Does someone know , for sure, if a rheostat can be applied to a small '12 vdc' Motor ?

[ilbebauck]

All the packages ive looked at in the store mention 115 v. , but none mention 12 vdc. Please advise. Thanks.

[Jon Danniken]

What kind of rheostat? What kind of motor?

A rheostat, of the type used in an old sewing machine pedal, will only properly control the speed of a universal (series-parallel wound) motor (AKA AC/DC motor) or a straight DC motor (the kind with brushes).

Beyond that, you need to select a rheostat with current capacity greater than that of your motor, and ideally, several times larger (a slower running motor will consume more current than a motor running at full speed).

Jon

[Tony]

Like Don said, it depends. I'll mention that using a rheostat to vary the speed of a 12 VDC motor isn't going to work very well if you have a varying load on the motor.

Use a DC motor speed control instead, it will give you much more torque at lower speeds where a rheostat would stall the motor.

I'm not affiliated with the below:

See ebay item number: 130268566396

or cut and paste this link:

Or do a search on DC motor speed controllers, I think they have virtually the same unit good for up to 30 amps.

[ransley]

I havnt seen a Rheostat sold in hardware stores for years, A Rheostat will work.

[The Daring Dufas]

A wire-wound rheostat of the appropriate wattage will do fine. An electronic speed control mentioned by another poster is more efficient because it can lower the speed but keep the torque fairly constant. You may obtain a speed control from a broken cordless 12 volt drill and it would work. You could check pawn shops or even call a couple of construction companies to see if they have any worn out cordless drills. You could also drop by your local Dewalt or Skill repair depot and ask them if they have any in their trash heap.

TDD

[David Nebenzahl]

On 8/2/2009 10:01 AM [e-mail] spake thus:

Both of these places have rheostats for sale for cheap; just do a search for "rheostat":

Electronic Surplus Inc.--

[Jerry - OHIO]

Old auto car heater switch !! Jerry

[Stormin Mormon]

Of course it can be applied.

Now. What did you want it to do? Depending on what you want it to do, it might work or not.

[Bennett Price]

I think you've been looking at AC lighting dimmers - these are not rheostats and won't work on DC - 12 volt or 115 volt.

[aasberry]

I used one of these on a 1/4 hp motor.

[David Nebenzahl]

On 8/3/2009 9:11 PM [e-mail] spake thus:

Looks to me like it uses PWM (pulse-width modulation), basically "chopped" DC with variable duty cycle. Just curious: what kind of 1/4 hp motor? Must be a 12 or 24 vdc one, obviously.

[Tony]

That's what it is. It give much much more torque at low speeds vs lowering the voltage. I think that one also allows you to vary the frequency of the PWM, but I'm not sure why you would want to do that?

Tony