how much voltage can a digital and analog pin take ?

I wanted to know how far you can go on a pin voltage before you can expect damage to occour ?

I have protected my inputs with zeners - but wanted to know how critical a overvoltage is

You can put in 0.5V above the supply voltage before you get damage.

Hi Mike, thanks for the reply

Am i right that the supply voltage can go up to 12v ?

No, you are confusing the supply voltage of the board with the chip. Maximum voltage on the chip is 5.5V.

If you think you are going to go over the voltage, you might think about getting a Ruggeduino, which appears to be better protected than a standard Arduino: http://ruggedcircuits.com/html/ruggeduino.html.

which appears to be better protected than a standard Arduino:

Considering an arduino is not protected at all that is not hard. See:- http://www.thebox.myzen.co.uk/Tutorial/Protection.html

Hi, I thought I read in the data sheet that the GPIO pins have protection diodes, not that you should use or rely on them, but section 13.1 of the datasheet suggests that they are there.

Duane B

rcarduino.blogspot.com

Yes there are diodes but that doesn't alter the answer.

In order for the protection diodes to be at all effective you need a series resistor to drop any excess voltage across. They can also take no more than 1mA so they do not offer much protection.

In order for the protection diodes to be at all effective you need a series resistor to drop any excess voltage across. They can also take no more than 1mA so they do not offer much protection.

Where did you find the 1mA value? I've looked around the 328 d/s and didn't see it listed. Sounds awfully low to me.

Also, no one mentioned but even if using zener diodes for protection, they still need series Rs.

Where did you find the 1mA value?

It was in an application note about using the chip as a zero crossing detector for mains.

Search for application note AVR182, it is on page 4.

Search for application note AVR182, it is on page 4.

Thanks, it would have taken me a long while to have run that one down on my own. :-)