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  1. #31
    BobL is online now Member: Blue and white apron brigade
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    In 2018 I posted some HP output tests on a DC treadmill motor powered by a simple triac and rectifier.
    For anyone interested to see how they perform (ie not very well) have a look here.
    https://www.woodworkforums.com/f271/...ormance-223851

    It also describes what happens if you crank the V up too high.

  2. #32
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    Quote Originally Posted by BaronJ View Post
    Attempting to remove the armature from a permanent magnet motor will cause loss of magnetism.
    Interesting. Haven't heard of that before.

    Is that because of the armature cores acting as a "keeper"?

  3. #33
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    Quote Originally Posted by nigelpearson View Post
    Interesting. Haven't heard of that before.

    Is that because of the armature cores acting as a "keeper"?

    Interesting thought. I hadn't heard of this phenomena either but I've removed plenty of DC brushed motor armatures, done maintenance and returned them, so I wonder if I've been damaging them!

    Bob, thanks for the link to your tests, looks like quite a comprehensive write-up. I have only skimmed so far but will have a proper look later. I wonder if a triac chopper type system with some decent filtering might have better results than the cheap Chinese dimmer + Bridge Rec. I will have access to a decent workshop with good test equipment in just over a week so I might be able to follow through on some of these ideas soon, will see how we go.

    I couldn't find the open source controller I thought I had seen but there is an open source coding repository for some Arduino code designed for treadmill use but that might be the end of the story on that one. The more I think about this the more I think I will try a DIY PWM controller, maybe a simple version first. I probably won't publish every detail as I know that in the wrong hands electricity can have lethal consequences. But I might write little summaries of what I am up to.

    I have read in many places (Just general comments but no scientific explanation) that the PWM method allows full torque (or close to it) at all speeds. I assume this is something to do with the full voltage pulses of the PWM waveform. I hope that this is the case, some basic tests with 36V pure DC worth of Ryobi 1.5AH batteries showed pretty miserable subjective torque with the claimed 2HP motor. I didn't do proper torque tests, but it felt pretty weak when I slowed the flywheel with my hand.

  4. #34
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by Metalmachine View Post
    Bob, thanks for the link to your tests, looks like quite a comprehensive write-up. I have only skimmed so far but will have a proper look later. I wonder if a triac chopper type system with some decent filtering might have better results than the cheap Chinese dimmer + Bridge Rec.
    Most likely - I was just debunking the claims made on more than one you tube vids about how the cheap chinese dimmer and rectifier was all that was needed.

    I have read in many places (Just general comments but no scientific explanation) that the PWM method allows full torque (or close to it) at all speeds. I assume this is something to do with the full voltage pulses of the PWM waveform. I hope that this is the case, some basic tests with 36V pure DC worth of Ryobi 1.5AH batteries showed pretty miserable subjective torque with the claimed 2HP motor. I didn't do proper torque tests, but it felt pretty weak when I slowed the flywheel with my hand.
    I agree a proper PWM should make significant difference.

  5. #35
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    Quote Originally Posted by nigelpearson View Post
    Interesting. Haven't heard of that before.

    Is that because of the armature cores acting as a "keeper"?
    Hi Nigel, Guys,

    Basically yes ! Heat doesn't do them any good either, fortunately the motor rarely gets that hot, usually the armature adhesives and soldering melt first.

    This is because the heat that they produce can only escape via the motor shaft and the bearings. The difference in temperature between the armature and the case can get to be as much as 70 to 100 degrees C.
    Best Regards:
    Baron J.

  6. #36
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    Hi Guys,

    With regard to SCR/Triac plus rectifier configuration, part of the problem is the speed of the rectifier !

    A perfect rectifier switches fast enough to prevent anything other than one polarity through. In practice a small amount of reverse voltage gets through first before the rectifier becomes fully conducting. This creates a ripple voltage that is quite hard to remove. Large capacitors help but don't completely remove it. As the load increases the ripple gets worse.
    Best Regards:
    Baron J.

  7. #37
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    PWM will provide near full torque (in theory full, in practice you have losses and kinetics to overcome). There’s no real science behind it, you apply a pulse of DC at the motors rated voltage, it sucks full current which provides full torque.
    Making a 180V motor run on a couple of cordless tool batteries doesn’t prove much other than it rotates when DC is applied. Running it at 1/6th of its input voltage won’t produce any useable torque.

