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  1. #1
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    Battery Monitor - Why do we need a diode?

    Hello,

    I'm using an Arduino Mega 2560 board with some custom code based on the AeroQuad code.
    I want to add a battery monitor, but I think I'm missing something:

    The battery monitoring is done using the analog input pins of the arduino, right? These pins measure 0-5VDC, so we need a resistor divider to get 0-5V from 11.1V.

    I followed the instructions on this page:
    http://aeroquad.com/showwiki.php?tit...tery%20Monitor

    On the electrical diagram you see a diode from Vin to the resistors, blocking current flow from the arduino to the battery. While this sounds like a good protection to have, why would we need this? The input pins do not supply voltage.
    Also, what resistors should I use? My logic says to use as large resistors as possible to minimize current through the battery monitor. Should I reconsider?

    Thanks
    Nitay

  2. #2
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    That would be a protection against wrong polarity, I believe.

  3. #3
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    Okay, thanks.

    What about the resistors? As large as i get?

  4. #4
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    please check:
    http://aeroquad.com/showwiki.php?title=Battery+Monitor

    (bat)----|>|-----[R1]----(ain)----[R2]----(gnd)
    D1
    I used for a 3S ( 11.1Volt )
    R1 15K
    R2 7.5 K

    Hope it helps.


 

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