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Question PSU keeps shutting off during rapid motor movement

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by armpit, Jul 10, 2017.

  1. armpit

    armpit Active Member

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    I'm working on a wiper motor build. I previously had a 400w psu that worked perfect for a single motor but would cut off when I added a second motor and introduced rapid motor direction changes, so I upgraded to a 750w dell 2950 server PSU.

    Now, with the more powerful PSU, I am experiencing the PSU shutting off with just a single motor during moderate (pwm rate around 150, not even as high as the 400w could get) motor direction change. I've checked for any kind of shorts in my wiring, nothing.

    My assumption is this is some kind of current protection and the PSU is being overly sensitive. Anyone have any suggestions on what I can do?


    EDIT: With the SMC3 setup tool, I have found that square wave does not cause the shutoff, but triangle causes it almost immediately, as well as motion. Seems to have to do with it slightly overshooting and correcting then going RIGHT back to moving the original direction again.


    EDIT2: I wrote a quick arduino sketch that just flicks both motors back and forth every 1-50ms random at full power and it worked fine.... it may be an issue with something unrelated to the PSU. This test also blew my 10A fuse going to one motor, so this test asked more of the PSU than anything SMC3 was doing
    Still open to ideas!
    Last edited: Jul 10, 2017
  2. Radioproffi

    Radioproffi Active Member Gold Contributor

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    You should use diode between + and - on PSU for protect from Back EMF.
    upload_2017-7-10_8-41-26.png
    • Informative Informative x 3
  3. armpit

    armpit Active Member

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    Thanks for the reply Radio!

    Sorry if this is trivial, but can you give a little more info on what I should do? What kind of diode do I need, something rated for around 12v 30-40 amps, probably? (A google search term would help me out a lot here, looks like "1N4007" might be what I want?)
    And does this just splice in anywhere between the PSU and the monster moto power input, or should it go on a specific side of my first fuse?
    Last edited: Jul 10, 2017
  4. ferslash

    ferslash Active Member

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    i has to be the psu, do you have some way to test with a bigger one?
  5. Radioproffi

    Radioproffi Active Member Gold Contributor

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    1.5KE24A or 1.5KE12A
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  6. armpit

    armpit Active Member

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    I do have a duplicate 750w I could put in parallel but I do not think it's an issue of insufficient current, this is happening with just a single wiper motor which worked fine with a 400w previously. I'm thinking the new one's protect circuit is just more sensitive to this reverse-current issue. I'll circle back to this if the diode doesn't change the behavior.

    Perfect, thank you! I'll see if I can source these local and get some testing done this evening
  7. ferslash

    ferslash Active Member

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    just think that this issue is not commond.... if you would need a diode, we all would need it...

    - guess you have a problem with psu or... your wiper motors are not "un-grounded"... did you check grounding in your motors?

    fer
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  8. armpit

    armpit Active Member

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    Good point.... I might be going down a rabbit hole here, more info would probably be available if it were a common issue....

    I modified my wiper motor to ground isolate it, and in doing so bypassed a component that I read was an "overvoltage protector" (the one that has the red circle on it below). It's possible the removal of it is what is causing my issues. I haven't done this on the other motor but it was late last night when I was experiencing this problem and can't remember if I tested with it or not. I'm at work right now, I will try when I get home to see if this issue is happening on an unmodified motor. Once I have a result there, I will know which route to continue on.

    [​IMG]
  9. armpit

    armpit Active Member

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    I tested some more last night and found that the monster moto I'm using may have an internal short... The controller chip for motor1 overheats quickly.. when motor2 is the only motor operating; and motor1 output operates at about half the power of motor2, while overheating and slowing down more almost immediately. Continuing to investigate this later today.
  10. ferslash

    ferslash Active Member

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    there you go! :D
  11. armpit

    armpit Active Member

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    Update:
    There were two issues at play:
    The moto monster was overheating because one of my motors has an internal short in the coils and overheats after just a minute or two. New motor on order.
    The power supply was faulty which caused the shutoffs. I swapped power supplies out and not only are the motors more powerful, there are also no more shutoff issues in my testing so far.

    Thanks for the advice everyone!
    • Like Like x 1
  12. Jymä

    Jymä Member Gold Contributor

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    I've had issues with motors shutting down for a couple of years now. I thought PSU was the problem because power led always turned off. But now I have upgraded PSUs and it still happens, though this time PSU power led stays on and they keep outputting voltage. I think my clone Moto Monsters have their limits in the same ballpark as previous PSUs. I had 2X HP DPS-600PB (47A) and now I have 2x HP DPS-800GB A (82A). I guess I try to tweak the settings a bit more and if it doesn't help enough then buy Sabertooth 2x60A...
  13. evolaco

    evolaco Member

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    It is necessary to use a battery in parallel or a large capacitors, I use a battery of 7ah and my dps800gb does not turn off, the cables must be very short towards the psu and with a sufficient section, I put a very long cord to put a stop of Emergency that also stops the battery and the source stops, the battery must be very close to the PSU
  14. Remishka

    Remishka Member

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    Aha i'm not the only one to get this problem, on mine it occurs at PWM 90( wich is a cool setting for me, it's the maximum I may use before the PSU shuts down for a second.
    I use parallel IBT2's and a 1000W PSU to drive two 250w (ungrounded) motors, it does that on both motors, might try the diode trick ( thanks for this radioproffi ), as i don't have any spare for the power supply..
  15. evolaco

    evolaco Member

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    uses a battery in parallel to the psu
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  16. BrassEm

    BrassEm G-Seat + SFX100 Builder

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    What type of battery would you recommend? My 12.02VDC rail is going to 14VDC with only one wiper motor on reversal on my test rig, and I have 4 motors to run. (Measured 1 Amp rms at full speed on the test motor.)
  17. Remishka

    Remishka Member

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    Thanks for the tip Evolaco I did consider this but i'm not too confident about those battery because the sit is close to where I sleep, also big capacitors yes but if I cut the power they are still dangerous untill discharged ? Or is there a way to discharge them safely when i turn power off ?.
  18. evolaco

    evolaco Member

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    I use a battery of uninterruptible power supply (UPS) and it is perfect, it is safe and with 7A it is more than enough, peak they give much more, even she alone can move the motion, when you stop using the simulator the current and there is no danger in it, cables of 4mm or more and as short as possible
    • Informative Informative x 1
  19. Remishka

    Remishka Member

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    Thanks, looks perfect, gonna get one !.
  20. BrassEm

    BrassEm G-Seat + SFX100 Builder

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    Thank you, will post how it goes.
    • Like Like x 1