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  1. #1
    the BOB requires a 5V supply if you fit jumpers JN1 & JN2
    or two 5V DC supplies if jumpers JN1 & JN2 are not fitted

    Click image for larger version. 

Name:	ebay opto-isolated CNC BOB  .jpg 
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    the circuit diagram is based on photos taken from the net !!

    John

    PS
    I assume the limit switches have NPN open collector outputs

    with just the 5V power connected to the BOB you should have close to 5V
    between the opto-isolator IC pins 3 & 4

    when you connect the opto-isolator pin2 to the input ground with a wire link the voltage across pins 3 & 4 should drop to close to zero volts (0 to 0.7v)

    it should be easy to change and damaged "817" opto-isolators

    PPS

    simple tester for similar BOB inputs

    Click image for larger version. 

Name:	BOB input  tester & partial TX14175 circuit.jpg 
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    TX14175 circuit
    Click image for larger version. 

Name:	TX14175 circuit.jpg 
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    Last edited by john swift; 07-01-2018 at 03:46 PM. Reason: add ref to testing BOB input plus input tester

  2. #2
    Wal's Avatar
    Lives in Stockport, United Kingdom. Last Activity: 15-12-2024 Has been a member for 9-10 years. Has a total post count of 491. Received thanks 71 times, giving thanks to others 29 times.
    Cheers guys.

    Panic over for now - turns out it was my brain cells that were fried and not the input pins. The switch was behaving differently to how I expected it to - rather than take a closer look at what the switch was doing, I began a campaign of button mashing which lasted well into the night - not a great idea after a full day of assembling the bugger..!

    A clearer head this morning, a quick chat with Clive and a better look at what my switches were up to yielded better results..! (Oh, and restoring my back up .ini)

    Should have it up and running in the next few days.

    Wal.

  3. #3
    no damage done and now working
    a good result

    if you go on too long without a break its too easy to make the wrong decision and dig your self into a deeper hole

    I know I have done it my self once or twice

    John
    Last edited by john swift; 08-01-2018 at 11:32 AM.

  4. #4
    I know I have done it my self once or twice
    Only once or twice, I must have done hundreds of times
    ..Clive
    The more you know, The better you know, How little you know

  5. #5
    Hi Clive

    that was once or twice that could not be fixed before management noticed and started to ask questions !!!!

    the others no body new about are just part of the iterative process

    John

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