Hello everbody! new to the community, look forward to learning lots! i would like to crossfade 1w rgb leds with pwm, but i cant directly do it off arduino. so i was thinking of using a transistor, but need help calculating values of base, and collector resistors..
Id like the leds to run around 300ma. by my Ohms math of R=V/I Blue/green(3.3v) - (13.8-13.2)/.3 = 2ohm red(2.1v) - (13.8-8.4)/.3 = 18ohm now i know just enough that, thats not right.. because somewhere, i have to factor in the base voltage from arduino to the emitter.. i found a transistor base calc, and it said for a 2n2222, to use a 1.3k resistor to be able to saturate the transistor.. not sure what/how to calculate R1 or R2, or where to add the .7V drop of transistor itself..
Any help would be greatly appreciated!!
Heres an example of the blue circuit from arduino: