fan speed

[ThePCmanWAnnaB]

does anyone knows how the fan tells its speed to the fan controler?
is there any way i can change a two wire fan(+ and - terminals ) into a three wire fan(+,- and speed)?
thanks

 

[ddviper]

i dont think the fan tells the fan controller its speed, i think the fan controller just supplys more or less power to the fan. u have to connect it to the mobo to find out the RPM's

 

[ThePCmanWAnnaB]

lots of fans have three wires,like the cpu fanand some case fans,they do tell the mobo their rpm, if i am not mistaken the wire the tells the rpms is yellow.so there i got to be way how they do it.my idea is that the mobo or fan controler get a return voltage on the yellow.but i need to make sure.

 

[Spike]

I have also heard that it is the yellow wire. Alot of fans are two pin and so you can't actually read the RPMs but some are three pinned and the mobo or fan controller can report RPM. Check your bios under "PC Health" or something like that and you can monitor RPMs, Temps, and Voltages or get a windows-based monitoring program.

-spike

 

[Operandi]

If it's a 3 pin fan it's the yellow wire (90%) of the time. If there is no third wire the fan lacks the RPM monitoring circuitry and RPM monitoring is not possible.