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using ADC to determine low battery ?

 
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M11



Joined: 30 Apr 2011
Posts: 9

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using ADC to determine low battery ?
PostPosted: Sat May 07, 2011 3:02 pm     Reply with quote
Hello,

I want to detect the battery voltage and give a signal when it falls bellow a certain value. I know how to do this using a comparator, but is it possible to do it using the ADC of the PIC16f877 ?

note: the battery is the power source of the PIC.

thanks is advance
temtronic



Joined: 01 Jul 2010
Posts: 9243
Location: Greensville,Ontario

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PostPosted: Sat May 07, 2011 4:06 pm     Reply with quote
Very easy.

Use a voltage divider to reduce the battery max to 5 volts.

Read the ADC, compare the reading to a lookup table of 'Ok, low, dead battery voltages.

Display on LCD or send to PC.

Done.
M11



Joined: 30 Apr 2011
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PostPosted: Sat May 07, 2011 4:23 pm     Reply with quote
but doesn't the reference voltage of the ADC changes when the voltage of the battery changes ?
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Sat May 07, 2011 4:56 pm     Reply with quote
Read these previous threads on the topic:

How to design low battery indicator?
http://www.ccsinfo.com/forum/viewtopic.php?t=24560

How to monitor battery level that is running the PIC itself?
http://www.ccsinfo.com/forum/viewtopic.php?t=27096

Low Voltage Detect interrupt
http://www.ccsinfo.com/forum/viewtopic.php?t=24577

newbee - battery level
http://www.ccsinfo.com/forum/viewtopic.php?t=23186

Checking battery voltage with A/D
http://www.ccsinfo.com/forum/viewtopic.php?t=24842
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