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  1. #1
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    Default Treadmill motor for belt grinder- will this board work?

    G'day guys, I've downloaded the planes for the Jeremy Schmidt belt grinder that has been on my project list for a while. I've scored a working commercial treadmill with a 3hp motor that I think should be good for the grinder. I'm hoping someone can tell me from these photos whether or not this treadmill control board will be able to be used with a potentiometer to run the grinder? Electronics is far from my strong suit but there are plenty of youtube vids on doing this, apparently some boards work and others don't. Which variety do I have?

    Motor:
    Treadmill motor plate.jpg

    Boards (I assume the small one runs the linear actuator as that's where the wires go)
    Treadmill circuit boards.jpg
    Treadmill circuit boards 2.jpg

    Unfortunately the rotation of the motor means that I'll have to mount it on the 'wrong' side of the grinder to avoid the pulley unscrewing itself, unless anyone can suggest a failure-proof method of securing the threaded pulley against three horses of unscrewing power?

  2. #2
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    Alexandra Vic
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    Default

    Difficult to tell from the photos provided. Do you have the control panel and cabling to connect to speed control. If so, and that uses a physical pot to control speed, its probable that the system could be rigged to use a pot. On the other hand, if the control panel has a set of up/down buttons or a rotary encoder to control speed, it's fairly unlikely to be able to easily addapt to pot control.
    I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.

  3. #3
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    Hi Pete,

    Treadmill circuit boards 2.jpg

    Can you do a close up picture of the part circled in red !

    The small board can be removed and discarded. As you say it only drives the lift motor.

    Now the motor has "Clockwise" rotation marked on it. If the brushes have square ends, not wedge shaped, then the motor will run in reverse by simply reversing power polarity. If the brushes are not square ends then the motor has reaction type brush gear and cannot be safely reversed.

    A lot of these treadmills have digital controllers and don't use a potentiometer to control the speed, but with a bit of circuitry can be adapted.
    Best Regards:
    Baron J.

  4. #4
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    If your board isn't suitable, you could try using an SCR controller feeding into a bridge rectifier.
    This YouTuber is Australian, so his setup is for nominal 240V.

    https://www.youtube.com/watch?v=ECKKXco3Oks

    Findlay

  5. #5
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    Default

    Quote Originally Posted by BaronJ View Post
    Hi Pete,

    Treadmill circuit boards 2.jpg

    Can you do a close up picture of the part circled in red !

    The small board can be removed and discarded. As you say it only drives the lift motor.

    Now the motor has "Clockwise" rotation marked on it. If the brushes have square ends, not wedge shaped, then the motor will run in reverse by simply reversing power polarity. If the brushes are not square ends then the motor has reaction type brush gear and cannot be safely reversed.

    A lot of these treadmills have digital controllers and don't use a potentiometer to control the speed, but with a bit of circuitry can be adapted.
    Ok, thanks for that, I'll take the cover off again tomorrow and get some more photos. The treadmill has digital push-button speed control but I'm hoping it can be adapted to a pot as you say; I've watched several online videos of this being done but don't have the skills to determine whether or not this one is suitable. Also I wasn't aware about the 'reaction type' brushes, probably safest for me to just run it in the designed direction and mount it on the right of the grinder instead of the left.

  6. #6
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    Quote Originally Posted by MacPuddock View Post
    If your board isn't suitable, you could try using an SCR controller feeding into a bridge rectifier.
    This YouTuber is Australian, so his setup is for nominal 240V.

    https://www.youtube.com/watch?v=ECKKXco3Oks

    Findlay

    Thanks for reminding me, I actually have a couple of those SCR motor controllers and bridge rectifiers sitting on the shelf from a failed treadmill motor conversion on another machine last year; a mate gave me a treadmill with an unspecified problem and I was going to run my furnace blower with it but all the smoke came out of the motor; I'm thinking now in view of Baron J's information above, that I might have been running a motor in reverse that was not supposed to. I thought at the time that the motor was already dead but maybe my ignorance killed it. Would be a crying shame to do the same with this 3hp motor that I know for a fact is working perfectly. After that experience I lost confidence in the SCR setup but maybe I should give it another crack?

  7. #7
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    Default

    I'll be really interested to see how you go with the build. Its on my list too, and jumped a few notches when I offloaded my old belt grinder recently.

    In regards to retaining the pulley if running in the wrong direction, just use a scotch key to lock it.
    Fit the pulley, drill and tap a hole for an appropriate bolt or grub screw so the center of the hole is on the outer edge of the shaft giving you half a hole in the pulley, and half in the shaft.
    Fit the grub screw and its locked.
    I think a proper scotch key is just a dowel pin, but the grub screw is better in this situation as you can easily remove it to unscrew the pulley if you ever needed to. A dowel pin - not so easy to remove....

    Steve

  8. #8
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    One wonders if controlling the speed of treadmill motors is as simple as a SCR speed controller with only 3 or 4 components - why do treadmills have controllers with complex looking boards ?

