Controlling fan speed

I am thinking of upgrading the fans in my case. 90% of the time the CPU, GPU, etc. are pretty much idle and don't generate much heat, however during games and other intensive tasks (like compiling large code bases and testing) quite a bit of heat is generated so simply removing most of the fans for 1 or 2 quite/low speed ones is not really an option (although I guess some quite and powerful ones might work if such a thing exists). For this reason I want a set up which can automatically change the fan speeds as required (like my PSU, GPU and CPU fans do already) so that the system is nice and quite during non-intensive use.

However my motherboard doesn't have enough fan headers with such a capability (I am currently running 4 fans, and the case has spaces for 5).

Can I connect multiple fans to one header, and if so how many would be safe to do? I realise they will all run the same speed, but I am more worried about burning the header or other components on the motherboard out (that is assuming connecting multiple fans is even possible).
Can I get some kind of fan controller (I am not talking about these manual fan controller things, I want an automatic/software controlled solution)? I am thinking that it could be done with a PCI slot or internal USB header (both I believe supply plenty of power, and I have spare ones), however I could not find any such device, just loads of these manually controlled things that just work straight off the PSU...
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More about controlling speed
  1. You can daisy chain multiple fans off one motherboard header.
    The safe number of fans depends on the amperage the motherboard header supports and how much power the fans draw. Check your motherboard manual and see if you can find the amperage the fan header(s) support.

    What motherboard are you using? It may have some included software utilities that will let you do what you want with fan control.
  2. This system is running a Gigabyte 870A-UD3 There are two sys fan headers, a 4pin and a 3pin header.

    I looked in the manual but couldn't find the amperage specifications :(

    1 GND
    2 +12V/Speed Control
    3 Sense
    4 Reserve

    1 GND
    2 +12V
    3 Sense

    The cpu fan is specified as:
    1 GND
    2 +12V / Speed Control
    3 Sense
    4 Speed Control

    there is also a PWR_FAN
    1 GND
    2 +12V
    3 Sense
  3. What amperage do your case fans need?
  4. Your motherboard BIOS allows you to set System Smart Fan Control ON in the PC Health Status section. Page 51 of the motherboard manual.
    Then you can use the included EasyTune5 software to control the fan speed.
  5. I haven't got the new fans yet. Right now I have:

    Two Antec TriCool (120 & 130mm) fans that came with the case, this version seems to have a speed control thing (looks to be just a resister on the +12v line) and uses a 4pin molex but no 3pin for fan headers...
    Two 120mm cheap LED fans that use a molex connector. I forget when I got these as I salvaged them from an old build, one has started making a lot more noise, most likely a cheap bearing wearing out or something.

    From what I can tell the motherboard smart fan control is only off the SYS_FAN1 header. I guess I am pushing my luck to connect upto 5 fans to that unless I can somehow draw additional power from another source?
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