PWM splitter circuit?

[rsquared]

After trying a few PWM-splitter cables from different manufacturers, I have to conclude that my BitFenix Spectre LED PWM fans—four of them, on my radiator—simply do not work with a simple PWM splitter. That is, with a cable that connects all the PWM wires together and plugs it into the motherboard fan header. The fans just run full speed, regardless of what the PWM is doing. This is unacceptably loud. I hate to replace them, though, because the LED lighting does look really good, and once they're turned down some they're quiet enough.

So maybe I need a PWM splitter that's a little less simple. I was thinking one transistor per fan, connect all the transistors' gates to the motherboard PWM signal. Would this work, does anyone have experience with this? But should the transistors be NPN or PNP (is PWM active-high or active-low), or maybe one of each?

Or can someone point me to where I can buy a PWM-splitter device that already does this?

 

[Abula]

After trying a few PWM-splitter cables from different manufacturers, I have to conclude that my BitFenix Spectre LED PWM fans—four of them, on my radiator—simply do not work with a simple PWM splitter.

Have you tried to connect an individual fan? and see if the mobo can control it? Gigabyte fan control is not the best though, but before buying a new cable or design i would check first that the mobo can control at least a single BitFenix Spectre PWM fan connected directly to the mobo 4pin pwm fan heather.

 

[rsquared]

Have you tried to connect an individual fan? and see if the mobo can control it? Gigabyte fan control is not the best though, but before buying a new cable or design i would check first that the mobo can control at least a single BitFenix Spectre PWM fan connected directly to the mobo 4pin pwm fan heather.

Yes; the rear-exhaust fan, another Spectre PWM LED connected by itself, PWMs correctly. The Swiftech MCP35X also plays nice with the mobo PWM.

Although... I am planning on going back to my Maxiumus IV Extreme*, so come to think of it the PWM-splitting issue might become a non-issue?

Well, either way I'd like to find or make something that works, and then I can know it'll work no matter what future motherboards I use it with. I've also tried the fans with simple splitter plugged into a Zalman PWM Mate, and they ran full-speed there, too, FWIW.


* Thought it had gone bad, bought the Gigabyte mobo, still had the same problems, so it seems the Maximus is fine. New PSU finally fixed the problems.

 

[Jorona]

http://www.swiftech.com/8-WayPWMsplitter.aspx

 

[rsquared]

http://www.swiftech.com/8-WayPWMsplitter.aspx

Yeah, tried that one. It's actually still plugged in now (with a Zalman Fan Mate dialing everything down). I had high hopes for it, since it looks like there might be a circuit in there, but (like the cables) it merely connects all the PWM pins together inside.

 

[Deleted member 184142]

You said all the fan wires are split, this could be the problem, you should only have 4 wires going to one fan, all the others should only have 3. If the RPM wire from all the fans is feeding into the header you can cause read errors and speed problems.

 

[mesasone]

You said all the fan wires are split, this could be the problem, you should only have 4 wires going to one fan, all the others should only have 3. If the RPM wire from all the fans is feeding into the header you can cause read errors and speed problems.

I guess it would depend on the splitter, but the Swiftech splitter only reads the RPM from the CH1 header.

 

[rsquared]

If the RPM wire from all the fans is feeding into the header you can cause read errors and speed problems.

All three of the splitter cables I've tried have the RPM sensor connected to only one fan. I am not aware of any manufacturer making cables that aren't like this.

 

[Unknown-One]

All three of the splitter cables I've tried have the RPM sensor connected to only one fan. I am not aware of any manufacturer making cables that aren't like this.

I've had some gear from Arctic Cooling come wired this way, had to snip one of the RPM Sense wires to get them to read correctly.

 

[Deleted member 184142]

All three of the splitter cables I've tried have the RPM sensor connected to only one fan. I am not aware of any manufacturer making cables that aren't like this.

Also sounded like you were wanting to make something, so I thought you might have made your own splitters, I make my own because I refuse to pay $7+ for something that costs 50 cents to make. And when I make my own I can make them to fit as well.

 

[Arcygenical]

I've tried to do something similar, and I found success by connecting all the 12v and 0v lines, and the 4th PWM (control) wires together, snipping all but one of the RPM sense (wire 3) wires.

Course, it was with two fans, so YMMV. It worked fine...

 

[Tsumi]

Seems like you need something to "boost" the signal? Not sure what the voltage coming out of the PWM is, but it might be possible to rig something up, with something like an H-bridge.

 

[Red Squirrel]

I wonder if arduino could work for something like this. Not sure if the pwm it provides is the same as what these fans take, or if it's a standard.

I always thought it would be nice to have a device with a temp sensor that will control a bunch of fans simultaneously, just like in pre built servers like Dells and such.

 

[Deleted member 184142]

I always thought it would be nice to have a device with a temp sensor that will control a bunch of fans simultaneously, just like in pre built servers like Dells and such.

There are many things out there that work this way, as well as allot of thermal fans to pick from. Sunbeam has a fan controller that has a PWM mode, so even 3pin fans can be controlled by the mobo PWM. They even have pretty cheap inline thermal sensors you can use on the fan that will kick on and off at given temps. Some are fully programmable, but are allot more price wise than what I listed but also have far more options as well as cheaper options as well, just depends on how automated you want the system and how much control over speed you want.