LM3914 12V Battery Monitor Circuit

Discussion in 'The Projects Forum' started by sammy123, Feb 12, 2015.

  1. sammy123

    Thread Starter New Member

    Feb 12, 2015
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    I am trying to make a Battery Monitor Circuit using a LM3914 to drive 10 LEDs. I have found this circuit design but don't know how to calculate the values of the resistors..as in what formulas to use etc. I want one LED to be on at 11.5V and all 10 to be on at 12.8V.
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You need to set the upper and lower limits to 12.8v and 11.5v, there is an internal lm317 regulator that needs to be set to 12.8v, using a 1.2K R1, and 11.6K R2 resistor. The lower limit resistor R3 is 86.9K. You can put your input on pin 5 direct to the supply on pin 3.
     
    Last edited: Feb 12, 2015
  3. sammy123

    Thread Starter New Member

    Feb 12, 2015
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    Can the vr1 and vr2 be any value ? And r4?
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You can omit the other resistors on pin 5.. you can use variable resistors to get the required voltage upper limit, and lower resistance.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    The 3914 datasheet and app notes have complete design methods and examples.

    ak
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
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