What exactly is PWM? Plus basic fan question

Chimp Paradox

Chimp Paradox

Chimp Paradox

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My understanding is that it is a hardware related way of controlling a fan. What is the point of this over just using software?

Does it require a 4 pin connection on motherboard? My motherboard only has 2 headers which are 4 pin, one is called case the other CPU. I have a passive CPU cooler so I assume its ok to use the CPU header for a case fan?

If so, if I am going to have 4 fans, I assume I just use a splitter on each one making 2 from each 1 header.

Finally, what are the basic rules of in and out flow? Should they be equal? Thanks
 
At a basic level...

PWM is controlled directly by the motherboard. The advantage is that's all you need, as well as it being more power-efficient. However, it relies on your motherboard deciding what speed it wants to set the fan at, rather than whatever you may want and could end up being noisier than you'd like.

Using a splitter can work... But it depends on how many watts each header can cope with. Some headers are only designed for one, so putting two on a splitter may fail.
There are ways around it (low wattage fans, for example), but it can get fiddly.

I do not believe it a good idea to use teh CPU header for casefans, as your CPU could be (relatively) freezing but the rest of the case really hot - In that case, the fan on the CPU header would stay low when you need it high.

I personally favour a fan controller, myself. Each channel can take loads of fans (3 or 4-pin, usually) and I have instant, precise control over speeds and volumes without having to reprofile a fan curve or assume my motherboard knows best.
Worth noting that some fan controllers do let you program a curve in anyway...

Rules for fan numbers... None. Not really.
A lot depends on your case. I have 9 fans - 5 intaking, one shuttling and 3 exhausting.
More intakes than exhausts = Positive pressure.
More exhausts than intakes = Negative pressure.
There are pros and cons to each...

What you want most is good airflow, which means all the air intaking from one direction (usually front and bottom) with it exhausting out the opposite side (rear and top).
Even then, with high SP fans on restricted slots and high airflow ones on the case, it can still be a bit of trial and error with various factors influencing your cooling efficiency.
 
Chimp Paradox said:
My understanding is that it is a hardware related way of controlling a fan. What is the point of this over just using software?

Does it require a 4 pin connection on motherboard? My motherboard only has 2 headers which are 4 pin, one is called case the other CPU. I have a passive CPU cooler so I assume its ok to use the CPU header for a case fan?

If so, if I am going to have 4 fans, I assume I just use a splitter on each one making 2 from each 1 header.

Finally, what are the basic rules of in and out flow? Should they be equal? Thanks
Click to expand...

Fans:
-1 pin positive, 1 pin negative
-3rd pin is for reporting the rpm the fan is running at
-4th pin is found on PWM fans and carries the PWM signal

3 pin fans have their speed controlled by adjusting the voltage
4 pin fans run at the full 12v constantly but are rapidly switched on and off by the PWM signal to control their speed.

You can use the fans on the CPU header if you want. The motherboard will usually manage the speed of that fan according to CPU temp. using a splitter like that is fine, I run 8 PWM fans off my CPU header.

You should have slightly more intake than exhaust, as long as those intakes are filtered. The filter will reduce fan performance so (assuming all fans are the same) I would usually have at least 2 more intakes than exhaust.
 
OK, this all makes sense. Sounds like a fan controller is the way to go. I like the look of the NZXT Sentry Mix 2. Any recommendations? Can a fan controller also completely turn all the fans off? Its a feature I want as a lot of the time I will be running completely passive.

Thanks
 
There are three things to look at when controlling a fan controller which IMO should be in the order of:

- Wattage: What are the wattage of my fans? Usually fans give their Amperage (A) just times by Voltage(V) and you have their Wattage. Does the fan controller provide enough to provide to all my fans.

- Channels: This leads on from above as each channel has a certain Wattage but do you have enough channels for what you want? If you only want to control intake fans on channel 1 and exhaust on channel 2 there is no point buying an 8 channel controller. Conversly the opposite applies if you want 5 or 6 sets of fans. Also to consider here is, as you questioned, how much control do I have? Can I turn them off or can I turn them down low.

