Stepper Motor Driver Fault Finding

Discussion in 'General Electronics Chat' started by Mad Professor, Oct 22, 2010.

  1. Mad Professor

    Thread Starter Active Member

    Apr 15, 2009
    133
    1
    Good Day All.

    I am trying to find out how to fix a problem with my TB6560AHQ based stepper motor driver board.

    I am sure most of you have seen these on eBay.
    [​IMG]
    They are made by: hyu68.com model number: HY-TB4DV-M.

    The unit works fine up to around 4.8KHz step pulses then the TB6560AHQ chip stops responding.

    Reading the datasheet for the TB6560AHQ say that it is good for up to 15Khz.

    Looking at the PCB and following the step input traces, this is what I have come up with for the step input schematic.
    [​IMG]
    All the resistors are very small SMD type, so quite hard to read the numbers, but I think I have got them all right.

    Lucky for me I have a USB PicoScope, so I could look at the step pulse from the PC and the step pulse to the TB6560AHQ chip.

    Here are a few scope screenshots.

    http://www.mad-professor.co.uk/Misc/TB6560 Step @ 300Hz.jpg

    http://www.mad-professor.co.uk/Misc/TB6560 Step @ 4.1KHz.jpg

    http://www.mad-professor.co.uk/Misc/TB6560 Step @ 5KHz.jpg

    TestPoint1 = Blue Scope Trace.
    TestPoint2 = Red Scope Trace.

    This is as far as I have got with testing.

    So if anyone could advise me to what the problem could be that would be grate.

    Thanks for your time.

    Best Regards.
     
    Last edited: Oct 22, 2010
  2. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,001
    1,512
    Go to CNCZone; http://www.cnczone.com/ There are several threads on just this problem and how it is solved. The manufacturer doesn't seem to care that people are having problems.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I'd replace the 1k resistor with a 22 Ohm resistor, and the 330k resistor with a 2.2k resistor for starters.

    Otherwise, you'll see that terribly slow fall time.

    If you replaced the 1k resistor with a piece of wire, you would probably wind up with "ringing" on the output signal.
     
  4. Mad Professor

    Thread Starter Active Member

    Apr 15, 2009
    133
    1
    SgtWookie: Thanks for your reply.

    I removed the 1K SMD Resistor, I did not have a resistor as low as 33R, the lowest I had in my parts box was 330R, so the 1K is now a 330R.

    Also removed the 330K SMD resistor and replaced it with the 2.2k as you said.

    I have only done a few tests, but I am report that the board is working much better.

    Thanks again.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You need to replace the 330R with a value between 20 Ohms and 47 Ohms. If you don't, you will likely still run into speed limits. It'll still be much better than it was before though.
     
  6. Mad Professor

    Thread Starter Active Member

    Apr 15, 2009
    133
    1
    I have now replaced the resistors with the values you said, 2K2 and 47R.

    But it now seems that I have gone from one extream to the other.

    I am now once again lossing steps no matter how fast or slow I try to run at.

    Looking at the scope traces show no missing pulses at the drive chip it's self.

    So I went back to reading the TB6560AHQ data sheet.

    On page 6 it says "Clock frequency (fCLK) = Max: 15kHz".
    On page 7 it says "Minimum clock pulse width (tW CLK) = Min: 30us".

    Now with this info I went back to the scope at looked at the High Pulse Width for to step coming from the PC and to the driver chip.

    From the PC, the step High Pulse Width avg is 4.5us, and a avg of 22us at the driver chip.

    So it seems that the pulse is now just a little to short to be always detected.

    Can you please advice.

    Best Regards.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    OK, in that case you should increase the resistors proportionately.

    Go back to 220 to 330 Ohms for the original 1k Ohm resistor.
    Replace what was originally 330k with 51k to 100k.

    With 220 Ohms and 51k Ohms, you should be able to get 6x the speed you were originally getting, but the pulse width may be too short.

    With 330 Ohms and 100k Ohms, you should be able to get 3x the speed you were originally getting.
     
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