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DC motors and speed control

Discussion in 'Sensors and Actuators' started by Sardis, Jun 21, 2015.

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  1. Sardis

    Sardis

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    0
    Jun 21, 2015
    Hi I have 2 DC treadmill motors but only one (gold) has working electronics. The one without electronics (blue) will work so much better for my application because of the spindle and motor dimensions. I know both motors work. I will be using the motor on my metal lathe, so I can have variable speed.

    I would like to know if I can use the working electronics with the second (blue) motor?

    Let me know if I need more pictures. Sorry for my electronic ignorance.

    Thank you for your time!
    WP_20150621_001.jpg

    WP_20150621_002.jpg
    WP_20150621_005.jpg

    WP_20150621_010.jpg
     
  2. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    The first one is lower torque/current so it should be fine to use on the controller, most TM controllers are PWM and give fairly smooth operation down to low rpm.
    You need to remove the flywheel on the motor if you haven't already.
    They are both pretty close in amperage so either should work OK, fuse appropriately.
    M.
     
  3. Sardis

    Sardis

    11
    0
    Jun 21, 2015
    Okay, thanks! I do not know how to fuse it though. I just removed all the electronic from the treadmill, so I am essentially "repurposing" the treadmill.
    Where would I cut it in? Just a 15 amp fuse and housing? Thank you again!
     
  4. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    The other thing you need to know is the speed input, some are via PWM, some you can use a 5k-10k pot (analogue) for speed control.
    Others have a control input that requires that you take the control to zero first before acceleration.
    Is there a number on the motor control board?
    You would normally fuse the live AC conductor into the board.
    M.
     
  5. Sardis

    Sardis

    11
    0
    Jun 21, 2015
    I'm using the original treadmill control. It was an older treadmill so it has analog controls instead of digital.

    Most of the numbers and letters look like they label different terminals but I found these numbers PN 155781 and V 1506.

    Okay I should be able to fuse it successfully.

    Sorry for the long response time. I just got back from an outing.
     
  6. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    Is it the MC-60M controller mentioned in the pic?
    If so I have a reverse engineered print of it, it not PWM output however but SCR bridge.
    M.
     
  7. Sardis

    Sardis

    11
    0
    Jun 21, 2015
    I am not sure. What would I do with a "reverse engineered print"? Sorry, I have never heard of it. The controller that I am using is the one in the pic.

    I did forget to ask if I can reverse the blue motor? The brushes seem to be set at a 90 degree angle.

    I have gotten a on-off-on switch for this purpose, and was planning on wiring it in on the wires from the controller to the motor.

    WP_20150622_002.jpg
     
  8. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    Not really a good idea to switch the motor leads, if the speed pot is not the zero-first kind, then it is possible to but full power across the motor causing excess current.
    If the brushes are at 90° you can reverse it, most TM motors specify CW or CCW because of a threaded flywheel, Not because it is not electrically advisable.
    Controllers such as KB & Baldor have a pair of input terminals to allow resetting the drive if using the motor leads for reversal in order for the motor to come up through acceleration when reversing polarity.
    If using the just unidirection, I would suggest placing the switch in the AC input lead.
    M.
     
  9. Sardis

    Sardis

    11
    0
    Jun 21, 2015
    Oh okay the ac leads will be easier. Thanks for all your help!
     
  10. Sardis

    Sardis

    11
    0
    Jun 21, 2015
    Thanks for your help Minder!
    I got everything hooked up, and the variable speed works great!

    The only thing I cannot figure out is the reverse.

    I wired the DPDT switch in the AC input lead, but my lathe runs CCW regardless of the switch position.

    Any thoughts?
     
  11. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    The reversal has to be done on the motor leads, on the switch you show, the motor DC feed would go to the centre pair, the motor would go to an outer pair, then take a wire from one outer to the opposite outer terminal for each. (Criss-cross).
    Remember to take the speed pot to zero RPM before changing direction.
    upload_2015-7-20_13-32-14.png

    This shows the power and motor going to the opposite pair than I mentioned, but same thing.
    M.
     
  12. Sardis

    Sardis

    11
    0
    Jun 21, 2015
    Oh okay. Can the switch I pictured safely take the current on the DC leads? Thanks!
     
  13. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    Should be OK, as long as you switch with low/no current, i.e. motor stopped.
    M.
     
  14. Sardis

    Sardis

    11
    0
    Jun 21, 2015
    Alright, thanks!
     
  15. Alec_t

    Alec_t

    2,759
    734
    Jul 7, 2015
    I note that the controller markings in the pic indicate it is rated at 1000W, whereas the first motor is rated 90V 15A. Don't know what the power factor is for the motor, but if it approaches 1 then motor Watts = 90*15 = 1350. The controller may be working ok now, but could be under stress.
     
  16. Sardis

    Sardis

    11
    0
    Jun 21, 2015
    Is there a way for me to confirm your suspicions Alec? The gold motor with the white sticker above is the motor the controller initially ran.

    Is there a fool proof solution to this?

    Just to be 100% clear I have the blue motor hooked up right now NOT the gold.
    Thanks for the help!
     
  17. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    Your loading of the motor is the deciding factor as to wattage, also the rate of acceleration, the application you may be using the motor in is most likely very different from the TM, where the motor was fitted with a Heavy flywheel and was accelerated/decelerated very slowly.
    With controllers that have no adjustment as to current limit it is important to fuse them for protection and inadvertent OC.
    Ensure that you do not switch motor on at full control posn and Never reverse when in motion.
    M.
     
  18. Sardis

    Sardis

    11
    0
    Jun 21, 2015
    Okay I left the original fuse on. Should I add any? I will make sure to always accelerate slowly from 0, and only reverse the switch when it is off. Thanks!
     
  19. Alec_t

    Alec_t

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    734
    Jul 7, 2015
    I can't think of a non-destructive method :(.
     
  20. Minder

    Minder

    2,922
    615
    Apr 24, 2015
    You could also check the part # of the switching devices, if SCR bridge, the diodes and SCR's are usually Teccor (now Littlefuse) or close equivalent.
    Check the current rating.
    M.
     
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