GB1513127A - Road vehicle electrical systems - Google Patents

Abstract

1513127 Vehicle electrical systems LUCAS ELECTRICAL LTD 2 May 1975 [8 May 1974] 20255/75 Heading H2H A vehicle electrical system includes an interior lamp which is illuminated when a vehicle door is opened and remains illuminated for a predetermined period after the door has been closed. Opening of a vehicle door closes one of the switches 18 or 19 thereby causing a transistor 23 to turn on by virtue of the current flowing in resistors 22, 21, 42, the diode 17 and the switch 18 or 19. Turn on of the transistor 23 causes turn on of transistors 26, 28, 31, when the interior lamp 37 is illuminated by way of a switch 36, normally in the position shown, resistor 32 and the transistor 31. At the closure of a switch 18 or 19 a capacitor 35 also charges by way of resistors 34, 42, diode 17 and the switch 18 or 19. When the door is closed so that the switches 18 or 19 are both open, the capacitor 35 discharges through the resistor 21, the base-emitter junction of the transistor 23 and resistor 34. Transistor 23 and hence transistors 26, 28, 31 remain turned on and the lamp 37 illuminated until the capacitor 35 is discharged, say, for a period of 8 seconds. Should however the ignition switch 14 be closed, the capacitor 35 rapidly discharges by way of resistors 34, 16 and diode 15 whereby no delay is incurred in extinguishing the lamp 37. Switch 36 allows manual ON-OFF control of the lamp 37.