why is it necessary to use a transistor here? why not just

>>60675585
the pin can't source enough current for the motor

arduino can only put out a miniscule amount of current

>>60675630
only 40mA, if I am not mistaken

The transistor acts as a switch, using the small current from the arduino to allow the 9V current to power the motor.

Welcome to why transistors are so important.

>>60675585 Too much voltage and not enough current

>>60675585
Why do you have a phototransistor in there? You should just have a normal NPN in there.

>>60675585
If you don't use PWM you can use that scheme, if you use PWM however, you should definitely use another resistor between emmiter and base (10k would be good)

>>60675765
He should have a resistor that works based on audio levels. You know, so he can make a fucking machine that speeds up if he stops moaning like a fuckbitch

try it for yourself and find out!

>>60675971
also for additional fun leave out that snubber diode

>>60675585
Hey. You know it's 2017, would you please use txsistor instead of that other word you used. Some people find that word offensive and I'm pretty sure it's against our Code of Conduct. Thanks, sorry I had to call you out. I'm sure you weren't being intentionally insensitive and it was just ignorance on your part.

>>60676082
You forgot to mention IGBT community. People have no idea what they have to go through every day.