3x7 Segment LED pinout?

Discussion in 'The Projects Forum' started by Art, Jan 13, 2010.

  1. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
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    Hi Guys,
    Does anyone know how to use these? or have a schematic/datasheet?

    [​IMG]

    I salvaged them from set top boxes years ago, and they'd be nice to use.
    Googled the part numbers and found nothing of use.
    Cheers, Art.
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    What codes are printed on the side of the display?

    Greetings,
    Bertus
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    Those types of displays are multiplexed; only one digit is lit at a time, but it happens so fast that persistence of vision makes them appear to be lit simultaneously. Find datasheets for CMOS 4000-series 4543 and 4553 IC's to see how easy it is to build a 3-digit counter.

    There will be one pin each for segments a, b, c ... through g. There will also be one pin per decimal point, and one common anode or common cathode for the decimal points. There are also three pins for either common cathode per segment or common anode per segment.

    It is possible to figure out what is what by using a low voltage source (4v to 5v) and a current limiting resistor (300 Ohms would be good) and trying combinations to see what lights up.
     
  4. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    I know how multiplexed displays work, and this one is multiplexed,
    but there is no common anode or cathode.

    But if I connect +ve to one of the left hand pins, three of the right hand side pins
    will cause a segment to light on each display.
    Change the pin on the left side, and three different pins on the right side will
    cause three different segments to light up (but they are the same segment for each digit).
     
  5. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    Actually, if I had 12 IO pins on a micro, I could figure it out from here.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    As I asked before:
    What codes are printed on the side of the display?
    I can see there is something there, but can not read it.

    Greetings,
    Bertus
     
  7. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    They are different codes, but I have determined the displays are wired the same.

    Unit 1:

    CST-538GN5
    S9809 R

    Unit 2:

    TOT-5361HG H

    Hope you're not planning on Googling them!
    Cheers, Art.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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  9. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
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    They both have commons which isn't what I've described here.
    If that were the case, you could connect to a common, and be able to light any segment
    of that digit by moving the negative along other pins.

    My second post here describes the behavior I've found, and I'm sure both displays arte
    wired the same internally.

    ie. If I connect the positive to the right pin, I can light all three decimal points by
    connecting the negative to the correct pins.
    If there were a common, I'd only be able to light different segments of a single digit.

    Allow me to demonstrate:
    http://www.youtube.com/watch?v=WP2Zm8NsgWc
     
    Last edited: Jan 15, 2010
  10. SgtWookie

    Expert

    Jul 17, 2007
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    Well, you were talking to someone while you were making the video.

    If you look at the video again, you will see that for each pin you struck, a different set of LEDs lit up.

    This CAN be figured out; you just have to document your results, and not be so impatient.
     
  11. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    Someone was talking to someone else, but the sound doesn't matter.

    Of course I could figure out how to light any segment.
    Gets a bit tough to create definitions so that you could print any three digit number though.
    The code would get fat if I had to store a 12 bit pin scenario for each of 999 possible combinations.
    I could also eventually figure out a schematic. Beats me why it would be made like this though.

    I've got another one that's even more puzzling, but I'll likely dispose of it :D
     
    Last edited: Jan 15, 2010
  12. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    Er idiot me, and no points for anyone else. Someone on another forum figured this out.

    For anyone else that Googles this, the 7 segments start from the left when looking at the digits,
    then the three common, then the three decimal points.

    What you see in the video is what happens if you assume the module is common cathode.
    Swap the supply and it's normal.
     
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