Sleepless Night Over Issues

So it is no secret to those close to me that I have an obsessive personality. When I get into something I am INTO it. Right now that is Arduino.

I ordered a low end kit to start with. Didn't want to spend a lot if it wasn't going to stick. It arrived yesterday so even though I got home late I couldn't help but open up the kit and get started.

Of course I started with Blink. But much to my dismay it wouldn't blink :frowning: I spent a few trying to troubleshoot it but had no luck and my eyes wouldn't stay focused any more. Couldn't sleep though. I kept going over the setup in my head, half the night. I am the controls guy for my work so I'm used to similar problems and kept looking at the schematic in my head and couldn't for the life of me sort the issue out. I finally fell asleep resolving to the fact that my cheap Uno knock off had an issue and I would sort it today after work.

This morning I woke up for work and I couldn't help but research and try to sort it. I finally stumbled on some info that said that pin 13 has the 220 ohm resistor already in line so when I added another 220 to the line it killed my voltage. I plugged the LED directly into the uno pins this morning and boom it blinks.

I had another small problem where my sketch would quit working after removing and reinstalling the usb. Found out that sometimes (or maybe all the time) when the usb is plugged back in the uno (or at least mine) goes into some sort of comms loop but if external power is used the sketch works as loaded. I hooked up a 9v and BOOM again, Led blinked away.

Who else loses sleep over their Arduino adventures?

"I finally stumbled on some info that said that pin 13 has the 220 ohm resistor already in line "

That is old information and no longer correct, and hasn't been since 2010 when the Uno came out. See U5B at the top middle of the schematic.

D13 drives a comparator, which drives the L LED.
You should use a current limit resistor between the D13 and the LED anode, cathode to Gnd.

There is a bug with IDE 1.6.8, something about it constantly opening/closing the COM port, which resets the Arduino.
Try an earlier, or a later, version, instead if that's what you have.