Measurement of Battery Voltage

[Bene]

Hi,

first of all i like to thank you for your work on this projekt - I like mysensors very much!

I have a question regarding voltage measurement of a battery.

On this site (http://provideyourown.com/2012/secret-arduino-voltmeter-measure-battery-voltage/) i read, that you can measure the voltage of the battery without the need of seperate analog pin using the internal reference only.
In the Guide on mysensors (Battery powered sensor) you use two resistors and an analog pin to read the voltage.

From my perspective the way only using the internal refenrece voltage of 1.1V needs fewer components (no additional resistors, no analog pin) and should save some current that would otherwise flow through the resistors.

Is there any advantage in doing it the way described on mysensors that i am missing?

Thank you for your help!

Kindly Regards
Bene

[Yveaux]

@Bene Hi and welcome to the forum!
Some time ago I wrote a library which exactly implements the method described on the site you mentioned.
There's a topic devoted to this Vcc library, which you can find here.
The drawbacks of this method are:

• you cannot use it when a regulator is used to power the AVR; it needs to be directly powered from the battery
• it isn't very accurate, but can be calibrated to increase accuracy.

[Bene]

@Yveaux Many Thanks for your answer!
Unfortunately, I had not found your article and sketch on the search.
That explains a lot :-)

[Yveaux]

@Bene Always use google to search on MySensors forum; it's much better than the integrated search.
Just add site:mysensors.org to your google query to limit results to this site only, e.g: search vcc