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Jibby

Junior Member

Monday, March 30th 2020, 9:26pm

If you supply fixed +5V to the PWM signal there are two things that can happen:

1. You are not able to control the fan as the controller will not be able to pull down this voltage to GND. So the fan can not be controlled.
2. If the controller is not protected by a inline resistor it can burn.

If you like to add a external voltage you need to supply it with a resistor (4k7 for example) to the circuit.

As we would like to be as compatible with our products as possible we are currently developing a solution for this problem that can adjust to the wrong fan behaviour.

Currently these issues have only be confirmed with Noctua fans. And it looks like Noctua has provided different kind of PCBs at the same fans so this is really somehting very strange. I still believe they did a mistake and then did this whitepaper to describe the issue. But that is something you need to discuss with Noctua. I don't find any engineering reason why to change this. Even at industrial devices (for example CNC, SPS) it is common to control devices with NPN signals why the device supplys the control voltage.

At EK fans we found issues that if you combine the RPM signals of the fans (which happens at many splitters like SPLITTY9) the PWM control of the fans will fail. We haven't investigate deeper in this issue. This can simply be solved by removing the pin from the connectors.

In total > 99,9% of all PWM fans will work with our hardware perfectly.


Ok thank you for the information and thank you for working on a solution.

Just to clarify, I was providing 5V to PMOS/NMOS configuration described in the noctua white paper. I agree, the resistor is a good idea for noise reduction/limiting current.

Noctua is taking their sweet time getting back to me on a potential fix so I may just go with the artic fans. They look great and are 1/3rd the cost


I have 15 of the Artic P12 PWM PST fans in my build right now and I have to say I am very impressed with them. At max speed they are very quiet so they can be ran at a high RPM and they move a good bit of air.
I also decided to pick up 3 of the Infamous Noctua NF-A12x25 pwm's and compared to the artics I don't think they are worth it. They are louder than the Artics by a good bit once you cross over the 1800rpm threshold and as far as moving air through a radiator I feel the Artics do a fine job and considering the price of them it's a no brainer especially if you want to do push/pull.


I just switched out my Noctua's for the Artic P12 and P14 and I could not be happier. The Noctua's definitely are more capable but for $8 a fan with dead silent operation below 1300rpm and barely audible 1400-1800rpm range, they are sweet. I'm definitely glad I made the switch.

Jibby

Junior Member

Monday, March 30th 2020, 9:34pm


It sounds like I can just redesign my own splitty9 and add a +12V to 5.5V switching regulator and then a 5.5V to 5V LDO and this should solve the issue.


Any chance you could explain this fix in laymans terms? I am an engineer, but not the electrical variety. I have a good multimeter, and I'm pretty handy with a soldering iron, but I don't posses a scope, or any more advanced equipment. Is this something I could do with my existing tools and a few components ordered online?



You can try to add a 4,7kOhm resistor or maybe also a 1k resistor between VCC (12V) and the PWM Signal pin.



With full understanding that Aquacomputer takes no responsibility if I wreck my equipment or burn down my house, would you mind explaining a little bit more in detail what you mean?

Are you talking about bridging the +12V line (pin 2, yellow) and PWM signal (pin 4, blue) with two resistors in series, one 4.7K ohm and one 1k Ohm?

I almost $500 in new Noctua fans for my new build which are past the time window for returns. I ahve reached out to their customer support, but I have no idea what I can expect from them. I may be on my own and have to figure out a solution.

Consider me pretty annoyed at Noctua right now.

I ahve also posted a news post in the HardForum community about this issue.

I'm hoping the added attention helps bring about a solution, but if it doesn't, I'd appreciate any and all suggestions on workaround in laymans terms.
This is what I was proposing. Its a fancier solution than needed but I have spare parts laying around that are up to the task. I believe I put the resistor in the correct place that Stephan was referring to.

Keep in mind, I did not say this was a good solution or will work longterm, I just did a quick test and it seem to fix the issue.
Jibby has attached the following image:
  • Schematic_Diagram.png

This post has been edited 1 times, last edit by "Jibby" (Mar 30th 2020, 9:36pm)

mattlach

Junior Member

Monday, March 30th 2020, 11:32pm

This is what I was proposing. Its a fancier solution than needed but I have spare parts laying around that are up to the task. I believe I put the resistor in the correct place that Stephan was referring to.

Keep in mind, I did not say this was a good solution or will work longterm, I just did a quick test and it seem to fix the issue.


Thank you for posting that.

I am going to have to revisit my circuit terminology and how to read schematics. It's been 20+ years since I played with this stuff.

Is there a reason you are pulling down the 12v source to 5v, instead of just using the 5v line already available to you from the PSU?

