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Forum Index : Microcontroller and PC projects : Battery Measurement

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lew247

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Joined: 23/12/2015
Location: United Kingdom
Posts: 1702
Posted: 08:36am 10 Mar 2016
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Is the circuit below sufficient to measure voltage on a micromite?
The battery I want to measure is a 5V battery.
I'm as assuming (hoping) the ADC will be measuring 0-2.5V?

Will the resistors drain the battery? ie if I expect the battery to last for a very long time without the circuit will it take much from the battery?





Edited by lew247 2016-03-11
 
matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10250
Posted: 08:44am 10 Mar 2016
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  Quote  Will the resistors drain the battery?


Yes, power consumed is (V*V)/R so in your example roughly 2.6mA

There is an easy way round this: Connect the bottom of the divider to another Micromite pin that is set as an input and then just set it to a low output when you want to take the measurement leaving a few milliseconds for the capacitor to charge before taking the reading. Once you have the reading set the MM pin back to an input.
 
lew247

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Posted: 08:48am 10 Mar 2016
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Thank you so much
 
matherp
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Posted: 08:54am 10 Mar 2016
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  Quote  Yes, power consumed is (V*V)/R so in your example roughly 2.6mA


Sorry should read "2.6mW" or 0.52mA
 
bigmik

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Joined: 20/06/2011
Location: Australia
Posts: 2949
Posted: 10:32am 10 Mar 2016
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Hi Lew,

I don't think you need the Capacitor at all..

Just the 2 resistors is fine.. You can always increase the values to minimise current drain..

Mick
Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<
 
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