https://www.engineeringtoolbox.com/fan-affinity-laws-d_196.h...
This is false. ATX provides both +12V and -12V: * https://pinoutguide.com/Power/atxpower_pinout.shtml
Hooking them together would provide 24VDC. On a 350W PSU, I see -12V rated to supply 0.3A, which would allow for 24V fans drawing up to 7.2W of power, if desirable.
I don't see any reason to prefer 24V fans, however. The current losses over such short ranges are minimal, and I would think the larger economies of scale of 12V devices will keep 12V fans less expensive.
24V fans in general are poorly stocked. 24V 4-wire PWM fans are, these days, more or less special order items. There are thousands of 12V 4-wire PWM fans in stock at Mouser and Digi-Key. There are less than a dozen 24V 4W fans in stock, and most of those are sizes you probably don't want.
I'm a consulting EE these days. One of the jobs I get to do is clean up designs that aren't working. We always flag these fans when we see them... then nothing gets done because they're "available enough"... then when build time comes we can't source the fans because the "stock item" is completely out of stock and all possible substitutes are out of stock. But 12V versions are available.
So, yeah, stick to 12V fans whenever possible (or 5V for the little guys). Also genuinely never use AC fans, but that's a different story.
I'm guessing the same holds for 48V fans?
People can easily overload 12V motherboard fan headers, too.
> if they are trying to get a lot of CFM.
If so, they probably have a PSU larger than the entry-level 350W unit I specified. Higher wattage PSUs will provide more power on the -12V rail as well.
> I don’t see a compelling reason to use 24V
Neither does anyone else. Still, correcting a bit of misinformation in the article.
'Ground' is not necessarily 0V, it is just convenient to use it like that. If 'ground' is 0V then 12V - 0V = 12V, but if you make 'ground' -12V then that is 12V - (-12V) = 24V.
Cheap fans often don't have actual proper speed controller on them which means they might start spinning at say 30% PWM but only stop spinning at 15% PWM. That was probably the thing that surprised me most when I upgraded to nice Noctua, at certain PWM it just started, always, and below that it stopped, always.
I wish folks took cooling more seriously. There are so many devices that benefit from active cooling but rarely get it, or even being strategic around placement, positioning, and mounting to make convective cooling more effective. Thermal limiting is such a common occurrence on modern electronics if you don't give due consideration to cooling, as we've moved towards more passively cooled devices, including PCs (laptop especially).
It seems to me you want fans controlled with something dedicated to it.
The other thing I don't get is all the plethora of options my motherboard gives me to set fans only to fixed RPMs. Am I crazy in that I want the fan to be controlled by heat? (More heat => more RPMs. Keep the system cool, but if there isn't much thermal load, spin the fans down and reduce the noise?)
But by fixing an RPM, it seems the only valid input is "100%"; anything else could be too low under stressful conditions.
I could also have a cheap motherboard. (I definitely won't be purchasing from this manufacturer again, and the motherboard does have other severe quality issues…)
Some people want to have a mode switch; normal use should be silent/quiet, but when you know you're going to do something big (game, big compile, etc), fix the fans at full so the noise is consistent and cooling is best. (the cooler the chip, the more the boost)
Some people have no good options from the system firmware, and getting _something_ configurable is better. I've run on systems where I couldn't tell the system to actually run the fan, so things would get hot and throttle. Userspace configurability is better than nothing. This tends to be a bigger issue on things that are sold as a whole computer, like laptops, and small formfactor things (which are often pretty much laptops without a battery and built in user interface devices) but also some name brand desktops.
My recent motherboards all seem to have a pretty nice fan configuration tool. Presets for quiet/performance/full speed, and a simple graph based UI to set % by temperature. Most of the fan headers can be set to follow the cpu temperature or the system temperature. When you buy the nice Noctua fans, they also ship 'low noise adapters' that I assume drop the voltage and limit the maximum RPMs and limit noise. Depending on your overall cooling design, that can be reasonable or asking for trouble.
Yeah, I don't doubt someone is like that … I'd just rather it be automatic.
> My recent motherboards all seem to have a pretty nice fan configuration tool.
Mine has a "flashy" tool, I would say. Certainly looks pretty, but again, it's all constant RPM options.
As I lament in the other thread, this is something that would differentiate boards at time of purchase, but no mobo manufacturers marketing dept. seems to have it's shit together enough to get such a differentiation across to the consumer. Instead the focus seems to be completely on the aesthetics of how the board looks.
And again, I've chalked this up to having chosen poorly. But there-in is the problem: assuming I chose poorly, assuming some mobos do support sane defaults/fetures … how do I end up finding and purchasing one of those? Any knowledge I acquire during a purchase is useless the next time around, given the constant product churn HW manufacturers nonsensically do.
