What Does That Treadmill Motor Coil Do?

What Does That Treadmill Motor Coil Do?


Hi this is Barry. Welcome back to the workshop. In this video I’m going to answer some questions
that came up from my treadmill variable speed motor conversion video. Specifically, they had to do with this component
right here. It looks like a transformer, but what is it,
really? And do I need it? And can you even tell the difference? So stay tuned, I have some answers for you. Ok, so here is the setup that I had at the
end of my conversion video. I have the speed controller, with the coil
in the circuit, the switch, and the motor. And then I have my 10K potentiometer that
I am using to adjust the speed. Now the question is about this component here. This is a coil, or an inductor. It has two wires going through it. If it was a transformer, it would have at
least four…it would have more like two pairs. Because it has only two wires, I know that
it’s an inductor or a “choke” or sometimes called a “coil”. Those are all three names for the same thing. In theory, it should smooth out the operation
of the motor. But let’s run some tests and see if that’s
actually true. So I’m going to do some experiments. I’m going to have the motor go
from stopped to a slow speed, stopped to a medium speed,
slow speed to a medium speed, medium speed to a slow speed,
and then I’ll put a load on it by adding some friction. And what we will do is listen to all those
scenarios and see if we can tell the difference. So I’m going to go ahead and turn it on. And then I’m going to use the potentiometer,
and I’m going to rotate it slowly until the motor just starts. Let’s see how that sounds. I head a little surge, and then it settled
right in at that slow speed. I’m going to go to a medium speed and see
how quickly it finds that medium speed. It went from slow to medium and settled right
in. I’m going to let it spin down. There’s a lot of inertia in that flywheel. Let it find that new speed. And again, one little surge and it settled
right in. I’m going to do one more experiment where
I go from stopped to a medium speed. I’m going to put my hand on here to simulate
a load. OK. In all those experiments, there was a little
surge as it sought to reacquire that speed, but it settled in on that new speed pretty
quickly, with one little bit of effort. Now I’m going to turn the power off and then
I’m going to disconnect the inductor. Fortunately, this has terminals here. So this is out of the circuit. I’m going to take the black wire from the
motor and plug it directly into the speed controller. Turn the power on and we’ll repeat those experiments. Start by going to a slow speed… I don’t know if you heard that, but it had
a harder start, then it backed off, then it surged again. It had a couple of oscillations. Let’s try it again to see if we can hear it… So there are two or three oscillations before
it settled on that slow speed. I’m going to take it up to the medium speed. And again, I can hear it pulsing and backing off… I’m going to turn it back to a slower speed
and let it find that new speed, as the fly wheel spins down. There are maybe two oscillations there before
it went from the medium speed to the slow speed. I’m going to put it back on the medium speed
and do a little load. Let it settle down. I hope you heard that. I hear about two to three oscillations each
time as it settles in on the new speed. It’s definitely not as smooth as it is WITH
the inductor in the circuit. So hopefully that answers the questions. What is it? It’s not a transformer, but an inductor. Does it do anything? Can you tell the difference? YES. It smooths out the behavior of the motor. Do you need it? Well, maybe… maybe not. It’s up to you if you want that added benefit. I’m going to leave it in place because I want
my motor to turn and transition a little more smoothly. But I don’t know any reason why you must run
with it. But you definitely can tell the difference. So I hope you enjoyed this video. I hope it helps answer some of those PRESSING QUESTIONS about variable speed treadmill motors like,
“What is that transformer-looking thing?” And “Can I even tell what it does?” And “Do I even need it?” Well, it’s an inductor or “choke” and you
CAN tell the difference. It smooths out the motor,
And do you need it? Well, that’s up to you. If you have any questions or comments, please
put those in the section below. And please subscribe to the channel if you
haven’t already done so. I really appreciate it. If you like the video, give it a “thumbs up”. If you don’t like the video, give it a “thumbs
down”. In any case, I appreciate you watching. Take care! I’ll see you next time.

27 Replies to “What Does That Treadmill Motor Coil Do?”

  1. Good info.. I've been wondering about this.
    Can you take an up close shot of the tag on the inductor choke? Mine has no info on it and I need to replace it.

    Thanks for the video….

