pc cooling fan rpm monitoring

[Kamikaze47]

does any1 know how the rpm monitoring pin works on pc cooling fans?

I assume it will send a pulse either once per revolution or maybe 2 or 4 per revolution?

i googled it but couldnt find info

[Kamikaze47]

found the info eventually after googling a while longer...

for any1 who also wants to know, a pulse is generated twice per revolution, and its an open collector output so requires a 10k pull-up resistor for input to a PIC.

[Luciano]

Hi,

Did you search for "cooling fan" on this forum?

Luciano