Fan speed hacking - Page 1
Forum section: electronics / projects

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 17, 2017, 02:39:44 am
content: I have a Lambda EWS600-12 53amp 12V power supply. It has a very noisy 80mm fan, a 109R0812S4N03 part.I would like to replace it with a super quiet Noctua 80mm fan. The fan in the unit is three pin, though the pinout is different from a normal computer fan. I have taken the pinout into account and know that is not the issue.It seems the microcontroller or something in the power supply does not like the new fan. It will not enable the output. I figured it was because the new fan runs at about 1/3 the RPM. I measured the sense wire output from the fan that came with it and see it is around 240Hz. My Noctua is 70Hz.So I figured I would use a 555 to generate a 240 Hz square wave, use that to control a 2n3904 to make it Open Collector. It seems most computer fan sense wires are open collector. I did not realize this when I measured the frequency of the sense wire on the built in fan initially. So I just looked at the very weak waveform on that fan. For the Noctua I put a 10K pull-up resistor on the sense line and measured that.Long story short, I have a circuit that is a 240Hz square, and is open collector. This works quite well, and behaves just like the Noctua (though at the higher frequency). But it won't fool the power supply into enabling the output!So I went back and am trying to measure the frequency of the original fan again, but I am finding that a pull-up resistor does not work on the sense line. When I try to pull it up I just get the entire wave form to have a DC Offset. The pull-up works perfectly on the Noctua and I get a nice square wave of the sense line.Any thoughts on what might be different about this fan? I am still looking for a datasheet. Any other thoughts on tricking the power supply to turn the output on? I have a basic schematic of the power supply, but it does not include this part of the circuit, and I had to sign an NDA to get it. So I cannot share it. But it is not helpful anyway.I plan on using this supply a low duty cycle, and it is also thermally protected. So I am not too concerned about increased heat.Thanks in advance.

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 17, 2017, 02:50:57 am
content: give upApparently, received opinion on this forum is that there have been no advances in fan technology in the last 15 years, so your microcontroller is just trying to protect you from fanfoolery marketing wank.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 17, 2017, 02:56:32 am
content: Uh, Ok. Not sure I get that...Any other thoughts? Curious why this fan doesn't seem to act like an open collector on the sense wire.

author: alm
author_rank: Super Contributor
timestamp: July 17, 2017, 03:04:50 am
content: Of course a fan is more quiet if it moves 66% less air. Possibly even less if it has to work against some static pressure, I seem to recall the Noctua fans to use very open blades, which usually means it only performs well in free air without much impedance. Compare the static pressure vs air flow graphs in both data sheets if you want to be sure. It will be even more quiet if you completely remove the fan. How about replacing it with a fan of the same rating, but hopefully better/less worn bearings? Or oiling the existing bearings? That might give you a reduction in noise, especially if the old one was very worn, and is more likely to work with the current fan control.If the power supply does not do variable fan speed control, then you could look into adding speed control with the existing fan.It may be that the power supply is measuring current draw to detect a jammed fan.

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 17, 2017, 03:16:55 am
content: see?All the coin miners and overclockers are just misguided fools, they should have been running shrieking Deltas and Vantec Tornadoes this whole time...Sorry man, my own horse to beatbut it does keep your thread up top 'eh?

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 17, 2017, 03:46:26 am
content: The original fan is brand new. It does not need oil. The power supply is for industrial applications where noise is not normally an issue.The reduced airflow will not be an issue given the duty cycle and reduced current usage vs. the rated output.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 17, 2017, 03:48:39 am
content: I was wondering if it was measuring current flow, though. I suppose I could try some parallel resistance.

author: alm
author_rank: Super Contributor
timestamp: July 17, 2017, 03:56:24 am
content: What did TDK-Lambda say when you asked about modifying the equipment for a lower duty cycle?Like I said, it may be monitoring current draw. What happens if you lower the fan speed / current draw with a series resistor? That alone may be sufficient without replacing it with an inferior fan (industrial Sanyo fan vs consumer toy). Just make sure it will still reliably start.What happens if you then add a parallel resistor so only the fan speed is lower but not the current draw? What happens if you power the fan from an external power supply, but with the ground and tacho wire connected to the fan speed header?

