# Arduino Forum

## Forum 2005-2010 (read only) => Hardware => Interfacing => Topic started by: dragonuv on Feb 23, 2009, 08:24 pm

Title: extend the 5v range of the analog pins
Post by: dragonuv on Feb 23, 2009, 08:24 pm
hi, is it possible to extend the range of the analog pins to check a higher amount of voltage? lets say 10, and it will show '1023' on the serial screen when it got the 10v.
Title: Re: extend the 5v range of the analog pins
Post by: etracer on Feb 23, 2009, 08:41 pm
The Voltage Divider (http://en.wikipedia.org/wiki/Voltage_divider) is your friend.
Title: Re: extend the 5v range of the analog pins
Post by: florinc on Feb 23, 2009, 08:50 pm
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1234714469/1#1
Title: Re: extend the 5v range of the analog pins
Post by: dragonuv on Feb 23, 2009, 09:07 pm
thanks very much, i drawed a little schematic with Vin, Vout and 2 resistors, the Vout is 5v and the Vin is 12v, i was still missing one variable on the equation 5/12=R2/(R2+R1) i decided that R2=1000ohms, considering that resistors have a limitted wattage they can handle, and the higher the ohms are, the lower the wattage is.
which means that R1 needs to be 1400 ohms.

i checked just to make sure the values are ok. I = 12/2400 = 0.005,

Vr2 = 0.005*1000 = 5

thanks :)
Title: Re: extend the 5v range of the analog pins
Post by: macegr on Feb 24, 2009, 01:49 am