LCD display

Discussion in 'General Electronics Chat' started by Voltboy, Oct 21, 2007.

  1. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    Hello.
    I found an Casio alarm clock/radio with an LCD display. I want to use the LCD but it have no specifications, no item #, nothing.
    The display is
    :88:88.
    The LCD has 30 pins which only 24 were connected to the alram/clock. the other 6 were left unconnected.
    The IC that controlled it is the Sanyo LM8562
    Anyone have any guesses on how I could make this work?
     
  2. Management

    Active Member

    Sep 18, 2007
    306
    0
    I'm not expert but I'll try to help.

    You can google the datasheet of that Sanyo IC, read and understand the pin out and then compare it to where they are connected to form some sort of a pin out for the LCD. Could be used to give you a rough estimation of which pin is doing what on the LCD.

    EDIT: I would check out page 6 of the data sheet. http://pdf1.alldatasheet.com/datasheet-pdf/view/41214/SANYO/LM8562.html
     
  3. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
  4. Management

    Active Member

    Sep 18, 2007
    306
    0
    If you look at the data sheet the LM8562 only outputs from 1-14 on it's pins.

    You would have to first understand a single 7 segment LED display. Starting from the top is 'a' and going clock wise and ending at 'f' with 'g' being the center. So when you look at the data sheet to see where the pins of 1 through 14 are connected you can understand the letters that they use on page 4 of the datasheet.

    MIN is for minutes
    HR is for hours

    When they say 10's they mean the tens digit of the minutes and hours. I hope that helps.
     
  5. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    Ohh.. now i get it.
    All the output pins say two segments, like MIN a&f. So how I do to only turn on "a", or only turn "f". It say something of drive phase, like phase 1 MIN "f", and phase 2 MIN "a".
    Thanks
     
  6. Dragon

    Active Member

    Sep 25, 2007
    42
    0
    Good job, Management!
     
  7. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    Here I got pics from the PCB.
    The first pic show which are the pins from the LM8562.
    And the second pic show how they are connected to the 7-Segment LCD.
    The second pic doesn't show three other pins that 2 of them are connected to black wires, and the other to a red one.
    If anyone have any guesses on how I turn on the 7-Segment, I'll appreciate it alot:rolleyes:
     
  8. techroomt

    Senior Member

    May 19, 2004
    198
    1
    since the number of display elements (4-seven segments = 28 plus 2 colons and a period =31 total) and the number of connection pins (14)don't match, it is likely the display driver circuit transmits the signal using multiplexing, commonly done. where a set of signals is applied to common data pins and only one seven segment is enabled at a time. this written refresh rate is performed fast enough that the human eye cannot detect the flashing of data. one of the signals would also include the backplane power, possibly a 100 hz square wave. a segment will be "on" if that segment is receiving an inverted (180 deg out of phase) square wave, and "off" it is receiving an in phase square wave.
     
  9. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    Do you have any idea on how I could make this work?
     
  10. techroomt

    Senior Member

    May 19, 2004
    198
    1
    i'm sorry i did not previously view the 8562 data sheet. first it appears the driver is for led, not lcd. so the square wave supply is not required here. second, there is no multiplexing, instead it appears they combined segments drive signals (e.g. a & f) since they know they only have to ever display numerals 0 - 9. so with the correct combination of segment drive/signals they can display a number. so unless your intention is to only ever use the predetermined pin out segment combinations, this led display is not for you. in other words, it appears you can not have individual segment addressability. hth
     
  11. Voltboy

    Thread Starter Active Member

    Jan 10, 2007
    197
    0
    Oh now I get it.
     
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