# Variable Speed Motor **URL:** \ **Category:** Factual Questions\ **Created:** [October 26, 2001, 8:34pm UTC](https://boards.straightdope.com/t/variable-speed-motor/89856 "2001-10-26T20:34:28Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![DanBlather](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@DanBlather](https://boards.straightdope.com/u/DanBlather)\ **Post date:** [October 26, 2001, 8:34pm UTC](https://boards.straightdope.com/t/variable-speed-motor/89856/1 "2001-10-26T20:34:28Z")
I want to make my wide an electric bobbin winder with a foot pedal to control the speed. My local salvage store (Wacky Willies) has a bunch of motors but I am not sure if I should get an AC or DC motor. I bought a foot pedal there last year which looks like it came off a sewing machine. If I get a DC motor, what do I need in terms of a transformer. Thanks. ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [October 26, 2001, 8:50pm UTC](https://boards.straightdope.com/t/variable-speed-motor/89856/2 "2001-10-26T20:50:42Z")
If your wi **f** e reads this board, I’m not sure that improving her sewing tools will be sufficient. 😉 ---
**Author:** ![DanBlather](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@DanBlather](https://boards.straightdope.com/u/DanBlather)\ **Post date:** [October 26, 2001, 8:51pm UTC](https://boards.straightdope.com/t/variable-speed-motor/89856/3 "2001-10-26T20:51:08Z")
I meant "wife. And no, that is not a freudian slip, she is really skinny. - Don ---
**Author:** ![scotth](https://avatars.discourse-cdn.com/v4/letter/s/b9e5f3/32.png) [@scotth](https://boards.straightdope.com/u/scotth)\ **Post date:** [October 26, 2001, 8:52pm UTC](https://boards.straightdope.com/t/variable-speed-motor/89856/4 "2001-10-26T20:52:27Z")
By far the easiest way to have variable speed is a dc motor. What you need in terms of a transformer will depend on what motor you get. Besides just a transformer, you will need some type of rectification and a simple capacitive filter would be a good idea. Depending on the current demands of the motor, picking a variable resistance to put inline with the motor may be the most interesting part. Typical potentiometers and variable resistors would overheat very quickly driving much of a motor. ---
**Author:** ![DanBlather](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@DanBlather](https://boards.straightdope.com/u/DanBlather)\ **Post date:** [October 26, 2001, 8:53pm UTC](https://boards.straightdope.com/t/variable-speed-motor/89856/5 "2001-10-26T20:53:47Z")
> [@](#): > > \*Originally posted by tomndebb \* > **If your wi** f\*\*e reads this board, I’m not sure that improving her sewing tools will be sufficient. 😉 \*\* You beat me to it. ---
**Author:** ![KP235](https://avatars.discourse-cdn.com/v4/letter/k/9de0a6/32.png) [@KP235](https://boards.straightdope.com/u/KP235)\ **Post date:** [October 26, 2001, 10:27pm UTC](https://boards.straightdope.com/t/variable-speed-motor/89856/6 "2001-10-26T22:27:14Z")
Just as a suggestion, why don’t you find an old variable speed sewing machine at a yard sale or flee market, take the motor and foot control off of it, and power your bobbin winder with it? To me, that sounds a lot easier than shopping around for motors and controls. …and you can make it as _wide_ as you want too. 🙂 ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [October 27, 2001, 12:00am UTC](https://boards.straightdope.com/t/variable-speed-motor/89856/7 "2001-10-27T00:00:37Z")
> [@](#): > > \*Originally posted by scotth \* > \*\*By far the easiest way to have variable speed is a dc motor. > > What you need in terms of a transformer will depend on what motor you get. > > Besides just a transformer, you will need some type of rectification and a simple capacitive filter would be a good idea. > > Depending on the current demands of the motor, picking a variable resistance to put inline with the motor may be the most interesting part. Typical potentiometers and variable resistors would overheat very quickly driving much of a motor. \*\* Mmmmmm… I would have to disagree. While your approach would work, it would be a needlessly inefficient way to do it. If you want simple and _efficient_, then I would go with a regular brush-type AC motor. Hook a light dimmer to the foot pedal, and away you go. ---
**Author:** ![DanBlather](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@DanBlather](https://boards.straightdope.com/u/DanBlather)\ **Post date:** [November 3, 2001, 9:18pm UTC](https://boards.straightdope.com/t/variable-speed-motor/89856/8 "2001-11-03T21:18:32Z")
> [@](#): > > \*Originally posted by KP235 \* > \*\*Just as a suggestion, why don’t you find an old variable speed sewing machine at a yard sale or flee market, take the motor and foot control off of it, and power your bobbin winder with it? > > To me, that sounds a lot easier than shopping around for motors and controls. > > …and you can make it as _wide_ as you want too. 🙂 \*\* Thanks, that is just what I did and it works great.