Speed Controls for NIB DC Treadmill Motors

[Maui]

Yesterday I bought a set of NIB treadmill motors off of Craigslist. They are 90V DC motors rated at 1.25 hp and 2.75 hp continuous duty. These would be perfect to power a Lathe or milling machine because they have high torque at low rpm and with the right controller allow you to dial in variable speed. But in order to operate them I need a PWM (pulse width modulation) DC speed control. I looked on Amazon and found what looked like some relatively inexpensive controllers. For example,

https://www.amazon.com/dp/B073Z7PB5G/?tag=atomicindus08-20

I don’t know yet if these motors are brushed or brushless. If they are brushed these should work, but reading through the comments section they do not seem to inspire all of the customers with their reliability.

Has anybody here found a speed control that works with these types of motors that won’t break the bank? I know that you can rip the electronics out of a free treadmill and finagle with them until they do the job. But after reading through many discussions where people did this it sounds like a major undertaking. I don’t want to go that route if I don’t have to. I’d rather just buy a brand new controller in a box that I can easily wire up and use. Any recommendations?

Maui

 

[tool_scrounge]

Looks to be brush type DC motors. The larger one appears to have a tachometer but it is hard to tell.

The issues I see with these motors are

1) they are high rpm. For most things you are putting a DC motor in because you want variable speed and low RPM. Most DC motors are around 1750rpm, not 3000 to 5000. Depending on your application you may want to add a pulley speed reduction.

2) The larger motor is 22A of current. You may not be able to get full current from a 120V 15A outlet. But you can run it at reduced current.

3) Unlike industrial motors they really are not meant for continuous operation at max power output. Yes, I see the label on the motor. I do not believe it. All the continuous operation rated industrial DC motors in this power range have integral fans to keep the from overheating. I would run them at reduced max current to better reliability.

I usually find industrial speed controllers for discount on ebay. The KB electronics KBMM-125 with external heat sink will output up to 16A at 90V. Be sure to buy the matching power resistor.

 

[Maui]

Thanks for the reply. I’ll check out ebay for one of those controllers. By the way, both of these motors have integral fans in place. I typically wouldn’t be running them anywhere near their maximum output. And if I did do that, it would only be for short durations.

For the 1.25 hp motor it looks like this controller from Harbor Freight should actually work:

https://www.harborfreight.com/router-speed-control-43060.html

I believe it uses PWM to control motor speeds. Thoughts?

 

[tool_scrounge]

Thanks for the reply. I’ll check out ebay for one of those controllers. By the way, both of these motors have integral fans in place. I typically wouldn’t be running them anywhere near their maximum output. And if I did do that, it would only be for short durations.

For the 1.25 hp motor it looks like this controller from Harbor Freight should actually work:

https://www.harborfreight.com/router-speed-control-43060.html

I believe it uses PWM to control motor speeds. Thoughts?

The issue with the inexpensive motor controllers you has posted is the lack of specifications. The KBMM-125 motor controller specs list Armature Feedback Load Regulation (0 - Full Load, 50:1 Speed Range) of 1% Base Speed. This means the speed remains relatively constant as you change loading. It is not listed as far as I could see for the $20 speed controllers you posted. But if cost is the biggest driver then try them out and see if it works for you.

 

[tool_scrounge]

One comment of the HF speed controller. It does not specify the output voltage range. So if the controller is putting put 0-115V, your 90V motor is probably going to have brush life issues at the top of the speed range.

 

[guy48065]

That router speed control is a glorified lamp dimmer that uses a triac to chop the AC waveform to reduce the "on" time and slow the motor. Your DC motor won't like the ugly AC output of that controller--it's intended for use with AC/DC universal motors.

 

[motofool33]

couldn't he just get one of the replacement treadmill controllers, i got lucky and got the whole assembly that works from a treadmill for my knife grinder project

 

[dogdog]

Yesterday I bought a set of NIB treadmill motors off of Craigslist. They are 90V DC motors rated at 1.25 hp and 2.75 hp continuous duty. These would be perfect to power a Lathe or milling machine because they have high torque at low rpm and with the right controller allow you to dial in variable speed. But in order to operate them I need a PWM (pulse width modulation) DC speed control. I looked on Amazon and found what looked like some relatively inexpensive controllers. For example,

https://www.amazon.com/dp/B073Z7PB5G/?tag=atomicindus08-20

I don’t know yet if these motors are brushed or brushless. If they are brushed these should work, but reading through the comments section they do not seem to inspire all of the customers with their reliability.

