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4pin case fan to 3pin controller

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Last response: in Components
October 22, 2012 11:08:10 PM

OK all, I've been looking for an hour and can't find exactly this question answered, so here goes.

I have this
NZXT Sentry Mesh
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

I just ordered some of these
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Without realizing at the time in my haste (because I'm an idiot) that they're 4-pin.

Of course my noob question is, "will this work?" Now I know the answer is no since pwm fans cannot be controlled through changing the voltage, but I'm still asking for this reason... The product description says 4 pin, but it does NOT say 4 pin PWM... are ALL 4 pin fans PWM?

And that friends, is the facepalm question of the day...

If not, I'm guessing I can just get a 3 pin to 4 pin adapter, however, I can't think of a single reason to have the 4th pin unless it's a PWM (since that's sort of the point of having that 4th pin, at least when I look at this http://www.allpinouts.org/index.php/Motherboard_%28CPU%...) so I'm assuming it is and I can't use a 3 pin controller.

Again, this is for my case fans ONLY, not my cpu fan.

Thanks all,

More about : 4pin case fan 3pin controller

a b ) Power supply
October 23, 2012 5:41:10 AM

You could buy a 3-4 pin adapter. This isn't something you really think about when choosing parts. You can find some of these on newegg or something. Shame its now backwards because my case fans are 3 pin but my mobo is all 4pins.
I would just check around online for a work-around. although i don't think the controllers would work (unless mounted on case?) Don't hold me to this, just my thoughts on it, i would call your local computer shop. or even call NCIX's toll free number they are very helpful and know what they are talking about.

haha, good luck
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Best solution

a b ) Power supply
October 23, 2012 5:37:24 PM

Yes, it will work - sort of. The "sort of" is about the lights.

A 4-pin fan has 4 connections: Ground, +12 VDC (constant), fan speed pulse signal output, and PWM signal input. When it operates in 4-pin mode as designed, it uses the PWM signal with a small controller chip inside the fan motor to regulate the flow of current from the +12 VDC supply to the motor.

4- and 3-pin fan systems were designed from backwards compatibility two ways, and that's why it can work for the fan part of the operation. First, the (female) 4-pin fan connector on the end of the wires that plugs into the pins of a mobo fan port will also fit onto a 3-pin standard mobo fan port. They only plug in one way - there's a finger and groove system to limit how they fit together. When you plug a 4-pin female connector onto a 3-pin male port, you just end up with no connection for the 4th pin that carries the PWM signal. So the 4-pin fan receives only the Ground and +12 VDC signals, and also can send its fan pulse speed signal back on the 3rd pin.

Now, if you did this on a mobo 3-pin fan port, the fan would not receive a PWM signal to control its speed. However, the design is such that the PWM signal is used as an inhibitor - it slows down a fan by limiting the current drawn from the +12 VDC supply line. When connected to a 3-pin port, though, that supply line is NOT always +12 VDC. 3-pin fan port operation achieves fan speed control by reducing the voltage on that supply line. Thus the 4-pin fan receives a varying DC voltage supply and makes NO effort to modify that with a PWM signal it does not receive - it just changes speed according to its voltage supply, exactly as a 3-pin fan would do. This is the second part of backwards compatibility. In your case, the 3-pin supply port is not on the mobo, it's on your fan controller module, and exactly the same performance will result. So your fans will work just fine!

Now, what about my "sort of" comment. It appears that the LED lights in the fan are powered by the DC supply line to the fan. By design that was supposed to be +12 VDC at all times, and the circuitry in the fan taps into that supply for the LED function. However, in your case you will be connecting it to a +VDC supply that is not always 12 VDC, so when the fan speed is reduced by your controller, the LEDs will also get reduced supply voltage and go dim, or maybe even turn off. I suspect that is OK by you. If you really need those LEDs to work properly all the time, you might have to investigate how to alter the fan wiring to supply a reliable +12 VDC to the LEDs, separately from the variable +VDC supply to the fan motor.
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October 23, 2012 9:34:49 PM

Best answer selected by slimgenre.
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October 23, 2012 9:34:51 PM

I was actually reading some stuff on overclock.net about how someone routed the led wires on all his fans to a toggle, so I kind of like the idea of them dimming, or turning off when I don't have the fans blasting. I should have them in the mail tomorrow so hopefully get it all together in the next few days and see if that's the case. Will post update as to how it all works out.

