Heavy duty PWM DC motor controller help

Discussion in 'The Projects Forum' started by eggplantparrot, Mar 25, 2015.

  1. eggplantparrot

    Thread Starter Member

    Mar 25, 2015
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    hello, I have salvaged a big 2 HP treadmill motor and have built a disc sander with it, but the treadmill controller stopped working during testing, and now I need a motor controller preferably PWM.
    if anyone can help me create a list of components to driver such a big motor it would be greatly appreciated.
    the motor is rated for about 105V DC at 18A I have salvaged a bridge rectifier from the treadmill driver and it works in converting AC to DC. I need a simple circuit, variable speed to start the motor at low speed, and can handle at least 15 A since the motor would be started at low speed and slowly turned up, and would never be run at full throttle. I can solder with no problems, but I have no knowledge of specific electronics like PWM chips. a list of parts and a simple diagram would be very helpful.
     
  2. eggplantparrot

    Thread Starter Member

    Mar 25, 2015
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    would a simple 555 timer controller work with the output on a big MOSFET and the MOSFET connected between rectifier and motor?
     
  3. MaxHeadRoom

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  4. eggplantparrot

    Thread Starter Member

    Mar 25, 2015
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    thx for reply. I see that the 555 timer input voltage is 6VDC and the output is also 6VDC, but the voltage I measured from my rectifier is ~100VDC (I don't remember exact number) that means I would have to step it down for the timer right? also the ground on the MOSFET in the diagram is a common ground with the rest of the electronics, but as before, my MOSFET would be receiving ~100VDC and then sending it to motor, I wouldn't be able to ground it with the timer then?
     
  5. MaxHeadRoom

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    The low voltage common and high voltage DC common can be connected.
    The low voltage could be sourced from a Wall Wart supply etc.
    Max.
     
  6. eggplantparrot

    Thread Starter Member

    Mar 25, 2015
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  7. MaxHeadRoom

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    You might go with a IRL540 100v @ 28A.
    Max.
     
  8. eggplantparrot

    Thread Starter Member

    Mar 25, 2015
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    dam I was hoping to reuse the ones I have, they had heat sinks too, any reason I shouldn't use them? I mean they were from the treadmill controller anyways, rated for way more than I need at 200V and 33A? I mean I will get the ones u suggested but I would prefer to use whatever I already have since it was all free lol
     
  9. MaxHeadRoom

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    You would need to check the gate requirements and modify the LV supply voltage to suit.
    Max.
     
  10. eggplantparrot

    Thread Starter Member

    Mar 25, 2015
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    oh, you mean like the IRL540 VGS is 5V but on the IRFP250 its 20VGS? im guessing the output on a 555 is the same as the input so if I were to use a 5v wall wart to power the 555 then the output of the 555 would be 5v, and that would be good for the IRL540 and not high enough for IRFP?
     
  11. MaxHeadRoom

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    Yes, the maximum supply for a 555 is 15v IIRC so you could design for this value to use the IRFP250.
    Max.
     
  12. eggplantparrot

    Thread Starter Member

    Mar 25, 2015
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    Wait, so it's ok if I use lower voltage supply for the 555? I have a bunch of 12v charger warts that I can use, what would happen if I use those? Since the IRFP calls for 20V what would happen? To be honest I think I would probably use the one you suggested for simplicity
     
  13. MaxHeadRoom

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  14. eggplantparrot

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    Mar 25, 2015
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    2005-10a-004.gif 2005-10a-004 ver2.gif so if I were to use this circuit and the IRL540 how would I connect everything up? I modified the first pic to what I think I'd hook up, but I feel like im missing some connections, particularly with grounding them.
     
  15. MaxHeadRoom

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    The first would be more appropriate.
    Max.
     
  16. eggplantparrot

    Thread Starter Member

    Mar 25, 2015
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    but the first one doesn't use an outside source of power for the motor, its the same supply as the 555 input power
     
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Use whatever suitable separate supply that will work for the motor and a separate one for the 18v and just connect the commons.
    The cheap ones you buy on ebay use a single high voltage DC motor supply and a simple zener to supply the 555 circuit.
    Max.
     
  18. eggplantparrot

    Thread Starter Member

    Mar 25, 2015
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    then I connect the negative end from the rectifier with the ground of the pwm circuit?
     
  19. BillB3857

    Senior Member

    Feb 28, 2009
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    PLEASE - show an isolation transformer before your bridge. Otherwise, you violate the terms of service as well as create a hazardous condition.
     
  20. eggplantparrot

    Thread Starter Member

    Mar 25, 2015
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