Possible duemilanove earthing issue

Hi all,

I have spent the last few days trying to set up a proof of concept for a project I'm planning on starting. I hit a bit of a road block very early on when I couldn't even get the push button sketch to work properly (using Duemilanove). The LED would switch off while uploading the sketch and then be dimly lit once the sketch was running. Pushing the button made the LED go full brightness. I was working on a breadbaord so I thought there might be a short or some other problem with my circuit. I uploaded the sketch to use the built in LED and switch on the arduino and I still get the same problem. The strange part is though when I tightly hold the edges of the board the LED goes off and only turns on when you push the switch, as it should. Even stranger is sometimes it will turn off by itself and somehow when I put my finger near the switch, without even touching it, the LED turns on and when I pull my finger away it turns off. I can get a video of this to give you a better idea of what is going on if anyone wants.

Has anyone seen anything like this before? Is there possibly a fault on my board? Any suggestions on how I could test for a problem with the earth connection on the board?

Thanks for any help :slight_smile:

Post a schematic & sketch.
How old is the breadboard? Might have dirty contacts.

The sketch I'm using is the button example sketch found here

I though a possible breadboard fault as well but I have completely illiminated the breadboard from the circuit. I'm just using the built in switch and D13 LED and I still get the problem.

It's weird because I haven't noticed the problem until now. I've had other projects running on it just fine. I haven't had any problems uploading sketches or anything really. Sus...

Check the switch - those kind of 4 button switches have 2 buttons connected, and the other two buttons connected.
Buzz it out with a meter and see if the connections you want are really happening, leading to this:

"If you disconnect the digital i/o pin from everything, the LED may blink erratically. This is because the input is "floating" - that is, it will randomly return either HIGH or LOW. That's why you need a pull-up or pull-down resistor in the circuit. "

So pin 2 may not really be connected.

Looks like everything is working again. I checked the switch with a multimeter and it was fine. Seems like it's just D2 that has a problem. I tried setting up the circuit for here http://arduino.cc/en/Tutorial/Button to work on D3 and there isn't a problem. This will be fine for my proof of concept work now and I've ordered a fresh board any way :slight_smile:

Thanks for your help!