Hello,
I'm using a 2 cell 7.4v LiPo to power my Arduino Duemilanove.
From what I was told by a friend the voltage cutoff for a 2 cell LiPo battery should be about 6.6v.
How would I safely monitor the LiPo voltage with my Arduino? I know I could use a voltage divider, but I'm unsure on what value resistors to use. (Possibly two 4.7K ohm resistors?)
Thanks for your help.
Michael
Yup, a voltage divider from the LiPo battery to an analog input pin would work fine. Using the same value for both resistors should be fine in this case as you'll get about 3.7V at the A/D input (down to 3.3V at cutoff). 4.7k should be fine, and there's no reason not to go higher to minimize current draw and protect the analog input in case the "lower" resistor gets removed. Even 10k/10k should be OK. Beyond 10k you might start seeing some inaccuracies in your analog readings.
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons
Wow, thanks for the quick response.
I wonder: what would happen if the circuit used two different resistor values?
For example:
LiPo Batt + ----- 4.7k? ------ 10k? ------ GND (LiPo Batt -)
|----- Analog Pin
You've got the analog pin in the wrong place. See here:
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The Rugged Motor Driver: two H-bridges, more power than an L298, fully protected
Ooops, sorry.... that was a spacing issue in the format of the post. It's corrected now. 