How can I read rpms at 7v ?

charger2000 · Post by **charger2000** » Wed Sep 13, 2006 2:31 am

I have a simple adapter from 12v to 7v, it even has the third wire for techimeter reading but..., I can't read the rpms of any fans on any MB.

I was thinking that the 12v to 7v adapter using the black wire (ground) to get the 5v (+12 + 5 = 7), can't provide the ground for the tachimeter reading.

Sorry for my questionable english ...

Bluefront · Post by **Bluefront** » Wed Sep 13, 2006 3:18 am

I suppose you are using the 7V mod using the 12V and 5V leads? This is a questionable mod, and probably causing your problem. I'd suggest using a Fanmate instead to get the 7V.....

charger2000 · Post by **charger2000** » Wed Sep 13, 2006 4:07 am

yes I have that too, but how can I be sure that the output is 7v, with a voltmeter to place on the exit, but with a load ?

Elixer · Post by **Elixer** » Wed Sep 13, 2006 1:50 pm

What's the fan's rpm at 12V? It's likely that your fan is spinning too slowly for your motherboard to detect it. My motherboard won't read the speed if the fan is spinning slower than ~1200rpm.

Bluefront · Post by **Bluefront** » Wed Sep 13, 2006 3:23 pm

Some boards won't read low rpms...very true. Just how necessary is it to run at exactly 7V? Turn your fanmate to the left....that's about 5V. Then turn it to the right slightly......that'll be about 7V.

charger2000 · Post by **charger2000** » Wed Sep 13, 2006 11:55 pm

no, the MB reads the rpms at 5v, so it must read them at 7v.
I'll play with the voltmeter, trying to avoid short circuits...