Laser Gun/Pointer Circuit: Need Help!

Thread Starter


Joined Feb 25, 2007

I found this circuit in the book 'Robotics, Mechatronics And Artificial Intelligence' by - Newton C. Braga

It seems like quite a simple circuit but I can't make head or tail of how it is supposed to act like a laser gun. :confused: The book doesn't give any explanation as to how the circuit functions. Can anybody please explain to me its working? I was told that the transistor BD135 is used to switch ON/OFF the laser module. Then, what's the use of the cascaded IN4002 configuration?

Any other model of laser gun with explanation is also welcome. :)

Replies are really appreciated.


Joined Apr 20, 2004
Placing a positive voltage where the schematic says "+ voltage in" will cause the BD135 to turn on (5 to 9 volts should work fine). The three 1N4002's keep the voltage drop across the laser module in an acceptable range. Be sure to use the chart to properly select the resistor.