To lengthen this discussion (just as a means of my personal knowledge) ...

If the led's dim or turn off when voltage is decreased on a 4 pin fan when using a fan controller like mine, does the same occur on a 3 pin fan or are they wired differently so you can regulate fan voltage but maintain led voltage?

Thanks again for the help :) 
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a b ) Power supply
October 26, 2012 5:38:26 PM

I expect that most 3-pin fans with LEDs also will do the same thing. That is because most are not wired with separate leads for the fan motor and LEDs. A standard 3-pin fan connector has no place for a fourth wire to connect to a guaranteed-always 12 VDC supply line, so the LEDs normally are just tapped off the line to the motor, which will be reduced by any fan speed controller system.
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July 26, 2016 1:36:47 PM

I just got some 3-pin fans on ebay ebay but my mobo has 4-pin ports. will tehy still work without any adapters?
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a b ) Power supply
July 26, 2016 6:32:00 PM

4-pin fan headers on a mobo cannot control the speed of 3-pin fans if they actually are working as 4-pin headers in PWM Mode. Now, SOME mobos allow you to change their 4-pin headers to do Voltage Control Mode instead, which is what is needed for 3-pin fans. Moreover, SOME other mobos have headers with 4 pins that actually are not - they operate as 3-pin headers with a useless 4th pin. Which is which? Often one can discern that from details in the mobo manual. So, post here the make and exact model of your mobo, and we'll look up the manual and see what we can figure out for you.

It would also help a lot if you tell us how many fans we are talking about. And whether you consider it important to have their speeds under automatic control by the mobo. Also include info on your CPU cooler system and its fan, which should be handled differently from case ventilation fans.
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July 26, 2016 6:41:46 PM

Paperdoc said:
4-pin fan headers on a mobo cannot control the speed of 3-pin fans if they actually are working as 4-pin headers in PWM Mode. Now, SOME mobos allow you to change their 4-pin headers to do Voltage Control Mode instead, which is what is needed for 3-pin fans. Moreover, SOME other mobos have headers with 4 pins that actually are not - they operate as 3-pin headers with a useless 4th pin. Which is which? Often one can discern that from details in the mobo manual. So, post here the make and exact model of your mobo, and we'll look up the manual and see what we can figure out for you.

It would also help a lot if you tell us how many fans we are talking about. And whether you consider it important to have their speeds under automatic control by the mobo. Also include info on your CPU cooler system and its fan, which should be handled differently from case ventilation fans.

i have 2 3-pin fans, and I belive my case has one fan, not sure which type, all 120mm. my planned cooling system is a deepcool gammax 120mm 74.5cfm setup
build: http://pcpartpicker.com/list/DKBrVY

i havent determined yet if ill do much of any OCing.
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a b ) Power supply
July 26, 2016 7:29:13 PM

CPU cooler first. That unit comes with a 4-pin PWM type fan as most do now, and your mobo clearly has a proper 4-pin fan header for that labelled CPU_FAN1. Nor problems there.

You bought two 3-pin fans. Your case has one fan pre-installed, and most such fans also are of the 3-pin type. This will be a problem with a few solutions.

Your mobo manual on p. 1-27 indicates that the two SYS_FAN1 and 2 headers operate only as true 4-pin headers in PWM Mode. These cannot control any 3-pin fan. It SYS_FAN3 and 4 headers are no help - their labels indicate that they exercise no control of any kind and only supply a fixed 12 VDC to their fans. So, here are some options.

