Molex to PWM with Voltage reducer?

[Ulijin]

Hi Guys,

I'm in the process of planning my first custom water build. I currently use 2 Noctua NF-F12 PWM fans on my corsair H100. I run them off my mobo fan header and it cycles up and down nicely as needed.

For my custom loop I plan on shamelessly copying TTLs method of setting fans at a constant speed. How do I do this with PWM fans? Can I use one of the Molex to 3xPWM fan adaptors? The ones I've found have a female port that I assume is supposed to be attached to a Motherboard header and used to control all the fan speeds. I don't want to have variable speed, I'd like to set it manually using voltage reducers and then leave it alone. Anyone come across this before?

I know I could just buy 3 Corsair QE SP120's but I've already got 2 Noctua's that I like and purchasing 1 more is a cheaper option for me.

Any advice appreciated,
Ulijin.

Edit: Just in case anyone else is as stupid as me.... It seems I can just run them off 3 pin headers. Doh! Why oh why did I not just think of trying this?

 

[PetetheSweet]

I'm using the Akasa AK-CBFA03-45 Adaptor.
It uses Molex for powering the Fans and a PWM Plug for the Motherboard Fan Header.

You can plug up to 5 PWM Fans in to it, but if you use only 4 e.g., you have to make sure that one Fan is connected to the full cabled Plug.

The rest remains on your Board (BIOS) and/or accordingly on your Software.
In MSI Control Center I got the opportunity to pre define curves, or let the Fans Run at full Speed all the Time. This can be safed in different Presets.
I personally would go nuts if the Fans are running at 100% all the Time.

 

[jamesriley94]

I'm using the Akasa AK-CBFA03-45 Adaptor.
It uses Molex for powering the Fans and a PWM Plug for the Motherboard Fan Header.

You can plug up to 5 PWM Fans in to it, but if you use only 4 e.g., you have to make sure that one Fan is connected to the full cabled Plug.

The rest remains on your Board (BIOS) and/or accordingly on your Software.
In MSI Control Center I got the opportunity to pre define curves, or let the Fans Run at full Speed all the Time. This can be safed in different Presets.
I personally would go nuts if the Fans are running at 100% all the Time.

That's not really constant speeds as it's still going off PWM.

@OP - Voltage resistors will do the job fine...
However, the you can change the wiring of a molex plug to give you 5v, 7v and 12v - so you'd just set it at 5/7v always, rather than 12v, then have a resistor taking it down to 5v or 7v.

You could use PWM splitters like: http://www.quietpc.com/gel-pwm-cable
Then just use a standard 3 pin connection to plug into the end of it?
Alternatively:
http://www.watercoolinguk.co.uk/p/Phobya-Y-Cable-3-pin-Molex-2x-3pin-Molex-30cm-UV-White_18066.html

They have open ends, so despite only being 3pin, you can plug a PWM fan into the ends?

 

[Ulijin]

Thanks guys, I've done as James suggested and run them off a molex with a voltage reducer. As my edit suggests I kinda wish I hadn't asked the question now.. I never thought to check if I could run them off a 3 pin header.

Cheers,
Ulijin.