Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

More than you cared to know about PC fans

nick-black.com

Post reply on HN
Print view View original

81–90 of 102 posts

Re: More than you cared to know about PC fans

#81

Post by wtallis »

amelius wrote: post #55
robotguy wrote: post #43

Earlier quoted context omitted.

3-wire is: TACH, DC, GND 4-wire is: PWM, TACH, DC, GND https://noctua.at/en/what-pin-configuration-do-noctua-produc...

In practice pwm is used instead of DC.

I can't remember the last time I encountered a motherboard that didn't offer you the choice between DC voltage and PWM for fan speed control. Both are still mainstream options; CPU heatsink fans are almost always 4-pin PWM fans but case fans are very commonly 3-pin DC fans. AIO Water cooling kits also commonly use 3-pin fans, especially when integrating their own fan controller or multiplexer so that they only need to occupy one or two fan headers on the motherboard.

(Edit: if you mean that in practice, the motherboard approximates DC voltage control using a PWM-based method, that may be true, but it's beside the point; a 3-pin fan is missing the control circuitry that a 4-pin PWM fan uses, and the 3-pin fan's behaviors like turn-on point will be specified in terms of DC voltage not PWM duty cycle, and you can't drive a 3-pin fan with the PWM signal intended for a 4-pin fan because the voltage and current supplied are both far too low.)

Re: More than you cared to know about PC fans

#82

Post by chipsa »

0cf8612b2e1e wrote: post #69
iknowstuff wrote: post #63

Earlier quoted context omitted.

I think the ATX12VO standard might be getting rid of -12V. All it does is 12V.

Any chance they are going to add something higher? 19v would align with laptops and make power hungry GPUs slightly more manageable.

I'd suspect they'd go up to like 48V. It's the max voltage for USB-PD 3.1, which corresponds with being the effective highest voltage you can have before you're no longer "low voltage". This is also why PoE is approximately the same voltage.

Re: More than you cared to know about PC fans

#83

Post by scns »

Markoff wrote: post #31

I haven't assembled PC in long time, by now I'd expect you can build passively cooled PC if you use PC just for some regular office job and surfing without gaming and resource heavy apps or we are still not there? Back in the days undervolting was for me for interesting than overclocking to make PC as quiet as possible.

It is absolutely possible, even with a high performance GPU! [0] A video review by LTT [1]

[0] https://www.monsterlabo.com/

[1] https://www.youtube.com/watch?v=_jYB-RpkmUc

Re: More than you cared to know about PC fans

#84

Post by owenversteeg »

michaelt wrote: post #18
owenversteeg wrote: post #11

Does anyone know if there are high-heat-resistant PC fans (and at what temperatures normal PC fans will melt)? The only fans I can find that claim to be heat-resistant are the Noctua Industrial PPC series which, aside from not being cheap at $33/piece are "only" heat-resistant up to 140C and the airflow isn't crazy high - subjectively the ones I've got feel like they move substantially less air than a standard diesel…

Unfortunately many plastics, and the most common types of solder, start softening before you get to 180C. You can get smoke extraction fans and chimney flue fans that will tolerate higher temperatures, but they're generally an all-metal affair costing more than $33. 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? T…

Yes, chimney flue fans were next on my list but surprisingly enough the airflow for most of the shelf models is quite low. Unsurprisingly with all metal parts and less competition in the sector the performance is also far worse in terms of watts/CFM. Pushing ambient air sadly doesn’t work for my application. That said those would have all been great suggestions though so thanks!

Re: More than you cared to know about PC fans

#85

Post by owenversteeg »

userbinator wrote: post #28
owenversteeg wrote: post #11

Does anyone know if there are high-heat-resistant PC fans (and at what temperatures normal PC fans will melt)? The only fans I can find that claim to be heat-resistant are the Noctua Industrial PPC series which, aside from not being cheap at $33/piece are "only" heat-resistant up to 140C and the airflow isn't crazy high - subjectively the ones I've got feel like they move substantially less air than a standard diesel…

If $33 is "not cheap" then you're not going to find anything lower. Perhaps an oven fan, but that's a different form-factor. The problem is that fans with integrated motors are limited by the temperature of the motor, and motors designed for high temperatures are also not cheap since special materials need to be used. ...and what's the reason behind needing such a fan?

$33 is cheap enough for a handful for myself of course but as you may have guessed I’m thinking of releasing a product that would need them. Not a serious thing, more so a handful of bulk bought parts sold together to scratch a long standing itch in a very very specific field. Sadly $33/ea would really eat into the BOM, even on an expensive mass produced item like an iPhone that would be one of the most expensive parts.

Re: More than you cared to know about PC fans

#87

Post by dankamongmen »

azalemeth wrote: post #3

Honestly this isn't more than I cared to know about PC fans. I've worked extensively with industrial appliances and fans are bloody important and underlooked: fan failure is often the step that precedes component failure. The one part of the spec I wasn't aware of was just how insanely high the maximum current draw is; I'm glad that we've made more efficient, longer-lasting, effectively silent air-movers that can fit…

yeah, if you look at the equations at the bottom, power goes up with the third power in relation to rpm. whippin' and drivin' that much air takes some oomph. connect that fan to any normal motherboard, and you're going to burn out your fan header pretty much immediately (especially since inrush current is probably even higher than the steady state).

Re: More than you cared to know about PC fans

#88

Post by dankamongmen »

axiolite wrote: post #34

> "there is no readily-available 24V source from an ATX power supply," 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 s…

huh, i didn't know they could be connected like that! i only knew of the -12V as a source for RS-232. thank you for the tip; i'll investigate this (i assume you're correct, just want to understand it for myself) and update the page. thank you very much!

Re: More than you cared to know about PC fans

#89

Post by dankamongmen »

deathanatos wrote: post #46

Also, one thing I've always wondered: why do people want to use hwmon to set fan RPMs? (Or really, why do this from userspace at all?) It seems inherently dangerous to me, as you're asking a process who might not receive CPU time for whatever reasons from the very much not realtime OS to control a fan; if the current RPM is too low, and the system starts generating heat, but the fan controlling process doesn't get CP…

you might want to use different algorithms for automatic control than those exposed through the motherboard firmware, which are pretty much limited to either constant, manual setpoints (usually with extrapolation), and a linear temp-to-rpm curve (ideally with different possible sources).

if you look at my linked Counterforce project, i believe there to be value beyond these simplest management schemes. we'll see.

Post reply on HN