Thread: Wiper Motor Controller

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OK, so I've been reading a lot of posts and it sounds like a lot of you have questions around controlling a wiper motor for your scares. I have put together a document and have a circuit diagram for a controller that controls a single wiper motor that allows you to do the following:

1. Closing a switch activates the motor in one direction, until the arm (or something attached to it) hits a limit switch.
2. Upon hitting the limit switch, the motor stops instantly! (No over-run problems!)
3. Releasing the switch allows the motor to run in reverse until a second limit switch is hit.
4. Hitting the second limit switch also stops the motor instantly.



If you have any questions about this, or discover any errors in the circuit (hey... it COULD happen!) let me know.
Email me at creepycreations@telus.net. I also have a PDF document with the circuit diagram and some discussion around the theory of operation.

And yes... this circuit is very "old school". No silly microcontrollers or power transistors to mess with. It's all relays and diodes. Why? a) It works! b) It's reliable as all hell! c) It's cheap d) The relays actually provide some fail-safe features. e) Temperature doesn't mess with its operation (important in this chilly northern climate).

Enjoy!

This is great! Can you post a pic of the actual circuit?

Sorry, but I don't think I've got pics of the actual circuit. I'm not sure how useful it would be anyway, but if I can get one, I'll definitely post. If you build the circuit, please let me know of any problems or errors in the circuit diagram. I did the drawing AFTER I made the circuit, so it is possible I missed something in the translation!
Also, please note that the trigger relay could optionally be fired with a timer circuit, or just about any other mechanism you want.

Nothing wrong with old school. I use it all the time, and it's cheap!

Looks good! I designed a circuit a few years back that automates this process, but doesn't reverse the direction of the rotation. Assuming that you're setting the limit switches for a 180° rotation, you don't really need to reverse the polarity - just continue in the same direction. Just curious, what do you use to close and release the switches? I used a striker plate with a single snap switch to halt the rotation. Here's what it looks like:

http://s73.photobucket.com/albums/i2...rmotordemo.mp4

We've found that, after many years of repeated use (and abuse) the best solution was to mount a stiff spring in front of the switch. Then, the moving object can hit THAT, instead of the switch directly. This solves two problems: First problem - Using anything else OTHER than a spring tends to develop a "memory" so that it gets stuck in either the open or close position. Second problem - A spring allows for rather generous play in the travel of the moving object so that the switch isn't destroyed if the object travels a bit farther than expected. See this diagram for an idea as to how I mount it.

Notice the mount point of the spring is closest to the switch. A simple sheet metal screw is used to hold it in place. This provides for maximum movement on the end of the spring, without overstressing the switch. Moving the switch up and down allows you to adjust the sensitivity.

Originally Posted by Otaku

Looks good! I designed a circuit a few years back that automates this process, but doesn't reverse the direction of the rotation. Assuming that you're setting the limit switches for a 180° rotation, you don't really need to reverse the polarity - just continue in the same direction. Just curious, what do you use to close and release the switches? I used a striker plate with a single snap switch to halt the rotation. Here's what it looks like:

http://s73.photobucket.com/albums/i2...rmotordemo.mp4

Another option would be to use a Picaxe micro controller (well what else did you expect me to suggest)



SteveO did a tutorial on how easy it is to do



It's easy to adjust the timing of the pauses as well as set exactly where the motor stops.

Nice, Steve! I knew you would have worked this out with a Picaxe LOL.

Is the motor power switched through the Pic, and can this be used with a wiper motor or is the current too high?

You're using the Darlington to switch ground. I haven't tried this setup with a wiper motor but I've used a Mosfet IRL520 with a 1N4001 diode and it works fine.