lm3914 flashing question

Discussion in 'The Projects Forum' started by Motl, Feb 1, 2012.

  1. Motl

    Thread Starter New Member

    Feb 1, 2012
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    I am using a lm3914 and led's in bar graph mode as a display from a battery charge indicator that outputs 0 to 5 volt. I would like the lowest (.5V) indicator led to flash when it is the only one on and then be on steady when the next led (1.0v) and above come on. The circuit that I am working with is the 0-5v bargraph meter in the typical applications in the data sheet. Thank You
     
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    What is the power supply voltage on your 3914? Do you use the same supply for the LEDs?
     
  3. Motl

    Thread Starter New Member

    Feb 1, 2012
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    I am using 8 volts for the chip and led's. I could use 24 volt with the negative in common with the 8 volt. Thank you
     
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    This should work if you have the LM3914 in bar mode. If you want to use dot mode, it will be even MORE complicated.:rolleyes:
     
  5. Motl

    Thread Starter New Member

    Feb 1, 2012
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    For some reason my problems are never simple. Guess I'll have to go shopping. Your assistance is greatly appreciated.
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    This is more efficient power-wise, as it uses a series PNP switch (Q1) instead of a shunt NPN as in the previous scheme.
     
  7. Motl

    Thread Starter New Member

    Feb 1, 2012
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    Worked out very nicely. I never thought of using gates in this manner. Thank you for the project help and the way of seeing things.
     
    Ron H likes this.
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