I'm new to Arduino. Recently bought a starter kit and was applying some tutorials I watched , was amazed how I could make some basic and some advanced LED light setups and animations. When I tried to upload a new sketch to my Arduino board (its a clone btw) I noticed whatever I did the upload process gets stuck at about 80-90% level. The reason I think its a short circuit problem is because my hand and fingers were keep touching the back of the board which made the boards pin13 LED to go dim. Could this be the problem? I ordered a new board and don't want to make the same mistake.
Plus what would you suggest me to do to seal the backside of the board to avoid short circuits ?
My boards do the same thing, (the LED dimming when the pin is an input), depending on what I sit them on. Even sitting them on the cloth cover I have on my printer can have an effect. It's never done any harm, though, and programs always upload to the boards without a hitch.
When pin 13 is an input, it can take any state that it wants, since it's floating, but if it goes high it turns the LED on via the LMV358 that drives it. It only takes the touch of a finger or even something else that conducts only slightly to pull it low again though. That's the behaviour you're seeing.
I just did it heaps of times a minute ago, and code still uploads fine, even when i hold the board with the back firmly touching my hand.
N.B. If pin 13 is configured as an output, you won't see that behaviour. The LED will either be on or off, depending on whether you write the pin high or low, and no amount of touching it will dim the LED.
Still, technically, you shouldn't touch pins, (including solder connections to pins), with your fingers due to the risk of static damage, so sticking something on the back is probably a good idea. You could attach the board to a small piece of plastic sheet with hot-melt glue, if you're really concerned.
Edit: If I set pin 13 to 'INPUT_PULLUP', the behaviour disappears, too, and the LED stays lit when I touch that area of the back of the board.
I reckon that most likely something else is causing your upload problem