automatic cloakroom light - to help your guests

to help your guests This circuit should put an end to your guests fumbling for the light switch in the cloakroom. It ensures automatically that the light is switched on as soon as someone enters the cloakroom and is switched off again when that person leaves. The principle of the circuit is fairly simple. The bistables in a 4013 CMOS IC are connected in series. One, FF2, is arranged as an R-S latch to debounce the switch. This switch, S1, must change over as soon as the door is opened and is therefore best located in the door- frame. When the door is opened, FF2 is set and its output (pin 13) goes therefore high. This clocks FF1 on pin 3 and this bistable toggles: its output goes high and this switches on transistor T1. The transistor cur- rent actuates a relay and the light is switched on. When the door is closed, nothing happens because FF2 is reset and its output on pin 13 goes low. It"s only when the door is 12 V 100 mA Lai 60 W opened again that FF1 changes state: pin 13 then...