DC treadmill motor with MC60 controll cuts in and out

Discussion in 'The Projects Forum' started by Garrett Goodman, Jul 18, 2015.

  1. Garrett Goodman

    Thread Starter New Member

    Jul 18, 2015
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    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.
     
  2. Garrett Goodman

    Thread Starter New Member

    Jul 18, 2015
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  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    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?
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    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.
     
  5. ebeowulf17

    Active Member

    Aug 12, 2014
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    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?
    [​IMG]
    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?
     
  6. Garrett Goodman

    Thread Starter New Member

    Jul 18, 2015
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    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/
     
  7. Garrett Goodman

    Thread Starter New Member

    Jul 18, 2015
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    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.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    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.
     
  9. Garrett Goodman

    Thread Starter New Member

    Jul 18, 2015
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    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?
     
  10. ebeowulf17

    Active Member

    Aug 12, 2014
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    Or possibly the circuit itself being overly sensitive to inrush current or back emf from the motor?
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    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.
     
  12. Garrett Goodman

    Thread Starter New Member

    Jul 18, 2015
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    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.
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That is also a symptom of going into current limit intermittently.
    There is no rpm feedback device on this motor, right?
    Max.
     
  14. Garrett Goodman

    Thread Starter New Member

    Jul 18, 2015
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    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.
     
  15. Garrett Goodman

    Thread Starter New Member

    Jul 18, 2015
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    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
     
  16. Garrett Goodman

    Thread Starter New Member

    Jul 18, 2015
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    "Royol 962 5w5k6j" is getting exstreemly hot.
     
  17. Garrett Goodman

    Thread Starter New Member

    Jul 18, 2015
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    ok well I guess I will wait till i get my wheel finished and see if gets to a high enough rpm for me to use before it cuts out.
     
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