Windshield wiper intermittent operation control circuit - uses transistor circuit to give wiper operation immediately it is requested with variable delay between sweeps

Abstract

Abstract When the intermittent wipe switch (8) is open a capacitor (24) is charged via two resistances (29, 23) and a zener diode (28). All the transistors are non-conducting. When the intermittent wipe switch (8) is closed a first transistor (16) is turned on bringing the potential at the emitter of the output transistor driver (21) below the potential on the capacitor, which is connected to its base, turning on the output transistor and feeding a relay coil (5) which connects (6) the supply to the motor (1). When the motor has moved far enough for a self-parking contact to be reached, the transistor (13) connected to this contact turns on, discharging the capacitor (24) and turning off the supply to the relay (5). When the wiper (2) has completed its sweep and moved clear of the self-parking contact (7) the output driver transistor (21) cannot turn on again until the capacitor has charged to a higher voltage than the emitter of the output driver transistor, set by the current through the first transistor (16) which may be adjusted by a variable resistor (9).

Inventors

• 👤 Maurice Charras

Bibliographic Details