# how to slow down a wiper motor?



## gooffy87

Hello all,

Can anyone explain how to slow a wiper motor down? I am making a ground breaker and the wiper is moving to fast, even on the slow setting. I am running it off of a 12v 6 A power supply. any thoughts? thanks!


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## halstaff

First option is to drop the power supply to a 5V, 5amp unit. Next, make sure you're running it on slow speed. Here's an example using a Monster Guts wiper motor - http://monsterguts.com/index.php?act=viewProd&productId=4
Another option is to use a Pulse Width Modulator like this one - http://store.qkits.com/moreinfo.cfm/MX033


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## Lunatic

A computer power supply gives you an option of 3.3, 5 & 12 volts. Also the motor itself should have a slow and fast terminal to choose from. Those are the options I typically go with.

Here's some good info from Scarey Terry. http://www.scary-terry.com/atxps/atxps.htm


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## corey872

Under a light load the voltage change will probably work. Though if it's moving a heavy load or needs to start/stop slowly and under load, the PWM is the best bet.

As the motor turns slower, the amperage draw goes up, so it may tend to overheat if there is too much load. Also, simply lowering the voltage reduces torque - especially at start up. A PWM will maintain nearly full torque across a 5-95% speed range.


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## Lunatic

corey872 said:


> Under a light load the voltage change will probably work. Though if it's moving a heavy load or needs to start/stop slowly and under load, the PWM is the best bet.
> 
> As the motor turns slower, the amperage draw goes up, so it may tend to overheat if there is too much load. Also, simply lowering the voltage reduces torque - especially at start up. A PWM will maintain nearly full torque across a 5-95% speed range.


I've had the same experience with lower amperage power supplies, but that is why I use a computer power supply...My understanding is that it has plenty of amperage at all voltage selections which maintains the motor torque. At least that is what I've experienced with all my props that use a wiper motor.


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## gooffy87

Thx for the input all! I went down to the local swap meet and picked up 2 12v 3A power supplies. Hopefully this will solve my problem .to be exact, One is 2.9A, the other is 3.4. Wish me luck!


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## gooffy87

I dont think my mechanism is too heavy, its mostly pvc and probably weighs 1.5 pound at most. Also. I ordered a few wipers from monster guts so im sure they will be reliable


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## gooffy87

So the 3.4 worked well, the 2.9 could not power the motor :-(


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## Screaming Demons

What about when you put the expected load on it? Will it still turn at 3.4? I don't that this will work well, because you went to lower amperage rather than lower voltage. You should usually (within reason) try to get power supplies with the most amps possible. You really can't have too many amps, while having too many volts can damage or destroy a motor. The voltage is really what determines RPM.


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## gooffy87

interesting, what voltage would you suggest? I have generally seen 12v 5A power supplies suggested but those always make the wiper run too fast for my use. I want it to run slow, just imagine something that would life a mechanism that weighs about 1 pound up and down slowly. thanks for the input


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## gooffy87

looking around on frightprops, they sell 5V 5A power supplies and that looks like what I want, looks like i know what im gonna be ordering. thanks again! I was wondering why changing the Amps alone wasnt really making much of a difference. thanks!


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## Screaming Demons

The motor is probably struggling to run at 3.4 amps. That's why it slowed down. It may work but if you experience the least bit of binding in the moving parts it will stall. The 5 volt, 5 amp is the power supply that everyone commonly uses. It is better to buy from one of the reputable suppliers (like Fright Props) because I have heard that some of the cheap ones on ebay don't work very well. Just about everything is made in China these days but Fright Props will stand behind what they sell.


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## gooffy87

Thank you sooo much for the input. I can stop wasting money guessing lol


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## diamonddave_k

I would recommend a speed controller like calman did. I ran a wiper motor with considerable weight for a Christmas prop which I had to slow down and I tried a voltage drop but it's too hard to get the speed just right. The speed controller is cheap, easy to use and worked really well in my case. I would keep your 12V 5A power supply and get a speed controller instead of dropping voltage/amperage.


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## greenjeep79

I like the PWM motor controller found on ebay, they are the same ones on Monsterguts site but much cheaper, I have have good luck with them. and the speed can be set with a turn of a dial. https://www.ebay.com/itm/12V-40V-10...or+control&_from=R40&rt=nc&_trksid=m570.l1313


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