Another Treadmill Motor Speed Controller conversion thread

[Inferno]

I guess I overlooked when you mentioned you had the 2100.
Honestly, on my grinder I actually liked the MC-60 board better than the 2100. The MC-60 was strong as hell, no fluctuations at all. I put it on the band saw. If I come across another 60 I’ll probably ditch the 2100

Yeah, the MC-60 looks like the way to go. If I ever have one I will definitely play with it.
I'd buy one to play with but my methodology often releases magic smoke and it's so hard to get the magic smoke back inside the little doodads.

 

[Inferno]

Not much progress this weekend. I'm spent from a long workweek.

Still, I do have 3 different controller methods to try. This afternoon I mapped the original treadmill buttons so I can wire those up.
The other two methods will be pwm simulators.

Stay tuned.

 

[RJSakowski]

Those are some pretty tough requirements, especially if you want to do multiple motor controls. If I had not started down the path that I am on, I would probably go with a cheap low power PWM controller and add the proper MOSFET and power supply for driving a high power motor.
Here is an example:

Low Voltage DC 1.8V 3V 5V 6V 12V 2A Motor Speed Controller PWM 1803B

Only US$2.59, buy best low voltage dc 1.8v 3v 5v 6v 12v 2a motor speed controller pwm 1803b sale online store at wholesale price.

www.banggood.com

http://edge.rit.edu/edge/P17054/public/Final%20Documents/PWM%20Data%20Sheet.pdf

This does pretty much what my controller would do for little more than the cost of the pot. Instead of driving the motor directly, I would drive an external MOSFET .

Add a 200v 20 amp bridge, a filter capacitor, and a power MOSFET and you're almost home. Yes it does require some work to maker a complete package but if you are making a bunch of them, you would have the advantage of having the same controller design for all your motors instead of a hodge podge of different controllers.

Heck, I might just order a couple for myself just to play with them.

My idea of a (near) perfect PWM controller would have some feedback from an encoder to provide rock solid speed control regardless of load, over current (stall) protection, and variable acceleration/deceleration. This in addition to return to preset speed and reversing, all with low EMI.

That is a future project though. My immediate goal is to have a basic functional VSD for my d.c. lathe motor.

OK, an update. I ordered three of the above boards. The circuitry appears to be fairly simple; a single NE55 generating the pulse and a 9926A MOSFET for power out to the motor. For my purposes, I will use the controller to drive an optoisolator which will in turn control the gate of my power MOSFET.

Powered by a 12 volt supply, The output swings between 0 volts and 11 volts. Although the intent of the board is to directly power a small d.c. brush motor, the output can be used to control an exrenal circuit. The phase of the output can be inverted by using the B- and the M- terminals instead of the M+ (B+) and M- terminals. The switching frequency is 20 kHz and the signal is clean. I traced out the circuit and here it is.

 

[Janderso]

I finished laying out my circuit board for the VSD in SolidWorks this morning and imported it into SprutCAM. The toolpaths have been calculated and G-code posted. 4700 lines of G code! It will take about a 1/2 hr to run the program. From there it is a short step to populating the board and firing up the circuit.

You guys blow my mind.
I have a treadmill motor and the circuitry/panel in a box.
When I get around to building my belt grinder, I know who to call.

 

[Inferno]

Not too much progress. Busy at work and need to get a couple outdoor things done before the rains set in. Not to mention the smoke all around drains all energy pretty quick.

I did, however, purchase a pulley. I ended up getting a 17mm bore. It's too snug on the shaft but could be forced on. The pulley was painted so I'm going to have to remove the paint inside the bore. Will be easy once I put the chuck back on the lathe.
I'm going to have to consider how to keep the pulley from rotating. The pulley has a keyway but the motor shaft doesn't. maybe add a shaft keyway or two set screws, on recesses, on the motor shaft.

Decision, decisions...

 

[wa5cab]

The keyway with a set screw in the pulley is 1000% better than a set screw by itself. With only the set screw, if it loosens just a little, the shaft will spin inside the pulley, damaging the shaft.

 

[Inferno]

Cor

The keyway with a set screw in the pulley is 1000% better than a set screw by itself. With only the set screw, if it loosens just a little, the shaft will spin inside the pulley, damaging the shaft.

Correct. That's why I would add recesses on the shaft coinciding with the set screws. The shaft length on the motor isn't very long. It's not as long as the thickness of the pulley.

 

[wa5cab]

Well, that is certainly better than just a set screw

 

[Inferno]

Minor setback.

Stupidity.

I decided to cheat a little and remove a little on the inside bore of the pulley to get it to fit the shaft.
The hole of the pulley was not true to the outside of the pulley. This meant that the little bit I was removing was out of true to the original bore.

Long story short. I mucked the bore on the pulley and it is too big for the motor shaft. I can always bore it out for something else later. No worries.
Another is on the way but it won't be here any time soon.

On a different note, I used my variable power supply to test different, non-pulsed, voltages and I couldn't slow the shaft with my hand at even the lowest speed necessary to get it to turn. These treadmill motors are pretty strong even with low voltage.

 

[Inferno]

I finally received my replacement pulley. I removed the paint from the bore of the pulley and it wanted to go on the shaft of the treadmill motor. I used a little emery cloth on the motor shaft while spinning it with 20v. It didn't take much to get it dressed enough to get the pulley on. I worked on it for all of 20 seconds, I'd guess.

While doing all this, it became very apparent that just using different voltages would not provide torque at low speeds. I think I'm going to have to focus on PWM for speed control.