Hi guys, I need some guidance please on the correct way to connect a 5V 30mm pc fan to o/p pin 9. I have 2n2222's but wanna get the resistors correct. Is the following skem correct?
this fan draws 138mA.
Move the 10k resistor from the transistor base to the output pin of the controller.
Adding a free wheel diode to the fan circuit would save the transistor in case of an inductive motor.
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Thanks for the resonse. Will do.
Also could I use a 12v fan instead of a 5v fan, using a 12v supply of course, with this configuration?
That 10k resistor is only needed for mosfets, and can be omited for bjt transistors.
1k is only 4.3mA base current, and might not be enough to saturate the transistor.
If the transistor is not fully saturated, it could get hot and release the magic smoke.
470 ohm (220-470) seems more suitable.
Wise to also add a (1N4004) kickback diode across the motor, to protect the transistor.
Battery symbol is drawn the wrong way round.
Leo..
Thank you.
Yes, 12 volt is fine.
Awesome. Thanks for clarifying all that. 
short and sweet.
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