3 case fans, 1 fan header

[scaryjim]

... This is an interesting controller:
https://www.amazon.co.uk/Cooling-con...y+fan+splitter

I quite like the PCI slot controllers. My searches have turned up a couple (on places like AliExpress and DX.com) that appear to have a single control to power multiple fans. Of course, they're only great if you have PCI slots you're not using....!

EDIT: amazon have a Lian Li version of what I'm talking about: https://www.amazon.co.uk/Lian-Li-PT-...fan+controller

Takes up to four fans, but uses a single control to set the speed. Quite pricey for what it is, though...

[Corky34]

I dont understand why a 5v/7v adaptor mod is an issue TBH :/

Its easy and I'm guessing everyone has a fair few of these kicking about in a drawer/box somewhere as they come supplied with fans so the cost is.. er... zero

https://www.techpowerup.com/articles/other/137

Because you have to know what you're doing as with the 7v mod it's possible to feed current back into the PSU.

[peterb]

Because you have to know what you're doing as with the 7v mod it's possible to feed current back into the PSU.

Very unlikely scenario, and could only happen if the 5v line was disconnected from the load. And even then, the fan impedance would limit the current flow, and that's assuming there aren't any cross over protection diodes in the PSU.

[peterb]

Any fan will run off a PWM cable - it just won't have the PWM speed adjustment

And (although not directly relevant, any three pin fan can be have its speed controlled by pulse width modulation from an appropriate PWM controller.

[Corky34]

Very unlikely scenario, and could only happen if the 5v line was disconnected from the load. And even then, the fan impedance would limit the current flow, and that's assuming there aren't any cross over protection diodes in the PSU.

Very true, it's why i said it's a possibility and found it odd that techpowerup didn't include a cautionary note.

[Taz]

Hi guys, I did the initial build last night. The Akasa splitter delivery was delayed and didn't arrive until late at night. So what I did for the time being was connect the two front fans via a simple Y-splitter cable that I had lying around to the SYS_FAN connector.

The system works fine with the rear fan not connected at the moment. I just wanted to get the OS on and leave it running overnight to check stability.

I've got the cable now and will fit it this evening. But I'm actually wondering whether it's even worth having three fans in the case? It's a new build for my dad so the system won't ever be stressed. I couldn't get the CPU over 40 degrees running full virus scans, for example. It's ridiculously quiet in that I have to check whether it's actually switched on sometimes.

I'm just wondering from a simplicity and tidiness points of view - that Akasa cable is very unwieldy and ugly - should I just keep the system down to two fans? I could just remove one of the two front fans and connect up the rear fan to the Y-splitter. Opinions please! Currently I have one two front intake fans operating and no rear fan.

[Biscuit]

If its only ever going to be used for basic stuff and there is no GPU in there, I wouldn't worry about the airflow too much. 2 Fans will be fine.

[Mr_Jon]

Use speedfan to control them mate, bit hard to grasp at first but can be learned in an hour or so. I have five 3-pinners working off one mobo header.

[ik9000]

Yes, I know that, but since the OP specifically asked about running all three fans at a lower speed, the lack of speed control means it won't work for what they want to do. Perhaps I should have been explicit about that in my answer, but I was kind of assuming people would infer that bit from the question.

As the OP wants to control the speed of the fans (even if that currently just means running them all at a single lower speed), a fan controller is the best option, and given you can get a 3 channel controller for < £15 it's not an exorbitant expense, and would then give them the option of individually controlling the speed of the fans later if they found that suited their purposes better.

And, you know, it's a better option than spending a fiver on something that won't actually do the job they want...

Sorry I'd totally missed the lower speed bit. Yeah, there's no way to change that other than a means of dropping the voltage. With molex you could just switch the pin wiring, but not so easy to do with a sata connector.

I use one of these Akasa ones for a couple of case fans - but it rarely gets adjusted as it sits on the back of the tower. Mobo to input on controller, splitter cable out from that. BUT as you say a PSU powered cable won't derive any modification to the driving voltage.

https://www.scan.co.uk/products/aset...otherboard-kit

[Taz]

Having listened to the noise from the system for several hours now, the two 120mm fans are almost inaudible and are running at around 960 rpm. I'll put details of the system in another thread as I built it for general home use and not gaming.

I was worried that they may be too loud but they're not, so I may leave things as they are for now (2 x 120mm fans into Y-splitter into SYS_FAN on motherboard). I did a fan calibration using Gigabyte's System Information Viewer app and the fans did all spool up to max during the calibration, so there does appear to be some kind of fan control provided by the motherboard, probably via voltage control. However, I think the temperatures in the case are quite cool so during normal use the fans stay very quiet.

[Pob255]

Unless a fan is really cheap (soft plastic, dodgy bearings and imbalanced blades) going to around 900-1000 rpm range is near silent, generally flow through the vents is a bigger sound issue at this speed.

Depending on the motherboard a header is often 1 amp, it is the most common, however some times it'll be 3amp but shared by multiple motherboard headers and I've seen 2amp per header before.
Fans are around 0.2-0.25 amps so normally 3 to 4 fans per header is fine, just remember to check the numbers first.