fan rpm cable

[Puco]

Does somebody know how does the thirt cable of a cpu fan works?, well im using a cpu fan in a univercity project and i need to know the fan rpm. I can conect it to the Motherboard (to cpufan1 or 2 etc) but how do i read for exemple what cpufan1 drops. Or there is another way?

thanks
Puco

good luck!
puco

 

[Crashman]

It pulsates to the revolutions of the fan. Some motherboards have a sensor for reading the pulsations (which are turned into frequency and reported as RPM). Some boards don't use that feature.

If your board is capable, you still need software to report it from windows, some boards come with the software, others don't.

You could also take a reading from the thing with an osciliscope if you like.

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[folken]

I dont know if I'm 100% correct about this or not but one way of looking at it would be sorta like those little things you put you your bike for measuring speed/distance. One piece on the spoke and one piece on the fork and a little device on the handle bars that gives you a speed. When the little things on the spoke and fork connect it gives a signal to the device. Faster succession of signals means faster speed. The motherboard would be sorta like the thing on your handle bars only it interpers the signals into rpms.
There are probably standards out there regarding this so that the rpm reading is correct all the time, such as how far to place the sensors from the center and such. I'm sure it would work fine on a regular motherboard if you got everything placed right.

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[Crashman]

I'm fairly certain the bicycle version uses an electromagnet that never actually touches the pickup however.

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