LM3914 resistor values for 4.2V to 3V Li-Ion battery

Discussion in 'The Projects Forum' started by gauravkothari23, Nov 13, 2015.

  1. gauravkothari23

    Thread Starter New Member

    Nov 13, 2015
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    Mod edit:
    Please don't hijack the other member's post, now you have your own.
    This thread was split from -- LM3914 resistor values for 3.7 V Li-Ion battery.



    can you please help me out of this.....
    i have tried building the same circuit.... but its not giving me a proper value.... it works for 4.2v to 0v... but i need it for 4.2 to 3v...
    its not giving me the proper output..... HAVE ATTACHED MY CIRCUIT DIAGRAM...
     
  2. Dodgydave

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    Jun 22, 2012
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    With the circuit drawn its set for 1.25v upper limit, the adjust pin8 needs a 1.2k resistor to pin 7, and a 2.9k to ground (pin2) that will give you the upper limit of 4.2v, and a 25k from pin 4 to ground to set the lower limit of 3v.
     
  3. gauravkothari23

    Thread Starter New Member

    Nov 13, 2015
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    I AM ATTACHING AGAIN A NEW REVISED CIRCUIT DIAGRAM.... CAN U PLEASE CHECK AND LET ME KNOW IF IT IS PORPER OR NEED SOME CHANGES.....
    THANKS.....
     
  4. Dodgydave

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    Jun 22, 2012
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    No, remove R3 and remove the link from pin 4 to pin 2, pin 8 goes to the junction of R4 and R5, R4 connects from the junction to pins 6,7.
     
    Last edited: Nov 14, 2015
  5. gauravkothari23

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    Nov 13, 2015
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    @Dodgydave..... kindly request you to please check it out my new edited circuit attached here.....
    is my circuit proper or need to change something again.....
    will this work for 3.7v battery.... between 4.2v and 3v
    Thanks Again for your efforts......
     
  6. Dodgydave

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    Jun 22, 2012
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    Looks better.
     
  7. gauravkothari23

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    Nov 13, 2015
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    but i tried with both 3v and 3.80v.....
    status shows is the same......
     
  8. gauravkothari23

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    Nov 13, 2015
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    what is the 10kpot use for....
    i am not able to adjust anything
     
  9. Dodgydave

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    Jun 22, 2012
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    Why don't you start by telling us what you are trying to do, what voltage supply, what voltage input, then we can design it better.
     
  10. gauravkothari23

    Thread Starter New Member

    Nov 13, 2015
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    actually i want to make a 3.7v 2600mah li-ion battery indicator.
    4.2v = battery status full.
    3.0v = battery low.
    as per your suggestions above i tried to make one circuit which is not working.
    i tried connecting two 3.7v batteries one by one....
    one of 3.80v which shows full indication and second one 3.10v which again shows full indication.
     
  11. Dodgydave

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    Jun 22, 2012
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    Ok, omit the preset R2, and connect pin 5 to pin3 supply, then when the voltage is applied it will read the supply, but the chip only works down to 3v.
     
    Last edited: Nov 14, 2015
  12. gauravkothari23

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    Nov 13, 2015
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    Is it the perfect one....??
     
  13. gauravkothari23

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    Nov 13, 2015
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    yes... but even at 3.80v it shows full indication.... atleast it should show 70 or 80%
    but at 3.10v it shows low indication which is perfect...
     
  14. Dodgydave

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    Jun 22, 2012
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    Ok so you need to alter the upper reference on pin6 by increasing R5, better to make R5 a 4.7k preset.
     
  15. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Does the voltage reference need a dropout voltage to function?
    I would set the sig in on a fixed divider and adjust the voltage reference to the divider.

    Bertus
     
  16. gauravkothari23

    Thread Starter New Member

    Nov 13, 2015
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    sorry.... but am not getting an satisfied output....
     
  17. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Try the following circuit:

    gaurav_voltmeter.png

    Bertus
     
  18. gauravkothari23

    Thread Starter New Member

    Nov 13, 2015
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    Even This Circuit Does not work.....
    It shows Full Indication on 4.0v And also 3.10v
     
  19. Dodgydave

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    Jun 22, 2012
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    go back to the circuit in post #12, and replace R5 for a variable one, and adjust it to give you the full scale when you input 4.2v.
     
    Last edited: Nov 15, 2015
  20. gauravkothari23

    Thread Starter New Member

    Nov 13, 2015
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    @Dodgydave..... Have you ever visited your primary school.... i doubt you had..... because if you had visited you would have easily realized that who's a stupid person.....
    Keep your ideas.. your knowledge with you.... before blaming someone else.... have you yourself tried if your ideas work or not.....
     
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