how to display E for error in seven segment display

Discussion in 'Homework Help' started by mohsen, Nov 13, 2010.

  1. mohsen

    Thread Starter Active Member

    Oct 24, 2008
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    how to display E for error in single seven segment display with lowest number of chips when i have an input for an error then i want it to display E
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    You can do this with 1 resistor.

    Remember the 7seg is JUST 7 LEDS.

    So wire the 5 segments that make the 'E' to light when a pin goes high or low.

    The 1 pin through a resistor to split to the 5 segments that make the 'E' then the common pin to high or ground..depending if the 7seg you are using is common cathode or common anode.

    Are you doing anything else with the 7seg or just showing an error when it happens?
     
  3. mohsen

    Thread Starter Active Member

    Oct 24, 2008
    37
    0
    no i'm doing add/sub BCD so i got the seven segment with another display +/-1 for the rest of the number cuz it will not exceed 18, and the problem is when each input exceed 9 i will have a light and want the segment display E for error ^_^ and i might get red off the light if the E worked.
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    The 'E' would be nice, but for ease of use, how about just lighting the Decimal point to show an error?
     
  5. mohsen

    Thread Starter Active Member

    Oct 24, 2008
    37
    0
    i didn't think of it that is good idea. but i want my project to look neat so i don't want it to display the number in the display cuz when an input exceed 9 it will still work but in this case it would be binary add/sub
     
  6. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    If you have the BCD driver constantly hooked up on the 7-seg, you can't just drive the segments separately to create the "E" display.

    A way to overcome this is to put 2-input OR or NAND gates (depending on wheather the driver has active LOW or HIGH outputs) between the BCD driver and the 7-segment. That way, when you disable the driver (have it raise no segment to light) you will be able to input a different signal (in this case the "E" configuration) directly into the segments.

    Is that clear?
     
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