# Powering wiper motors



## Bilbo (Dec 13, 2007)

Got a simple question for the electrical gurus around here. I picked up some wiper motors from a surplus store a while back and am about to order some power supplies and connectors from Monster Guts. I did find my wife's power converter from her old laptop. I know the wiper motors run on 12V and the output of this converter is rated as 18.5v 4.9 A. I know it will run the motor, if a little faster than I'd like. My question is... will I prematurely burn out my motor by running it at this higher voltage? And is there any safety issue other than the increased speed? 

I ran 2 of them off a computer power supply, but sadly managed to burn that out last year and the other ones I have must be a different breed because the aren't working the same as the ATX one I used. No need to bring up Scary Terry's site, as I've already committed that to memory! ;-D

Anyway, any help you can give would be great. Ideally I'd love to be able to hook up a cheap pot to control the speed but without losing torque, but that's just a pipe dream...


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## hedg12 (Jul 6, 2008)

My guess is that you'll be fine with the 18 volt unit if the speed isn't a problem. It might shorten the lifespan a bit, but that'll likely be many Halloweens from now. You might keep an eye on the temperature of the motor - if there's much of a load on the motor it'll be a little warm, & that's ok. If it gets too hot to hold your hand on, there's trouble. Wiper motors generally have pretty good torque, & with 18v & 4+ amps there's potential for the motor to do some real damage, so check things before flipping the switch.


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## Bilbo (Dec 13, 2007)

Thanks, Hedg, that was just what I wanted to hear. I'll buy 2 power supplies instead of 3 and spend the extra on something to dial down the speed with, perhaps. Thanks for the advice about watching the torque and connections, I'll be sure to do that.


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## Bilbo (Dec 13, 2007)

So does anyone know what happened to the 5V power supplies Monster Guts carries/carried? The video showing the difference between the voltage is still there, but I cannot find a link to the 5V supply. Do I really have to order a full kit if I want a slower motor?


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## The_Caretaker (Mar 6, 2007)

running higher voltage will shorten the life of the motor, it can cause the windings to burn out.


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## Zombie-F (Apr 12, 2004)

With no load, the wiper motor I have draws about 2.2A. Under a load, it will definitely be drawing more. In addition to a mechanical load causing the motor to draw more current, the higher you push the voltage, the more current the motor will be drawing.

You may find that the motor at 18.5 V will draw more than the 4.9 A the power supply can provide and that will burn out your supply.


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## Bilbo (Dec 13, 2007)

Thanks for the clarification, Caretaker and Z-F. I might look into actually learning something about electricity to come up with a way to lower the voltage from the power supply. I'm not _as_ worried about burning that out since it was free. The wiper was only $10 so it's not a huge loss either, but I'd rather not kill either if I can help it.

I did order 2 5V supplies along with connectors and a gallon of Froggy's Fog Juice from Monster Guts. They were nice enough to email me the link to the 5V supplies. Ask and ye shall receive, huh?

So, anyone have a simple, cheap and safe way to lower my voltage? I know from reading here if I use a pot I'll lose a lot of torque. All I want to do is either make a chair rock, or a head turn back and forth...


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## Zombie-F (Apr 12, 2004)

If you use a pot drawing the current you're using, you'll burn up the pot.

You can get 12v supplies @ 5A from All Electronics for about $19. 
http://www.allelectronics.com/make-a-store/item/PS-1262/12-VDC-5-AMP-POWER-SUPPLY/1.html

Also check eBay for 12v supplies. You can sometimes find used ones on there really cheap.

As for slowing the motor down, some of the wiper motors have multiple connection points for different speeds. Here is some info from Monster Guts on that. Keep in mind, not all motors are the same, so yours may vary from this.
















If you need finer control over speed, a pulse width modulator is the way to go. It connects between the power supply and the motor and pulses the motor with 12V. The shorter the pulses, the slower the motor moves and you don't lose torque that way:
http://www.electronickits.com/kit/complete/motor/CKMX033.htm


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## Bilbo (Dec 13, 2007)

Thanks again, Zombie-F. I found plenty of suppliers for the 12v supply, just hoping to find something so I can use what I already have, and maybe gain some electrical knowledge along the way. 

Besides, I'm a cheap bastard and I'm already going to be in the doghouse with the wife for the $85 I spent on the 5v's, connectors, and fog juice. ;-D


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