Windshield wipers time switch

The system is based on microcontroller AT89C2051. It is used for programming the cycle repeats of the wipers. It controls the relay, which should be properly plugged into the vehicle electrical system.
The device is controlled by existing wiper lever. The position used in which the factory relay of constant interval was turned on.
Parameters:

• repeats time from 2,5 to 128s (resolution 0,25s)
• time of the pulse that controls the relay is set by jumpers from 0,125 to 2s (resolution 0,125s)
• time, after which the system finds that the button was pressed for long (set by jumpers) 0,25s, 0,5s, 0,75s or 1s
• mode with a lever or button (selected by jumper), instead of the button may be the lever, which returns to its rest position when released

Principle of operation:
After turning on, the system goes into standby mode. You drive a car, it begins to rain. Press the button shortly, the wipers perform one work cycle, the system begins to countdown the time (the countdown state). After a certain time (e.g. 15 seconds), the window again requires wiping so the button should be pressed shortly once again. The wipers move and from this moment they repeat work in the same periods of time (working state), ie every 15 seconds. The system works, the window was cleaned, but the rain is stronger. After 8 seconds, for example, the window requires wiping so you press the button again. Since this was done in 8 seconds, the period of repetitions is reduced and since then the wipers repeat the cycle every 8 seconds. You are still driving a car, rainfall is decreasing and now the wipers repeat their work too fast. So you press the button, but this time for long. The system switches to the countdown. The time will be counted not from the moment you press the button, but after the moment of last work cycle of the wipers. Now you can press the button shortly once again and the system switches to the work mode with the new time. If the system will be able to countdown, and you did not press the button shortly for the second time, after counting the maximum possible time, the system goes into standby mode.

Controlling the lever is similar. First turn on (and leave the lever on or return to the home position) – one work cycle of the wipers and start of the countdown). Second turn on (after return) – time counted, the system works. Return of the lever to the home position – the system goes into the countdown state. Another turn on the lever – the system works with a new time (longer or shorter).

There is no need to zero the set time, the system works so that during the operation, the period of repeats can be shorten or lengthen. If by the lever – you can short the time by moving the lever in home position and immediately back turn it on. To lengthen the time, you can move the lever in home position and turn on when the situation no longer requires that.

LEDs seen on the scheme indicate the state of the system, countdown, work mode. They are useful during the tests, but in the finished device not visible, because the controller is placed under the cockpit.
The system has a protection against turning on the wipers in the moment of starting the car, and the lever would be on.

Pictures and the scheme:



Link to original thread (useful attachment) – Programator czasowy wycieraczek samochodowych.