I would like to make a laser activated switch using a photo-transistor or an LDR, by which I can switch off the lights in a room from a long distance. I just have to point the laser and it will detect my signal and the light must turn off.

Can anybody please help me with a circuit diagram?

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    \$\begingroup\$ Lots a ideas, but why don't you take a swing at it first and then we'll have some idea of your skill set. \$\endgroup\$ Jul 23, 2014 at 12:55

1 Answer 1


With help of Latching switch and LDR we can do that.

Latching Switch

Latching Switch.

Load Circuit


Replace Load with the circuit as shown above and push button (S1) with LDR.


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