Building a Laser Alarm Circuit for Security

Do wish to be the hero of your own house security system?

This article will explain how to construct an easy laser alarm circuit that can be used by an actual spy.

Compared to expensive store bought alarms it is less expensive and a fun project to make oneself to secure its belongings.

What is a Laser Alarm Circuit for Security:

A laser alarm circuit for security is an electrical device that is meant to detect when a laser beam stops functioning and sound an alert.

This type of circuit is often used in security applications where the laser beam functions as a fake wall and that when violated it activates the alarm.

The circuits primary components usually include a laser diode, a photodiode and other related electronics.

To generate the laser beam a laser pointer circuit that is connected across the area needs to be protected.

• Equation 1: Laser Power (P) = (Energy per Photon) x (Number of Photons emitted per second)

Carefully place along the laser beams path the LDR sensor that is protected from other light sources by a light proof container that has a tiny hole for the laser beam to pass through.

The LDR sensor is connected to the base of a BC557 transistor through a 1M resistor.

This transistor is required for the circuit to work.

Pin 2 of the IC 555 is connected to the transistors collector pin.

This IC 555 serves as a monostable multivibrator making it a important component of the alarm security system.

Pin 3 of the IC 555 has a relay connected to it and the relays contacts are configured to work with the alarm.

The circuits resistors represented by the letters R and a capacitor decide how long the alarm goes off.

• Equation 2: Time Constant (τ) = R x C
• Equation 3: Output Pulse Width (t) = 1.1 x R x C

Building the Laser Alarm Circuit:

Arrange the laser pointer circuit such that it shines a laser beam over the region you want to keep safe.

Be sure the LDR sensor is protected by a light proof container and position it at an exact spot along the laser beams path.

To let the laser beam in while keeping other light sources out this container should have a tiny opening.

To make the connection use a 1M resistor to connect the LDR sensor to the base of a BC557 transistor.

Connect pin 2 of the IC 555 monostable multivibrator to the transistors collector.

Connect a relay to pin 3 of the IC 555 and wire up the contacts on the relay so that they line up with the alarm.

Set the alarms activation period through combining the resistors and capacitor into the IC 555.

Parts List:

Working Principle

A laser pointer and a light dependent resistor LDR are used in the Simple Laser alert Circuit to detect intrusions and sound an alert acting as a security system.

The LDR which is kept in a light proof container is placed to respond to the laser beam once it has been projected across the protected area.

Advantages and Disadvantages of Laser Alarm Circuit:

Advantages:

• Building a laser alarm circuit is a budget friendly approach to enhancing your security.
• This circuit can be tailored to safeguard various items or spaces such as jewelry boxes, cabinets or rooms.
• Beyond basic security this circuit can be adapted for scientific experiments, educational projects or simply for amusement.

Disadvantages:

• Laser based security systems have a limited range restricting their application in larger areas.
• Obstructions in the laser path can lead to false alarms or reduced effectiveness.
• The circuits performance is be affected by ambient light conditions potentially impacting its reliability.

Conclusion:

The Simple Laser Alarm Circuit emerges as a best yet efficient security solution for safeguarding agricultural areas and open spaces from unauthorized access.

Farmers and landowners can confidently protect their crops and property with this user friendly DIY system.

If there is any queries or require further clarification please do not hesitate to ask in the comment section.

References:

Introduction to Laser Security System