If this works well, without long term damage, you should have a small board outfit in china build a small order of a couple of hundred of them, and open a shop on Amazon or Ebay. I'd buy a few :p

This post has been edited 1 times, last edit by "mattlach" (Mar 30th 2020, 11:35pm)

mattlach

Junior Member

Tuesday, March 31st 2020, 12:13am

This is what I was proposing. Its a fancier solution than needed but I have spare parts laying around that are up to the task. I believe I put the resistor in the correct place that Stephan was referring to.

Keep in mind, I did not say this was a good solution or will work longterm, I just did a quick test and it seem to fix the issue.


So, I have been reading the Intel PWM spec document to better understand what is going on. (I googled and found a copy here.

So, the spec (on page 9) is what Sebastian quoted on the previous page of this thread.

Quoted


PWM Control Input Signal The following requirements are measured at the PWM (control) pin of the fan cable connector (see Figure 7 and Table 1:)

PWM Frequency: Target frequency 25 kHz, acceptable operational range 21 kHz to 28 kHz
Maximum voltage for logic low: VIL = 0.8 V
Absolute maximum current sourced: Imax = 5 mA (short circuit current)
Absolute maximum voltage level: VMax = 5.25 V (open circuit voltage)

This signal must be pulled up to a maximum of 5.25V within the fan.

Note:New fan designs are strongly encouraged to implement a 3.3V pull up for compatibility with buffer design limits on Hardware Monitor Devices e.g. Super IO devices.


So, is the issue that they are not pulling up the PWM signal in the fan hub? This spec above, only has a max (5.25v). Is any value below that, down to the 0.8V incoming signal acceptable?

It seems like they strongly suggest pulling up to 3.3v for new designs though.

Further down the document (page 11) they make the following comments:

Quoted


1.The trace from PWM output to the fan header must not have a pull up or pull down. The pull up is located in the fan hub. The presence of a pull up on the motherboard will alter the fan response to the PWM Duty Cycle. In some cases this may prevent the fan from achieving full speed even with the Hardware Monitor device issuing a 100% duty cycle.

2.If driving multiple fans with a single PWM output, an open-drain / open collector output buffer circuit is required. Consult your Hardware Monitor vendor for layout suggestions.


Is #1 above what you are effectively doing? Pulling up the signal before it enters the fan? Have you had any inability in reaching max fan speeds as they suggest might happen?

And #2, what is this? Could this also be a contributing factor to our issues? That this output buffer circuit doesn't exist?

Again, much appreciate thoughts on this.

This post has been edited 1 times, last edit by "mattlach" (Mar 31st 2020, 12:16am)

mattlach

Junior Member

Tuesday, March 31st 2020, 12:30am


I just switched out my Noctua's for the Artic P12 and P14 and I could not be happier. The Noctua's definitely are more capable but for $8 a fan with dead silent operation below 1300rpm and barely audible 1400-1800rpm range, they are sweet. I'm definitely glad I made the switch.



Oh, I see. You wound up switching fans instead of using this fix.

I'm giving Noctua's support a chance to fix this or refund me.

If they fix the issue somehow (like the aforementioned swapping out my fans for older models) I'll be happy.

If they refund me my money, I'll also be happy, and I'll probably give those Arctic fans a try.

If they neither refund my money or fix my issue I will be pissed, and make one hell of a stink. And then I might give those arctic fans a try.

I understand they have pigtails so you can daisy chain them one after another. That sure should make wiring easier...

Jibby

Junior Member

Tuesday, March 31st 2020, 12:49am

This is what I was proposing. Its a fancier solution than needed but I have spare parts laying around that are up to the task. I believe I put the resistor in the correct place that Stephan was referring to.

Keep in mind, I did not say this was a good solution or will work longterm, I just did a quick test and it seem to fix the issue.


So, I have been reading the Intel PWM spec document to better understand what is going on. (I googled and found a copy here.

So, the spec (on page 9) is what Sebastian quoted on the previous page of this thread.

Quoted


PWM Control Input Signal The following requirements are measured at the PWM (control) pin of the fan cable connector (see Figure 7 and Table 1:)

PWM Frequency: Target frequency 25 kHz, acceptable operational range 21 kHz to 28 kHz
Maximum voltage for logic low: VIL = 0.8 V
Absolute maximum current sourced: Imax = 5 mA (short circuit current)
Absolute maximum voltage level: VMax = 5.25 V (open circuit voltage)

This signal must be pulled up to a maximum of 5.25V within the fan.

Note:New fan designs are strongly encouraged to implement a 3.3V pull up for compatibility with buffer design limits on Hardware Monitor Devices e.g. Super IO devices.


