08-16-2017, 10:41 PM
A continuously working wiper is a big problem when it is raining slightly.The wiper control given here makes the wiper to sweep at rates from 1S to 10 S.
The circuit is build around an astable multivibrator using NE 555.Here the output at pin 3 remains high for a time period set by R2 ,and low for a time period set by R3.The low output pulse drives the transistor pair to drive the wiper motor to make one sweeping cycle and waits for next low pulse to arrive for next sweep.The high going pulse at pin 3 determines how many time should wiper should sweep in a given period of time.
Components required
IC 555
Transistor BC 548
Resistor (1K,10K,1M,)
Capacitor(0.1uF)
Relay (12V,10A)
Rain sensor (Two metal sheets as figure)
How rain sensing wipers work?
Working of this circuit is same as the working principle of monostable multivibrator. Here the trigger to the second pin is given by rain sensors.
A small water drop on the rain sensor will connect the negative voltage to the trigger pin of 555 IC which in turn will turn the output pin of 555 high. 5
55 Output is connected to the base of transistor through a 1K resistor which forward biases the transistor. Thus relay gets negative and it switches ON the wiper motor. You can refer our previous post on how relay works for better understanding of relay.