# Arduino Due Ohm Meter and 5V issue

I am familiar with electronics but I am confused.

I want to make an Ohm-Meter with Arduino Due. I had previously made one with an arduino mega 1280 BUT, I have read that there is a danger of burning the Arduino Due if i apply an input voltage higher than 3.3v as an input. I have see many simple circuits and they are really simple, but they use 5v to pass from the Ref Resistor and the Unknown Resistor.

I do not understand if using the 5v will damage my Arduino due.

Questions are:

1. Should I use this circuit with 5v?
2. Should I use a different Ref resistor with 3.3v input to get equivalent results?
3. Help me understand when will I have a problem using 5v with Arduino Due.

Thank you for your time and sorry for my bad English grammar.

No, don't use 5V with the Due, use 3.3V - this is clearly indicated everywhere!

Resistor ratios are exactly that - a ratio. Google "ratiometric" for more details.

It would help you provided some background of your experience (electronics in particular). The fact that you are even asking the question you asked suggests you have not looked up the DUE specs

Input and Output

Digital I/O: pins from 0 to 53
Each of the 54 digital pins on the Due can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 3.3 volts.

or have little
electronics experience. This is not an attempt to make you feel bad. It is a conclusion based on observation
and suggests that the first thing we should ask you is if you are familiar with Ohm's Law. (?). Is your only
question about the input voltage level ? Are you familiar with the concept of a voltage divider ? Do you need further assistance in that area ?

Should I use a different Ref resistor with 3.3v input to get equivalent results?

Yes, Changing the reference resistor would lower the voltage of the input to the analog pin. You need
to calculate the correct value for the reference resistor from the analog input pin to GND. Without knowing
the input to your ohm-meter I couldn't comment. Can you post a schematic ?