# 12 v power supply question



## grismcdonald (Aug 23, 2011)

What is the best power supply to run a wiper motor. Had a 12 v 500mA doing a test run. Burned out but I think it was due to a bind up issue with a lock nut tightening up on the drive arm. I can buy these at the local thrift shops all day for 1.00 a piece but thinking I need something with more Amps. I see some on line that are rated for 2A for $6.50 plus. Been looking to hack a AXT but have not been able to get it to cut on by grounding the green and providing a load resistor on 5 v. This has become a two question post. Any recommendations on where to buy power supplies or a good tutorial on a ATX hack?


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## hedg12 (Jul 6, 2008)

500 ma is pretty light for a wiper motor, but you'd probably be OK with the 2 amp supply. You might want to add a 2 amp fuse in the positive lead between the motor and the power supply. That way if the motor does bind you'll blow the fuse instead of the power supply.

There are tons of how-tos for hacking an ATX power supply online, but it sounds like you've got the just of it. If you connect the green wire to any of the black wires it should turn on. The resistor's not a bad idea, but it's probably not necessary. If it's not turning on, check to make sure there aren't any shorts. Otherwise, you may have a bad supply.

Just curious, what value resistor are you using on the 5v line? If it's too low, it could be tripping the protection circuitry in the power supply. Try it without the resistor & see if it turns on.


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## DarkLore (Jan 25, 2009)

While I agree with the recommendation of a fuse, I don't think you need a 2 amp wart. I've run several wiper motors on 500mA and 1amp. I never had any issue. But then again, my props are only up for a night or two. Sounds like you have some adjusting to do on your linkage.


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## Thisaintmayberry (Aug 23, 2010)

Many ATX power supplies require a load of some kind in order to turn on. Wire a light bulb or something in the line and then test it. I wouldn't recommend running a wiper motor on 5v; you're giving up all the main benefit for using a wiper motor in the first place: massive torque. If your concern is slowing the motor down, use a speed controller like this one. A PWM speed controller lets you use all of the torque available from a wiper motor, at any speed. I actually installed mine inside the ATX box. An ATX will supply all the power you need for most props, plus they're cheap and plentiful.


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## grismcdonald (Aug 23, 2011)

It is my understanding that the ATX power supply will provide a range 3v, 5 v, and 12v. Right now I am mainly trying for the 12v but the first one I am trying to fire up will not stay latched. Tried a 10 ohm 10 w resistor across the 5v as recommended on several hacks. Also tried the signal source lead tied back to power. There seems to be something missing. Have a old AT supply I am going to try next.


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## hedg12 (Jul 6, 2008)

The 10 Ohm resistor should be enough load to make the supply run - sounds like you might have a bad power supply.

The old AT supply should be much easier to work with. Just be careful with it - the leads going to the switch are usually mains voltage (120v AC in U.S.) and are dangerous. Make sure they're insulated before you plug the supply in!


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## grismcdonald (Aug 23, 2011)

Should know this and could google it but wired 2 - 10 ohm in parallel. Add ohms in parallel? Anyway. This worked. Power supply up and running. Next issue is only 11.8 v. I know there is a cure for it


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## hedg12 (Jul 6, 2008)

Nope, 2 10 ohm resistors in parallel would be 5 ohms. Odd that made the difference, but as long as it's working you're golden.

The 11.8 volt issue really probably won't be a real problem. I'd bet that any 12v item you want to connect to it will run just as well with 11.8.


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## Haunted Spider (Sep 6, 2010)

11.8 is good. I have two supplies. One is running at 10.7 and the other at 11.8. Both fire up LEDs just fine and run a wiper motor as well. But the 10.7 has an issue that if I rock the motor on and off, it signals an internal issue in the supply and it auto shuts down. You won't know which supplies will do that until you test them. Make sure your's does not or you will be frustrated when your effect stops working.


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## grismcdonald (Aug 23, 2011)

How about this. Got a 12v 3A monitor supply. Hooked it up to a wiper motor and got a 1/8 rev out of the motor and stopped. This was the case each time I connected/reconnected it. Does this type of supply sense load?


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## Haunthunter (Sep 19, 2011)

This is the best tutorial I had found. I converted my ATX power supply using this one


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## coolbotz (Oct 21, 2009)

Gris, your 12v 3A supply is 'crowbarring' (shutting down from excessive current draw). You should try at least 5A supply per Scary Terrys tutorial. If you have a battery charger with 10A setting try that to verify motor.


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## grismcdonald (Aug 23, 2011)

but a 12v 1A Wall wort works. I think a .5A will too for my hanging man. Just burned up a couple doe to a binding. This supply looks like a laptop supply with 12 v 3A but cuts off like it is not sensing a current draw. I do not think I am over driving it


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## bert1913 (Oct 27, 2011)

i use at least 5amp 12 volt power supplies


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