In the old days, it kinda was - at least to your hardware.
Then people realized that blowing up components because a fan failed, or became unplugged, or a filter clogged with dust, maybe wasn't a great user experience and/or caused more in-warranty returns that required replacing hardware ($$expensive$$!), and implemented thermal throttling and thermal cutoffs. Nearly two decades ago at this point, I helped a friend diagnose his computer randomly turning off. It turned out to be a CPU fan unplugged itself, causing overheating to trigger a thermal cutoff. No other apparent harm done.
Fans aren't the only means of limiting heat: slowing stuff down and turning stuff off also works. And it turns out users sometimes would rather stuff run slow than run loud, and maybe your crappy motherboard vendor shouldn't be writing a ton of code running in kernel space - with all the potential stability and security issues that might entail - for whatever network-connected bloatware syncs your RGB lighting and fan settings to the cloud. And they will do exactly that, if that's what's required to give their customers what they want.
Just exposing fan RPMs to userspace might be far less dangerous.
This wasn't the suggestion I was making. I was suggesting that the motherboard, itself, should be controlling the fan RPMs (or should at least provide such a mode). I don't feel like taking a temperature input, and mapping that to an RPM output should take much circuitry at all, but it that (somehow) required a full-blown CPU, I was thinking a (very small) auxiliary chip, dedicated to the task.
But yes, if you're going to do it on the main CPU, then in userspace. But now you incur all the problems I mentioned in the original comment, some of which can exhibit death spirals: CPU has to throttle due to heat, meaning less CPU time, meaning it will take longer to get to the code responsible for alleviating the problem of heat by notching the RPM up!
In the worse case, you hit the CPU's critical trip point before the problem can be brought under control.
if you look at my linked Counterforce project, i believe there to be value beyond these simplest management schemes. we'll see.
I think the female side is right, it's the male connector that's reversed.
Not if both connectors are drawn looking top-down.
Note the ribbing and clip on the female connector, the bottom of the female connector is at the bottom of the drawing. You'd mate these by lifting the female straight up, rotating about 90 degrees along the vertical axis, and pushing down onto the male connector. And when mated that way, the labeled pin-outs line up perfectly.
(Edit: in my defense, the CAD model's square holes on that end are pin holes, not wire holes, which would almost certainly be wider, not square, and take up more of the space available on that side, and do on the connector I have. Hard to find a photo on Google, as nobody photographs the non-business-end…)
Cheers!
Seems like using USB connected microcontroller with open-source firmware instead of embedded SuperIO seems like easiest way to have reliable fan control in PC.
How do y'all like to manage (chassis) fan speeds? I have been out of the PC world for so long that I forget all pieces of hardware need to be managed.
Ideally I'd be interested in something that's >180C resistant but if there are any other options around say 140C max then I'd also be interested.
Assuming the 180C is at your system's ventilation output, could you move your fan to the air inlet so it only has do deal with ambient temperature air? That's what's done for blacksmith's forges etc
...and what's the reason behind needing such a fan?
For our little rendering cluster I bought a bunch of 12.000 rpm fans to cool the rack mounted threadrippers. Worked fine, no watercooling in the rack needed and 4ghz on all cores under load.
I tried once to terminate it myself but I was too cheap to buy the correct tools, so that did not go well. and am now a bit bummed about the whole thing, I found a vendor I can trust to sell me real delta fans.. and they have no plugs. sigh will probably stick with nocturna as a good second best.
Hypothetically, knowing the heatsink airflow curve, one can find the amount of air a fan will move across.
There are PQ curves (either reported or measured) for a bunch of fans and some radiators out there.
So far I've been lazy and just replacing them, but I'd be nice to know as they seem fine when I spin them manually.
You can often extend the life of such bearings by adding a drop of light machine oil to the bearing (usually you have to pull off a sticker on the back of the fan to access the bearing).
Not enough movement to sense by hand, and no roughness, but enough looseness / free-play to allow a kind of resonant vibration or "wobble" when the fan is spinning faster.
Edit: or maybe it's just very slightly worn, has debris in the bearing or something, such that it's out-of-round. I think it's the former though (resonance) as that kind of noise can be intermittent.
It's a lot easier to make one that's quiet, but not silent. Big fans that spin slow and not going crazy with bleeding-edge hardware do wonders. Yeah, if you really want, you can try to underclock/undervolt some things here and there.
https://nick-black.com/dankwiki/index.php?title=InaMORAta https://nick-black.com/dankwiki/index.php?title=Counterforce
hack on!
(Of course those aren't so reliable over the long term, so transistors are usually used. But swinging a base or gate around is all that's needed, and that is easy to do with almost any available power source. Like the main power for the fan!)
