DC treadmill motor with MC60 controll cuts in and out

Thread Starter

Garrett Goodman

Joined Jul 18, 2015
10
the motor will start up fine and run about 1/4 up the potentiometer then it begins to cut in and out. the SCR TRIG led flashes in sequence with the motor cutting in and out. If I turn the potentiometer up well past this point the motor spins up and runs smoothly. turn it back down and the motor cuts in and out untill rpm is adjust back down. I can post a video of the motor in running if that would help.

I tried replacing the potentiometer, all my connections, and looking for anything that may have shorted but I see nothing visually wrong. (great with engines, carbs, my hands not so much electronics. does this board have a mid range circut like a carburetor does?

All this came out of a used treadmill it worked fine untill i shortened the potentiometer wires and bolted the setup to a table.

Thanks for the help.
 

Alec_t

Joined Sep 17, 2013
11,755
Sounds like the pot has a worn/damaged spot on its track. Was the replacement pot a brand new one, or just a salvaged one?
 

MaxHeadRoom

Joined Jul 18, 2013
21,637
Monitor what is happening on the 12vdc rail, this is where the supply comes from for the trigger LED which is in series with the Opto signal, also try it with a different load such as a lamp etc, to see if this is the cause.
Max.
 

ebeowulf17

Joined Aug 12, 2014
3,274
This may be a little out there but, if this circuit is based on SCR speed control, then wouldn't the low and high ranges be switching AC at much lower voltages, while the mid range would be switching at the highest voltages?

In that case, electrical noise generated by the switching would be at its worst in the middle speed ranges. The op mentioned changing wires and bolting the setup to a table. Could a change in shielding or grounding be making this circuit more vulnerable to its own switching noise?
 

Thread Starter

Garrett Goodman

Joined Jul 18, 2015
10
replacement pot was a brand new one from radio shack. (10kohm linear taper potentiometer) with the motor and controller wired up the same thing happes just more frequently. If I leave the rpm's low and put a load on the motor is will cut out then compensate for the load then remove the load on the motor it cuts out then return to normal. The votage reading on at the terminal where the pots connects under lead follows a nice linear path.
Ive got this schematic pulled up. help me figure out where to put the meter and i will.

http://forum.allaboutcircuits.com/t...0-treadmill-motor-controller-schematic.77083/
 

Thread Starter

Garrett Goodman

Joined Jul 18, 2015
10
If anyone is actually reading this now and would be willing to talk to me, please pm me.

Mods Edit: Please do not left phone num or Email, thank you.
 

MaxHeadRoom

Joined Jul 18, 2013
21,637
Try it with a lamp to see if it load/motor related.
BTW the first circuit in the link #6 I believe shows an error, there would never be a 1K 1W resistor in series with the motor, the .01Ω, yes, but 1K would cause problems in motor current.
Max.
 

Thread Starter

Garrett Goodman

Joined Jul 18, 2015
10
When I hook a lamp up to the controller it runs the lamp the full range of the potentiometer with out cutting out. So this would point to a problem with the motor right?
 

MaxHeadRoom

Joined Jul 18, 2013
21,637
So this would point to a problem with the motor right?
Not necessarily, it could be due to sudden motor current, I could not quite see from the video how it reacted when the LED flickers, do you hear anything?
The .01Ω resistor I would expect to be a current monitor but i see nothing attached to it in the DWG's.
Max.
 

Thread Starter

Garrett Goodman

Joined Jul 18, 2015
10
I have a hunch tat when I tooled the shaft perhaps some metal made it into the motor and is causing the issue I am going to go over that. It makes a pulsing sound I will try to get a better video as soon as I tear down and clean the motor.
 

Thread Starter

Garrett Goodman

Joined Jul 18, 2015
10
front bearing is verry gritty sounding so while I am not certain that is the cause of my problem it is not heaping the winding look good and show not wear or burnt smell. Not that I can see, I have a Red Black, two blue wires(supposedly a thermal switch) Hot, ground, line in to thermal switch and line out to board.
 

Thread Starter

Garrett Goodman

Joined Jul 18, 2015
10
Cleaned it and still same problem the 12v side seems to be working on the controller output side the voltage jumps around once past about 110v. once above 150V is stays consittent.110-140v and the reads seems to jump around. the little white box next to the terminals labelled "royal 962 5w
 
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