Update 1 :
After some help and advices from nice people here i'm going to use this circuit : http://everycircuit.com/circuit/5857347480322048
the 25 ohm resistance being the fan.
I'm requesting your help for a little electronic circuit, a simple transistor switch. I need help because i don't know how to choose the right transistor or the right resistance for my circuit. I need advice for adding a protective diode.
I explain myself :
it's a circuit that switch a 5v 0.2A dc fan to cool my raspberry pi because i use it intensively.
here is the circuit i designed :
updated (look up)
the online link to it : Updated to new link (look up) (the 25ohm resistance is the fan's resistance, i didn't know how to modelise it).
I use the 5v pin to power the fan and a gpio pin (3.3V 16mA) to turn the transistor on/off by a python code i will do myself later.
is the resistance choosen ok ? how can i choose the right transistor after it's specs ?
if i get to make the circuit work fine, i will then use the PWM pin of the RPI to make it's speed variable with the temperature of the CPU, but that's after.
i hope my question is complete, What do you guys think ?