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 Post subject: Clicking fans on fan controller
PostPosted: Wed Jun 19, 2013 4:44 am 
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Posts: 218
Location: East Sussex (UK)
I have been running Scythe S-Flex E fans for quite some time now without problems. I ran them from a Scythe Kaze Server for a while also without issue.

I recenly bought a Corsair Link Cooling Kit and straight away the fans started to click. I returned the kit and went back to motherboard control - but want to be able to control the fans externally.

I then bought a NZXT Sentry Mix, which arrived today. Hooked it up - clickety click! :cry:

Is this common for the Scythe S-Flex fans? If so, which fans work well without clicking, and are as good if not better than the Scythes?

Please help the clicking is driving me mad and it was only fitted just now... Gonna probably switch back to the motherboard for the time being as I doubt I will be able to RMA this controller to - or if I do it will be at a cost.

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 Post subject: Re: Clicking fans on fan controller
PostPosted: Thu Jun 20, 2013 4:32 am 
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Location: UK
It's nothing to do with the fans, it is to do with how some fan controllers such as the NZXT Sentry Mix work with 3 pin fans. You might think that the controller is supplying pure DC to the fans but this is not the case. What will be being supplied to the fans is low-frequency PWM. This is done primarily to allow a fan control range of typically 40 to 100% and avoid the issue of 3 pin fan starting voltages. It works but one of the potential side-effects are fans buzzing, clicking and whining. LED fitted fans may also flicker.


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 Post subject: Re: Clicking fans on fan controller
PostPosted: Thu Jun 20, 2013 6:03 am 
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Location: East Sussex (UK)
Do you know which controllers use the analogue method of reducing voltage?

Are any still available?

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 Post subject: Re: Clicking fans on fan controller
PostPosted: Thu Jun 20, 2013 10:54 am 
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Maybe it's possible to add a bit of capacitance to the output, to smooth it out a bit?

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 Post subject: Re: Clicking fans on fan controller
PostPosted: Thu Jun 20, 2013 11:06 am 
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Location: East Sussex (UK)
That's exactly what my dad said. His company make electrical transformers so he is more into electrical stuff than me. I phoned him last night and we were chatting it through. It is a possibility for sure.

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 Post subject: Re: Clicking fans on fan controller
PostPosted: Fri Jul 05, 2013 10:30 am 
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It's more subtle than that. It's true that almost all controllers output PWM rather than DC, but the frequency is in the kilohertz range, which can't generate mechanical noise.

The real cause is that the controller goes to full voltage several times per second for a brief period so that the RPM sensing circuit will work correctly. This dramatically changes the torque of the fan motor, which is where the click comes from.

Good luck finding a DC controller; I haven't seen one for several years. The other approach (which is painful) is to find a fan that doesn't click. About 2/3 of the Nexus fans I've used don't click; the other 1/3 do.

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 Post subject: Re: Clicking fans on fan controller
PostPosted: Tue Aug 20, 2013 3:58 am 
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cmthomson wrote:
The real cause is that the controller goes to full voltage several times per second for a brief period so that the RPM sensing circuit will work correctly. This dramatically changes the torque of the fan motor, which is where the click comes from.

Very informative & interesting, clearly stated!

cmthomson wrote:
Good luck finding a DC controller; I haven't seen one for several years.

As for me, I prefer the "good old" possibility to obtain 7V and 5V from standard MOLEX connector by simply interchanging the pins. 5V is directly on MOLEX and 7V is between 12V and 5V pins. With 12V (base), this gives you three speeds.

I do realize that this is no substitute for continuously variable controller though and it is not that much convenient to interchange the pins. Perhaps there is (should be) available some simple switch? (Molex on one side, than box with say just mechanical switches, 5V/7V/12V on output.)

EDIT: After reading viewtopic.php?f=9&t=22943 I learned that the "7V trick" mentioned above can be dangerous to the PSU, as you are feeding current back to PSU through 5V branch (thing the PSU is _NOT_ designed for). Anyhow, here is a how to with proper warning/explanation about the limitations of the "7V trick": http://www.silentpcreview.com/article6-page1.html


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