Introduction
Laser security alarm system it is a type of security alarm system that can catch any irregular activity and produce a sound using buzzer. We have seen its use in many movies where it is used to protect a diamond or other valuables from thieves.
This is also very good science project, you can show this project as a science project in your school or college by making this project. It is very easy to make, in this tutorial we will learn how to make a security alarm system using very few components. So, the components we need to make this project are given below –
Components Required
Circuit Diagram
Working Explanation
The main component of tis circuit is LDR ( Light Depended Resistor ) , It’s a type of resistor whose resistance decreases with increasing of light intensity and vice versa. It’s also known as a photoresistor or photocell.
The transistor that we have used in this circuit is NPN type, that means when we give positive supply to the base pin of this transistor, the transistor will be ON and the current will start flowing from emitter pin to the collector pin of the transistor.
The LDR and the 10K resistor together form a voltage divider network. The voltage across LDR sensor drive the transistor switch. When the voltage drop reaches a certain threshold, the transistor turns ON.
So, when light falls on the LDR, the transistor will be off and when no light falls on the LDR, the transistor will be on.
A buzzer connected to the collector pin of the transistor. So, when the transistor is on the buzzer will also be on.
In this circuit we have a laser diode that continuously emits light and falls on the LDR. The transistor will be off due to continuously falling light on the LDR sensor. But when an object or something comes between laser and LDR and prevents the light from falling on the LDR, the transistor will turn on and the buzzer will start beeping. This beep sound gives the indication of some security failures. This is how the circuit works.
