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  1. #1
    i have two ballscrews, motors and drivers on my long axis, x and c. all of a sudden my c axis screw decides to turn the wrong way. if i move it posotive its fine and x and c both move posotive. if i move negative x axis moves negative and c moves posotive. i checked all the wiring it all seems fine and even changed to outputs on my bob to see if the bob is iffy. I just cant seem to find the cause as it has been running well for a couple of months now. any ideas anyone

  2. #2
    Sounds like the C-axis stepper driver direction input has stopped working as it's just stuck in one direction. If you can, measure the voltage at the direction pin of the C-axis stepper driver. If it doesn't change when you move the axis the other way then it's most likely a problem with the breakout board. If it does change then it looks like a problem with the driver. To check the driver try moving the input wires to a different driver and see if it works properly...

    Have you got any spare outputs on the breakout board? If so you can use one of those for the direction input to C instead and just redefine it in the ports/pins settings. Probably easiest to try this first.

  3. #3
    alredy tried moving the wires on the bob and its the same so i'll try measuring the voltage tomorrow and post my results tomorrow. cheers jonathan

  4. #4
    measured voltage across the direction pin on all of the drivers. 2.99v one direction, 0v in the other direction so it can't be that. all seems to have happened just after i greased the ballnuts. any other suggestions

  5. #5
    What stepper driver is it? 2.99V might not be enough? What's the equivalent voltage for one of the drivers that is working.

    For instance, if it's a M752 driver they have a 270 ohm resistor in series with the opto-isolator, which gives the correct current for those to switch on with 5V, not 3V ... 3V may not be sufficient.

    Just re-read your post and noticed you said all the drivers, so that's all irrelevant! I'll leave it just in case it helps someone else.

    It doesn't sound like a mechanical fault, as the motor isn't stalling it's just moving the wrong way? Have you tried putting a different driver on the C-axis? Swap Y and C for instance...if it works then you know it's not a mechanical fault and must be something wrong with the driver. I once had an optoisolator break on one of my drivers, connected it wrong, so I just soldered a new one in and it's fine.

  6. #6
    actually just came in from doing it. the driver obviously has problems. they are 452 drivers, all of them. any ideas what could be wrong with it.

  7. #7
    So just to be clear, the suspect driver works fine except for only going in one direction and the symptoms are the same if you feed it from the breakout board outputs that work with other drivers, and the motor/slaving works if you use a different driver for C?

    Is the driver heating up abnormally?

    Assuming the above is right, the driver is ignoring the direction input. That implies the opto-isolator inside is broken (so the PGA isn't getting the signal), or something else which will be more difficult to fix. If you want to post it to me I can have a look at it and hopefully fix it, just send me the return postage.

  8. #8
    just tring to get hold of bloke i bought them off to get replacement, refund seeing that they are less than 3 mnths ols. if not i will take you up on your offer. thanks a lot

  9. #9
    Quote Originally Posted by johngoodrich View Post
    actually just came in from doing it. the driver obviously has problems. they are 452 drivers, all of them. any ideas what could be wrong with it.
    If the voltage going to the direction is only 2.99V, it is unlikely a problemn with the driver but the signal is too low for the opto to change.
    What are you using to power the 5V on the breakout board?
    If you are using USB, dont and get yourself a 5V power supply.

  10. #10
    Quote Originally Posted by Gary View Post
    If the voltage going to the direction is only 2.99V, it is unlikely a problemn with the driver but the signal is too low for the opto to change.
    3V is borderline, more susceptible to interference, (driver manual says minimum 7mA, 2.99V gets about 4-5mA) yes, but as the same signal works with the other drivers it's less likely to be that. Still it's worth just applying 5V and 0V to the direction pin from a power supply, or directly from the USB +5V to check.
    Last edited by Jonathan; 11-12-2011 at 03:15 PM.

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