Has anybody here found a speed control that works with these types of motors that won’t break the bank? I know that you can rip the electronics out of a free treadmill and finagle with them until they do the job. But after reading through many discussions where people did this it sounds like a major undertaking. I don’t want to go that route if I don’t have to. I’d rather just buy a brand new controller in a box that I can easily wire up and use. Any recommendations?

Maui

It's brushed, motor. that controller probably will not work alone by it self... you'll need a AC to DC power supply that does 90V or lower if you don't mind slower speed.... means you can run that motor from 12V to 90V DC... at 12V it's pretty weak and crappy though... but you can hook it up to a car battery just to see if it runs or what nots.




in other word.... that controller you linked it's just A PWM controller, for speed... missing is the DC power supply

here is the fine print from that link...

Using Instruction & Considerations:

A. The input of the DC motor speed regulator must be DC input, cannot be connected to AC input (e.g. Household AC 220V), otherwise, the motor speed regulator will be burnt.

 

[dogdog]

Thanks for the reply. I’ll check out ebay for one of those controllers. By the way, both of these motors have integral fans in place. I typically wouldn’t be running them anywhere near their maximum output. And if I did do that, it would only be for short durations.

For the 1.25 hp motor it looks like this controller from Harbor Freight should actually work:

https://www.harborfreight.com/router-speed-control-43060.html

I believe it uses PWM to control motor speeds. Thoughts?

THIS WILL NOT WORK FOR YOUR DC MOTOR... some have tried connecting a Bridge rectifier to that output and take a chance... it is NOT a PWM controller,, I think the proper term is phase fire controller... same thing as your electronic dimmer for AC... there is that German guy that explains these really well... if you want the technical aspect of these controllers, probably won't work for your DC motor....

Maybe google this

"kb electronics dc motor speed control"


or get a matching treadmill motor controller....

The most PITA part is finding the proper voltage power supply to drive it 100% and not the speed controller.... any PWM ones like the one you linked would work....

 

[paulsomlo]

in other word.... that controller you linked it's just A PWM controller, for speed... missing is the DC power supply

And that's why it's so cheap.

If you're going to use those motors to run machine tools, you will probably want to reverse them. You can use an SCR type controller, although it's not going to be as smooth or quiet as PWM. What you're looking for is not going to be cheap as new - you might try ebay for the controller as well.

By the way, what do you estimate the larger motor's weight at?

 

[dogdog]

Not sure if that is a larger motor, weight wise, I have 2 of those treadmill motors, one claims 2HP the other claims 2.5HP (this thing both are about 15-lb-ish without that counterweight belt pulley) @300ORPM -ish ....
and a 1/2 HP @1700-ish RPM real PM DC motor Leeson or what not brand (at 25-30 LB-ish)
and a 1 HP DC motor , all wires... ( this one is Heavy at aleast 40LBs or 50...0 I have to measure it....)

I think I asked a question about this, didn't really get a straight answer... few years back here.


I am not sure the HarborFreight SCR type controller are for DC motors even if you add an approiate bridge rectifier and smoothing capacitor... these treadmill motors are Permanent magnet DC motors.... Not universal motors.

 

[paulsomlo]

I have a 3/4 hp Leeson DC motor that I used on my lathe for a while - it weighs about 37 pounds. I'm skeptical about 2.75 hp treadmill motor.

 

[Maui]

The fellow I bought the motors from called me back and said he had another one. So I stopped by last night to take a look at it. This motor has the same armature voltage as the others, and is rated at 1 hp. The power supply and speed control are there with it too. So I may be able to use the components from this set-up to power the 1.25 hp motor (if they work). I paid $10.00 for this older motor set-up, so it is worth it in my opinion just to see how this can all be be put together if nothing else.

 

[Packard V8]

or get a matching treadmill motor controller.

For those of us who didn't get the EE degree, finding the compact, one-box controller seems a lot more difficult than it should be, given how many surplus treadmill motors there are available and how many want to drive small machines with same.

Anyway, because I couldn't find a readily available solution, I kept the treadmill power supply and dashboard. It doubles the size of the install and wouldn't be practical on a drill press, but sorta works on a lathe. Picture this mounted on the wall above the lathe:

jack vines

 

[tool_scrounge]

I have a 3/4 hp Leeson DC motor that I used on my lathe for a while - it weighs about 37 pounds. I'm skeptical about 2.75 hp treadmill motor.

Let's see...

The 2.75 HP motor is rated at 22A at 90 VDC. This is 1980W or 2.66 hp input power. They show it as a 2.75hp rated motor. So either:

1) the motor is 103% efficient and we have a perpetual motion machine.

2) the Chinese mfg lied and rounded up the input power requirements and listed that as the output horsepower. For all we know that it the locked rotor current.

I suspect 2 is the correct answer.