3 Wire PC Fans

[lamborgini8]

Just to make myself clear on this the 3 wires on PC fans are + - and one for the speed sensor right?

 

[MarioMaster]

Just to make myself clear on this the 3 wires on PC fans are + - and one for the speed sensor right?

yep the third wire is RPM monitoring, some fans have a fourth lead for PWM input

 

[nikokapo]

Try googling it, there are lots of guides on how to connect various coolers in which they tell you which pin is which =)

 

[sad_sagi]

ive been wondering that too... i see more 3 pin fans than 2 and would like some cheap fans for other uses than in a computer

 

[nikokapo]

ive been wondering that too... i see more 3 pin fans than 2 and would like some cheap fans for other uses than in a computer

That was addressed in this thread

the third pin is for information (RPM Speed, etc.), if there is a fourth one is for PWM control

 

[Archane]

it could also be powered by a Stepper motor like harddrives.

 

[sad_sagi]

[quote author=sad_sagi link=1236716198/0#3 date=1236731806]ive been wondering that too... i see more 3 pin fans than 2 and would like some cheap fans for other uses than in a computer

That was addressed in this thread

the third pin is for information (RPM Speed, etc.), if there is a fourth one is for PWM control [/quote]
i know i meant when i shop for fans on newegg and dx i look for a dc 2 wire fan, but only see the 3 wire ones, because i assumed they were "brushless" 3 wire ones that needed a special controller.
now i'm going to buy some to play with the area i put my ps3 in gets toasty, i was gonna help it out with some fans

 

[charleytown55il]

i think some brushless 3 wire fans use 3-phase ac voltage from variable fequency drives, just like large industral 3-phase motors. the only difference it that they use 5 or 12 volts ac instead of 208, 230, 460 volts ac.

 

[erdabyz]

yeah, indeed most of them have 3phase motors, but they have integrated circuitery to drive the motor from 12VDC, so there's no need for external 3 phase input because the fan generates it itself. That's why you can't easily change rotation direction changing polarity.

The third wire is for communication, some kind of serial port communication

 

[pseudolobster]

Today I replaced a noisy fan in a computer power supply, I used a 3-wire case fan but the power supply's fan only used 2 wires. Since the case fan's connectors went black, red, yellow (-, +, rpm), and the header went black, red (-, +), I just plugged it in with the yellow wire not connected to anything. Works fine, I do this on a regular basis.

As long as you make sure the positive and negative are connected correctly, the extra wire is optional.

 

[lamborgini8]

Whoops, forgot about this thread.

Its going to be used in my scanner build hence the fans I am looking at are 40mm. I just wanted to confirm the wires because the fan will be wired to the scanners PSU, last thing I want is to wire up the wrong ones.

The fan will be run at 15V instead of 12V, im sure it will be fine but I don't think there are any 15V fans about.