# 12 volt motor controler. need to slow down.



## Jay R (Sep 23, 2012)

Hello,
New to the forum and building moving props. Been haunting a while, but I'm trying to tackle my first DIY motion prop, Monster in a box, and am running into some trouble with the motor, specifically slowing it down.

I'm running a 12v motor I got off one of those electric bike kits I had no use for and have it running off a small 12v lawn tractor battery. Not a lot of torque but it spins real fast. It doesn't have any markings but I think it's this one for a big fan. 
http://www.action-ac.com/AC-Part/26-31301.html.

I bought the controller below to slow it down and everything was working really well until today. I was playing around with it adding some chains for looks and extra noise and the controller smoked. Is this for some sort of small motor? Is the battery putting out too many amps? Any recommendations on one I can use that can handle the motor and battery supply?
http://www.ebay.com/itm/360685305289?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649


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## typoagain (Feb 27, 2012)

I can't get the page for the motor to load right now. 
(Might be due to the fact that the browser is so out of date on the POS computer at work.)

BUT, I suspect that the added mass you are moving, combined with the slowing of the motor may have brought your load up over 5A. In which cash you need a larger heat sink and forced air cooling.

Also how long were you running ti before it fried? running it in short cycles is easier on the motor than running for several minets or longer at a time.

(Hummm, I think I might just buy one fo thee to play with . . . .)


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## Jay R (Sep 23, 2012)

Thanks for the reply. I ran it for 10 min or so a few times, then the last time I was running it for a couple minutes at a time total maybe 10 min while I was adding extra load by hanging some chain over the lid. I was for sure adding additional load and it stopped the low torque fan motor a couple times. 
The controller said it can take 10 amps. Is it possible I went over that?
Would my solution be to get a controller with a higher amperage rating?


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## Jay R (Sep 23, 2012)

Would something like this be better?
http://www.ebay.com/itm/10-50V-40A-...418?pt=LH_DefaultDomain_0&hash=item3cd346aa2a


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## corey872 (Jan 10, 2010)

When a motor stops or locks up, it can draw quite a few more amps than the nameplate rating or what the running motor does. Most likely you drew too much amperage and blew out the mosfet (the big part with the heat sink) on the motor controller.

On most controllers the mosfet (and the printed circuit board wiring) are the limiting factors to current handling. If you were to replace the mosfet with one having higher current capacity and beef up the traces on the circuit board, you could likely increase the current carrying capacity of the speed controller.

Other options could be to counterbalance the assembly so it draws less power from the motor - preventing lock-up, and/or put a fuse in the line so it blows slightly before the motor controller.


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## Zombie-F (Apr 12, 2004)

Jay R said:


> Would something like this be better?
> http://www.ebay.com/itm/10-50V-40A-...418?pt=LH_DefaultDomain_0&hash=item3cd346aa2a


That might be better than what you already have. However, given it is from China and doesn't have a data sheet, you could be taking a risk and getting something that could wind up getting smoked too.

The more weight the motor has to move, the more current it is going to draw. You may want to purchase a multimeter (or even just an ammeter) and try to monitor how much current the motor is drawing. Then, you will have an informed way of figuring out how much current your speed controller will need to sink.





. It has some nice features and isn't terribly cost prohibitive. If you have aspirations to tackle more electronic projects, I highly recommend it.


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## Jay R (Sep 23, 2012)

Thanks,
I'm not circuit board savy so I didn't really follow all that other than I likely need to go bigger on circuit parts. It will be something I have to buy, I'm not going to be making it so if there any suggestions on units out there I'll take them. I'm not really big on M.I.C either bit it's all I could find. 
I have a decent mulit meter but just hooking up the motor to the battery spins it so fast I can't even set down the lid on the monster in a box enough that I could get a reading at an appropriate speed. That thing is flying. I guess I could push down on the lid and physically slow it to somewhere around where I want it. Then I would check the amperage across the pos. and neg terminals on the motor?


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## Kelly_A (Sep 24, 2013)

Just suggesting this as an alternative. Enough of an amp draw will take out any of the smaller PWM controllers. I'm running three of these currently. 2 at 6v and 1 at 12v. No issues under load so far. Usually 7 days from order to arrival.

http://www.ebay.com/itm/6V-12V-24V-36V-40V-60V-90V-15A-DC-Motor-Speed-Control-PWM-Controller-New/350827102622?_trksid=p2047675.m1850&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D17515%26meid%3D1638350455812296904%26pid%3D100011%26prg%3D8141%26rk%3D5%26rkt%3D5%26sd%3D360685305289%26


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## Jay R (Sep 23, 2012)

Lowering the voltage to the motor wouldn't lower the amperage under load would it?
What do you use for a 6 volt power supply? Is there an adjustable way to lower the voltage? That would slow down the motor, but would it build up too much heat and burn out the motor?


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## Jay R (Sep 23, 2012)

did some digging on the fan motor and while they don't make this particular one any more, it looks like when used as a auto cooling fan with the blades similar motors draws 10-13 amps at 12v.


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## corey872 (Jan 10, 2010)

That could be the problem. If the motor is rated 10-13 amps running, it could easily be 20+ with the rotor locked, so that would kill off the speed controller.

Given the old V=IR (voltage = current x resistance) equation, and knowing the 'effective' resistance of the motor is constant for any given operating condition, lowering the voltage would proportionally lower the amperage. ie - running 1/2 the voltage would draw 1/2 the current. But, 1/2 the voltage will also give 1/2 the torque, so if you are already locking up the motor now, it will lock up much sooner at the lower voltage.

Your best options - would either be to build some type of gear reduction drive. You'd have a small cog/pulley on the motor and a larger one on the driven output shaft. This would give you a speed reduction AND torque multiplication - both of which seem to be the direction you are trying to head. Alternately, you could switch to a motor with those built in - such as an auto window power motor or a windshield wiper motor.


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## Zombie-F (Apr 12, 2004)

Have you considered using a windshield wiper motor for this prop?


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## Jay R (Sep 23, 2012)

I have, and just ordered one for another prop. I was just trying to make due with what I had on hand but it may not work out. I did order the higher amperage pwm controller from e-bay just to see if it would work. I have two of these motors so I'll see what happens.
Any prop suggestions that need high speed motors...?


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## Hippofeet (Nov 26, 2012)

A shaker?


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## Jay R (Sep 23, 2012)

Just got the larger amperage PWM from E-bay today and it works good. Left it running for about 30 min and the heat sinks were just slightly warm to the touch. Think it might work out ok.


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