LASER ACTIVATED SWITCH

This circuit is built around a 555 timer using very few components. Since the circuit is very simple, even a novice can easily build it and use it as a controlling device. A laser pointer, now easily available in the market, can be used to operate this device. This circuit has been tested in operational conditions from a distance of 500 metres and was found to work satisfactorily, though it can be controlled from still longer distances. Aiming the laser beam exactly on to the LDR is a practical problem. The circuit is very useful in switching on/off a fan at night without getting off the bed. It can also be used for controlling a variety of other devices like radio or music system. The limitation is that the circuit is operational only in dark or dull-lit environments. By focusing the laser beam on LDR1 the connected gadget can be activated through the relay, whereas by focusing laser beam on LDR2 we can switch off the gadget. The timer is configured to operate in bistable mode. The laser pointers are available for less than Rs 30 in the market. The cost of the actual circuit is less than Rs 25.

Circuit Diagram


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