistors on the top. I placed 0.22µF and 1000µF capacitors on the bottom so that the signal works properly.

Step 4: Sensor and Transistor Connection.

I have connected the LDR to the 12-volt line. Then I have connected a 1 megaohm resistor and a BC547 transistor below. The circuit can generate a signal when the light is cut.

Step 5: Laser, Relay and Bell Connection.

I have connected the laser light in front of the LDR. Then I have connected a 12-volt relay and a buzzer to the output line. When someone cuts the laser, the relay is activated and the alarm sounds.

My Proof

After finishing the art I have drawn by hand, I have written my username and community name below. Then I have taken a selfie to prove that I did the work myself.

Conclusion

I have made this laser alarm circuit very easily. When the light is cut, the alarm sounds, so it can be used for small security purposes. I have drawn everything by myself and made it step by step so that even beginners can easily understand.

List of used parts

S.no	Components	Value	Qty
1.	Resistor	10k, 1M	2, 2
2.	Diode	IN4007	1
3.	Polar Capacitor	1000µF	1
4.	IC	555 Timer	1
5.	Relay	12v	1
6.	Non-Polar Capacitor	0.22µF, 10nF	1, 1
7.	Jumper Wire		1
8.	LDR		1

🟩 Thank you for reading my post and giving your valuable time. Stay well and stay healthy. God bless you. 🟩

Photography Details	📱 Device: Walton Xanon90	📍 Location: Narayanganj, Bangladesh	📷 Captured By: @imranhassan