I'm sorry, I shorted 5V to ground. Fixable on Uno R1?

So, while I was playing with LED’s, I accidentally shorted the 5V supply (not I/O, but the 5V pin) to ground. The LED died, but my arduino is also acting weird. I’m having trouble getting windows to recognize the arduino (unrecognized usb device). If I tap the arduino, the amber LED sometimes turns off, tap it again it turns back on.

Is it dead?

I read this in another forum post, but I dont’ know if it applies to my Arduino Uno (R1).

If using external power either via the arduino board’s external power connector or the shield Vin pin, the results of a short circuit on the Arduino +5vdc bus would be that the on-board +5vdc voltage regulator will go into self protection mode and turn off the +5vdc bus until the short circuit is removed.

Have you left it for at least two hours for the polyfuse to cool down fully?

Yes, I've left it over night now. I just googled about the polyfuse on an Uno...is that only on the USB portion of the circuit? I was powering the Uno with the 9VDC adapter at the time I fried the LED.

i think NOT the LED but the RESISTOR in series with the LED is burnt. One tweak. you can connect a diode in reverse condition with the supply in parallel, so that if anything wrong happens, the current can pass through the diode not through the device.

This simple tweak can save a lot amount of time & money.

arusr: Yes, I've left it over night now. I just googled about the polyfuse on an Uno...is that only on the USB portion of the circuit?

Yes.

arusr: I was powering the Uno with the 9VDC adapter at the time I fried the LED.

Oh dear! Can't offer much more help then.

What's the 5V pin voltage now? Could be a damaged regulator. The protection on those things isn't always fast enough.

I electronics is pretty weak. I took a look at what I think is the 5V regulator. On pictures of other Uno's, there are 3 pins on what I think is the 5V regulator. On my damaged one, the middle pin is totally gone. Did I burn it off somehow when I shorted the 5V to ground?

Here's a picture of what I'm talking about:

http://i44.tinypic.com/9rrcyh.jpg

On my damaged one, the middle pin is totally gone. Did I burn it off somehow when I shorted the 5V to ground?

Sounds like it. You need to replace the regulator chip. You probably need a hot air resoldering station to replace it as there is a pad underneath soldered directly to the copper track and you can't get enough heat from a normal iron to remove it. While there is a thermal shutdown on the regulator it doesn't not always stop it from burning out as you have found.

It's weird. The middle pin is no longer touching the PCB, but I can still power the board up with the regular 2.1mm AC adapter plug. It's just that the board acts funny - the pin 13 LED come on...then turn off if I shake the board or just randomly it seems. I might try reconnecting that middle pin back onto the PCB with a short wire.

I might try reconnecting that middle pin back onto the PCB with a short wire.

Thought you said it was gone not that it had just lifted.

but I can still power the board up with the regular 2.1mm AC adapter plug.

I hope you are not putting AC into the board.

It's just that the board acts funny

Best not to try and power the board up witha regulator miss wired, you could be applying too much voltage to the board.

I don't know about that particular regulator IC, but sometimes the tab is electrically connected to one of the pins, so it may not be a missing pin -- it might not have ever been there, if the tab is taking its place. Do you see any evidence of damage? If it were hot enough to destroy a pin, there would be discoloration somewhere.

From my experience (which, granted, is limited), when a regulator goes poof, it usually splits the case. The pins don't vaporize.

oh, ok. I don't remember what it looked like before. And the case of the regulator (if I'm looking at the correct component) is intact and looks ok. There is no evidence that there was heat damage, I'm going purely from the picture of the Uno I see online - online the pictures show the middle pin connected to the PCB, on mine the long lead on the middle pin is just floating there, no connection. The "pad" where the lead goes is pretty smooth - like a nice round mound. I have no experience with soldering, but I'm guessing if heat damage cause the pin to break off somehow I should see evidence of it on the pad.

Still, it's a mystery why all the pictures I see online show that pin connected.

on mine the long lead on the middle pin is just floating there, no connection.

It sounds like you have a faulty board that only passed the factory tests because it was touching the track. Now it has lifted. So either send it back and report it as faulty, tell them about this lead. OR solder it back yourself.