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### Topic: Problems finding Vcc using bandgap voltage method (Read 23533 times)previous topic - next topic

#### bilica

#15
##### Jan 13, 2014, 08:14 pm

Would you mind giving more details (or other pointers) ? I am total beginner in this area.

Thanks again,

If you have a spare analog input pin, then a simple solution for any micro is to just wire a precision voltage reference chip to one input and use that value to map the correct range used for the other analog inputs of the ADC.
One of many possible examples:

#### duntax

#16
##### Jun 11, 2014, 05:18 pm
I plan to use this method to protect my LiPo battery pack. Does it make sense to monitor vcc to determine if there is enough power in my 7.4 V battery connected to Vin ? I hope drop in Vcc signals battery undervoltage but I have doubts.

#### retrolefty

#17
##### Jun 11, 2014, 06:11 pmLast Edit: Jun 11, 2014, 07:39 pm by retrolefty Reason: 1

I plan to use this method to protect my LiPo battery pack. Does it make sense to monitor vcc to determine if there is enough power in my 7.4 V battery connected to Vin ? I hope drop in Vcc signals battery undervoltage but I have doubts.

No it won't. The Vin voltage goes to a voltage regulator that maintains a steady Vcc voltage even as Vin is dropping over time. A LiP0 two cell battery will have a voltage output from 8.4 vdc at full charge down to 3  6 vdc where most recommend to stop drawing power from it. You are better off using a voltage divider and measuring the battery directly via a analog input pin to decide when to alarm or shutdown.

#### duntax

#18
##### Jun 11, 2014, 06:14 pm
Just as I guessed. One analog pin lost.

#### duntax

#19
##### Jun 11, 2014, 06:18 pm
And if I have two single cell batteries with a tap between them? Is it enough to measure the voltage at the tap without the divider?

#### retrolefty

#20
##### Jun 11, 2014, 07:40 pm

And if I have two single cell batteries with a tap between them? Is it enough to measure the voltage at the tap without the divider?

Sounds good to me, saves needing the voltage divider.

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