Digital Readout of actual Voltage on an analog pin

Forum 2005-2010 (read only) Hardware Troubleshooting
#1

I understand that the Analog pins take an analog voltage from wherever source and represent this with a numerical value via a ADC,

what would i need to return the actual voltage read on that pin instead of a numeric value?

is it even possible?

and please dont say "A voltmeter!" hahaha

#2

Multiply the reading by the reference voltage and divide by 1024. The reference voltage is around 5v unless you change the aref setting. The actual 5v line would need to be measured on your particular board if you wanted it exactly. It should be within 2 or 3% of 5 volts in most cases.

#3

Well the input on my board is regulated with an external 7805 Voltage Regulator which offers decently stiff regulation, so just multiply that and divide by 1024 and that should do it huh...

I dont like to connect tons of stuff and have it draw it's power from the arduino 5V line, id rather have a seperate regulator and power everything from that.

Thanks alot!

#4

Don't exceed 5V input. Using a resistor voltage divider, you can read higher voltages.

http://sites.google.com/site/adifferentlemming/Home/projects/arduino#TOC-Voltage-Dividers

#5