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

Thread Starter

gauravkothari23

Joined Nov 13, 2015
14
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...
 

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Dodgydave

Joined Jun 22, 2012
8,373
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.
 

Thread Starter

gauravkothari23

Joined Nov 13, 2015
14
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.
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.....
 

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Dodgydave

Joined Jun 22, 2012
8,373
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.
 
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Thread Starter

gauravkothari23

Joined Nov 13, 2015
14
@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......
 

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Dodgydave

Joined Jun 22, 2012
8,373
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.
 

Thread Starter

gauravkothari23

Joined Nov 13, 2015
14
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.
 

Dodgydave

Joined Jun 22, 2012
8,373
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.
 
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Thread Starter

gauravkothari23

Joined Nov 13, 2015
14
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...
 

Dodgydave

Joined Jun 22, 2012
8,373
Ok so you need to alter the upper reference on pin6 by increasing R5, better to make R5 a 4.7k preset.
 

bertus

Joined Apr 5, 2008
20,044
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
 

Dodgydave

Joined Jun 22, 2012
8,373
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.
 
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Thread Starter

gauravkothari23

Joined Nov 13, 2015
14
@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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