LPT connecting cable for CNC

Discussion in 'The Projects Forum' started by Pader, Feb 13, 2012.

  1. Pader

    Thread Starter Active Member

    Jul 17, 2010
    30
    1
    Hi folks,
    I haven't been here for a while. I have been busy on other pursuits. I have been building a CNC machine. It has been a long and quite expensive exercise. However, I have come up against a problem that I hope you guys can help me out with. I needed a breakout board from my LPT input that required a hand control and a digital readout facility. I have managed to get hold of a breakout board that has these facilities but I am concerned that it does not have opto-isolation. I do have another very simple board that does have opto-isolation and it appears to be a straight through board from the input without any other facilities except it seems to be nothing other than the I/O signals are intercepted by 17 opto-isolators for all the I/O signals except for the ground connections.

    My question is; if I give the simple board the same power supply as the more complex board, can I insert this board in series with the parallel connection from my PC and thereby give me opto-isolation?
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    Probably....But u need to show us in details to clarify anything.
     
  3. Pader

    Thread Starter Active Member

    Jul 17, 2010
    30
    1
    Hi, I have photographed the simple board and drawn a block diagram. How do I upload them?
     
  4. Pader

    Thread Starter Active Member

    Jul 17, 2010
    30
    1
    Hii R!f@@,

    I have managed (I think) to upload the pics. The first (BOB.jpg) is a photograph of the simple break out board and the second is a sketch showing the pin connections to termiinals.

    The two small ICs are 74HC14D Hex, schmidt inverters. The 5 opto-couplers to the left are connected to Pins 10-13 and Pin 15 on both the terminals and lpt D-sub socket. The remaining opto-couplers go from the D-sub to the terminals. It was my idea to connect the terminal connections to another D-sub for onward connection to the more complex break out board.

    Is this enough information for you to give me an idea whether it will work?
     
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    U know I have the same one.

    But I never used it since I have not yet finished my stepper drivers

    But I believe it will do the job

    I would say try it.
     
  6. Pader

    Thread Starter Active Member

    Jul 17, 2010
    30
    1
    Thanks for your opinion. What a coincidence that you have the same BOB. What are you building? I am building an 1800 x 870 milling machine but using proprietary drivers and boards with 4 Nm, NEMA 23 steppers.
     
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    I am building a CNC.

    There is a thread.
     
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