  8. #38
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    Ive been using these boards for last 25 odd years for DC motor control. Very versatile as just change load resistor to suit HP of dc motor. Very reliable with excellent speed control via voltage or 5K pot.
    https://www.kb-controls.com/product.sc?productId=3

  9. #39
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    I see a few different controller options on Aliexpress for running treadmill motors, I've link a couple for more knowledgeable people to look over and give their thoughts.

    https://www.aliexpress.com/item/1005...79882947%22%7D

    https://www.aliexpress.com/item/3273...rch-mainSearch

    https://www.aliexpress.com/item/4001...rch-mainSearch

    I would happily spend $70-$80 for a controller to make good use of the 180V DC motors I have laying around

  10. #40
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    I'm with Sparksy on this one - I have the same Kbic controller for my drill press motor - very happy with it, a local purchase on Ebay around $70 from a buyer saying it was from a project that never got off the ground - if was looking for a controller from Aliexpress I'd be going with this one


    https://www.aliexpress.com/item/3273...rch-mainSearch


    The only possible concern to me would be the input voltage of 220V, my mains sits on 242V - 243V and can at times hit 246V

  11. #41
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by familyguy View Post
    I'm with Sparksy on this one - I have the same Kbic controller for my drill press motor - very happy with it, a local purchase on Ebay around $70 from a buyer saying it was from a project that never got off the ground - if was looking for a controller from Aliexpress I'd be going with this one


    https://www.aliexpress.com/item/3273...rch-mainSearch


    The only possible concern to me would be the input voltage of 220V, my mains sits on 242V - 243V and can at times hit 246V
    I should buy one and slap it into my HP meter to see what it can do. Another one for the WIGRTI list.

  12. #42
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    Quote Originally Posted by familyguy View Post
    I'd be going with this one


    https://www.aliexpress.com/item/3273...rch-mainSearch


    The only possible concern to me would be the input voltage of 220V, my mains sits on 242V - 243V and can at times hit 246V
    I notice it doesn’t have the large capacitor/s found on some of the other boards, I have no idea if that matters at all?

    It would be nice to finally have a working, economical solution to the treadmill motor problem i.e.

    A common generic replacement PWM board, a potentiometer of correct value for the board and a wiring diagram.

    one thought I had would be to add an On/Off/On style switch between the board and motor which could be wired to reverse polarity at the flick of a switch, providing these motors are capable of running in reverse.

    from what I can tell there appears to be 4 main types of boards on AliExpress, a single capacitor board with either 2 or 3 wire speed sensor, and a twin capacitor board also with 2 or 3 wire speed sensor.

    I guess the speed sensor depends on the type of motor you have?

  13. #43
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    Hi Guys,

    Just a note to warn that all these controllers do not provide any isolation from the mains voltage supply ! That includes the controllers from inside the donor treadmill.

    For safety the motor must be earthed and the controller board placed in an insulated plastic or an earthed metal box.
    Best Regards:
    Baron J.

  14. #44
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    Quote Originally Posted by BaronJ View Post
    Hi Guys,

    Just a note to warn that all these controllers do not provide any isolation from the mains voltage supply ! That includes the controllers from inside the donor treadmill.

    For safety the motor must be earthed and the controller board placed in an insulated plastic or an earthed metal box.
    Absolutely true for the treadmill controllers.

    Haven't looked at the suggested controllers yet, but if they have a speed sensor and a feedback loop then that might indicate a pretty good solution, the absence of a capacitor on one of them is a bit weird.

    Interesting problem to have, this one.

  15. #45
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    Quote Originally Posted by Metalmachine View Post
    Absolutely true for the treadmill controllers.

    Haven't looked at the suggested controllers yet, but if they have a speed sensor and a feedback loop then that might indicate a pretty good solution, the absence of a capacitor on one of them is a bit weird.

    Interesting problem to have, this one.
    Hi Steve,

    I looked at that as well ! I suspect that it chops the incoming AC directly, no rectification. It would be the only way to get enough current to drive the motor.
    Best Regards:
    Baron J.

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