  2. I believe you're correct.  The coil is functioning as an inductor to thwart both the inrush current on startup (it's fairly drastic) and it also spreads out (softens) the speed changes because in an inductive circuit, current always lags voltage changes.  Usually you see capacitors in parallel to inductive motors like that both to equalize the reactance and to deliver maximum current at startup and quick response to speed changes, and that's totally an option here if your needs warrant it.  In a treadmill, however, you want the opposite to make the changes as soft as possible so it doesn't throw the user off (despite how funny that appears).  Running without either a capacitor OR inductor to condition the load will always shorten the life of the motor due to heat loss during longer transitions from stall to run and speed changes.

    This would be super fun to demonstrate on an o-scope.  You'd have to use current clamps, or an equivalent current to voltage converter to sample it since an o-scope shows voltage in the frequency domain but that's totally doable.

  3. Could you hash together a wiring diagram for your assembly?
    I believe I have the exact collection of parts but was short on time taking the treadmill apart.
    Some of my wiring is much less plug and play.

  4. Great video. I am building a belt grinder and could not decide if I should buy a controller and bridge rectifier plus a Potentiometer or salvage the treadmill controller and just add the pot. Is a 10 k Pot sufficient to provide a proper range of speed control.

  5. hi
    sir I am having problem with my theardmill when I on the machine all electricity go off
    from curcuit bracker
    there is one speed sensor in side the motor with 2 blue wires
    u can call it speed sensor or overload cut out sensor
    when I remove the blue wire electricity doesn't cut off
    can u guide me plz where is the problem .
    and how to check speed sensor or overload cut out sensor

  6. i have the same motor but it's 90V, i was wondering how it's possible to go down 120v to 90V without a transformer in that electronic board, i'm going to buy one because i was trying to do an analog H bridge but i have to many problems with that circuit

  7. Barry, just discovered your site, its great, but where are you now, please come back, there must be a lot of people missing your great videos.
    regards Colin. UK.

  8. I've just dismantled two different make and model treadmills and neither of them had the inductor coil on the control board. Do you think this may have been eliminated in some treadmills?

  9. Didn't find one of those inductor coils in the treadmill I took apart, but did find a small yellow one on a separate circuit board that was mounted next to the main board. If you're familiar with it, do you know if that little yellow inductor/transformer can be used as the choke to mellow out the motor just like the inductor you're using?
    Cheers

  10. I think the ramping up of speed has more to do with the controller ramping the voltage so you don't have a sudden full speed on the treadmill…not a pretty picture! I think it's called a "soft start",. which can be a problem with using the controller from the treadmill.

  11. Thanks Barry just what I was looking for. I have pulled apart several treadmills I got for free and 1 had a choke like yours and the other 2 had emi filters housed in a metal box. To be safer / safer? I decided to use the emi filter as they run both active and neutral through the unit as well as the metal box being earthed. Also ran the ferrite coil in the line to the motor. Some of the other benefits I have heard of but can’t prove is that the filter can help block a spike from blowing the motor controller and the dc motor itself will last longer as the voltage it receives is smoother. I think your demonstration helped show how much smoother the motor was. Cheers and thanks, Stuart. 🇦🇺

  12. thank you for doing this video….i took this out of my build…it does not seem as wacky sounding as yours. is that a mc-60 controller?

  13. great video. was it ac power supply you used? where is the part that converts the ac to dc voltage? seen no rectifier!thanks

  14. Just as a capacitor will smooth out voltage ripple on a voltage source from a power supply, this inductor smooths out the CURRENT. At each make/break of the commutator, the inductors magnetic field collapses, and self induces a current to smooth out the CURRENT ripple. This allows the power supply to appear as a current source, as opposed to a voltage source. The collapsing magnetic field in the inductor at the break of the commutator on the motor, provides additional current from the inductor for the next make of the commutator.

  15. Awesome video. I need some help though. I have an MC-60 treadmill speed
    controller. I'm trying to eliminate the soft start and stop. Putting a
    switch from the board (red wire to the motor) gives me what I'm looking
    for but I am concerned about whether the board needs the load from the
    motor. Is it safe for the speed controller to run with a switch on the
    motor lead?

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