Drive circuit for vehicle windscreen wipers - varies wiper speed according to engine or wheel speed

摘要

The drive circuit is arranged so that the interval between each stroke of the wipers across the windscreen made variable between zero and a given upper limit. The upper limit may be related to the speed of the engine or wheels. Two push-pull transistors (T1,T2) are alternately switched on and off by a capacitor (C2) whose charge state depends on the speed of the engine or the wheels. The capacitor controls the duration of the interval. The change from zero to the upper limit may be smooth, passing through other settings, or sudden with no intermediate settings.