Simple and Portable Laser Tripwire for Under 2$

Introduction: Simple and Portable Laser Tripwire for Under 2$

Hi guys .This is my first instructable .In this instructable I'am going to tell you how to make an easy and cheap laser tripwire. This is just a model circuit and not purposed for practical uses, although this circuit can be used for other light projects as well (with slight modifications).

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Step 1: Things and Materials

Things that you'r going to need :-

BT169 Transistor

1uf electrolytic capasitor


6.8K resistor

100ohm resistor

1.5V LED (any colour)

2 X 1.5V battries

3V Beep speaker

Bread board / circuit board

Laser pointer


Battry holder

A transpsrant plastic box for circuit

Step 2: Assembly

Assembly Use the schematic to make the buzzer circuit an add a switch .Now put the circuit in the box. You'r alarm circuit is ready.

Step 3: Using the Tripwire

Turn the alarm switch to on and point the laser on the photoresistor. Now, if anything disturbs the laser light the alarm starts beeping. This tripwire is a basic and simple one, so when the laser light reaches the photoresistor again, the alarm stops beeping. Thanks for reading guys and please leave good comments and suggstions for improving.

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