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 17, 2017, 04:03:42 am
content: I find a lot of sub 120mm fans start reliably down to 5V, of course you have to gather some real data if you value your equipment

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 17, 2017, 04:25:27 am
content: I have not asked Lambda about the mod.Ok, I found a schematic that does have the fan. It looks like the sense wire is connected to a 1uF capacitor to ground. This then goes to a pin in the controller. So perhaps it is just reading a DC voltage from the fan, rather than looking edges. I need to measure the existing fan more carefully and start with no assumptions.It could be that the uC has an internal pull-up, but there is no external pull up resistor.The Noctua blades are designed to be quiet. The existing fan is designed without thinking about the noise at all. I am sure it moves more air.Is there some widespread hatred for Noctua fans or something? I normally drive computers with very loud fans, but they are in an isolated server room, so the noise does not matter.If I can figure out the signaling perhaps I can drive driving the existing fan more slowly, or with variable power levels based on temperature, which would be the ideal. Even just a comparator to kick it up to high when needed would be better than it is now. The fan does not have PWM drive.The supply does not sweat at all under my load of about ~12A with on and off duty cycles of around 30% over five minutes.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 17, 2017, 04:27:11 am
content: Perhaps I just try something like this:https://www.amazon.com/dp/B000292DO0/ref=sxbs_sxwds-stvp_1?pf_rd_m=ATVPDKIKX0DER&pf_rd_p=2972357942&pd_rd_wg=7fBVr&pf_rd_r=AQ1B9SHHJ077BTYEV0ZZ&pf_rd_s=desktop-sx-bottom-slot&pf_rd_t=301&pd_rd_i=B000292DO0&pd_rd_w=adljR&pf_rd_i=Fan+temperature+controller&pd_rd_r=34TJX27V6GNHSKWF8K80&ie=UTF8&qid=1500265451&sr=1It looks like that probably uses something like a low drop out lm317 driven by a temp sensor. Says it will only put out up to 11V +/-20%.EDIT: nevermimd, that unit is not temperature controlled. Duh.The fan is getting around 13.5V.I do still to figure out what the uC is expecting/reading.

author: alm
author_rank: Super Contributor
timestamp: July 17, 2017, 05:20:17 am
content: Quote from: FlyingHacker on July 17, 2017, 04:25:27 amNoctua is a fan that is certainly marketed as very quiet (read: low speed). But they are sold as aftermarket accessories for hobbyists assembling computers, where they get decent reviews. Usually for case fan (i.e. low static pressure) applications. Are any of the big computer manufacturers like Dell, Lenovo or HP using Noctua fans? Hence my comment about it being a consumer toy and having more faith in fans marketed to engineers designing industrial equipment. Just compare the Noctua data sheet, which is mostly marketing fluff, to one made by Sanyo, Delta or Papst. Where can I find static pressure vs airflow curves for Noctua fans? And why all that nonsense about the series diode/resistor '(ultra) low noise adapter' that they sell? Just give me performance at multiple supply voltages.It may be that the Noctua provides sufficient cooling for your application. But if it is designed for low static pressure, the actual air flow might be much lower than 33% of the original airflow, and you might be better off with a fan with a lower rotational speed but a different blade design for high static pressure. Comparing static pressure - airflow curves for the original and new fan might be useful for this.Quote from: FlyingHacker on July 17, 2017, 04:27:11 amThen there is certainly room to drop the voltage (if the micro tolerates that). I suggested a couple of steps that should let you isolate if it is the PWM scheme you are using or the current draw that is preventing the fan from working.

author: RoGeorge
author_rank: Super Contributor
timestamp: July 17, 2017, 08:24:40 am
content: Some circuits detect the current through the fan, and if the current is not in the expected range, then it will not work. (E.G. the Rigol DP832 will not power a fan that has a lower I nominal).Try to put a resistor in parallel with the fan power lines, so the new Noctua will be seen as the same load as the old fan. I saw this trick on a video for modding the Rigol DP832 power source by replacing its original noisy fan with a silent but also less power hungry one. No circuit to trick the RPM was necessary for that power source, just a parallel load resistor.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 17, 2017, 12:28:20 pm
content: The fact that the schematic shows the sense line going to the uC (in series with a thermal cutout switch) makes me think it is using the sense line rather than reading the current, but perhaps it is doing both; however, I don't see a current sense resistor.

