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Help me understand a little please

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TransformedBG

Member
Joined
Jul 24, 2013
So Im fairly well educated when it comes to computers. Granted Most of my experience has been plug and play and it works. Ive fiddle with Overclocking and such, but honestly i have never really taken the time to understand small aspects, such as fan control. currently im in the process of changing fans out to PWM fans, and ive settled on the new corsair ML fans 120/140 4 wire setup.. Its static pressure fans from what i understand, and i chose these so if i do decide to swap over to water cooled it shouldn't be a massive cost for me. So on my motherboard i have 5 Case fan outputs, but if in the future i want to add more and make them controllable, how do i go about doing that? Will my OS be able to monitor all fans? Or will i have to get a manual fan controller and do it myself... Ive seen people making or buying PWM injectors? but im not sure what they do. Ive been trying to google an answer, but im not sure what i should be googling.. So i would just appreciate some help, Even if its an off site link. Thanks
 

JrClocker

AKA: JrMiyagi
Joined
Sep 25, 2015
He linked a fan hub.

You can also get splitter cables to power more than 1 fan off a MB header. Just keep the total current draw to under 1 A. (The fan's current draw is on a sticker on the fan hub.)

I run 11 of the Corsair ML fans in my case...6 ML120 (on radiators) and 5 ML 140 (case fans).

I use the motherboard BIOS to control the fans.


 

trents

Senior Member
Joined
Dec 27, 2008
There are two issues. First, there are a limited number of fan headers on any motherboard. Second, each fan header can only handle so much power draw. Typically, fan headers are rated fro a max draw of 1 amp. Large and powerful fans can exceed that limit. The limit can also be exceed if multiple not so powerful fans are connected to the same header by a splitter or splitters.

The Silverstone block I referenced in the link transcends this current draw limitation because the block is powered by a SATA connector coming from the PSU. The tach and PWM wires still go to a PWM header on the motherboard so that you still can monitor and control the speed of the fans. What you can't do with the Silverstone block is control the speed of each individual fan. They will all be running at the same speed because the RPMs are being controlled from that one motherboard fan header.

If you really need to control individual fan speed then you would want to go with a drive bay controller. These are powered of the PSU as well and have pin outs for each individual fan and a speed controller for each individual fan. They come in "analog" (speed is controlled by turning a knob that adjusts the voltage) (e.g. https://www.amazon.com/YueYueZou®-S...82860671&sr=1-6&keywords=fan+speed+controller) or digital versions that digitally control the voltage (e.g. https://www.amazon.com/NZXT-5-4-Inc...82860671&sr=1-2&keywords=fan+speed+controller). Neither of these use PWM as the fan speed control mechanism but use voltage variation instead. However, PWM four wire fans can be used on either.

PWM (Pusle Width Modulation) controls fan speed by sending short bursts of electrical power to the fan. The longer the duration (width) of the pulses the faster the fan will turn. The adjustment is in controlling the width or duration of the pulses. The advantage of PWM control is that it allows you to run the fan at lower speeds than you could with voltage control. The voltage is always the full amount but it comes in bursts whose lengths can be varied so the "stall speed" of the fan is considerably lower than it would be with voltage control. The disadvantage of PWM is that it doesn't scale well in bios. Setting the PWM "speed" to 60% doesn't mean you will reduce the fan speed by 40% necessarily. You really have to tinker with PWM to get it like you want it.

Voltage-based controllers allow for more granular control of the fan speed but only allow you to go so low before he fan stalls out because of impedance.

Personally, I have opted for the Sunbeam Rheobus Extreme analog controller but what is best for you will depend on what effect you want to achieve and also the fans you choose. My water cooling radiator has three powerful fans that draw more than 1 amp apiece and I like the granular control the Sunbeam affords.

Hope this helps.
 
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trents

Senior Member
Joined
Dec 27, 2008
I should also add that fan speed controllers using voltage to control fan speed do not need PWM fans. Three wire, non PWM fans work just s well since the PWM wire is not even used. Non PWM fans are less expensive.
 
OP
TransformedBG

TransformedBG

Member
Joined
Jul 24, 2013
There are two issues. First, there are a limited number of fan headers on any motherboard. Second, each fan header can only handle so much power draw. Typically, fan headers are rated fro a max draw of 1 amp. Large and powerful fans can exceed that limit. The limit can also be exceed if multiple not so powerful fans are connected to the same header by a splitter or splitters.

