Thread: 12V DC power supply/motor speed control problem

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I am using this 12V DC Motor Speed Control to slow down my wiper motor for my rocking granny. The power supply I am using is a ATX 400W computer power supply, at 12V it is putting out 15A. I testing the unit with a coworker and he used a regulated power source and the motor was only drawing 9A at peak power, when we slowed it down it was only about 4A.

When I hooked it up today to test it, the power supply started a high pitched hum and then when I turned it up thinking it may start the motor it started to smoke right behind the motor and power connections at D1.

I don't know why it worked the first time and not when I brought it home

D1 is a diode , the short explanition is that it allows electricity flow only one way. It almost sounds like you had the connections reversed. The motor was hooked up to the power connection and the power supply was hooked up to the motor connection. Do you have a wiring diagram or schematic for the speed controller?

it/s never good when the magic blue smoke escapes from electronics they never work once it.s gone

Originally Posted by bfjou812

D1 is a diode , the short explanition is that it allows electricity flow only one way. It almost sounds like you had the connections reversed. The motor was hooked up to the power connection and the power supply was hooked up to the motor connection. Do you have a wiring diagram or schematic for the speed controller?

Thanks bfjou812, I'm a newbie when it comes to electricity, my coworker on the side installs emergency lights and he only did a kit like this once before, so we could of for sure reversed the polarity. Yes I do have a wiring diagram, I have attached a link to the instructions and it has the wiring diagram. The picture I posted is from the is from the website, I should compare it to my controller.

http://www.kitsrus.com/pdf/k67v3.pdf

Looking at the schematic, if you are only using one power supply, the motor gets hooked up to M+ and M- terminals and the power supply gets connected to V+ and V-. If you hooked them up backwards, power supply to motor terminals, I think you could have burned out the diodes. If you hooked up the power backwards , V+ to V-, I think you could have done a lot more damage. If you have a DMM you should be able to see if the diodes,resistors, transistor or capictors are burned out. It looks like all the components are installed correctly. If the diodes or any of the parts are burned out they are pretty cheap to replace. The only thing I'm not real sure how to check is the IC chip. Hope this helps.

I think I would just replace that diode (1N4004) where the smoke came from and see if it fixes it. Amazon has it for 25 cents and Radio Shack has it for $1.19