- Looks: This is last because the others are needed for the controller to work. This is here because everyone wants their PC to look cool :)


Turning to the NZXT Sentry Mix 2, it doesn't appear you can turn the fans off as the description says minimum power to fans if 40% so would assume you can't turn them off.
 
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Thanks v much Greboth. This is the fan I am going to use, as its the quietest 140mm on the market.


Brand

PHANTEKS
Type

Case and Radiator Fan

Colors Frame: Black; Blades: White

Bearing Type

UFB (Updraft Floating Balance) Bearing

Fan Dimensions

140 x 140 x 25mm

Blade Geometry

Nine Blades with MVB(Maelström Vortex Booster) Design

Speed (RPM)

600-1200 ± 250 rpm

Max Airflow

40.9 - 85.19 CFM

Acoustical Noise

15.22 - 19 dB (A)

Static Pressure

0.39-1.52mm H2O

Speed (RPM) with QSA

300-900 ± 250 rpm

Max Airflow with QSA

49.14 CFM

Acoustical Noise with QSA

17 dB (A)

Static Pressure with QSA

0.77mm H2O

Input Current

0.14 A

Rate Voltage

DC 12V

Input Power

1.8 W

MTBF

>150,000 h

Speed Sensor

4 pins

Cable Length

500mm

Scope of Delivery

1x 140mm PWM Premium Fan
1x QSA (Quiet Speed Adapter)
1x 4 to 3 pin adapter
1x 400mm Extension Cable
4x Anti-Vibration Compensators
4x Fan Screws

Warranty

5 Years
 
Phanteks give you the wattage which is nice and saves doing a calculation. 1.8W fan with 30W per channel (180 W in total) you could in theory run 100 fans off the controller :D

If you need 6 channels and definitely want to be able to turn the fans off, I would look at the Lamptron FC2 5.25" Bay Fan Controller out of stock at the moment at OCUK but a whopping £1 cheaper too.
 
Chimp Paradox said:
Can a fan controller also completely turn all the fans off? Its a feature I want as a lot of the time I will be running completely passive.
Click to expand...
You can on most of them, yes.
My Lamptron FC6 lets you do this. You just turn the dial down.

Chimp Paradox said:
Thanks v much Greboth. This is the fan I am going to use, as its the quietest 140mm on the market.
Click to expand...
Silence is an admirable trait in case cooling, but check this against the performance specs of other fans.
Performance should always come first, IMO. You may be able to go for a fan that is only a few dB louder but far more powerful. You'd barely notice the noise, if at all but get better performance to boot.
 
The only thing that bothers me about Lamptron, and I think I will email them about it, is because their controllers are high powered, what sort of PSU they need. One review site said that with their most powerful option you'd need a 700w PSU! I have the 400w Seasonic Platinum, which is a passive design.

Taskmaster - I use my PC as an audiophile transport, so silence is very important to me.
 
Haha what?! The controllers themselves aren't powered, the main power draw is always going to simply be down to the number of fans attached. If you want to be very specific the controller will draw some power for the LED's and there is a small effeciency loss but if you are running your PSU to close to the max that a few LED's and a small percent inneffeciency puts you over the top I would suggest getting a new larger PSU anyway.

Edit: Have you got a link to the review? would make some lolable afternoon reading.

Edit 2: Unless they were on about the maximum you could load it with, being 6 channels x 45W per channel = 270W total. That it stupid to work it out like that though as i doubt anyone is running 100 fans in their PC. The larger Watts per channel is mainly useful if you want to run some of the bigger fans like 200mm or 230mm.
 
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Greboth, I think that's what they are getting at. They are assuming you are going to load it up. On Lamptron's website they recommend 700w for some of their controllers!!! At least 500w for most of them....
 
