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hrmes

Junior Member

Aquaero 5 PWM fan signal

Friday, May 13th 2011, 3:07pm

Hi everyone, this is my first post.

I want to replace my T-Balancer with an Aquaero 5 but first I want to know a few details so that I can decide what fans to use with it.

What I want to know is, when you are using channel 4 in PWM mode, if the PWM signal is in any way calibrated to reflect the real percentage of maximum fan RPM, or if the PWM signal is simply a raw PWM signal.
I'm asking this because I have tested a Noiseblocker 120mm PWM fan with a speed of 1000 to 2000 RPM with the SpeedFan utility.

I connected it to a 4-pin motherboard fan header and saw that the fan spins at about 900 RPM when the PWM signal is at 0%, at about 1500 RPM at 50% PWM signal, and at about 2000 RPM at 100% PWM signal.
This may seem normal but look at page 14 of the attached 4-wire PWM Developer Specs PDF. developer_specs_4_Wire_PWM_Spec.pdf

There it states: "The fan RPM (as a percentage of maximum RPM) should match the PWM duty cycle within +-10%."

If I understand correct this means that when the PWM duty cycle is at 50% then the fan should spin at 50% of maximum RPM, so in the case of the fan I tested when the PWM signal is at 50% the fan should spin at 1000 RPM and not at 1500. Obviously this happens because the fan manufacturer does not fully comply to the PWM fan guidelines.
If Aquaero 5 can't calibrate the PWM signal to reflect the true percentage of maximum fan RPM, then in the case of the Noiseblocker fan when Aquaero 5 sets the fan to run at 50%, it will actually be running at 75% (1500) of max RPM (2000).
In that case I think that a calibration option could be added to the firmware of Aquaero 5. It could run the fan from 0% to 100% PWM duty cycle and read the corresponding fan RPM at each PWM duty cycle. Then it could use that RPM data to calibrate the PWM signal.

This post has been edited 1 times, last edit by "hrmes" (May 14th 2011, 6:38pm)

hrmes

Junior Member

Wednesday, June 1st 2011, 5:54pm

No official reply... :( Can any Aquaero 5 owner test a PWM fan and see if 50% fan channel power means 50% fan RPM ?