LM3914 Question

Discussion in 'The Projects Forum' started by iONic, Oct 29, 2010.

  1. iONic

    Thread Starter AAC Fanatic!

    Nov 16, 2007
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    I believe this is possible.

    Not that I want to do this exactly, but can you tie LED Outputs 0 & 1, 2 & 3, 4 & 5, 6 & 7, 8 & 9 each to a single LED, thus creating a 5 LED indicator instead of a 10 LED indicator? And in doind so, without any additional parts?

    Can they be staggered... Output 0 to one LED, Output 2 & 3 to another LED...?

    Can you tie three outputs to one LED, and perhaps 1 per LED for the remainder?



    Thanks guys!
     
  2. BillB3857

    AAC Fanatic!

    Feb 28, 2009
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    Should be no problem in "DOT" mode. If "BAR" mode is used, the outputs would combine their currents. Others may see it differently and straighten out my thinking. Is there a reason you would not be able to just use the first 5 outputs and scale your input accordingly?
     
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    From the datasheet:

    If you halve the output drive via pin 7 on the LM3914, you could use 2 pins to sink enough current to not overdrive 1 LED.

    All outputs would need to be dual output for 1 LED though, it may be easier to go 50% = full scale, and only use the first 5 comparators to avoid any problems.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    You can't cheat
    the datasheet.

    If you try,
    Your parts will die.
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    This would be bad,
    And you would be sad.
     
  6. iONic

    Thread Starter AAC Fanatic!

    Nov 16, 2007
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    You guys are too funny.

    If you do not use output 0 - 9 can the voltage range be as large, for example using only outputs 0 - 5...?
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    The IC is designed for a 0-5V display, each LED being 0.5V.

    Change/Add voltage divider on input so the max is only 2.5V instead of 5V. Use the first 5 taps. Some resolution is lost, but that would happen in any case when going from 10 to 5 outputs, no matter the method.
     
  8. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    LMAOF....Sorrry.
    Like seeing humor every now and then.
     
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