O.k. so im trying to power a relay with a tip120 transistor. When I look online at other peoples projects they say to use a 1k or 2.2k base resistor. I cant for the life of me figure out how they figured this out.
The transistor is a darlington pair.
It is going to switch the relay on and off.
I will use my arduino uno to control the transistor.
Below is the link for the tip120 data sheet.http://www.azettler.com/pdfs/az973.pdf
Below is the link for the relay data sheet.http://www.azettler.com/pdfs/az973.pdf