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Looking for Help! 120v ac to control variable speed 90v DC motor Answered

I'm at best a novice when it come to electrical and circuits so if what I've put together is a total disaster maybe you can inform me on a better solution. I've taken a treadmill that was given to me and salvaged the motor control board along with the 90v DC motor the control screen on the treadmill was smashed so i didn't bother to keep it. After a few days of googling and YouTubeing I ordered a scr motor controller but it was only single phase 220v... we here in Canada run a double phase 120v.. so to the best of my ability I wired up the single phase with a rectifier also purchased online. As I would flip the switch the motor would come on full tilt at what I'm assuming would have been 160v DC..I decided to scrap that idea. So after more googling and youtubing I found a page where someone had cut parts out of an old circuit board and just used the main circuit that took ac power in and DC power out.. so I figured I'd give that a try... and of course that didn't work either hens why I'm here writing this now. so I thought to my self, well what if I take the main components like the transfomer (tested the transformer to 120v on primary and on the secondary i was reading 18v av onmy multimeter) to step my power down the bridge rectifier to convert to DC along with a capacitor to clean up the ripple and a potentiometer to control the voltage. I wired these items up roughly then pluged it into the wall and when I flipped the switch nothing caught on fire so I figured I'm off to a good start, but as I started to turn the dial on my pot nothing happened.. until it was turned to the very top that was. then the motor started to turn probably at about 14rmp now I plan on using this set up for a wood lather. Am I going about this like a total buffoon? any help would be greatly appreciated


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Best Answer 2 years ago

Your motor is a 90 VDC, 10 ADC, 2.25 HP, 4700 RPM machine.

You need a 90v 10amp Power Supply, see the schematic in the other comment.

If you wish to run the circuit from 120 VAC the resistor values will need to be lowered.

Do not expect that pot to survive running more the milliamps..

The transformer is much to (little)

The bridge is excellent 600 VDC @ 25 ADC !


See a low cost line power supply, a bridge or diodes needs at least 10 amp 400v


2 years ago

Add a switch and a slow blow 12 amp fuse.

Always start with the low speed setting.