I have tried many schemes devices to automatically turn off lighting in utility room (pantry, bathroom, toilet, etc.), but none of them worked steadily when the temperature changes in different seasons of the year. Due to the large number of electronic components. these schemes often had to be repaired. Eventually I came to develop his scheme with a minimum number of components.
Produced three devices that are installed in all utility rooms in the apartment. And during the operation (over nine years) never been repairing these devices and had no malfunctions.
The proposed device works as follows. On the door is mounted the magnet to the door frame and fastens the reed contact. It is convenient to use a set of reed switch-magnet from the alarm. The magnet, closing the door acts on the reed switch SF1. The contacts of the reed switch are closed, and the output of flip-flop DD1 appears the level of logical "1" that opens the transistor VT1, which in turn opens the thyristor VS1. In the room the lights are on.
Light bulb lit HL1 until then, until the door closed a second time. Then the influence of a magnet on the reed switch switches the trigger to the second stable state. The output DD1 appears logical "0", the transistor VT1 is closed, turns off the thyristor VS1, and the light goes out.
Author: V. Lazovic, Makeyevka; Publication: N. Bolshakov, rf.atnn.ru