Chimp Paradox said:
Taskmaster - I use my PC as an audiophile transport, so silence is very important to me.
Click to expand...
For performance vs silence, I've always favoured Noctua fans.
Enermax are pretty good too and Silverstone make some rather reasonable budget fans.

Remember also that a fan itself may be silent, but you will still get noise from the airflow especially if it passes through grilles, mesh, radiators and the like.
 
Ultimately this thread has moved onto the more practical subject of how you want to control your fans, but PWM vs software is an incorrect argument.

Yes, PWM is a hardware way of controlling fan speed, but it's just a different way of doing it rather than changing the input voltage (by resistance for example). Software will just tell your motherboard what speed to run the fans and the motherboard will oblige by whatever way it can.

PWM controls fan speed by "pulsing" power into the fan - the faster or longer the pulses, the faster the fan spins. Voltage regulation controls fan speed by increasing or decreasing the power going into the fan. PWM fans will have the 4pin plug on it and need the 4pin which carries the PWM signal. otherwise you're going to have to use voltage regulation instead on the 3pin plug (PWM fans can plug into 3-pin headers with no problem).

So you could just load up your fans onto the motherboard (there are proper splitters available to ensure your motherboard headers don't draw too much power and burn out) and use some software to set the fan speeds as you need. or you can do the same with a hardware fan controller as discussed.

But the thing is to check HOW the fan controller does its thing - does it use PWM, does it use voltage regulation, can it do both. Because that will determine what type of fans you need to buy - there's no point buying PWM fans if you can only use 3-pin voltage regulation for example.
 
Chimp Paradox said:
On Lamptron's website they recommend 700w for some of their controllers!!! At least 500w for most of them....
Click to expand...

And that's no different than Nvidia or AMD listing what power supply you need for a graphics card - it's a rough figure talking about the entire system, not just one component. And that rough figure is going to be WAY higher than you need to allow for silly people buying sub-standard crap stuff from China that can't do what it says it can.

Ultimately the fan controller is going to draw power from the PSU, so you do need to factor in how much juice it's using, but there is no way ANY fan controller is going to cause problems on overall power draw in the real world - if for example you need to run 12 fans at once then you clearly have a lot of powerful hardware to cool, so you're not going to have a wimpy PSU. Common sense really.
 
Thanks mate. The only thing to correct is your statement that pwm fans are pointless if you aren't going to use pwm. Silentpcreview just Raye it the quietest and it can go down to 600rpm. The non pwm cannot
 
Fan controllers for 3 pin fans are ok but they get hot because the extra volts you don't use are dumped as heat which is why they need the heatsinks. PWMs only take the voltage they need so if running at 6v, the draw is 6v .. nothing more.
 
Chimp Paradox said:
Thanks mate. The only thing to correct is your statement that pwm fans are pointless if you aren't going to use pwm. Silentpcreview just Raye it the quietest and it can go down to 600rpm. The non pwm cannot
Click to expand...

That'll be because the voltage required for 600 rpm is too low to even get the fan spinning. The PWM version has the same voltage going into the motor to spin it, but the PWM signal can ensure the "pulses" are infrequent/short enough to only juice up the fan for 600rpm rotation. So PWM or not, you won't be able to get that fan down to 600rpm on voltage regulation, even if you use the PWM version on a 3pin plug.
 
Admiral Huddy said:
Fan controllers for 3 pin fans are ok but they get hot because the extra volts you don't use are dumped as heat which is why they need the heatsinks. PWMs only take the voltage they need so if running at 6v, the draw is 6v .. nothing more.
Click to expand...

True dat. A big omission from my explanation up top :D
 
Admiral Huddy said:
Fan controllers for 3 pin fans are ok but they get hot because the extra volts you don't use are dumped as heat which is why they need the heatsinks. PWMs only take the voltage they need so if running at 6v, the draw is 6v .. nothing more.
Click to expand...

Exactly why I ended up caving and getting the waterblock for my new fan controller instead of just the heatsink. Madness I tell thee!
 
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