Have I fried my Arduino Pro Mini?

So, as the electronics and Arduino n00b I am, I think I might have fried my Arduino Pro Mini, but I'm not sure.

To power the Mini, I have connected one cable to GND and one to +5V. To test it all out, I connected these cables to the same outputs of a Arduino Duemilanove, which worked fine. Then I connected the cables to a 2.1mm DC plug, with a 9V positive tip adapter connected to it. Since this did not work, I fiddled around a bit with the cables from the Mini to the plug. It still did not work.

Then I tried to connect the Mini to the Duemilanove again, but this did not work either. I opened up the box in which the Mini is installed (a project of mine) and when using the Duemilanove, a LED on the Mini lights up. However, the sketch does not work (a LCD should light up, but it does not).

I realize that I really should have connected the power cable to the RAW input on the Mini and not the +5V. However, since the light on the Mini is on, have I fried it or is it possible that something else is wrong?

I noticed that the cable to the TX connection on the Mini was loose (bad soldering), but I thought that this would just stop the Mini from sending data, the LCD would still work?

Help and advice would be appreciated!

Putting 9V threw the 5V pin likely fried the micro controller itself. The rest of the components may be OK but on that unit with the controller fried you've trashed the entire thing. Unless you have the right equipment and are a wiz at soldering. Then you could replace the chip.

Okay, that's what I was afraid of (but also what I expected) :frowning:
How come the power LED on the Mini still lights up? Is this because this LED doesn't run through the chip or something similar?

Also, when trying this the next time (hopefully doing things right), can I fry the chip by connecting it to a negative tip instead of a positive tip? And, to be sure, the 9V should be run through the RAW pin?

I’ve fried the voltage regulators on a couple of Pro Minis, and they still work just fine through the FTDI cable and the 5Vin pin. It’s quite possible that if you fried everything EXCEPT the voltage regulator and attached circuit, that stuff is still working fine.

Is this because this LED doesn't run through the chip or something similar?

It is more likely that the LED is a bit more robust in resisting over voltage. The current is limited by a resistor and is normally run way below the maximum current anyway so you probably didn't exceed the rating of the LED.

Okay, but next time connect to RAW instead of 5V, right?

If you connect a pro mini raw input with the wrong polarity, you fry the electrolytic cap on the input as well. Mine still works though.

And, just to directly answer the question, yes, plug the positive into the raw VIN input.

Okay, so then I'll connect the voltage from the positive tip to the RAW and GND to GND. Thanks for all your help! Better luck next time :sunglasses: