DC motor speed controller for treadmill

Discussion in 'General Electronics Chat' started by Ayoob Elmasry, Oct 26, 2014.

  1. Ayoob Elmasry

    Thread Starter New Member

    Oct 26, 2014
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    Hello Friends,
    I have a treadmill that was bought many years ago. I do not have the pack of information that usually come with it when it is newly bought. Its motor controller went bust. I do not have circuit diagram for it. By doing some simple measurements, I found the driver transistor IRFP460A was blown up. I replaced it, the motor would work but there is no speed regulation, when the motor is heavily loaded this transistor will burn again. The speed feedback link is done using a reed magnetic relay., which I checked ok.
    I am hoping that one of you may have the circuit diagram of this controller to do proper repair of this pcb. I attached a photo of this controller unit.
    Kind Regards
    Ayoob
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    But I don't see any photos?
     
  3. Ayoob Elmasry

    Thread Starter New Member

    Oct 26, 2014
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    Sorry, I thought I uploaded the image.
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Check that the IRFP460A gets a full 10+ volts to the gate (you will need a scope, not just a volt meter since it is pulsing). Low gate voltage will cause the mosfet transistor to heat. Also, low current to the gate will cause the gate voltage to rise slowly (also causing heating).
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    If the FET is still ok and the reed-relay feedback is still ok then there's a fault elsewhere on the controller board.
    I don't like the look of that mounting hole just above fuse BXF2. Could a mounting bolt have shorted the heatsink/chassis to that heavy copper track?
     
  6. Ayoob Elmasry

    Thread Starter New Member

    Oct 26, 2014
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    The pcb is mounted above the allu. frame by about 1cm, so the mounting bolt head does not touch the pcb when fitted.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Are you trying to revive the T.M. itself or just want to run the motor separately?
    Max.
     
  8. Ayoob Elmasry

    Thread Starter New Member

    Oct 26, 2014
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    The motor runs ok if supplied with the appropriate power, I need to repair its controller to get full functionality of the treadmill. I am looking for the circuit diagram of that controller, if I do not find it then I shall try to draw it my self by following the tracks physically on the pcb, you can imagine how difficult and prone to mistakes that is to be .
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Also it appears to have the incline motor/actuator control on board also!
    Max.
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Here is a reverse engineered one that is similar.
    Max.
     
  11. Ayoob Elmasry

    Thread Starter New Member

    Oct 26, 2014
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    Yes, but it seems to work ok without problems.
     
  12. Ayoob Elmasry

    Thread Starter New Member

    Oct 26, 2014
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    Thanks Max. It seems the speed sensing is different where the problem could be. I shall try to find the similarities between your diagram and the pcb I have and hope to find the fault and let you know.
     
  13. IamJatinah

    Member

    Oct 22, 2014
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    Hi All, I am assuming this no speed control is with all connections plugged in. It also looks that this unit is built for 220vac, and/or 115vac with the 400v capacitors on the input. I see this loss of regulation often, can be caused by an open/faulty motor speed sense, roller sense, or pinched cables between upper consoles and lower control boards, bad CPU or peripheral IC. Chances are we have repaired these critters if it gets to worse case and you need to find repair for it. If you have an oscilloscope, isolate it via transformer as the primary motor drives on most controllers are H O T grounded(meaning output ground is NOT Motor rail Ground) and care must be taken to not cross grounding planes when working with powered controllers. The main motor power rails are normally supplied via a safety relay, and an off-line switching drive scheme ;o) If you check the Gate of the IRFP460, you will most likely not find any PWM signal present, or an incorrect pwm stretched beyond 50% duty cycle, but I am thinking that gate is floating high as RC allows and that motor would ramp up to hyper speed and fry things if left to. Message me if I can help further, good luck!
     
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