Zero-Fan mod, controller, or adapter for PWM fans?

LostEnergy

Chassis Packer
Original poster
Sep 25, 2019
16
7
Kind of an external fan control is what I am looking for.

I want the fan on my cpu cooler to stop completely, because the idle power draw (<3W) is such that the Al heatsink can dissipate the heat without any help. And for that I am looking for a small board or adapter to go between the 4-pin PWM header on the mainboard and fan, perhaps with USB, to turn off the fan. Either controlled by a thermistor or signal by aforementioned USB. (With or without then faking the rpm reading.)
  1. Does something like this exist for SFF to your knowledge?
    I know external fan controls, such as from NZXT can do this for I did have one.
  2. If not, anyone fancy to make a batch?
The adapters from Noctua and similar are mere resistors, and won't turn off a fan completely unless choked.
 

Valantar

King of Cable Management
Jan 20, 2018
728
522
I just discovered the Aquacomputer Quadro, which ought to do what you are looking for. Perhaps a bit overkill for a single fan, but it's the smallest full-featured USB fan controller I've come across.

Probably ought to thank @August for finding this, as I spotted it in their (amazing!) triple-rad Streacom DA2 build.
 

LostEnergy

Chassis Packer
Original poster
Sep 25, 2019
16
7
Thanks! That might indeed help someone.

The A300 I'm wanting this for has no 4-pin molex connector to deliver power to the contraption.

Meanwhile I've decided to make my own.
 

LostEnergy

Chassis Packer
Original poster
Sep 25, 2019
16
7
Thing is, I'd like this to be internal.

To switch off a PWM controlled fan (4-pin ones) you disconnect the GND line. Merely playing with the actual PWM line, setting that to 0% (pulling it to ground), will have the fan spin at its minimal speed or 50% speed, depending on the fan's controller. (Sever and it'll be on 100% due to a pull-up.) So anything that plays with the PWM line—as those fan controls with dials do, afaik—won't turn it off.

Yet when on, sophistication is not needed: Just pass-thru the mainboard's signal.

One can even make this fully automatic, without another USB connector: Snoop on what the mainboard sets for the fan (as is necessary anyway to fake the outgoing “tacho” signal), and switch off if below a threshold (5%?) + the last halt was more than t seconds in the past; and enable above another.

Anyway, CAD is installed, and I've already read the specifications. :-)
 

Stevo_

Airflow Optimizer
Jul 2, 2015
319
192
Depending on the mobo etc, I've used fancontrol under linux to program the pwm low enough to shutoff during idle. Unfortunately some of the new mobo's are unpredictable. I was able to find a config to make "sensors" read the the mobo sensors on my MSI b450i but lm_sensors will not automatically detect until the next version according to Git, if that doesn't run right then pwmconfig is a mess for configuring fancontrol.
 

LostEnergy

Chassis Packer
Original poster
Sep 25, 2019
16
7
sensors and pwmcontrol work fine with the Asrock A300. But the fan (a Wraith Stealth) won't stop, just go to 600 RPM. And does sound awful at 800RPM tbh.
 
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Stevo_

Airflow Optimizer
Jul 2, 2015
319
192
sensors and pwmcontrol work fine with the Asrock A300. But the fan (a Wraith Stealth) won't stop, just go to 600 RPM. And does sound awful at 800RPM tbh.
The stock fan on my stealth is silent til about 1200RPM(bottoms out at ~780ish) and doesn't really sound horrible until ~1800RPM. IIRC, I can turn the system fan header to 0RPM but not the CPU header using fancontrol, but presently using BIOS as it's good enough.
 

smitty2k1

Master of Cramming
Dec 3, 2016
605
295
What do you guys use for software control of fan speeds in windows? Sadly as FanSpeed hasn't been updated in so long a lot of functionality is broke on newer hardware
 

LostEnergy

Chassis Packer
Original poster
Sep 25, 2019
16
7
[…] Meanwhile I've decided to make my own.
Further, regarding:
I am surprised someone hasn't invented a teeny board + PWN fan controller that hooks up to your USB and gives you a GUI to control fan.
Fans run at 12V and draw 0.6W and more; 2.8W is no unusual draw on 100%. USB 2.0 has its limit at 2.5W (and 5V). Tight.
You can design a controller that needs very few mA or even µA, but as soon as someone connected a more beefy fan you'd get a bad reputation for frying USB ports.
 
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Valantar

King of Cable Management
Jan 20, 2018
728
522
Further, regarding:


Fans run at 12V and draw 0.6W and more; 2.8W is no unusual draw on 100%. USB 2.0 has its limit at 2.5W (and 5V). Tight.
You can design a controller that needs very few mA or even µA, but as soon as someone connected a more beefy fan you'd get a bad reputation for frying USB ports.
To keep the board as small as possible the best solution (though not the most durable/repairable one) would be a soldered-on power lead. It could be either a fan connector or SATA (or a fan connector+a bundled SATA-to-fan header adapter), that way you would avoid frying USB ports. USB power also has the drawback of either needing 5V fans or needing a boost converter to generate 12V. Also, 2.5W is at 5V, converting that up to 12V will lower the maximum output wattage significantly.