Tinyg failure

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  • November 30, 2014 at 12:19 am #7051
    gwandad
    Member

    I have had small success with my OX cnc router powered by tinyg. However today the X axis stopped working. It managed to continue cutting, up & down in the Y axis with periodic changed in depth by the Z. The motor light flashed & the stepper checks out OK. It looks like the driver chip has given up the ghost!
    However I’ve been badly wrong before now, so I’m here to ask if anybody can give me a pointer to something I’ve missed, please?
    Next Q: is there a repair service, or do I just buy a new tinyg? I’m 75 & repairs to this type of thing are now beyond me.I’m in Australia, so the turnaround will be awful, but “that’s the way the cookie crumbles”.

    November 30, 2014 at 3:38 am #7052
    Zootalaws
    Member

    You can add an external driver pretty easily. Wire it to the external connectors on the TinyG board.

    You should be able to buy something in Australia easily enough without having to send it back to .

    If you want the same – a Ti DRV8825 – you can get a ‘Polulu’ type external driver: http://www.robotgear.com.au/Product.aspx/Details/707-DRV8825-Stepper-Motor-Driver-Carrier-High-Current-V2

    November 30, 2014 at 5:46 am #7053
    gwandad
    Member

    Thanks mate, Hopefully I can find the necessary connections. I can’t see them being external, though. Wouldn’t the faulty chip be a problem & if I manage to get it off without damage to the rest, won’t that isolate the external pins? Now that I know the existance of the external driver I will certainly try!
    I just had a thought. Could I redefine the drivers in tgfx & double up the Y driver? ie. turn it into a 3 driver board instead of a 4, then use an external driver to handle the extra load?

    November 30, 2014 at 7:39 am #7055
    cmcgrath5035
    Moderator

    Thanks mate, Hopefully I can find the necessary connections. I can’t see them being external, though. Wouldn’t the faulty chip be a problem & if I manage to get it off without damage to the rest, won’t that isolate the external pins? Now that I know the existance of the external driver I will certainly try!

    I’m going to assume you have a tinyG V8. The driver inputs (uC ports) are on male pin headers and would survive a clean removal of the driver device. But, unless the driver failed shorted on these inputs, you could likely just leave it in place.
    If you have a V7, the pwb has pattern for the driver input pins but no header, IIRC.

    I just had a thought. Could I redefine the drivers in tgfx & double up the Y driver? ie. turn it into a 3 driver board instead of a 4, then use an external driver to handle the extra load?

    Early dual Y Shapeokos (NEMA 17s) controlled with gShields (3 drivers) were often configured to drive two motors from one driver. NEMA 23s will take a bit more current(crank up the pot, be mindful of device heating).

    I think Zoots’ suggestion is the best, assuming you can source the external driver reasonably.

    The tinyG schematics can be found here

    Give a review before you start, layout is fairly straightforward.
    As you will see there, the “driver led” is connected to one of the four motor output pins, so at least one output of your driver is still working.

    November 30, 2014 at 7:56 am #7056
    cmcgrath5035
    Moderator

    I just reread

    I just had a thought. Could I redefine the drivers in tgfx & double up the Y driver? ie. turn it into a 3 driver board instead of a 4, then use an external driver to handle the extra load?

    If the controller output is the issue (i.e. the signals driving the driver are bad) then you could, as you suggest, reconfigure tinyG as a three axis and drive two motors with three possibilities:
    1. Wire two motors to the onboard driver. (this is my gShield comment)
    2. Use one external ‘Polulu’ driver to drive two motors (your suggestion)
    3. Use two external drivers wired to the pin headed, the controller should easily handle two external driver loads.

    In all three cases you have to wire one motor to move the opposite of the other.

    As a generic comment, IF the controller outputs (port pins) have failed for some reason, I would expect more to fail in the near future, so you could end up replacing the tinyG anyway. A uC failure would suggest that either bad voltages made it to the uC device or some sort of device defect; both of those conditions tend to migrate around the device over time.

    • This reply was modified 9 years, 11 months ago by cmcgrath5035.
    November 30, 2014 at 7:57 pm #7065
    gwandad
    Member

    Thanks Zootalaws, I pulled the card out & can now see what you were referring to and thanks cmcgrath5035.for your input. I’ve been looking at a driver board on eBay that uses a TB6560 which handles 3 – 3.5A. It seems good to me. Could I ask both of you for your thoughts, please? They are cheap as well.

    December 1, 2014 at 7:56 am #7067
    cmcgrath5035
    Moderator

    I do not have direct experience doing this, have observed others from this forum do it.
    In my pre-planning to give it a try, I was focused on this Polulu module

    but only because it is the driver device family that the Synthetos guys focus on. I don’t recall others posting specific suggestions, but you could search ‘external drivers’ at at the Forum level and look for yourself

    I would imagine other solutions work well too. It is important that the external module have a 4 wire interface (Step,Dir,Enable,Gnd) which is typical but not universal, and that it be 3.3V compatible.
    New driver chips seem to enter the market frequently, so specific recommendations do have a lifetime or can be superseded.

    Yes, they are not real expensive. I tend to focus on designs that appear to support good thermal management.

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