Electronic control for windscreen wiper - with two complementary transistors as switching amplifier and RC delay

摘要

The windscreen wiper control circuit is reduced in complexity by having two transistor (P2,P3) coupled as a switching amplifier with the emitter-collector circuits parallel to the current supply. The coil of the switching relay is in the collector circuit of the first of the transistors and an RC timing circuit is coupled to the parking switch to control the wipe frequency. The base of the second transistor can be reset, in a delay time, to a higher potential than the emitter, using a switching element. This determines the wash and wipe programme of the system.