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Topic: Connecting strange wiper motor, help selecting diodes (or other suggestion) (Read 3 times) previous topic - next topic

Aqualize

Hello

For a big project I need a strong and slow engine. As I gathered it is common get a used windshield wiper motor. I got a used one from my neighbor who fixes cars but the motor turned out to be something strange, not like any other wiper motor I can find on the internet (doesn't look like them either). I experimented with it to understand it. If I remember it has 5 connections and I guess two are for this auto-parking feature but I'm not interested in that. Leaves three connections and now to bizarre(to me).
Let me call them c1, c2 and c3. The possible connections that can be made with a power source (plus and minus) is listed here and what happens:
+c1 -c2 motor rotates one direction.
-c1 +c2 motor rotates the same direction (even though I reversed polarity).
+c3 -c2 motor turn the other direction.
-c3 +c2 motor turns the other direction (again, I reversed polarity and it spins the same, but at a different speed).
+c1 -c3 short circuits
-c1 +c3 short circuits

The thing about different speed I guess is for the different speeds of the wipers.
And the c2 should be the "ground", because it would be in touch with the rest of the metal of the car it was mounted in at the beginning.

I understood that I needed to control high currents with the arduino, but I didn't want a mechanical relay (the direction might be changing quite often, perhaps a few times per second). I bought a Parallax HB-25 Motor Controller (bought it in fact before my strange wiper motor).


You might see the problem here, to control direction of a motor the HB-25 changes polarity of its output ports (M1 and M2). That wouldn't help me.
And now I'm getting out into the more deep waters, for me at least. I think that adding a few diodes might solve my problem.

I attach my suggestion. I hope people can tell me if this will do what I want. When the HB-25 puts positive on M1 and negative on M2 the motor rotates one way and when changing polarity of M1 and M2 it rotates the other way.
Second, I need help with selecting the diodes. I plan to buy from conrad.com, they have a big selection of diodes. Is a "standard" diode okay? Or a Schottky diode? What I've tried to read other diodes aren't of interest here.
So... the voltage I guess will be around 13-14VDC and the motor might get stalled (high current draw). I don't know anything about the motor's power. But looking around there seems to be wiper engines in the range of 50-150 watt. So if buy diodes that are good for up to 15A, which should I buy? Or if the price would be the close for 25A I would take that (25A is the max continuous for the motor controller).

zoomkat

Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

Aqualize


The below has some wiper motor wiring info.

*youtube*


I have seen that video but that isn't similar to mine, neither wiring or look. As seen the output shaft of the typical motor in the video is at a right angle to the axle of the DC motor inside it. My motor has the output shaft (after reduction gears) parallel to the DC motor axle. I don't have it here so I can't take a picture of it, sorry.

zoomkat

Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

Aqualize


Stuff to look at. You might ask the source of the wiper motor what car it came out of. The short circuit wires might be across an internal limit switch when it is closed

https://www.google.com/search?q=Windshield+Wiper+Motor+Wiring&num=100&hl=en&lr=&tbo=u&as_qdr=all&tbm=isch&source=univ&sa=X&ei=1NauUKT0IcPf0gHG8oCABQ&ved=0CIcBELAE&biw=1201&bih=641


The neighbor had pulled it out of some car at the scrap yard. He don't remember which car. There are no markings or name at all on it of what I remember (the motor is at my parents house, can't check).
But I did sit and test all the ports on it, had connected a ATX PSU modded for such task.
I tried to pry it open but I couldn't. It is something internally that makes it behave as it do. As far as I know all DC motors change direction when the polarity is changed, or this is some kind of strange engine that won't do that.

Just to clarify, it is not that kind of small motor that connects directly to a wiper via a shaft (used in old tractors and trucks), which also has automatic reversal at the end zones.
On my motor it is a little gear, no long shaft out of it. The linkage to a standard wiper blade setup would be connected to this gear.


But given the characteristics of it what I wrote in the first post, would the diode setup work?

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