1. Ignore the issue. Use the fans you have. Since you do not have any way to control speeds of those fans, the fact that the SYS_FAN3 and 4 headers offer no control does not matter at all. Simply plug those three 3-pin case ventilation fans into three of the mobo SYS_FAN headers. All those case fans will only run at full speed all the time. This will give you plenty of cooling, but it will be noisier than having a control system to slow the fans down when max cooling is not needed.

2. Buy three new 4-pin fans and replace the 3-pin units. The 4-pin fans will need one fan splitter, but it MUST be a 4-pin splitter. Use that to connect two of these to the SYS_FAN1 header, and the third fan on the other SYS_FAN2 header. Then you can have your mobo control all three of them from your SYS_FAN1 and 2 headers.

3. Buy and install a third-party fan controller that mounts in a slot in the front of your case. Plug all three case fans into that. This unit gives you NO automatic control of fan speeds by the mobo. BUT it gives YOU the power to set their speeds as you see fit. It also means YOU are the one who has to adjust them when you do heavy work and decide what is the right speed.

4. Buy and install one Phanteks PWM Hub for fans, like this:

http://www.newegg.com/Product/ProductList.aspx?Submit=E...

Among 4-pin fan hubs it is unique. It MUST have a true 4-pin fan header on the mobo to connect to (one that uses PWM Mode) and your SYS_FAN1 or 2 header will do that. It must have a connection to a PSU power output for SATA devices, and I'm sure your system will have those. Then you plug all your case ventilation fans into the Hub and they all will be under control by the mobo. What is unique about this particular Hub is that it uses the PWM signal from your SYS_FAN header to create its own group of six 3-pin fan ports that operate in Voltage Control Mode. That is exactly what you need for your 3-pin fans. As it happens (for your future info) 4-pin fans fed by a 3-pin Voltage Control Mode port also will be under control, so this Hub can handle any mix of 3- and 4-pin fans.

One note about using the Phanteks PWM Hub (that last option). Its instructions advise you to connect its fan lead to the CPU_FAN header, and then to connect your actual CPU cooler to the Hub's Port #1 (the white one). You do NOT need to do this. That advice is only to help people deal with mobos that have "fake" 4-pin fan headers that do not actually provide the PWM signal on their Pin #4 that this hub MUST have to work. But your mobo does have proper 4-pin headers with PWM signals in its SYS_FAN1 and 2 headers, so their cautious instructions are not necessary for your case. But do ensure that one of your case fans is connected to the white Port #1 of the Hub.
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July 26, 2016 8:31:43 PM

is there a lot of difference between the phanyeks and silverstone model also shown on that link?

Ill probably ignore it for the time being until i get my system completely set up, but Im goig to plan to get a fan controller like that once I get it running, I may get anotber fan anyway. Thank you for the information!
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a b ) Power supply
less than a minute ago

Yes, there's a difference. The Silverstone model is like virtually all the other 4-pin fan Hubs. It draws power from the PSU directly and the PWM control signal from one mobo SYS_FAN true 4-pin header operating in PWM Mode. Then like all other such Hubs, it merely shares that PWM signal to all its 4-pin fans so they can be controlled. But what this means is that the fans plugged into that Hub get a normal 4-pin fan set of signals, and that can NOT control any 3-pin fan. If you read the information about such Hubs carefully, it will say it is "compatible" with 3-pin fans, BUT they will only run at full speed.

The only Hub I know of that changes the PWM Mode signal from the mobo into the Voltage Control Mode signals of a 3-pin fan port (which is necessary to control 3-pin fans) is the Phanteks PWM Hub.

By the way, just FYI in terminology. "Fan Controller" is the term usually used to mean a separate module (sometimes built into the case, sometimes from a third party) that draws power for its fans directly from the PSU but has NO connection to the mobo at all. Thus it cannot perform automatic control of the fans guided by temperature sensors in the CPU chip and mobo. It does allow YOU to set fan speeds manually, and MAY be able to display for you the speeds of its connected fans. But it means that YOU are the "brains" of the controller because it is you who decides when to change fan speeds and to what target speed, and why.
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