Delay circuit for internal lighting of motor vehicle - delays switch=off of lighting after door closure by using RC circuit, trigger and transistor switch

摘要

A delay is provided by an RC circuit (R1, C) connected to the input of a trigger (T1). The trigger operates a transistor switch (T2, T3) connected in parallel with the door contact (4). The internal light (2) is connected to one terminal of the vehicle's battery and via the door contact to the vehicle's bodywork, i.e. eath (6). When the door contact opens, the residual voltage across the transistor switch charges the capacitor (C). This residual voltage is large compared to the trigger's threshold but inadequate for supplying the light. The circuit can be incorporated into a vehicle's electrical system without adversely affecting the functioning of the internal lighting. Only one line and an earth connection are needed.