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Speed Controller

Discussion in 'Grinders' started by John Noon, Sep 18, 2016.

  1. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    Hi Dan. Did you figure out problem #1 ? I don't recall reading about it. I found this solution:
    "add a normally Closed momentary Switch between the trim pot and the 12 volt supply
    A treadmill motor controller is designed to not turn on until there is user input
    You do not want a treadmill to start up full blast and possibly injure the person using it
    Breaking the voltage connection with a momentary switch seemed to do the trick"

    I get what they're doing but can't figure out where it goes, in terms of the wires. Not great with schematics but I can usually follow a drawing or sketch
     
  2. dancom

    dancom Dust Maker Best Shop Tool

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    Yes,

    A "one-shot" time delay relay that waits a second after powering up to close the circuit that sets the speed signal.
    [​IMG]

    This video shows exactly the solution I used:


    Dan
     
  3. bubba682

    bubba682 New Member

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  4. dancom

    dancom Dust Maker Best Shop Tool

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    I found the same. Basically doubled the cost when shipping was factored in.
     
  5. Tom Morgan

    Tom Morgan New Member

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    I am almost done converting my HF to variable speed using treadmill motor, MC60 controller & choke. I am a bit confused on where to put the DPDT switch to make it reversible. Do I put it on the AC line from the wall or on the DC line to the motor ?

    Also, is there a simple way to eliminate the soft start safety feature ?

    https://photos.app.goo.gl/gG58tiqyXSqZARJn6
     
  6. Tom Morgan

    Tom Morgan New Member

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    Thanks, I saw the post on the delay start relay (which I bought) but it's not very trivial. Seem to remember someone mentioning cutting a resistor on the MC60.

    Have fun, let's go Rams from a Jet fan in New Jersey
     
  7. dancom

    dancom Dust Maker Best Shop Tool

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    The DC to the motor gets reversed with the DPDT switch. The motor will be getting + and - to the red and black leads or - and +. I can sketch a picture of the switch wiring.

    [​IMG]
     
    Last edited: Feb 3, 2019
  8. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    I had the note on my phone. Who woulda thunk it?

    Anyway, you put a switch on the connection between the potentiometer and the "W" connection on the MC60. If memory serves it just needs a momentary off switch while you're starting it up. I will double check my notes and I know I have a schematic too, tomorrow.
     
  9. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    I should add here, I'm not trying to pass myself off as an electrical guru here. I think I only know this because I bothered Dan for days about it then, naturally, my brother scrapped the treadmill on me and I never got to try it.
     
  10. dancom

    dancom Dust Maker Best Shop Tool

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    If the wiper voltage is greater than zero at start up, the controller requires it to go to zero then positive to start the motor. When you leave the pot set to something other than zero and power up the board it waits for you to turn it back to zero. By opening the wiper wire momentarily on power up it defeats the soft start protection. A time delay is set to keep the wiper line open circuit (0 V) until after power up. I set mine to about 2 seconds. You have to use the normally open contact on the timer relay and adjust the trimmer pot to close that contact after a second or two.

    I used this as a reference.

     
  11. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    Cool. So, the momentary off switch should work as well then? It would have the same effect of resetting it to 0.

    I only ask because I sort of like the idea of having the button to start it. It would also be like having an old push putton start car (or a new push button start car, suppose). You would have a "power" switch and then a "start" button.
     
  12. Tom Morgan

    Tom Morgan New Member

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    I suppose then I need two switches. One "regular" for the AC line to turn on the system and a second one (DPDT) for the DC line for reversing.
     
  13. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    It seems like it, yeah. I had it completely wrong. I really should just let Dan handle these wiring questions.
     
  14. dancom

    dancom Dust Maker Best Shop Tool

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    Yes. If you grabbed the MC-60 and motor from a treadmill the power switch and circuit breaker from the treadmill can be used. You only need a single pole single throw switch for the main power, but it should be rated for at least 15 Amperes and 125 Volts. (regular household light switch can be used)

    Todd: The push button to hold off the speed control line would have to be latching otherwise you'd have to keep pressing the button the whole time you want the motor running. This is because releasing the button would cause the wiper line to go back to zero and that would stop the motor. That's why the one-shot time delay relay is handy.

    Dan
     
  15. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    So, not a mometary on, just a toggle on/off. Ugh... i hate this stuff. I'll just look at doing the delay. (once i get my hands on another mc60, that is)
     
  16. dancom

    dancom Dust Maker Best Shop Tool

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    I think it should be mentioned that not all DC motors like to be reversed. Specifically those ubiquitous ICON Health motors from Nordic Track brands.

    Firstly, there's the flywheel which is left hand threaded on to the motor shaft. Running the motor in reverse wants to loosen the flywheel. I tacked mine with a small weld to keep the flywheel from loosening. Some red Loctite should work too. Removing the flywheel amounts to taking the cooling system away, so I advise to keep the flywheel on.

    Secondly, the brushes may not like running in reverse after being run in forward their whole life. If you experience a lot of arcing, (look inside the ventilation holes around the back of the armature and you'll see some blue arcs going on in there) you may want to replace the brushes and wear them in evenly using both forward and reverse directions.

    See why I like AC induction motors? ;)

    Dan
     
  17. Tom Morgan

    Tom Morgan New Member

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    Interesting result tonight. I installed the single pole single throw (SPST) switch (on/off) on the main power line and the DPDT (Fwd/off/Rev) on the DC lines coming out of MC60 to the choke (black wire) and the motor.

    I started with both switches in the off position. I turned the SPST switch on and the DPDT to Fwd (or Rev), rotated the Pot to 0 then to a desired speed. Motor turns fine. I then turned the DPDT to off, then Rev (or Fwd). Motor turns fine in the opposite direction. If I turn the SPST switch to off then I need to rotate the Pot to 0 again BUT if I use the DPDT switch to turn off the motor (SPST still on) then turn the DPDT switch to Fwd (or Rev) the motor goes to the previously set speed right away. Now that I am writing this it sounds obvious.

    Is this a problem (keeping the MC60 powered for an extended time - like all day) ?

    I also found that using the choke minimizes the motor noises dramatically.
     
  18. dancom

    dancom Dust Maker Best Shop Tool

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    Yes, your results make sense. Leaving the MC-60 on all the time shouldn't be a problem as there will only be load on the SCRs when you are running the motor proper. (SCRs are where the bulk of the heat is generated.) If you think about it; a zillion people probably leave their treadmills powered on when they are not using them. The choke smoothes the sharp pulses that would be getting to the motor without it. Another recommended component to keep when salvaging.
     
  19. Tom Morgan

    Tom Morgan New Member

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  20. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    Do you have a 3D printer? This is one of those things they shine at. Or maybe some acrylic plastic you could glue together in a box? I think Dan's used these motors a fair bit. He'll likely have some better ideas.
     

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