Thread: Low Volt & High Current Power Supply for Wiper Motor?

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Hey guys-
I need to run my wiper motor fairly slow. I was thinking about 3 volts or so- according to Scary Terry, this will run it at about 10rpm, which is perfect. I'm having trouble finding a 3-4v power supply that also has a high current rating. I tried a 3v 1a and it wouldn't turn the motor on. I think it needs around 4amps to run with decent torque.

Any ideas for a CHEAP solution? Space constraints on this prop won't allow me to gear down the motor. I DO have some computer power supplies- but every time in the past I tried this method, it turned into a nightmare... trying to rig a side load circuit so that the PS stays on- it just turns into a whole 'nother project just to get the thing to work right! I'm open to trying it again, but... would prefer a simple wall wart or something.

Ideas?
Thanks!

I have a multi voltage power supply, 3,4.5,6,7.5,9,and 12 volt dc rated @ 2 amps. I got it from MPJA.com. It is model 9902ps @ $19.95, also they have a 3.3 volt @ 20 amps model 13650 ps. HMPJA - Power Supply, Power Supplies, Security Cameras, LCD, Fans, Etc.Hope this helps

Dang, I was hoping to find something a little smaller/cheaper... thanks for the help! Anyone else have any ideas?

You will have a hard time finding a power supply that provides 4A for less than $20, and even a harder time finding an odd voltage like 3 or 4V. To be honest, changing the voltage for a motor may be the cheapest way to control the speed but when you use that method you also give up torque. When you are using a motor with some kind of gearhead the problem becomes even worse because the motor has to overcome that initial surge necessary to get the gears turning. The better solution is to use a speed controller which allows you to keep the voltage to the motor at the rated level and instead sends a pulsed signal to the motor. The longer the pulses the faster the motor goes. The advantage with this method is that you hardly lose any torque at low speeds. Here is a kit that you can purchase that allows you to adjust the speed and handles up to 7A.

LOL. Yeah, tried that kit before. It never worked. Any others out there?

Try this site 12 volt power supply catalog. also look at the possibility of using a computer power supply.

Yeah, I have some computer power supplies. Those are always a nightmare to work with- see my above comments. UNLESS someone has an easy way to deal with them?

Hey AZDude-
If I use a computer PS, and use the 3v supply line- will that drop the amps/torque down quite a bit?

You may try this.

You need and old 12 volt car battery that measures well below 12 volts and a wall wart or other power supply that puts out 4 or 5 or 6 volts or so dc. If you connect the wall wart to the battery it will keep an old worn out battery charged to 4 volts. (Make sure the output is DC and you get the polarity correct) The battery will give you the ability for a few amps and the wall wart will limit the voltage the battery charges to. The battery needs to be pretty well run down and useless for a car, or it soon will be. The current the wall wart (or other power supply) can put out as well as the state of the battery will determine how long you can run the motor. Best if it is intermittent use.

Andy

Motor torque is (generally) proportional to the current passing through them. As long as your power supply is capable of delivering the voltage you need (for the speed you want) at the current required (for the load you're pushing) you should be okay.

I'd highly recommend using a PWM motor speed controller to achieve what you're looking for. This will let you use a higher battery/supply voltage, and yet still control the speed of the motor. Batteries don't like being way below their nominal charge.

Here's an interesting site I just found. Or, if you're adventurous, you could pick up a used/surplus brush motor servo amplifier on ebay. Apparently, these can go for pretty cheap (as little as $30-40).

- Hook