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Low battery indicator

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psmeets

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I made a mobile PIC uc application but when the battery is low the PIC just stops working all of a sudden.

How can I make a Low Battery Indicator which generates a sound when the (rechargeable!) batteries are low? Used batteries are NIMH type.

Best Regards,
Patrick
 

hI,

There are PIC processors that have a special feature on board to detect low voltage levels see if you can use those...

PIC18F1320 or better PIC18LF1320 !!..

regards,

Paul
 

There are PIC processors that have a special feature on board to detect low voltage levels see if you can use those...

PIC18F1320 or better PIC18LF1320 !!..
Click to expand...

Thanks for your reply but those PICs are way too expensive. I am searching for a solution as an add-on to my existing application (with a 16F628)
 

use a voltage monitor like MAX811/812 or something and connect it to an (interrupt) input of your PIC. These monitor circuits are available in different threshold voltages, are very small and not too expensive.

Mik
 

Hi,

If you want the circuit to be low cost you can use one transistor and two resistors plus a zener.

Take a BC847 or some other low power NPN... connect a 10 K to the collector to plus VCC and your CPU.. connect the other resistor to base and ground and connect the zener to the BATT and base of T1... if the voltage drops below the zener voltage + 0.65 the transistor will give a high level otherwise a low level on the collector...

regards,

Paul.
 

i think the lowest cost approach would be the lm558 used as a voltage comparator
 

Because your circuit is a battery powered unit you cant use normal Comparators which will drain lot of power.
you can use low power CMOS comparator to detect undervoltage.
 

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