FWIW: Controller/brain transplant for 3-axis Chinese CNC router to use parallel port


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Thread: FWIW: Controller/brain transplant for 3-axis Chinese CNC router to use parallel port

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    Default FWIW: Controller/brain transplant for 3-axis Chinese CNC router to use parallel port

    This is just an FYI for someone finding themselves in my situation: having a Windows-only machine with a gameport interface and wanting LinuxCNC and a parallel-port interface.

    The 3-1/2-axis[1] 1200x1200 Chinese CNC router that I imported (another story, :^p) came with "NC-Studio" and a 15-pin "gameport" interface and a CDROM to install a device driver into Windows.

    The driver would not install into a modern version of Windows, and I quickly tired of hunting through older and older versions of hackbait.

    Besides, I had been running LinuxCNC on my old DIY and wanted to use the intellectual capital from that, and a parallel port.

    So, ignorance being the better part of valor, I got a "5-Axis CNC Breakout Board for MACH3 Stepper Motor Driver Module" [2] with no instructions and tried to work through it.[8]

    The pictures I'm posting are of the working result--FOR THIS ONE MACHINE, but they may be valuable, firstly, in suggesting that it might be possible for other machines with the same interface, and secondly, in suggesting some particulars. Obviously, this is not for everyone. I'm not recommending you change. I cannot support you if you have problems[3]. If you're going to do it anyway, take PLENTY of 'before" pictures, so you can go back.

    My reasoning was this: "Regardless of how the computer talks to the controller, in the end, the controllers themselves have to talk "the same language" to the downstream CNC components." The stepper motor controls are "step" and "direction" (or rather the reverse, "direction" is set first, then "steps" are sent). That was the easy part. I had to get the reference for my spindle controller to learn that the original interface was supplying a 3-digit "octal" signal (3 binary voltages to 3 of its pins) to select "1-of-8" pre-programmed speeds. I learned too that it had the capability to respond to a 0-10V "analog" signal which, from the size of the analog voltage at the control input, would select a proportional speed from the 0-full range. The new board happened to provide that, but until I worked that out, I was reaching under the table to dial-in the speed on the spindle controller's knob.[4]

    I noticed that my home switches which I had relocated to "central" positions on the machine, from their far, far away corners, were operating erratically. I guessed they were picking up electrical noise, and after weighing the cons of replacing everything with shielded wire, guessed again that the problem might be overcome by "swamping" the noise by applying a larger DC voltage to them. Thus I found a 24Vdc[5] wall wart from ebay, filed down its prongs so it would fit into the narrow sockets of a standard computer cable, connected it to the new controller and ran it off the same 240Vac[6] as the machine, and the spindle's water pump.

    I've also convinced myself that I "blew up" the new controller, twice. The first time because my machine didn't have a parallel port (who knew dumb companies had stopped supplying them??) and I misconnected the "part": it didn't plug in to a slot like a normal card, but plugged into a jumper: I picked the wrong one. I thought I'd applied voltage TO the controller and bought another. As it happened, I had the wrong parport activated... So I had a spare. I bought a second spare in an emergency situation when the machine just stopped, cold, and I had a deadline, so I couldn't trust that the spare I had would work. (It did, and my "emergency" was created by me stepping on the USB cable[7].)

    As a result of these misdiagnoses, I changed out the new controller, twice. The wires were just barely long enough to re-route to connect to the new controller from the old, so when I replaced it the first time, I added a distribution manifold and landed the machine's wires onto it, so I could add longer wires to the controller's side and reach a convenient mounting point.

    In summary, it can be done.

    Notes:
    [1] I got a "fourth" lathe-style axis with the machine, but it requires switching the x-axis control to the rotation connector; in my book that's not full 4-axis.
    [2] Today's price on ebay: $4.07, shipping included from "China/Hong Kong/Taiwan".
    [3] I really, really, can't.
    [4] Getting this 0-10V thing to work required reprogramming the spindle controller via its front-panel pushbutton interface too. Again, I wrote down ALL the current settings before trying ANYTHING.[5]
    [5] This 24Vdc may have been required to provide the 10V for the 0-10V signal too. I actually had to buy a second one of these because when I tried to un-plug it the first time, the pins stayed in the sockets... destroying it. getwhatyoupayfor
    [6] Interesting thing: the 240Vac single-phase power receptacle for the main machine power is configured for a standard computer power supply cable. I looked it up and verified that it is in fact approved for this use in the United States. (I doubt very much that my home-made extension-cord version of a string of these together is, but I'm going to replace it. And I'm going to paint the house this summer. For sure this time.)
    [7] The board I have has both a USB port AND a parallel port. The USB is only present to supply 5V for the board logic. You may be surprised, as I was, to learn that the parallel port spec does not include providing any power.
    [8] I was "motivated" by the fact that, after days of continuous frustration at failing to get the driver to install, I took a hammer to the "NC Studio interface card" so that I could not be tempted to think it might work some day. I DO NOT RECOMMEND THIS. While relieving the frustration, there came upon me an anxiety of equal intensity.

    Similar Threads:
    Attached Thumbnails Attached Thumbnails FWIW: Controller/brain transplant for 3-axis Chinese CNC router to use parallel port-original_15-pin_receptacle-jpg   FWIW: Controller/brain transplant for 3-axis Chinese CNC router to use parallel port-5-axis-breakout-board_wires-moved-jpg   FWIW: Controller/brain transplant for 3-axis Chinese CNC router to use parallel port-distribution-manifold-jpg  
    --
    Dan


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FWIW: Controller/brain transplant for 3-axis Chinese CNC router to use parallel port

FWIW: Controller/brain transplant for 3-axis Chinese CNC router to use parallel port