So, is the issue that they are not pulling up the PWM signal in the fan hub? This spec above, only has a max (5.25v). Is any value below that, down to the 0.8V incoming signal acceptable?

It seems like they strongly suggest pulling up to 3.3v for new designs though.

Further down the document (page 11) they make the following comments:


Quoted


1.The trace from PWM output to the fan header must not have a pull up or pull down. The pull up is located in the fan hub. The presence of a pull up on the motherboard will alter the fan response to the PWM Duty Cycle. In some cases this may prevent the fan from achieving full speed even with the Hardware Monitor device issuing a 100% duty cycle.

2.If driving multiple fans with a single PWM output, an open-drain / open collector output buffer circuit is required. Consult your Hardware Monitor vendor for layout suggestions.


Is #1 above what you are effectively doing? Pulling up the signal before it enters the fan? Have you had any inability in reaching max fan speeds as they suggest might happen?

And #2, what is this? Could this also be a contributing factor to our issues? That this output buffer circuit doesn't exist?

Again, much appreciate thoughts on this.
I went with my own +5V just because I am familar with the hardware I was using and I like to use things I built myself previously to troubleshoot electrical problems. You could probably use the +5V rail as long as it doesn't exceed +5.25V but I have no idea what Noctua's actual limit is. I seemed to be able to apply a tightly regulated +5.0xV voltage and it seemed to be fine but I only ran it for like 5 minutes.

What the +5.25V max is referring to is the max voltage. The 0.8V just means that 0V- 0.8V range is just giving you the low threshold range (the low point range of the PWM signal). I have no idea what the threshold voltage for Noctua's fans are (the point at which the low becomes high or 0 becomes 1) but I assume that if they followed the intel spec and 3.3V is fine for a logic high, then the voltage threshold is somewhere around 2.4V-2.6V.

I attached a crappy picture again to try to illustrate what I am saying
Jibby has attached the following image:
  • Digital_Logic.PNG

Tuesday, March 31st 2020, 7:28am

This is what I was proposing. Its a fancier solution than needed but I have spare parts laying around that are up to the task. I believe I put the resistor in the correct place that Stephan was referring to.
Keep in mind, I did not say this was a good solution or will work longterm, I just did a quick test and it seem to fix the issue.

<img src="https://forum.aquacomputer.de/index.php?page=Attachment&attachmentID=7326&h=0fa7732369f603cb7acda7e0b81df15a3108a98d" alt="index.php?page=Attachment&attachmentID=7326&h=0fa7732369f603cb7acda7e0b81df15a3108a98d" title="index.php?page=Attachment&attachmentID=7326&h=0fa7732369f603cb7acda7e0b81df15a3108a98d" style="font-size: 0.81em;" />

This is not working, the output signal is inverted and a input pull up (10K) is missed.

Jibby

Junior Member

Tuesday, March 31st 2020, 6:41pm

This is what I was proposing. Its a fancier solution than needed but I have spare parts laying around that are up to the task. I believe I put the resistor in the correct place that Stephan was referring to.
Keep in mind, I did not say this was a good solution or will work longterm, I just did a quick test and it seem to fix the issue.

<img src="https://forum.aquacomputer.de/index.php?page=Attachment&attachmentID=7326&h=0fa7732369f603cb7acda7e0b81df15a3108a98d" alt="index.php?page=Attachment&attachmentID=7326&h=0fa7732369f603cb7acda7e0b81df15a3108a98d" title="index.php?page=Attachment&attachmentID=7326&h=0fa7732369f603cb7acda7e0b81df15a3108a98d" style="font-size: 0.81em;" />

This is not working, the output signal is inverted and a input pull up (10K) is missed.


You could just cascade two of the CMOS inverter circuits together and that would correct the output signal. Can you draw where the input pull up resistor goes?

caronen

Junior Member

Wednesday, April 1st 2020, 12:25am

Any chance you could explain this fix in laymans terms? I am an engineer, but not the electrical variety. I have a good multimeter, and I'm pretty handy with a soldering iron, but I don't posses a scope, or any more advanced equipment. Is this something I could do with my existing tools and a few components ordered online?

It is not easy to give a solution without knowing what the problem exactly is.

I would strongly advise against connecting anything to +12 V line since this may work but as well may not and some collateral damage may occur.

An easy thing to test is to add a resistor between +5 V line and PWM pin. Since Noctua is expecting a 5 V push-pull driver this is perfectly safe for the fan and for Aquacomputer gear. +5 V is readily available in a standard PC – from Molex, SATA or USB connectors.
As for the resistor, 4,7 kOhm would be OK. As a rule of thumb, don’t go below 2,2 kOhm and not above 20 kOhm.

