I need to control 4 panels of 4 leds with the Arduino, I could not simply connect them up to the io pins as 4*4=16 and 16*15ma=240ma. Therefore I plan on using a transistor as a switch to control each of the 4 panels so 4leds*15ma = 60ma a panel.
I plan on using the BC548B transistor (http://www.philohome.com/sensors/gp2d12/gp2d12-datasheets/bc548.pdf) which has a gain of approximately 50x at 1ma so I need to supply it with roughly 1.2ma. Are my calculations correct? Will the transistor run ok with this little base current?
My next possibly stupid question is: The Arduino supplies 5v via it digital io pins and the base max voltage is 5V so do I need to be worried about that or does the resistor stop the 5V from being reached, I presume the latter.
So if I need 60ma flowing from collector to emitter and I have a 9v battery connected and the voltage drop of the led panel is 3.3V, I should have a 100ohm resistor between the battery and the collector?
Thanks in advance :)