Battery voltage indicator using bar graph

[p.gholap93]

I want to do battery voltage indicator using LED bar graph and LM 3914. When battery voltage falls below 10V all the LEDs in bar graph shopuld be off. And when battery voltage is full i.e. 12V all the LEDs should be on. But the problem is if I apply 12V directly to SIG pin of LM3914 then the IC gets heated. Should I connect current limiting resistors externally to the display?

 

[ericgibbs]

I want to do battery voltage indicator using LED bar graph and LM 3914. When battery voltage falls below 10V all the LEDs in bar graph shopuld be off. And when battery voltage is full i.e. 12V all the LEDs should be on. But the problem is if I apply 12V directly to SIG pin of LM3914 then the IC gets heated. Should I connect current limiting resistors externally to the display?

hi,
If the LM3914 is powered from 12V the input voltage has to be less by approx 2V for the LM3914 to work correctly.
A simple solution is a resistive voltage divider for the 12V battery that you want to measure, in this way the LM3914 input is limited to approx 6V.

Use this link to calculate the LM3914 resistors

https://www.electro-tech-online.com/blogs/ericgibbs/136-single-dual-lm3914-v3-0-calculator.html

 

[crutschow]

If you want the circuit to respond between 10V and 12V, then you need to use the Expanded Scale Meter circuit such as shown on page 11 of the data sheet. You can use a resistive divider on the input to reduce your 10V to 12V range to the 4.46V to 5.54V range of the example.

Incidentally, if this is a 12V lead-acid battery, then the full charge voltage is 12.6V, not 12V.

 

[p.gholap93]

If you want the circuit to respond between 10V and 12V, then you need to use the Expanded Scale Meter circuit such as shown on page 11 of the data sheet. You can use a resistive divider on the input to reduce your 10V to 12V range to the 4.46V to 5.54V range of the example.

Incidentally, if this is a 12V lead-acid battery, then the full charge voltage is 12.6V, not 12V.

I didn't get how to calculate the resistance values.

 

[alec_t]

Incidentally, if this is a 12V lead-acid battery, then the full charge voltage is 12.6V, not 12V.

If this is for a car battery the voltage could be up to ~ 14V.

 

[p.gholap93]

If this is for a car battery the voltage could be up to ~ 14V.

I am using lithium ion battery.

 

[ericgibbs]

I am using lithium ion battery.

hi,
Look at this option.