LM3914 resistor values for 3.7 V Li-Ion battery

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WonHungLo

Joined May 9, 2011
22
i have the circuit built for a 12v dc monitor and i would like to adjust the values to read between 3.0V and 4.2V.
i can not figure out for the life of me what the resistor values would be for the upper and lower limit. i know it's got to be simple.
here is my original schematic and it works great. what would i modify to make it work on a li-ion battery.

 

Dodgydave

Joined Jun 22, 2012
9,400
datasheet remove the resistor R3 and connect pin 4 to pin 2, short out R1, this will give you a full scale of 1.25V.

However the chip wont work below 3V, ideally it should have its own supply, and input the signal into pin 5, the led brightness is controlled by R4.
 
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Thread Starter

WonHungLo

Joined May 9, 2011
22
ok so far so good. i removed R3 and connected pin4 to pin2. when i adjust the 10k pot i can only get the lower half of the LED's to light (its a fully charged battery @ ~4.17V)
what is the resistor i need to change to make all of them light up (i guess you would call it the upper limit)
 

MikeML

Joined Oct 2, 2009
5,444
I was more interested in the underlying science of being able to determine the state of charge of batteries using a voltmeter.
 
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