Arduino Forum

Using Arduino => General Electronics => Topic started by: Deepak_s on Feb 14, 2020, 02:48 pm

Title: Analog internal reference
Post by: Deepak_s on Feb 14, 2020, 02:48 pm
I want to know if I power my Arduino mega with less than 5v, what will be the internal reference value that Arduin take to compare my analog input. Which is say 0-5v.
Title: Re: Analog internal reference
Post by: groundFungus on Feb 14, 2020, 03:39 pm
The default analog reference is Vcc so if Vcc is less (or greater) than 5V so will the analog reference. 
Title: Re: Analog internal reference
Post by: DVDdoug on Feb 14, 2020, 04:40 pm
There is also an optional internal 1.1V reference which is very stable (but there is a tolerance so it may not be exactly 1.1V).

If you are have a pot some other voltage-divider/proportional type of circuit it's better to have the reference tied to Vcc.   If you need to measure absolute voltage accurately then of course, you need a stable reference.
Title: Re: Analog internal reference
Post by: groundFungus on Feb 14, 2020, 05:26 pm
The reference (https://www.arduino.cc/reference/tr/language/functions/analog-io/analogreference/) also mentions a 2.56V analog reference for the Mega.

INTERNAL2V56: a built-in 2.56V reference (Arduino Mega only)
Title: Re: Analog internal reference
Post by: JCA34F on Feb 15, 2020, 04:47 am
Quote
I want to know if I power my Arduino mega with less than 5v
How much less? There's a limit to how much you can reduce power supply and still run the clock at 16MHz.
Title: Re: Analog internal reference
Post by: CrossRoads on Feb 15, 2020, 05:51 am
4.5V is the lower limit for the Atmega2560.

There is an Atmega2560V that can run at lower voltages, but it is not used on Mega2560 boards.