How to control my 12V Fan with my raspberry?

Hi, I'm fairly new to the "electronic" world, and I recently bought a Raspberry Pi, I made a perspex case for it, and I still had a 12V fan laying around.

So my question is now, how can I manually control the fan speed with my raspberry? and since it's 12V, be safe from frying my raspberry.

If anyone would be able to help me with this, I'd be very grateful!

bprewit over 13 years ago in reply to e14 Contributor

The ground (the downward triangles) connects from the negative terminal of your power source to the circuit. You will also need a ground between the circuit and your board.
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel
e14 Contributor over 13 years ago in reply to bprewit

http://learn.adafruit.com/adafruits-raspberry-pi-lesson-8-using-a-servo-motor/overview
Would this actually be the same, or isn´t it safe enough when I´m using 12V?

also thanks!
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel
bprewit over 13 years ago in reply to e14 Contributor

From a hardware standpoint this is closer. As far as the software, there's a gpio lib in the Adafruit WebIDE .. you set the pin to 1 to turn on the fan and set it to 0 to turn it off.
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel
mcb1 over 13 years ago in reply to bprewit

Bruce
I'm curious why you have included a 100Ohm resistor in the emitter.

its inclusion will limit the amount that the Oi can turn on the fan, so it will never reach its full current of 100mA.

If the fan was able to switched on hard enough, then there would be 10v generated across it at 100mA, which would turn off the drive from the Pi.
By my calculation the maximum fan current will only be 27mA before the 3.3v from the Pi is unable to turn the transistor on.

My suggetsion is to remove the 100Ohm resistor as you already have a 1K in series with the base thereby protecting the Pi GPIO.

Mark
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel
bprewit over 13 years ago in reply to mcb1

Good catch, Mark .. I thought up that circuit without doing any homework on it .. that'll teach me!

You are completely correct, with the 100 Ohm resistor on the emitter, the maximum current is limited to ~30mA. Without the resistor, the circuit will supply >100mA
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel