small problem with 7-segment

Discussion in 'Homework Help' started by mr.harm, Oct 28, 2009.

  1. mr.harm

    Thread Starter Member

    Nov 24, 2008
    29
    1
    Hi
    guys, my problem is with displaying 6 & 9. the upper bar of siX doesn't light & the lower of nine doesn't too. could u show me the connections between 7447 & 7-segment. I connected each output of 7447 to the respected of 7-segment, I don't know where the problem is...
    thanks
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The 7447 has outputs called a, b, c, d, e, f, &g. Those tie to the similarly labeled inputs on the display. The complication is in limiting current in each segment. A '47 has active low outputs, so the display must be a common anode type. If it uses the same =5 supply as the logic, each segment drive must have a resistor of about 330 ohms in to to limit the current safely.
     
  3. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    The Fairchild Semiconductor data sheet for the DM7447A seems to suggest the upper horizontal bar on the 6 and the lower horizontal bar on the 9 are not lit when those numbers are requested.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    This is consistent with the Texas Instruments' datasheet for the SN7447.
     
  5. mr.harm

    Thread Starter Member

    Nov 24, 2008
    29
    1
    Thanks guys very much, I checked the datasheet, 6 & 9 are by default lightening that way,,,,,,
    many thanks
     
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