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What's the sense pin for in a processor cooling fan?

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Hi all, i want to use a processor cooling fan in my project and i found a sense pin. Do someone know what is this pin for and how it works? Thanks for your help

Regards
 

case fan pinout

i think that would be the i/o of a temperature sensor.
 

    R

    Rooftop

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3 pin fan pinout

It is for measuring RPM of the fan!! You get two pulses per revolution as output....

Hope this helps
 

    R

    Rooftop

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motherboard fan pinout

thanks, but is the output still TTL level or another level? thanks for your attention

Best regards
 

system fan pinout

Sorry....I don't have much inforamtion, I said what all I read in the datasheet of P4. Try measuring it and remember its open collector output, so you will need a pullup resistor!!

Fan Heatsink Power Supply
The boxed processor's fan heatsink requires a +12V power supply. A fan power cable will
be shipped with the boxed processor to draw power from a power header on the
motherboard. The power cable connector and pinout are shown in Figure 35.
Motherboards must provide a matched power header to support the boxed processor.
Table 37 contains specifications for the input and output signals at the fan heatsink
connector. The fan heatsink outputs a SENSE signal, which is an open-collector output
that pulses at a rate of two pulses per fan revolution. A motherboard pull-up resistor
provides VOH to match the system board-mounted fan speed monitor requirements, if
applicable. Use of the SENSE signal is optional. If the SENSE signal is not used, pin 3 of
the connector should be tied to GND.
Click to expand...

Good luck
 

    R

    Rooftop

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pinout fan

Thanks for the repply.
Now can i connect the sense pin to the interrupt pin of AT89S52?
Is 11.0592 MHz fast enough to detect the interrupt? I know that i need to divide the Clock by 12 but i want to know from someone that ever test the realibility of interrupt pin. Thanks for anyone who helped me

Best regards
 

3 pin case fan pinout

Hi,
Yes this is enough, the frequency on this output is not a very high. But if you want to measure the speed of fan, the better choice is using the internal timer as counter, and count this impulse for the fixed period. In this case you no need to dating every impulse.
 

    R

    Rooftop

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cooling fan pinout

i'm planning to use Interrupt timer 0 and set it to 1 sec. when timer count i will activate the external interrupt so it will count if there's some pulse after the timer overflow i will stop the external interrupt and send the result to the LCD.
That's what i planned.
Anyone have another idea?
Thanks a lot for your help and attention....


Best regards
 

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