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AC Motor speed control? Is it doable?

Shackman55

Shackman55

Super Member
I know this is a dumb question, but I am making a DIY record cleaner and I found an ice cream machine motor that I want to use, it has a built in cooling fan so no over heating. I want to do direct coupling of the platter to the shaft, however it seems to be going too fast, around 60rpm the motor is direct wired to the ac cord, ie:no switches controls or circuits. Is there a way to slow down an AC motor? :scratch2: Like a pot in line with it, or does that only work for DC motors? Ideally I would like between 15-25 RPM The alternative is doing a rim drive sort of thing and that would get me the right speed but a heck of a lot more work and I am not sure I could get the torque I want either. Thanks in advance for any tips or suggestions.
 
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Get thee to Lowe's, Home Depot, etc. and buy a heavy-duty rotary speed adjuster for a ceiling fan.. I used one in my RCM, it works just fine to adjust AC motor speed.
 
If the motor has brushes, it should be do-able, maybe even with a drill speed controller.

IIRC, the ceiling fan style motors dont like running slow.

Most AC motors suffer torque loss through speed controllers. I am not suggesting you do it, but a rim drive/mechanical reduction will increase torque.
 
Do-able??? It's done-able. Many Reel To Reel motors are AC (brushless) motors. It's done by rectifying the currents, then using DC control (transistor) to vary the resistance across the DC portions of the bridge.

Look no further than a Revox A-77, B-77 for the circuit.
 
Aussiedan's suggestion is worth considering. If you're at all mechanically inclined, a simple pair of pulleys and a belt will allow you to both slow down the speed and increase the torque for good brushing without bogging down the motor, without any electrical changes at all.
 
Well there in lay the problem. I am somewhat electronically agile, but when it comes to the mechanics, I was voted least likely to get my soap box racer out of the garage. Just seemed like a nice setup that lent itself to being mounted whole under a platter. Now I am starting to get the heeby jeebies about that too. This motor is geared such that no matter how much force I put on it, it won't stop. It slows down a bit, but not much. I may have to sit with all the parts laid out and look it over to see if any ideas flash into my head. Yes this motor has brushes. I was afraid these motors somehow took their speed que based on the 60hz, and not the voltage. It occurred to me that my soldering station has a voltage control to adjust the iron temp. I should perhaps test out the theory before I go further lest I get the darn thing built and the albums go sailing across the room like flying saucers.
 
If you are willing to use a foot pedal to control the speed instead of a steady speed when you turn it on (hardwired) then you can use is a sewing machine foot controller. These have an AC receptacle already on them or you can cut that off and wire it directly to the motor. The more you push the pedal down, the faster it will go. I've used this kind of setup in MANY situations with great results.
 
Sam Cogley said:
Get thee to Lowe's, Home Depot, etc. and buy a heavy-duty rotary speed adjuster for a ceiling fan.. I used one in my RCM, it works just fine to adjust AC motor speed.
Click to expand...

I have a fan speed switch on mine that uses a bread machine motor... it doesn't work well. It doesn't like to start the motor unless it's turned all the way up, and then it doesn't like to keep the motor turning if you get it under half way..

I found an old craftsman BBQ rotisserie motor I'll be putting on my RCM.. turns nice and slow..
 
similost said:
I have a fan speed switch on mine that uses a bread machine motor... it doesn't work well. It doesn't like to start the motor unless it's turned all the way up, and then it doesn't like to keep the motor turning if you get it under half way..

I found an old craftsman BBQ rotisserie motor I'll be putting on my RCM.. turns nice and slow..
Click to expand...

Is the start circuitry wired in right? I had a bread machine motor and control board laying around. I never could figure out exactly how to wire it up properly, so I tossed it out and used the tone wheel motor. It has an extra "start boost" winding, which I wired in with another switch to get it going if necessary, but it never needs it when running a light load like a turntable platter.
 
If I could really dream big, I would want to be able to reverse the direction too. But I'll be happy if the fan control slows it down enough to use.
 
MoparMan said:
If you are willing to use a foot pedal to control the speed instead of a steady speed when you turn it on (hardwired) then you can use is a sewing machine foot controller. These have an AC receptacle already on them or you can cut that off and wire it directly to the motor. The more you push the pedal down, the faster it will go. I've used this kind of setup in MANY situations with great results.
Click to expand...

Oooooo I like that idea! I am used to using one so it wouldn't be hard to learn either. Stop the running rather than leave it spinning all the time.... Hmmmmmm
 
You know, a good RCM motor option would be one of the old Singer motors. The ones used on the black cast-iron models were separate items bolted to the back.
 
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