Found in the May 1975 issue of Radio Electronics magazine, this circuit turns on after a certain amount of time. This gives the owner of the premises time to leave before the alarm is activated.
Photoelectric cells can be used as sensitive light sensors. However, the low voltage they generate...
With the illustrated circuit we can run a DC motor in one direction or the other, depending on...
In this circuit the relay triggers on when light falls onto the sensor, a common LDR. Power supply...