Would this speed controller sold on Ebay suit a sewing machine from the 70's?

[wilfred]

I just caught this old video BigClive did 6 years ago about a speed controller he bought on Ebay. It was an interesting video with reverse engineering of the circuit. BC learned something he didn't know. So did I of course.

He referenced this App-Note describing a key feature. https://www.littelfuse.com/~/media/electronics/application_notes/switching_thyristors/littelfuse_thyristor_phase_control_using_thyristors_application_note.pdf.pdf

I searched on Ebay and found this which looks like the one. https://www.ebay.com.au/itm/394249590685

I recently acquired an old Husqvarna 5610 sewing machine without the foot pedal. I think machines of this vintage just used a rheostat but I'm not sure this one did. My question is would this device be suitable for this application as a replacement throttle control. The 4kW might be a bit fanciful but a sewing machine is nowhere near that anyway.

BC also mentioned the RF noise this circuit would generate since it doesn't have any suppression components. Where would you add the choke? And could it be an old one from a PC power Supply? I have a collection of them.

[floobydust]

What type of motor does it have? Nah, it would not work well.
Nevermind that speed controller is pretty junky, mine didn't last before a blown triac and potentiometer, and I had to mod it for reasonable 120VAC operation as discussed here.
I did some repairs and schematics on Elna sewing machine controllers. Those are a brushed DC motor with back-EMF monitoring so they are controlling for near constant speed despite required torque varying. An SCR and bridge rectifier are used in the pedal.
So that 4,000W eBay special would be awful to control speed with and might not even be compatible with your motor.

A better controller is used on power tools, where you want constant speed regardless of load, like discussed here.
Those controllers are more sophisticated and use an IC.

[james_s]

Older sewing machines have brushed universal motors, the original foot controls are just variable resistors, I believe they use a carbon pile. Anything that varies the average voltage the motor sees ought to work, triac speed controller, variac, rheostat, etc. I bet you can buy replacement old style foot pedals.