In case you don’t want an extra cable to bring 5 V where it is needed, you can use a 7805 regulator to convert 12 to 5 V. This is a 0,50 € part. Resistors are even cheaper.

Tuesday, April 7th 2020, 2:21pm

I am having this exact same issues and it is a major bummer. I bought this most recent batch of Noctua fans ages ago, I am curious to see what Noctua says to the most recent person to contact them. Just when I thought I was finally going to get to use this build, now this happens haha. ;(

Monday, April 13th 2020, 2:58pm

Disappointed in the brevity of the reply. A short explanation would have been helpful.
Too often the consumer is bounced between manufacturers, being told 'it;s the other guys issue'.

The problem is exclusive to the splitty9 active?
I have a splitty9 (not active) driving nine Noctua A14 industrialPPC-2000 IP67 fans, on fan port 4 of an aquaero 6 XT with a curve controller.
I have 20% minimum power and no issues with PWM control.
Noctua had the great idea to add some kind of protection circuit to newer revisions of fans which is causing this problem. We do not know what they did there in detail but we know it is causing the problem because it is also Noctua that confirmed that to one of our customers. Their solution was that they offered the customer fans from an older batch that do not suffer from this problem.

I guess your fans are from an older batch because otherwise you would have problems too.

There is no way for us to solve this - or at least not without raising new problems with regular working fans. We already sent out modified Splitty9 active boards for testing purposes to affected customers. Feedback so far is that it only partially helped but a normal operation with affected Noctua fans is still not possible. Noctua will have to fix this with a new revision and we know for sure that they are well aware of this problem.
Ok I was in contact with Noctua and they confirmed the compatibility issue with their Industrial line fans (other fans series should be fine, as they told me).
The problem lies in their PWM protection circuit added to guarantee the industrial fans lifespan in hars conditions of factorys.

They told me that because of the problem they went back to the old version of the production so there would not be a compatibility issue anymore. In the mean time they are also working on a new version of their PWM proctection cicruit so that you would have the PWM protection and no compatibility issues with PWM fan splitters.

So normally every industrial line fan comming of the production line right now should be good without compatibility issues (but actually knowing when the fans are produced or which version it is can be difficult)

Currently i am using two octo's (one connected to the aquaro 6 over aquabus) because each fan connector is a sepparate channel and thus no problems with my industrial fans, the only problem is that I need 2 octo's for all the fans and it would be a nice feature to control 2 octo's via aquabus in the future (as this is not possible right now).

So i hope this info was a bit usefull (i know nothing new but still).

@ shoggy Sry i didn't immediately believed you when trying different splitters but everything is cleared out now and once again thank for the responses.

Friday, April 17th 2020, 12:07pm

Disappointed in the brevity of the reply. A short explanation would have been helpful.
Too often the consumer is bounced between manufacturers, being told 'it;s the other guys issue'.

The problem is exclusive to the splitty9 active?
I have a splitty9 (not active) driving nine Noctua A14 industrialPPC-2000 IP67 fans, on fan port 4 of an aquaero 6 XT with a curve controller.
I have 20% minimum power and no issues with PWM control.
Noctua had the great idea to add some kind of protection circuit to newer revisions of fans which is causing this problem. We do not know what they did there in detail but we know it is causing the problem because it is also Noctua that confirmed that to one of our customers. Their solution was that they offered the customer fans from an older batch that do not suffer from this problem.

I guess your fans are from an older batch because otherwise you would have problems too.

There is no way for us to solve this - or at least not without raising new problems with regular working fans. We already sent out modified Splitty9 active boards for testing purposes to affected customers. Feedback so far is that it only partially helped but a normal operation with affected Noctua fans is still not possible. Noctua will have to fix this with a new revision and we know for sure that they are well aware of this problem.
Ok I was in contact with Noctua and they confirmed the compatibility issue with their Industrial line fans (other fans series should be fine, as they told me).
The problem lies in their PWM protection circuit added to guarantee the industrial fans lifespan in hars conditions of factorys.

They told me that because of the problem they went back to the old version of the production so there would not be a compatibility issue anymore. In the mean time they are also working on a new version of their PWM proctection cicruit so that you would have the PWM protection and no compatibility issues with PWM fan splitters.

So normally every industrial line fan comming of the production line right now should be good without compatibility issues (but actually knowing when the fans are produced or which version it is can be difficult)

Currently i am using two octo's (one connected to the aquaro 6 over aquabus) because each fan connector is a sepparate channel and thus no problems with my industrial fans, the only problem is that I need 2 octo's for all the fans and it would be a nice feature to control 2 octo's via aquabus in the future (as this is not possible right now).

