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Thread: Chinese Breakout Boards

  1. #13
    Registered john-100's Avatar
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    Hi alcor

    without the USB cable supplying the 5V to the breakout board
    if any of the printerport input pins 10 ,11 , 12 , 13 or 15
    can supply enough current ( a standard TTL IC its input terminals can source1.6 mA from its +5V supply )
    current will flow into the breakout board pin and via the first 74HC14 IC's input protection circuit to the +5V printed circuit to power the other IC's and the power indicator LED

    normally I'd connect both the USB and the LTP printer cable before switching on the PC

    http://www.ti.com/lit/an/scla007a/scla007a.pdf
    shows some of the protection circuits used


    if when testing the breakout board when its powered by the +5V USB supply from the PC
    the output voltages switch between 0V and +5V as expected when you operate the limit or the Estop switches

    but does not switch correctly when connected to the printer port
    the printer port must be faulty or the B.O.B and printer port are not compatable


    if the PC printer port logic is powered from 3.3V instead of +5V the older TTL versions used

    may be a +5V logic 1 from the breakout board is causing the transistors in the printer port to latch up

    a possible solution could be use 5 diodes (1N4148 ?) to connect the breakout board to the printer port,
    the cathode connected to the B.O.B

    john

    Attached Thumbnails Attached Thumbnails Chinese Breakout Boards-b-o-b-5-diode-cable-mod  
    Last edited by john-100; 02-16-2013 at 01:50 PM.


  2. #14
    Registered alcor's Avatar
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    I use a separate power supply to 5V via USB. In my tests, everything is plugged in, then I turn on the BOB and then the PC. I noticed that the PC also fed the BOB after completing my tests, when I turned off the BOB and the PC.

    I'll try to use diodes but I currently lack the equipment for it and I'll buy diodes, DB25, board, etc.. I am interested to know, but I'll need a more practical, so I will also try to replace this card.

    I will update this thread as soon as i'll receive the diodes.

    John, I want to thank you for your help.

    NB : i'm not sure about the diodes because even when the BOB is unplugged from the PC, all the pins 10, 11, 12, 13 & 15 are set to 5V when only one input is closed.



  3. #15
    Registered john-100's Avatar
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    Hi alcor

    I'd assumed the PC USB port was supplying the breakout board and not a mains PSU
    the only advantage with taking the power from the PC is the breakout board is switched on and off at the same time as the printer port cicuit


    It looks like you have a problem with the breakout board or the limit switch wiring .

    with only the 5V supply connected you should have 0V between the ground terminal and the printerport connector pins 10 , 11 , 12 , 13 ond 15

    since the inputs are pulled high by resistors and the output of a
    74HC14 inverter is connected to the printerport
    ( only 1/6 of the 74HC14 is used in each of the 5 input circuits )

    connecting a wire link between ground and the Estop should only make pin 15 switch from 0V to +5V

    connecting the A axis input to ground should only make the printer port pin 13 switch from 0V to +5V

    the X , Y and Z limit switch inputs should control only the corresponding pins
    10 ,11 and 12

    removing a link or opening a switch should only make the corresponding printer port pin switch from +5V to 0V

    once you have used wire links at the terminal blocks and proved the breakout board is working
    you can repeat the tests with the limit switches and machines wiring


    John



  4. #16
    Registered alcor's Avatar
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    Last try ...

    I unplugged and completely removed the breakout board from the rack.
    I only powered the card with a USB 5V supply.
    I get the same results than before :

    The outputs 10, 11, 12, 13 and 15 provide the 2.6 V (GND on pin 25). Not 0V as expected.

    Next i added 5 normally opened switches to each 5 BOB L/S & Estop inputs. Grounded individually to their respective GND inputs.

    I get 2.6V when all 5 switches are opened and 5.1V when only 1 switch closed on all 5 DB25 input pins at the same time. Not attended behaviour.

    I also noticed that when my fingers are close to inputs Y, Z and A, it makes the system unstable and the inputs (always all at once) are randomly and quickly set to 0 or 1 until i stay close.

    This breakout board is broken. Too bad, the outputs work well though. I will not try with the diodes.

    Edit : I replaced this board by a Mechapro Interface II (55€). No more stepper jitter, inputs are all functional and stable.

    Last edited by alcor; 04-02-2013 at 09:58 AM.


  5. #17
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    Default Re: Chinese Breakout Boards

    have anybody make or orden 3 axis 7-segment display and hand jog box to hy-jkm5/hy-jk02-m board, i has try google search many day but no found, were can buy or schematic how build own dispaly to 3 axis display and hand manual jogging box encoder hand wheel and buttons. but no found anywere how connect display and were orden ? working fine my cnc whit hy-div 268n-5A tb6600 drivers.



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