Somewhat OT (I think) Electrical question

[Justin Time]

Though, this isn't specifically about "Home Repair" it is an item in the home.

I made a project for the wife which required the use of a sewing machine motor (but not the sewing machine) which has the speed control foot pedal. I want to remove the foot pedal and connect a dial speed controller, preferably one with variable speeds, as opposed to a 3-speed type. I tried a ceiling fan speed control which does contain the 3 speeds of high, medium and low, and it's not what I want. For starters, low is obviously too low since the motor only hums, medium appears to be OK speed wise but high is too fast. I want to provide the wife the option of variable speeds. Therefore, the big question is, doesn't anyone know if and/or what type of speed control I can connect with the motor?

BTW, if it helps, according to the label on the motor, it's a 110v, 150watt and 1.3 amps.

Thank you

[Justin Time]

The pedal is not a dial type. When viewing the inside, the pedal makes connects with layered contacts. In other words, as you push the pedal, it connects with one contact, then further push connects with another contact and so on as if stacking chips at the end of an arm. A dial controller has the contacts in a circumference and increases power as the dial increases.

[Justin Time]

That could get costly if I don't find the correct one soon enough.

[Tony Hwang]

Hi, Depends on motor design ie. number or amature poles, windings, etc. If my wife wants something like that, I'd just experiment with electronic rheostat until I hit the jack pot to her satisfaction.

[gfretwell]

Back in the olden days these were universal motors and the foot pedal was just a rheostat. Put a meter on it and see what you have.

[aemeijers]

If that doesn't work, wander around at MPJA.com. They carry all sorts of strange stuff like that.

[Charlie]

Go to eBay and search for variac or powerstat. There are all sorts of configurations. You need to compare the current/power ratings of the sewing machine and select one of the smaller units. I have a big variac but it is not up for sale as I can still find some use for it.

Charlie

[clare]

Sewing machine motors are universal motors. A router speed control will work perfectly - you really want one that current (and counter EMF) senses and PWM controls the speed. A simple rheostat type control will cause overshot on startup and speed decrease under load.

[clare]

And unlike a rheostat, a Variac can be grossly oversized and still do the job

[Justin Time]

After doing a Google search and reading a bit of info, that's exactly what I decided to do. By chance, we had an extra dimmer from work and I brought it home, connected it and it works very well.

[Kuskokwim]

I have used these on several motors:

[Charlie]

One consideration, other than physical size and weight, is cost.

[hrhofmann]

Try a heavy-duty light dimmer, they work quite well. Get one rated for as much wattage as the max motor wattage, probably a 200W dimmer would give you some margin for a 150 Watt motor.,

[clare]

If using a dimmer, you want one designed for dimming low voltage lighting with magnetic transformers - not electronic. These have the circuitry to handle the high voltage spikes caused by the circuit opening (or commutate on the rizing edge instead of the faling) Standard (decent quality) dimmers are 600 watt

[harryagain]

The normal sewing machine speed control has a stack of carbon disks. Control is effectedby squeezing them together. (reduces resistance.)