In a previous question I posted to the exchange I asked for some instructions on trying to variable speed control a motor. Someone suggested utilizing PWM from my Arduino to open and close a Darlington pair to control speed. I wired it up and ended up frying my darlington pair. I am afraid that I screwed up something with the flyback diode... I am not certain. I am not sure where to trouble shoot what I did wrong. The transistors and flyback diode were very hot to the touch.
What kind of ratings and type of diode should I look for when looking to eliminate flyback voltage from a 18 VDC, 1.5 motor? How would I wire this correctly when using PWM from an Arduino to control a transistor pair?
I am a very new hobbyist and am having trouble wrapping my head around this issue.