low battery indicator

[gauravkothari23]

hi all...
i am in need of a low battery indicator..... i am using 3.7v li-ion battery... i want to use the led as a warning...
so at 3.2v i want the led to glow and give a warning of low battery....
can anybody help me with the circuit diagram...

 

[KlausST]

Hi,

One solution is to use LTC1540.
Please read datasheet completely and come back if you have any questions.

***
The problem is you did not decide how to switch off the LED. So it will discharge the battery to an unhealthy level.
The under discharge really may kill your battery.

Please provide complete informations.

Klaus

 

[gauravkothari23]

sorry klaust... i tried.. bt not geting anything...
as i am new to electronics... understanding the datasheet and components is bit difficult for me...

 

[KlausST]

Where is the difficulty?

A 1.182V reference voltage..
A comparator...to compare the reference voltage with the voltage divider signal
And a two resistor voltage divider to divide your 3.2V input to 1.182V...

In the datasheet on the first page you see exactely what you need, but for 2.9V.

Klaus

 

[gauravkothari23]

Where is the difficulty?

A 1.182V reference voltage..
A comparator...to compare the reference voltage with the voltage divider signal
And a two resistor voltage divider to divide your 3.2V input to 1.182V...

In the datasheet on the first page you see exactely what you need, but for 2.9V.

Klaus

yes.... it shows but at 2.9v....
but i want it to work for 3.7v battery and low indication at 3.2v

 

[KlausST]

Hi,

You really should learn about ohm's law.
It's the most basic knowledge in electronics.

You should also learn how to calculate a resistive voltage divider.

And if you don't know how there are two chapters in the datasheet with well explained examples.
* "Level detector"
* "Low-battery detect"

Klaus