Breaking out Step and direction pins

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  • November 2, 2017 at 2:07 pm #10662
    JeromyReno
    Member

    I’m back at building a cnc plasma table. I’m going to be using this proma 150 sd torch height controller(thc). It basicly wires inbetween the processor and the z axis stepper driver. When the torch is running it takes over and keeps a perfect arc length using the current from the plasma machine as a reference. Then goes back to letting the processor take over after the torch disengages. I can just bend up the pins from the traces to wire it between them but I see that there is a header that has step and dir indicated on it. Is that header between the processor and stepper driver, or parallel with it?

    November 2, 2017 at 2:53 pm #10663
    cmcgrath5035
    Moderator

    I would call it Parallel, pluging-in into the header does not disconnect the logic drive to the Stepper driver.

    You could consider using an external stepper driver for Z, rather than messing with cutting and reconnecting traces on the PCB: Header to Torchcontrol, then Torch control to external Z stepper driver. Just leave the tinyG Z winding leads (4) un-connected.
    Schematics are here https://github.com/synthetos/TinyG/tree/master/hardware/v8schematics/v8h

    November 2, 2017 at 3:51 pm #10664
    JeromyReno
    Member

    Oh damn that’s a great idea! I was going to remove the whole chip and put it on a breakout board and run little wires back to the pads but I have some small pololu drivers that I can just run off the headers. I’m so greatful for your insight! Thanks again!!

    I might make a little YouTube video on it cause I haven’t found much on how to build a cnc plasma and think it could help others along the way, so you will get to see it unfold or go up in smoke haha

    I have 4 tinyG’s on my Shapeoko’s and and other projects but I might order another just in case haha.

    Jeromy.

    November 2, 2017 at 4:50 pm #10665
    cmcgrath5035
    Moderator

    Something like this

    might provide better thermal and noise performance.

    I have to assume the Plasma process is a tad electrically noisy

    BTW, the driver devices on tinyG are in head slug packages, takes a good bit of heat to remove them alive from the PCB

    November 2, 2017 at 9:28 pm #10666
    JeromyReno
    Member

    oh damn that’s pretty cheap for a quality stepper driver. i got all caught up in the moment and designed a board and sent it out to a board house to get made haha. it’s just a breakout for a DRV8825 but if it doesn’t work out well i’ll swoop up one of those in a heart beat.

    thanks again for all the help.

    do you think leaving the driver on the board will cause any problems when running another driver parallel on the same step and dir line. im sure trying is the only way to find out haha.

    November 2, 2017 at 10:58 pm #10667
    cmcgrath5035
    Moderator

    No issue at all pulling logic control for Step-Dir-Enable in front of the driver device. Some folks used to get dual Y drive by using onboard for Y+ and external for the Y- via the header.

    I can’t vouch for the “Quality”of that driver, never used it. You can spend $15 to way over $50 for drivers on Amazon, check the specs.

    It caught my eye because it was low cost, used a popular driver device and has a big heat sink.

    November 2, 2017 at 11:23 pm #10669
    JeromyReno
    Member

    Yeah I’m still going to buy one to test what it’s capable of. I love the single board complete package of the tinyG though. I program massive machines at work and laugh at the complexity of some of the systems that this tinyG can replace.

    Worked on a 10′ x 25’waterjet of a friends and it had a full networking tower with motor controllers, power supplies, old ass computer with a parallel port and the worst GUI ever, very Atari like. All to control 3 nema 34’s with pretty short bodies, probably 2A motors. When I told him we could put on a single board and power supply and he could run it off his old surface pro with chillippr (the name didn’t help sell the idea) he looked at me like I was crazy. At worst if we couldn’t run strong nema 23’s inplace of the small 34’s we could use those clear step servos that replace steppers and his machine would actually be more powerful haha. The future is now wooo!

    November 3, 2017 at 6:19 am #10670
    cmcgrath5035
    Moderator

    Be aware that the Controller device has limited logic drive power and some on-board EMI protection. you might want to consider buffering the raw signals on the tinyG header before running thru harnesses to items like the plasma torch height regulator. You might also consider additional filtering on AC inputs to power supplies, the low cost ones used here in DIY space may not be compatible with a real industrial machine room environment.
    Good luck with your project.

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