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10 Pin Dual 7 Segment Display cant find documentation

  1. Aug 17, 2009 #1
    Hey Guys,

    So I was scrapping parts from an ancient present I found up in the attic called the "Singing Machine". Point is I managed to retrieve a dual 7 segment display. The only documentation I can find online is for 14 pin versions of these things. Strangely this only has 10 pins and I can assure you none broke off. Anyone have any idea what these pins match to?
     
  2. jcsd
  3. Aug 17, 2009 #2
    It should be pretty simple to figure out. Put a 10K resistor on a 5-15V power supply, then in a darkened room touch the leads to different pairs of pins. Once you know what's what, crank the current up for reasonable brightness.
     
  4. Aug 17, 2009 #3
    I kinda expected to get that answer. I have been playing around with the pins for about 2 hours now but most of them seem to be multiplexed.
     
  5. Aug 17, 2009 #4

    berkeman

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    Staff: Mentor

    Can you post a picture? Are there any markings on it?
     
  6. Aug 17, 2009 #5
    Picture is attached
     

    Attached Files:

  7. Aug 17, 2009 #6

    berkeman

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    Staff: Mentor

    Interesting. Googling the part number doesn't turn up anything helpful (but you knew that already). To drive two sets of seven segments takes at least 9 pins if you share the segments and just have two different common cathodes or common anodes per digit.

    You said you did some beeping -- were you able to identify a CC or CA or two?
     
  8. Aug 17, 2009 #7
    The strange thing is this was used for a track number display for a CD so both 7 seg's must have been controlled differently. Pin 7 when + turns on the right screen and Pin 8 + turns on the left screen. When both are + both screens go on. Whenever I change the other pins they change both screens so I am confused as to how to change each screen individually. Pin 2 when - is the d.p. Each Pin is an annode because it is only affected when in the - side. I believe I am describing this correctly. Sorry I am not very familiar with describing it other ways.
     
  9. Aug 17, 2009 #8
    If I were designing this, I would use the 10 pins for Vcc, ground, and two BCD 1248 signals. The 4 line to 7 line decoders would be inside the chip.
     
  10. Aug 17, 2009 #9

    berkeman

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    So it sounds like each digit is configured with a common cathode (- side), with the two CC pins providing multiplex access to the digits. Each of the pairs of 7 segments share an anode pin. So your drive circuit will need to drive the two digits in an alternating fashion, with each digit being on for 1/2 of the time. Drive them above the flicker fusion frequency of the human eye -- something like 50Hz should be fast enough, but you can experiment.
     
  11. Aug 19, 2009 #10
    Berkeman, that actually makes alot of sense. Thanks for the help everyone.
     
  12. May 3, 2011 #11
  13. May 3, 2011 #12
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