How to make Laser Light Security Alarm?


Lasers and laser technologies are widely used in defense and security fields and laser technology one of the most reliable photonics technologies available today. In this tutorial I m going to show you how to make your own “Laser Light Security Alarm” in just few easy steps.


Components Required for Laser Light Security Alarm 

laser light security

  • LDR (Light Dependant Diode)
  • L.E.D (Light Emitting Diode)
  • BC547 Transistor (1)
  • 100 ohm or 330 ohm resistor (1)
  • Buzzer (1)
  • 9v Battery with holder
  • Breadboard


Description of components used

LDR (Light Dependant Diode)

LDR (Light Dependent Resistors) is a resistor which terminal value of resistance changes with light intensity. In other words, those resistors, which resistance values changes with the falling light on their surface is called Photo Resistor or Photo Conductive Cell or LDR (Light Dependent Resistor). The material which is used to make these kinds of resistors is called photo conductors, e.g. cadmium sulfide, lead sulfide etc.

L.E.D (Light Emitting Diode)


It is an electronic device which glows up when current is passed through it.A light-emitting diode (LED) is a semiconductor device that emits visible light when an electric current passes through it. The light is not particularly bright, but in most LEDs it is monochromatic, occurring at a single wavelength. The output from an LED can range from red (at a wavelength of approximately 700 nanometers) to blue-violet (about 400 nanometers). Some LEDs emit infrared (IR) energy (830 nanometers or longer); such a device is known as an infrared-emitting diode (IRED).

BC547 Transistor


A BC547 transistor is a negative-positive-negative (NPN) transistor that is used for many purposes, it can be used as the active component for switches and amplifiers. Like all other NPN transistors, this type has an emitter terminal, a base or control terminal, and a collector terminal. In a typical configuration, the current flowing from the base to the emitter controls the collector current. A short vertical line, which is the base, can indicate the transistor schematic for an NPN transistor, and the emitter, which is a diagonal line connecting to the base, is an arrowhead pointing away from the base.


metal detector 4-engineeringprayog.comA resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.Resistors are used for many purposes. A few examples include delimit electric current, voltage division, heat generation, matching and loading circuits, control gain, and fix time constants. They are commercially available with resistance values over a range of more than nine orders of magnitude. They can be used to as electric brakes to dissipate kinetic energy from trains, or be smaller than a square millimeter for electronics.



IR-Sensor-Module8-engineeringprayog.comA buzzer or beeper is an audio signaling device, which may be mechanical, electromechanical, or piezoelectric. Typical uses of buzzers and beepers include alarm devices, timers and confirmation of user input such as a mouse click or keystroke.


metal detector 11 engineeringprayog.comWhen a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode.The terminal marked negative is the source of electrons that when connected to an external circuit will flow and deliver energy to an external device. When a battery is connected to an external circuit, electrolytes are able to move as ions within, allowing the chemical reactions to be completed at the separate terminals and so deliver energy to the external circuit. It is the movement of those ions within the battery which allows current to flow out of the battery to perform work.


IR-Sensor-Module7-engineeringprayog.comBread Board is a type of  dotted pcb .here difference is we can soldring on dotted pcb but we cant sold on bread board we generally use it for circuit testing .


Circuit diagram of Laser Light Security Alarm


Steps to make Laser Light Security Alarm

Step 1Place the BC547 Transistor on the breadboard,As shown in the fig.below.

1st step of laser security


Step 2:Then connect the LDR from the base and emitter of the BC547 Transistor. Now connect one end of the 330/100 ohm resistor to the base of the BC547 Transistor and the other end of the resistor to a blank space on the breadboard. Connect the anode of the L.E.D to the resistor and the cathode of the L.E.D to the collector. Connect the buzzer in the same way you connected the L.E.D. Now connect the Battery; positive side of the battery to the resistor and negative part of the battery to one side of the LDR,As shown in the fig.below.

2nd step of laser security


Step 3: Now comes the testing time.

3rd step of laser security



As soon as you connect the battery the L.E.D and buzzer will come “ON” (if you’re in a dark room). Focus the Laser diode/light on the LDR and you will see the L.E.D and Buzzer going “OFF” If you interrupt the laser light focusing on the LDR the circuit will trigger and the alarm will ring….


Advantages of Laser Light Security Alarm

  1.  They are simple to install and can be used effectively inside or outside a home.
  2. The systems can be used as a highly effective perimeter alarm for property boundaries or even for pools

So now your Project is Ready to work ,Keep enjoying this project.

So, Friends I hope you understand this project very well . In upcoming Tutorial  I will be back with some new interesting Projects and we will discuss about some useful development topics. Here if you want to recommend that what I should write in upcoming Tutorial then please leave your comments. and if u need any help or query please don’t Hesitate to discuss with me. Thank You  🙂

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