PWM Question

BikingViking11

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Can I control two more PWM fans by a CPU PWM header using the signal wire, yet power them separately? I don't have room for a hub.

As far as I understand, pins #1 & #2 are 12V power, #3 is RPM and #4 is PWM signal that is sent to an IC built into the fan. The only issue I see is if that signal is "read" differently from fan to fan. Anyone tried this?
 

Thehack

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Can I control two more PWM fans by a CPU PWM header using the signal wire, yet power them separately? I don't have room for a hub.

As far as I understand, pins #1 & #2 are 12V power, #3 is RPM and #4 is PWM signal that is sent to an IC built into the fan. The only issue I see is if that signal is "read" differently from fan to fan. Anyone tried this?
You can use a PWM Y splitter. Only difference is you can only get the RPM reading of one fan, and both fans are synced to same speed.
 

BikingViking11

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You can use a PWM Y splitter. Only difference is you can only get the RPM reading of one fan, and both fans are synced to same speed.
I get how that works on an ATX board. The problem is this is a NUC8i5BEH and has a tiny CPU header. I'm not sure it can handle adding two fans to it so I'd like to power it independently, not from the fan header like a splitter would, but use the PWM signal wire to control the speed of the additional fans.
 

Thehack

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I get how that works on an ATX board. The problem is this is a NUC8i5BEH and has a tiny CPU header. I'm not sure it can handle adding two fans to it so I'd like to power it independently, not from the fan header like a splitter would, but use the PWM signal wire to control the speed of the additional fans.
In that case, yes, it'll work just as you expect it to.
 
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BikingViking11

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In that case, yes, it'll work just as you expect it to.
Thanks for the vote of confidence!

I had asked this same question in a FB group and got, "You can't do that" and "You need a controller". After looking at what this PWM hub does (Independently powers 10 fans via a SATA plug) and what this PWM hub does (Powers 4 fans via the PWM header), neither controls a 3-pin fan which tells me it's not voltage controlled as it states they'll run at full speed, or 12V. With either all the fans run at the same duty cycle, so basically they're just a fancy version of a splitter for the PWM signal.
 

BikingViking11

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The Intel spec of NUC8i5BEH says its fan header supplies a max of 0.5A. An online search of the fan used is AVC's BAZB0808R5H (https://nucblog.net/2018/11/coffee-lake-i5-nuc-review-nuc8i5bek-nuc8i5beh/) which is exactly 0.5A.
So, if the 2 fans do not add up more than 0.5A, then it is OK.
If not, just follow your plan above to get power directly from the PSU.
Thank you for the well researched answer.

Looking through my pictures of the fan, it's actually a Delta BSC0805HA-00 rated at DC05V and 0.60A. I had assumed that any CPU fan would be a 12V model and that the 4-pin design was PWM. I am not unhappy with the function of the CPU fan at all, it's nearly dead silent at idle. Haven't done any stress testing yet though.

Taking a step back, it would be very easy to run case fans separately on manual control, find a setting I like and just leave it there. Software control is nice, but perhaps unnecessary.
 

BikingViking11

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When you are done with your mod, please post a pic or two. I like to see the final result. Thanks.
Thank you for your input @tinyitx . You can see the mod here. I have a lot more parts in but couldn't work on it today since my workspace is flooded from melting snow.


The two fans I wish to add are 40mm and go in the front to cool the SATA controller card and PSU. I was looking at a pair of Noctua NF-A4x20 PWM in 12V. Until you posted and I checked my specific fan I hadn't realized the potential to run 5V fans. There's a Noctua NF-A4x20 PWM in 5V too.

What I will do is test a few 12V PWM fans on a donor system. If that works as expected I don't see why it wouldn't for 5V. Noctua also makes a tiny PWM controller (12V) that would be easy to mod in for manual control, but any extra space I can gain helps.