I have very little electronic background so I am sorry for the simple question. Could someone look at the attached schematic and help me determine R2? I would also like to add a led and resistor to show the power output, ie. when the TIP120 output is zero the led is off, when the TIP120 is outputting 1/2 power the led is 1/2 bright, etc.
Thank you so much for your help.