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Full Version: LiPo Voltage Measurement
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Dear All,

I'm in the process of designing a simple voltmeter with PIC32MX440P Pinguino, do you think it is safe to directly connect a relatively high capacity li-po battery terminal to one of the ADC inputs? Confused I am not sure if a buffer opamp (along with its own supply etc) is absolutely necessary, could you please let me know about your experience/suggestions? I don't want to burn my Pingu! Shy
Thank you

sorry wrong section, has nothing to do with displays, meant to ask this in "Interfacing"...
So long as the voltage is in range, yes.

John
Yes if it's in voltage range. Remember that you can measure only voltage that is less or equal the voltage reference
Thanks, what a relief Smile the voltage range is 2.7-4.2, should be alright if i use the 5V supply voltage as reference. I hope i can share more details as i progress in a few days, cheers
I think not! Check max voltage which is roughly 3.3V for a PIC32.

Only the digital inputs are 5V tolerant.

Use a voltage divider...

John
Please check your datasheet first, If you're processor runs on 3.3V, it'll most probably have an ADC range of 0-3V (not 3.3V remember). Also, it won't be harmful to use a little protection, a zener diode in inverse direction, maybe.

prototype pcb assembly
You can use a simple resistor voltage divider.

Connect 4.7K from LiPo (to measure) to ADC pin, connect 10K from ADC pin to ground. It will provide the range of around 4.9V input to 3.3V operating PIC32. The current passing through is less than 0.5mA.

Don't forget to calibrate the ADC count to voltage using a known voltage source.