Output broken?

Hello,

I just wanted to start a new project and noticed that somehow, Pin 12 of my Arduino UNO (rev 3) seems to output only very low current. So, i took my multimeter and was able to measure only .142 mA, at every other output, i was able to measure around 33 mA. Is it a hardware issue or maybe even software-wise?

Tell us more. Like, how did you measure output current? (It may not have been broken before, but if you got the method wrong, it may well be now)

I measured it directly at the output jacks (between pin and ground).

All pins are about 30mA, Pin 12 just gives me ~140µA

I measured it directly at the output jacks (between pin and ground).

How?

Is the chip warm to the touch? That's usually a good sign the pin is damaged. You do have pinMode set to Output, yes?

AWOL:

I measured it directly at the output jacks (between pin and ground).

How?

Multimeter (Range: 200mA, set to dc of course) -> Test prod #1 to Pin 12, Test prod #2 to GND. Before i took my multimeter, i also tested it using a LED and see if it lights up, it just lights up a bit.

Is the chip warm to the touch? That's usually a good sign the pin is damaged. You do have pinMode set to Output, yes?

Its not warm. Yep, set to output.

What is the current going thru? Just the meter? If so, you probably smoked the pin. The meter has a very low resistance shunt inside to act as a series element, and a voltage measurement is taken across it to calculate the current.

So, you shorted the output to ground via your multimeter? (Can you see where I'm going with this?)

Hah, seems to be my fault then (I thought it would be okay to do so).

But even before i used my multimeter, i used a LED and it didnt really light up but only slightly.

LED with no current limit resistor? Would have similar effect. Poof!

It sounds to me that the transistor that drives the pin high is blown, but the pullup resistor is still working. The transistor that drives the pin low may be working too.

Okay, thank you then. I really have to be more cautious on that ;)