Somewhat OT (I think) Electrical question

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.

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

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.

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.

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

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

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.

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

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.

I have used these on several motors:

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

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.,

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

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