    I suspect that a simple SCR controller has no form of feedback from the motor and will not compensate for loads so it is a limitation you need to be aware of, treadmill controllers probably use back emf generated by the motor to adjust motor power to try and maintain a constant speed.

  9. #9
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    Quote Originally Posted by familyguy View Post
    One wonders if controlling the speed of treadmill motors is as simple as a SCR speed controller with only 3 or 4 components - why do treadmills have controllers with complex looking boards ?

    I suspect that a simple SCR controller has no form of feedback from the motor and will not compensate for loads so it is a limitation you need to be aware of, treadmill controllers probably use back emf generated by the motor to adjust motor power to try and maintain a constant speed.

    The treadmill has what appears to be a hall sensor and magnet on the driven pulley, i.e. the shaft that drives the running belt. It would be very nice to be able to incorporate that into the grinder to obtain load compensation. One of the reasons I'd like to use the treadmill's own control circuitry if possible. Off to take that photo now...

  10. #10
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    Here's the photo of the harness connector with the pin-out ID's hopefully visible. The small connector on the right goes direct to the hall sensor.
    treadmill board- harness plug.jpg

  11. #11
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    I had always assumed that the hall sensor and magnet was for the Km/hr display - it's entirely possible that it is for some sort of speed control as well.
    I fitted a DC treadmill motor to my drill press and found that the original controller needed the signal from the hall sensor to keep going at all - I assumed it was some sort of safety feature, treadmill stops turning - cut the power to the motor.
    I managed to pickup a US made Kbic controller from Ebay, it works very well. In fitting the motor I used the existing treadmill motor pulley so the only way to vary the speed is with the controller, I can dial in 200 rpm(I fitted a tacho as well), when the drill starts to cut the speed momentarily drops and then instantly picks up to just under 200rpm.

  12. #12
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    Hi Pete, guys,

    Quote Originally Posted by Pete O View Post
    Here's the photo of the harness connector with the pin-out ID's hopefully visible. The small connector on the right goes direct to the hall sensor.
    treadmill board- harness plug.jpg

    I've edited your picture to try and get a better view of the legends on it.
    From top to bottom. Not sure what the "F" stands for,

    "F-DC +" I think these two are the 5 volts DC power feed to the control panel.
    "F-DC -"

    "S-UP" Speed up. These two almost certainly use a 5 volt pulse to step the speed counter.
    "S-DOWN" Speed down.

    "STOP" This may be a series of pulses that disappear when stop is wanted, or just a single voltage or pulse used to stop the motor.

    "5V +" Again this might be fed up to the control panel or down from it, to check that the control panel is connected.

    "RPM" Speed feedback. NOTE that it is printed twice. It could be an error, or just to indicate that the socket is for speed sensing.

    "F-DC -" These two are probably Hall power and feedback.
    "F5V +"

    Generally the treadmill will not run unless certain connections are made. But if the control panel is removed you will need to provide the pulses for the up/down speed. The only other up/down would be the lift motor and that can be disconnected without causing the treadmill not to run.

    Somewhere I have a circuit for a pulser that will provide the pulses needed for the control board and some notes on using a pot to control the speed.

    I couldn't find my notes but did find the original source.

    https://el34world.com/Misc/Cnc/TreadmillMotor1.htm
    Best Regards:
    Baron J.

  13. #13
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    Thanks again for looking this over. The connector block in the photo is actually two separate connectors; the bottom part with three pins goes direct to the hall sensor so yes 5v+ and 5v- and then the RPM hall signal, the RPM pin on the larger block is bridged directly to the RPM input from the hall sensor so sends the hall sensor signal straight up to the control panel. What happens from there is a great darkness to me. I'll have a look at the link this evening some time.
    I tried running the motor with the SCR controller and bridge rectifier; it ran but made noises that i did not like at all; when adjusting speed upwards with the potentiometer the motor sounds like it is arcing internally and when running at a steady speed there is a humming / groaning sound that is to my ear just NQR. I'm not confident running this good motor with the cheap eBay option unfortunately. If I can somehow give the speed commands to the existing control board it will b happy days.

  14. #14
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    Hi Pete,

    I couldn't tell from the picture that there were three pins in the Hall sensor socket. There seem to be a number of PWM controllers and they all seem to have similar connectors on the PCB's.

    I did have some pictures but they seem to have disappeared !
    Best Regards:
    Baron J.

  15. #15
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    A little more internet trawling based on the link in Baron J's post above, thank you...the control board that seems to be the holy grail is the MC60, it can be used by adding a speed pot at the board and bob's your uncle; the MC2100 can be used with the addition of a pulse generator (way over my head) and this treadmill has DCMD75 in large font right in the middle of the board so I guess that's what it is. I can't find any info on how it might be used in my application. I'm starting to think maybe I should sell the treadmill and buy a motor and VFD.
    There seem to be two types of people; one type looks at a perfectly functional treadmill and sees an opportunity to improve their fitness. The other type looks at a perfectly functioning treadmill and sees a power unit for a machine tool. I would guess most of us here are the second type.

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