Another newbie Q… trying out this transistor.
I put a LED & 220 ohm in the C-E line on 5V on Arduino (10 mA).
Even without any connection to the Base, the LED is burning! :o
I can get even more mA on the C-E line, the Base unconnected.
Who can explain this to me, tnx.
2N3904 transistor.pdf (66.1 KB)
It is a high gain transistor and the floating base is acting as an aerial.
Ground the base and it should go out.
Weedpharma
Even with the base grounded the LED keeps burning... 
I'm not sure what you mean by "the C-E line"... post a schematic.
I mean LED between 5V and Collector, same as here, but other transistor
Maybe it's a breadboard/layout issue.
Maybe it's a bad transistor.
"220 ohms": so it's red-red-brown? (red-red-black is 22 ohms, that might make for some heat etc)
Hi,
I think we need a picture of how you have set it up.
Tom... 