The Silverstone block I referenced in the link transcends this current draw limitation because the block is powered by a SATA connector coming from the PSU. The tach and PWM wires still go to a PWM header on the motherboard so that you still can monitor and control the speed of the fans. What you can't do with the Silverstone block is control the speed of each individual fan. They will all be running at the same speed because the RPMs are being controlled from that one motherboard fan header.

If you really need to control individual fan speed then you would want to go with a drive bay controller. These are powered of the PSU as well and have pin outs for each individual fan and a speed controller for each individual fan. They come in "analog" (speed is controlled by turning a knob that adjusts the voltage) (e.g. https://www.amazon.com/YueYueZou®-S...82860671&sr=1-6&keywords=fan+speed+controller) or digital versions that digitally control the voltage (e.g. https://www.amazon.com/NZXT-5-4-Inc...82860671&sr=1-2&keywords=fan+speed+controller). Neither of these use PWM as the fan speed control mechanism but use voltage variation instead. However, PWM four wire fans can be used on either.

PWM (Pusle Width Modulation) controls fan speed by sending short bursts of electrical power to the fan. The longer the duration (width) of the pulses the faster the fan will turn. The adjustment is in controlling the width or duration of the pulses. The advantage of PWM control is that it allows you to run the fan at lower speeds than you could with voltage control. The voltage is always the full amount but it comes in bursts whose lengths can be varied so the "stall speed" of the fan is considerably lower than it would be with voltage control. The disadvantage of PWM is that it doesn't scale well in bios. Setting the PWM "speed" to 60% doesn't mean you will reduce the fan speed by 40% necessarily. You really have to tinker with PWM to get it like you want it.

Voltage-based controllers allow for more granular control of the fan speed but only allow you to go so low before he fan stalls out because of impedance.

Personally, I have opted for the Sunbeam Rheobus Extreme analog controller but what is best for you will depend on what effect you want to achieve and also the fans you choose. My water cooling radiator has three powerful fans that draw more than 1 amp apiece and I like the granular control the Sunbeam affords.

Hope this helps.

Thank you this is pretty much wat i was looking for. Really do appreciate it. So would you say there is an advantage/disadvantage to all of you fans spinning at the same speed if they are all static?
 

trents

Senior Member
Joined
Dec 27, 2008
Thank you this is pretty much wat i was looking for. Really do appreciate it. So would you say there is an advantage/disadvantage to all of you fans spinning at the same speed if they are all static?

I wouldn't say there is an advantage or a disadvantage to having them all run at the same speed except that it simplifies things.

One question you will need to ask and answer for yourself is do you want "negative case pressure" or "positive case pressure?" Negative case pressure means that you have more exhaust vacuum than you do intake pressure. This gives optimum air flow and cooling but brings in more dust. I prefer this personally. I have an air compressor and it's no problem for me to blow the dust out a couple three times a year.

Positive pressure is created when the total intake is stronger than the total exhaust. I.e. you are pushing more air into the case than you are removing. So there is back pressure on the intake side that causes the dust to "drop at the door" as it were.

These positive/negative pressures can be created by using fan speed controllers or simply by choosing intake and exhaust fans of different strengths to begin with. An intake fan pushing 70 cfm of air setup as intake will create positive case pressure if the exhaust fan only moves 50 cfm, for example. Alternatively, you could put two 50 cfm fans as intake and one 80 cfm fan as exhaust and create the same net effect.

More often than not, fan speed controllers are used to limit noise when not needing maximum air flow. So if you are gaming hard and things are heating up you turn the fans up. But when not, you turn them down for quiet.

Choosing fans wisely to meet your criteria for air flow and noise level is perhaps the most important step and can eliminate the need for fan speed controllers altogether. Well-made cases with lots of spots for fans is an advantage in this regard. Multiple slow, quiet fans is preferable to one loud powerful fan. For instance, two fans that each move 50 cfm of air but each have a noise level of 20 decibels will move the same amount of air but be much quieter as one fan moving 100 cfm of air having a decibel rating of 40.

I would also point out that what is noisy for you may not be for me. That's a very individual thing. Not only is "noisy" dependent on hearing acuity but on ambient noise in the area the computer is located. Loud computer fans in a library setting become quiet when you move that same computer to a foundry.

Keep in mind also that the law of diminishing returns applies to case air flow like it does to most other things. If the case air flow is inadequate then you will see elevated CPU and motherboard component temps. If it is already adequate then doubling the case airflow will have little or no impact on temps but will only drive up the noise.
 
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