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  1. #11
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  2. #12
    Having a think about a suitable test to confirm whether or not the BOB is being changed by Mach 3. If I took a red LED and a 150ohm resistor and connected them between the 5V supply on the BOB and pin 3, the x axis Dir, would it light when the axis was moving on one direction and not in the other? I was under the impression the BOB would give a High output for one direction on the motor and a Low output for the other?

    Many thanks

  3. #13
    Kitwn's Avatar
    Lives in Exmouth, Australia. Last Activity: 6 Hours Ago Has been a member for 1-2 years. Has a total post count of 109. Received thanks 20 times, giving thanks to others 2 times.
    Strictly speaking the BOB open-collector outputs are either a low impedance path to earth or a high impedance. This is why you need the pull-up resistors to get the required 0v or +5v output to your external transistors.

    The LED circuit should work. The LED must be connected the correct way round, test it first. You probably already know that but just in case there's somebody reading who doesn't know about diodes.

    Check that all three outputs, STEP, DIR and ENABLE are under MACH3 control. The step output will make the LED glow less bright than dir or enable when jogging since it will be pulsing when you tell an axis to move. This is a good sign!

    I don't use MACH3 and obviously know nothing about your individual mill so I'm at the limit of how much help I can offer.

    Engineering is the art of doing for ten shillings what any fool can do for a pound.

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  5. #14
    A quick update, after much head scratching I've worked out that the Mach 3 software will run on a 64bit windows OS, but it will not send any commands to the BOB as I am unable to install the drivers. I'm in the process of sourcing a 32bit copy of Windows then we should be in business.

    Thanks again to everyone for their input.


  6. #15
    Ive just skim read this so might have missed something but I had that exact same bob several years ago and couldn’t get any pulses out at all. Given that I have made quite a few machines I should know how to wire them up and how to configure Mach and what to expect. Only cost me 8 so not much lost other than time. I tried lots of things but that was my conclusion in the end. Did a straight swap for my current (even cheaper!) board and everything worked. These boards are made to Kit’s strap line.

    To answer one of your earlier questions a multimeter on the direction pin of the bob and on the ground pin of the bob (the terminal blocks that go to the driver) will read 5V or 0V depending on direction. If that is not happening no amount of downstream circuits with get it going.

    Another thought is to get the pin out diagram for the parallel port connector, unplug from Bob (but still in at PC end) and check direction pin vs ground in the cable end. Then toggle direction of that axis in Mach3 using the cursor keys (should see DRO move accordingly) and read 5V or 0V on the cable pin according to the direction. If this works then Mach3 is working and bob is under suspicion.

    Also the parallel cable needs to be the right type, one is crossed over and one is straight through. Can’t remember which you need but a quick search should find it.
    Last edited by routercnc; 1 Week Ago at 09:53 AM.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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