Fault detector for vehicle indicates failure of one or more lights - using single transistor coupled via decoupling diodes to each light

摘要

The fault detector has each connection point between a light and its associated resistor connected via a decoupling diode (18A,18B) to a transistor. The transistor turns on when a light fails and turns on a semiconductor switch. The base potential of the transistor is set by a biasing diode (23,24). The characteristics of the biasing diode are chosen according to the base-emitter junction of the transistor and the decoupling diode. Any number of lights can be monitored using only the one transistor even when the supply voltage and temp. change.(DS).