Question x3 molex fan connectors daisy-chained. Looking for a fan speed control solution.

[tomachas]

Hi,

I have an Aerocool Hexform case with x3 preinstalled fans. They are daisy-chained Molex connectors. What is the cheapest solution for fan control?
Convert? If so, would one converter to 4=pin do a job? My motherboard is ASUS PRIME B650M-A WIIFI II. Ideally, I would settle for a few pounds solution if not, I would buy a set of new 120mm fans for around £15 and I am done.

Many thanks!

https://www.pinterest.com/pin/472385448434454145/

 

[Lutfij]

I looked up the cases and it's price. It's a 17USD case, so the fans are bound to be powered only by molex which are pretty much bottom of the barrel. This is a good read;

[SOLVED] - How to control Molex fans speed?

My 3 Molex chassis fans are "daisy chained" and connected directly to the PSU, making them run at 12v, full speed and very loud all the time... my Asus Prime B450M-A has a CHA_FAN2 empty connector right over the CPU_FAN connector, if i get a Molex to 3-pin cable can i connect them all on the...

forums.tomshardware.com

You'd be best off with a cheap DC or PWM fan pack akin to this;

Amazon.co.uk

 

[punkncat]

You can get a rheostat controller for Molex fans, but some of them don't respond as you might expect with the reduced voltage.

I would also suggest looking into new fans. Something PWM/PST or a fan hub alongside.

 

[steveb1976]

you can get a triple pack rgb fans with hub for £15 and for £18 5 fans and hub on ebay and amazon..

 

[dev_cyberpunk]

I know you guys marked this as solved, but to make 4 pin fan controller from the drive plug is pretty simple.

To give you a background of these fans and the associated circuit, they tried to force pwm control by using a device called a mosfet with a built in schmit trigger on the gate so that a pulse would be the only control for them. Over time, the industry had noticed that the fans was missing some of the pulses so their speed would never get to 100%. Later they changed the mosfet to a normal type. Since the mosfet is now an analogue type all you have to do is vary the 0-5V to what ever relative speed you want.

So all you would need is a 5K pot tied to the 5V and ground and the wiper feed the pwm pin through a 2K resistor to protect the gate of the fan from any inrush current while turning on the computer.

 

[tomachas]

Thank you all for your input. I will at some point by new fans with 4-pin connectors for my board. Until then molex fans will spin and do the labour as intented.

 

[Paperdoc]

You CAN do what you want using one of these adapters

https://www.amazon.com/3pin-power-4...+fan+to+molex,aps,125&sr=8-10#customerReviews

NOTE that it has a FEMALE (with holes) 3-pin fan connector at one end to plug into one of your mobo CHA_FAN headers, and a FEMALE (again) 4-pin Molex output. So you unplug the stack of fan connectors from its current feed from the PSU and plug the stack into this adapter.

In doing this you MUST take into account these three points.
1. The mobo fan header can supply power up to 12 VDC at up to 1.0 A max current load to ALL fans connected to that one header. So to start, look closely at the fans' labels for a spec of max current, and add those up (3 fans). If the total max load is less than 1.0 A (likely) you are OK. If not (odd!), you might need two of those adapters to separate the fans from a group of three. IF the fan labels specify in WATTS only, divide Watts by 12 to get max Amps per fan.
2. Control of the speed of these fans is done only by reducing the VOLTAGE supplied to them from the header. So in the BIOS Setup page (see p. 76 of the BIOS manual) for that particular CHA_FAN header you must set the CPU Q-FAN Control option to DC Mode, not PWM or Auto Detect.
3. These fans do NOT have any way to send back to the mobo header the SPEED signal of the fan, so you will never "see" any of those fans' speeds anywhere. This does NOT have any effect on ability of the mobo header to actually DO speed control, so your fans' speeds WILL be altered.