What exactly is PWM? Plus basic fan question

Chimp Paradox · 22 Sep 2014 at 15:44

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

Chimp Paradox · 23 Sep 2014 at 09:02

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

Chimp Paradox · 23 Sep 2014 at 10:10

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

Chimp Paradox · 23 Sep 2014 at 13:34

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.

Chimp Paradox · 23 Sep 2014 at 15:09

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 · 23 Sep 2014 at 15:10

eg http://www.lamptron.com/product/controllers/cw611/

Chimp Paradox · 23 Sep 2014 at 16:30

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

Chimp Paradox · 23 Sep 2014 at 18:10

LePhuronn said:
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.

Very helpful, thank you!! Why is there not something like voltage based PWM, then? Can you use something like speedfan on PWM as opposed to having to use mobo software?

Chimp Paradox · 24 Sep 2014 at 05:59

But does speedfan only "read" PWM or does it read any fan header?

Also, it turns out I have 2 pwm fan headers. If I want 2 fans, presumably this means I will only have pwm control in pairs of 2 when I use a splitter from the header?

Chimp Paradox · 24 Sep 2014 at 14:28

"yet you still get PWM control from the 4-pin connector."

Does that mean, presumably that all fans would fun at the same speed, right? Speedfan would only be able to control.

Shivvy - does Speedfan allow you to turn fans off?

To be honest, for what I want, I think I only want 3 things.

1. Off
2. Setting for 600rpm
3. Setting for Full 1200 rpm

Chimp Paradox · 24 Sep 2014 at 15:18

So fans don't need to be PWM to run on speedfan? Ive emailed Phantek to ask whether their PWM fan can run on 600rpm through voltage regulation or whether it needs PWM to do so.

Chimp Paradox · 24 Sep 2014 at 17:08

"Speedfan would only be able to control." - that's a typo, I meant speedfan would only be able to control the speed of all of them at once and not individually.

So the long and short of it is, get the PWM fans, and control them using speedfan, which allows me to:

1. Turn them off
2. Turn on full

Who is it I need to ask if I can get them running as slow as 600rpm, then? My understanding from silentpcreview is that everyone over there runs slow fans.

Chimp Paradox · 24 Sep 2014 at 17:09

Also, I should have made this clearer earlier but the ONLY fans in my system are case fans. PSU and CPU are both passively cooled.

Chimp Paradox · 24 Sep 2014 at 17:28

Thanks LePhuronn - in that case I was misunderstanding you earlier.

Can I therefore assume you mean that if a PWM says you can go down as low as 600rpm, then it can, provided you use PWM. You wont be able to do it with voltage (at least until you figure out how to modd the fan somehow).

Can I also assume that, for speedfan to work correctly, you need to disable all fan control in the BIOS, which is presumably where the mobo based PWM is set?

Finally on the fan point, I am using the phanteks simply because they are currently the quietest as rated by silentpcreview, but understand what you are saying.

According to them, the result of the thyphoon is

Scythe GT120-12 is 24 and 27 degrees at 12 and 11db @ 1m

The Phantek are 22 and 25 degrees at 12 and 11db @ 1m.

Not a lot in it. Full results here

http://www.silentpcreview.com/article1345-page7.html

Chimp Paradox · 25 Sep 2014 at 07:27

LePhuronn - keen to hear if I am correct above!