Periodic turning on the windshield wiper of the vehicle when traveling in bad weather can be realized by using the automatic device assembled according to the scheme shown in the figure. In this automatic switching frequency of the wiper motor is set depending on the driving conditions.
The device is an asymmetrical flip-flop on the low-power transistors of different conductivity. In the open state of the transistor T1, with its load, is composed of resistors R5, R6 to the base of transistor T2, a positive voltage is supplied. The transistor T2 is open and the capacitor C1 is charged through R4 and the emitter junction of transistor T1. When the level of locking the transistor T1 at the same time closes the transistor T2. Capacitor C1 begins to discharge through the circuit R1-R3, R8, relays P1, R9. At the time when the bias on the base of the transistor T1 will have a negative potential relative to the emitter, the latter is unlocked, opens T2 - charge cycle of the capacitor C1 is repeated.
The on time of the relay R1 (contacts P1.the motor 1 is turned on purifier) is determined by the interval during which through the relay coil flows through the collector current of the transistor T2 is of the order of 1-2 seconds. That's enough for a full cycle of brush cleaner. Following this time interval is chosen (depending on weather conditions) switch P1 so that the upper circuit position of the switch corresponds to the normal speed of the wiper, the average cycle is slowed down to 10 h, in the bottom - up to 20 sec.
The device is mounted on a printed circuit Board size 100X100 mm and comes close to the wiper switch.
In the device, you can use transistors KT315 (T2) and KT361 (T1).
Literature
Publication: N. Bolshakov, rf.atnn.ru