Help with DC motor speed control?

[Doc Nickel]

I happened across a small, used treadmill the other day, and hauled it home for the cost of tossing it in the truck.

It turns on, but I can't get the motor going. There's a spot that looks like some magic smoke escaped from the heart-rate/speed-readout board, but that appears- key word- to be seperate from the actual motor speed controller.

Anyway, just from a casual glance at the speed controller, it looks like it might be as simple as stabbing in a pot in place of the heart-rate board. Lower left corner:



If that's the case, it looks like it might almost be easy to use this thing. Yank the motor, controller and transformer, plug in a pot and away we go. Maybe?

Here's the PN of the speed controller:



Another board that I'm not entirely sure what it does, but it's 'between' the heart-rate board and speed controller:



And for good measure, one of the motor data:



I haven't unplugged or unwired anything, other than pulling the plug off the heart-rate board so I could dismantle part of the stand. If it's as simple as connecting a pot to those two terminals, what value and capacity pot do I need?

And is this thing really a 1HP? The motor is only a bit bigger than a can of Fosters' beer- I have a hard time believing it's three times the power of the four-times-larger 1/3rd HP 110vac motors on either of my lathes...

And last- any guesses on the max RPM? Doesn't seem to say anywhere.

Doc.

[cebump]

Doc,
the three legs labled speed pot, should do the trick for a pot. I will look for you when i get to work in the am for a pot rating from a similar machine. I sell and service this stuff for a living. For what it is worth about the motor, they usually put out rated horsepower untill just after they are unboxed . the manufactured for weslo is our industries version of the harbor freight crap. Not bad if you are not going to use it much.

[Maker]

The typical pot value for one of these controllers is 5K.
Pretty much any power rating will work.
Just as easy to use as you surmise.

Alex

[wierdscience]

I got a few treadmill motors laying around,most I have are accurate hp wise,but the rpm is in the 4500-6000 range which expains the size.

[J Tiers]

That appears to be a reasonable controller, it has all the right adjustments, min& max speed, IR compensation, and current limit.

I notice that apparently they made some changes to the wire colors to obey US standards... no green power wire!

The power is indeed developed at high speed, whch is the major drawback of the motors. Slowing them more than a little will lose power, since they have little torque, and not much overload torque, especially with the current limit set right.

Probably 3:1 or 4:1 speed range in general, more if you do not need low speed torque. You will need some back-gear type arrangement of pulleys to get the 4000+ rpm down to the usual 1750 or 1150 rpm motor speed. Then you can talk about slowing from that point.

The "extra" board is to power the heart rate board and display etc, as well as possibly part of the controller "brains", looks like it may have a voltage regulator, as well as a relay that may start the motor.

A pot might well fix it. Be aware that the pot and wires are likely at line voltage unless there is an optocoupler on that control board.

[This message has been edited by J Tiers (edited 02-22-2006).]

[snowman]

there's an optocoupler.

U1 looks like.

What is the part # on U3?

5K is about right too for the pot.

still treat it like line voltage.

[CCWKen]

I've got one of those driving an 8" 4-jaw chuck in a vertical setup. Granted it doesn't have much punch on the low end but it sure spins that chunk of semi-steel just fine. I'd have to measure the pulleys but I set it up with about a 3:1 reduction.

Your PWM board looks more advanced than mine. I don't have all the fine adjustments. I used the original slide pot that was mounted in the console. The distance, calorie and heart rate monitor console was standalone.

[J Tiers]

Ah-yes, I finally found U1.

Only opto-couplers are typically available in white packages.

Toshiba makes a series of opto gate drivers, I want to say they are TLP-26 or a similar number....memory escapes me.

Good to 25kHz switching frequency for PWM. NOT good for 250 kHz, as a competitor of ours seems to have found out.........

That may well be one if the controller is a PWM type. Otherwise they have some that would be good for SCR or triac drives also.

[This message has been edited by J Tiers (edited 02-23-2006).]

[darryl]

Quite likely that you have to turn the pot to minimum speed before the thing will start the motor. I got tricked by this until I did that. I guess I was expecting the motor to start right up at the speed that was set, but no.
My pot was also 5k.

[Evan]

The opto on there is white. However all the ones I have in my stock are black. The controller I have is low volts DC to the pot, 10-12vdc I believe.