Multiple PWM fan adapter

bilbat · 10-04-2008, 01:03 AM

If you need to get an additional fan running of your MOBO's PWM CPU Fan header, this will work, and provide monitoring of the second fan:

If you need more than one extra, you can simply 'daisy-chain' them:

PWM JEDEC spec says MOBO PWM headers 'should' supply 1.5A steady-state, and tolerate a 2.2A start-up surge. Most of the fans I've checked seem to run around .11 to .16 A, so several should be OK. Your mileage may vary. Good luck trying to find your MOBO's spec for this!

**Lsdmeasap** · 10-04-2008, 08:04 PM

Nice diagrams!

PrairieDawg · 10-04-2008, 10:32 PM

Your diagrams are nice but I'm curious how many fans one could run from a single mobo header before the thing fries? I always try to hook up all extra fans directly to the PSU to avoid the possibility of drawing too much power through the motherboard.

bilbat · 10-04-2008, 11:23 PM

Artic Cooling's multi-fan FAQ says:

"In most cases, we recommend users to connect maximum 5 PWM fans. With 5 PWM fans running at full speed, the current consumption will still remain within the motherboard specification. Recent mother boards (i.e. P965) supply up to 3.0Amps current from the CPU fan socket. In this case, one Arctic Fan 12 PWM fan consumes 0.13Amp during maximum speed operation. When up to 5 fans are connected: 0.13Amp x 5 = 0.65Amp. It is still far below the specification. Some older boards (i.e. i865) supply 1.8Amp current from the CPU fan socket, still sufficient enough to handle. For more information please consult your motherboard manual to obtain the maximum current your motherboard can supply to the CPU fan."

I am assuming that, as a manufacturer, Artic has access to MOBO data that I don't. I haven't done a really thorough search for specific board info, and am generalizing from the nine or ten MOBO manuals I DL'd and read in the process of eliminating the finalists for my next development system (which will be a Gb GA-X48-DQ6). I certainly could have missed something, as it's a total of more than a thousand pages of PDF's, but it seems to me that actual technical data (unless it pertains to OC'ing) is scarcer than hen's teeth. That said, though, if you think about it, the PWM spec's 1.5A seems pretty likely to be accomodated: my little 'handy cheat sheet' says I can put 1.4A through a 28Ga wire, and that's less than thirteen thousandths in diameter, or roughly two or three times the diameter of a black human hair! I don't know offhand what the current thickness of board traces is, but I would guess they have at least that cross-sectional area, and therefore at least that current capacity...

If anyone locates these spec's for THEIR MOBO, please post 'em here so we can make some better informed guesses