Automatic Windshield Washer Control


Posted on Feb 7, 2014

Most, if not all, recent cars have an impressive amount of electronics, whether it be ABS brake systems, engine control with injection calculators, airbag activation, or other various functions, called comfort functions. Among them is one which we tend to forget because it has become so common today. It turns on the windshield wipers automatically


Automatic Windshield Washer Control
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for a few seconds after the windshield cleaner. This practice is almost indispensable because it avoids any dripping of excess rinse product right in the middle of a just-cleaned windshield. Unfortunately, many low end` cars or some of the older cars are not equipped with this automatic function which is a very nice convenience to have. So, since all that is required is a handful of components that any electronics hobbyist worthy of the name already has in his/her drawer, we will discuss the circuit proposed here. This project is super simple and simply keeps the windshield wiper activated for a few seconds after the windshield washer control contact has been released. While the windshield washer pump is operating, the 12 volts delivered by the battery are present at the terminals and are therefore charging capacitor C1. Once the windshield washer has stopped, this capacitor can only discharge through R2, P1, R3, and the T1 emitter-base junction, due to the presence of diode D1. It thus keeps T1 in the conductive state during a certain time, the exact period of which depends on the setting of P1. T1 in turn saturates T2, which then does the same for T3. The Re1 relay is therefore connected which maintains the windshield wiper in operation because its work contact is wired in parallel to the control switch. Once C1 is sufficiently discharged, T1 is blocked, which then blocks T2 and T3 and deactivates relay Re1. The type of...




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