Interfacing digital weighing machine with PC [with pics]

Discussion in 'The Projects Forum' started by Sulaiman, Aug 14, 2010.

  1. Sulaiman

    Thread Starter New Member

    Aug 13, 2010
    6
    0
    Hi all,

    I'm working on a personal project where I want to connect my digital weighing machine with my PC so that whenever I check my weight, it is recorded in my computer (excel file) and I can check the progress of my weight. (I'm bordering on marginally underweight, and am desperate enough to make devices to increase weight :p)

    This is what the weighing machine looks like
    [​IMG]

    [​IMG]

    I'm assuming that if I just connect the LCD display to the PC, I'll have the bit's needed to compute the numbers through software. (Connection on the inside:-
    [​IMG]

    I need to send the 2 bytes from the LCD to the PC, most probably serially. I'll be using a parallel to serial shifter (16 bit shift register) to transmit the 2 bytes serially.
    My question is this: Should I use USB or the serial port?

    From my research on the internet and this forum, USB seems like a very complicated solution. I only want to use it because it would be simple to use anywhere: serial ports aren't there on laptop's and some PC's now...
    Isn't it possible to just poll the usb port for bits and store them?

    I've been researching on this for a couple of days now to no avail, so any help would be really appreciated.

    Thanks in advance kind people :)
     
    Last edited: Aug 14, 2010
  2. netwillie

    New Member

    Aug 10, 2010
    11
    3
    We use serial outputs from weighing equipment to PC's and the easiest solution for us is to stay with serial by using a USB to serial converter on the PC side. They are not expensive. Hope this help.

    Willie
     
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  3. Sulaiman

    Thread Starter New Member

    Aug 13, 2010
    6
    0
    Thanks. I'm assuming you mean these ?
    [​IMG]

    So I can just send the bits to this cable, and have a program to the poll the bits continuously right? No need for "start flags" and "end flags" ?
     
  4. netwillie

    New Member

    Aug 10, 2010
    11
    3
    That’s correct, something like hyperterm, terraterm,...etc and then you can export the data in "," delimited form to excel.
     
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  5. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    Before you decide on whether to use USB or serial for the data, you should be aware that the on/off of LCD segments is NOT driven simply via constant DC level. Instead they are driven by a rectangular wave either in phase or out of phase with respect to the voltage signal on the LCD back plate.

    This make reading the value of the LCD display result directly off the LCD pins difficult. :(
     
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  6. Sulaiman

    Thread Starter New Member

    Aug 13, 2010
    6
    0

    Awwh man :( So is there absolutely anyway to get the bits from the machine ??
     
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