Windshield Wiper Interval Controller

  
The windshield wiper interval circuit presented here is very compact and is noteworthy for its use of
Windshield Wiper Interval Controller - schematic

two thyristors, instead of a relay. It has only two connections and operates without any problems-even in conjunction with multistage wiper circuits. The connecting wire between the wiper motor and terminal 53 is cut and new connections are made (as shown in the diagram). When the interval switch, SI, is closed, capacitor CI charges via PI and the wiper motor. After a time set with PI, transistor T1 switches on and triggers the thyristors. The wiper motor is then energized via the thyristors and D3 and sets the wipers into motion. At the same time, CI discharges via D2 and the thyristors. After a short time, the wiper stop switch connects terminal 53 to the +12-V line so that the wiper motor is energized via D4. The thyristors are switched off because the voltage drop across D3 plus Thl/Th2 is then greater than that across D4. When the wipers reach the end of their travel again, the stop switch connects terminal 53 to ground and enables CI to charge again.




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