So i hope this info was a bit usefull (i know nothing new but still).

@ shoggy Sry i didn't immediately believed you when trying different splitters but everything is cleared out now and once again thank for the responses.
I received this same response about a week ago, I responded right away asking what the next steps were to do an exchange and a week or so later I still have not heard back. My Aquaero 6 XT and my D5 Next need to regain control!

mattlach

Junior Member

Tuesday, May 26th 2020, 6:37am

Disappointed in the brevity of the reply. A short explanation would have been helpful.
Too often the consumer is bounced between manufacturers, being told 'it;s the other guys issue'.

The problem is exclusive to the splitty9 active?
I have a splitty9 (not active) driving nine Noctua A14 industrialPPC-2000 IP67 fans, on fan port 4 of an aquaero 6 XT with a curve controller.
I have 20% minimum power and no issues with PWM control.
Noctua had the great idea to add some kind of protection circuit to newer revisions of fans which is causing this problem. We do not know what they did there in detail but we know it is causing the problem because it is also Noctua that confirmed that to one of our customers. Their solution was that they offered the customer fans from an older batch that do not suffer from this problem.

I guess your fans are from an older batch because otherwise you would have problems too.

There is no way for us to solve this - or at least not without raising new problems with regular working fans. We already sent out modified Splitty9 active boards for testing purposes to affected customers. Feedback so far is that it only partially helped but a normal operation with affected Noctua fans is still not possible. Noctua will have to fix this with a new revision and we know for sure that they are well aware of this problem.
Ok I was in contact with Noctua and they confirmed the compatibility issue with their Industrial line fans (other fans series should be fine, as they told me).
The problem lies in their PWM protection circuit added to guarantee the industrial fans lifespan in hars conditions of factorys.

They told me that because of the problem they went back to the old version of the production so there would not be a compatibility issue anymore. In the mean time they are also working on a new version of their PWM proctection cicruit so that you would have the PWM protection and no compatibility issues with PWM fan splitters.

So normally every industrial line fan comming of the production line right now should be good without compatibility issues (but actually knowing when the fans are produced or which version it is can be difficult)

Currently i am using two octo's (one connected to the aquaro 6 over aquabus) because each fan connector is a sepparate channel and thus no problems with my industrial fans, the only problem is that I need 2 octo's for all the fans and it would be a nice feature to control 2 octo's via aquabus in the future (as this is not possible right now).

So i hope this info was a bit usefull (i know nothing new but still).

@ shoggy Sry i didn't immediately believed you when trying different splitters but everything is cleared out now and once again thank for the responses.
I received this same response about a week ago, I responded right away asking what the next steps were to do an exchange and a week or so later I still have not heard back. My Aquaero 6 XT and my D5 Next need to regain control!


Same here. I had a very positive interaction with Noctua's customer support.

Here is what they told me:

Quoted from "noctua.at"


Greetings from Noctua!

Thank you very much for your patience!

The issues have occurred because we have increased the protection of the PWM control line in order to further improve electronic robustness in industrial environments. This extra protection has increased the capacitance of the PWM line slightly. In a situation where multiple fans are connected in parallel, the capacitance of the PWM line will end up in parallel, increasing the capacitance. This means that the PWM control line driver will have an increased capacitance load to drive, which can cause the signal to deteriorate. If a large number of fans is used, it is therefore important that controller or splitter board have independent outputs for each fan. If they don’t and if the output driver is sensitive to increased capacitance this can cause a signal degradation, which, in return, can lead to reduced fan speeds when controlling multiple fans.

We have already reverted our production back to the original version in 2019 in order to make sure that there are no more compatibility issues with controllers and we are working on a new, updated version that will feature the extra protection while still being fully compatible.


They proceeded to offer exchanges for all 18 of my fans for newly manufactured fans on their reverted production line, which I accepted.

For what its worth, my old fans which exhibited the issue had a date code starting in 1908. (which I can only presume is August 2019) The new ones I received had a date code starting in 1911. I do not know when the switchover occurred.

Anyway, kudos to Noctua on responding well to an unfortunate situation. As anyone who has worked in engineering design or manufacturing knows, eventually mistakes happen. I try not to judge companies based on whether or not they have mistakes (eventually they hit everyone) but rather on how they respond to them when they happen, and in this case Noctua did the right thing, explained the situation and offered to fix it.

They even sent me fans priority express shipping from Austria which I can't imagine was cheap, and was totally unnecessary.

So, after briefly flirting with removing them from my preferred brand list, I can say they are back with a vengeance. It's nice to know that a company takes care of it's customers.