One way to check whether anybody is at home is ring the doorbell.Burglars too employ this very technique to check whether youare at home!
The circuit described here comes handy in such a situation.It is a simple doorbell-controlled multipurpose electronic switch that instantly powers up a connected security device, for instance, a night-vision door camera,for functioning.
The circuit works off a 9V DC supply.The input of the circuit is connected in parallel with the 230V AC electric doorbell.An electromagnetic relay is used at the output of the circuit to activate the security device connected to it.Note that the output socket (J1) works as a power switch and is designed for activating the 9V security device (night-vision door camera).Similarly, you can use this 9V supply to energise another switching relay in an existing home security system.The circuit can be reset by pressing switch S1.
Courtesy: www.efymag.com