author: RoGeorge
author_rank: Super Contributor
timestamp: July 17, 2017, 12:42:48 pm
content: In theory it should work with the new fan, but since it didn't, I supposed the reason might be the same as in this video:Of course, there might be something else, but it's very easy to try a parallel resistor.

author: ZeTeX
author_rank: Frequent Contributor
timestamp: July 17, 2017, 01:29:06 pm
content: Connect it to the 12V supply and leave it running 100%.I don't understand why people don't do that for FDB (Fluid Dynamic Bearing) fans. They are so quiet even at 100% it's ridiculous to make them quieter, you can barely hear a thing.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 17, 2017, 03:36:36 pm
content: I would do just that with the new fan, as it is so quiet. However, the uC disabled the output of the power supply because it thinks the fan is non-functional. See the original post.I need to re-characterize the output from the original fan to determine what the uC is looking for. The original fan doesn't seem to have an open collector output like a standard three wire computer fan.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 18, 2017, 04:10:57 am
content: So I took the time to properly characterize the built-in fan while connected to the PSU. It seems that it puts out a logic high (well, I think it was about ~150mV) when the fan is stalled, and a logic low (~2.5mV) when it is running properly. I think it must be doing this open collector.So all I had to do was to put some resistance between the sense wire and the ground. It took below 100Ohms to get it to respond. This could be due to the new fan putting out its own open collector pulse (which I think the uC is indeed pulling high). 68 Ohms seems to work well.I could *Almost* get it set to a value where stalling the replacement fan would turn off the output, but putting it right on this edge made it too sensitive and it would sometimes shutdown under load, (possibly because the voltage would go up to compensate for cable loss) and the fan voltage would go up a little bit. I may be able to smooth out the new fan's square wave with a good sized cap and get it to work. For now it is working well.

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 18, 2017, 04:14:11 am
content: Interesting, I'm glad you got to the bottom of it. I'll file this tidbit away for future reference.

author: ConKbot
author_rank: Super Contributor
timestamp: July 18, 2017, 12:00:01 pm
content: Dunno why some people are prattling on about the guy wanting to replace the fan. No HP/Dell and the like don't use noctua fans, they are expensive, so not suited for consumer goods, and in professional they don't care about quiet, it's as simple as that. They also make pressure optimized fans for going on high fin density heatsinks and radiators, not just case fans. And finally, I'd be willing to bet the lamda supply is probably rated for continuous duty at full power to at least 50C ambient before starting to derate. If OP is making it quieter because they are going to be around it, so it's probably not going to be that hot. Save the "REEEEE" for r/tendies or audiophile threads here.

author: alm
author_rank: Super Contributor
timestamp: July 18, 2017, 12:24:09 pm
content: Quote from: ConKbot on July 18, 2017, 12:00:01 pmDell and HP make a large number of office desktops. These users certainly care about noise.Quote from: ConKbot on July 18, 2017, 12:00:01 pmIn 80mm size?Quote from: ConKbot on July 18, 2017, 12:00:01 pmI do not know this supply specifically, but older Lambda supplies were specified at full load up to 30°C ambient, and were derated by something like -10% for every 10°C above that.Quote from: ConKbot on July 18, 2017, 12:00:01 pmOne brand provides detailed datasheets with characteristic curves and multiple supply voltages. The other does not provide detailed technical data, but instead talks about 'Ultra Low Noise Adapters' that are just simple series resistors with a fancy name. Which of these seems the most like a company appealing to audiophiles? Why are they not providing this technical data that pretty much every big fan manufacturer provides?Again, I am not saying that Noctua makes bad fans, just that they are no silver bullet, and without more technical data, it is hard to know how they compare in situations other than free air. How much is the air flow reduced in this case?

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 18, 2017, 05:01:54 pm
content: This unit is rated for continuous 100% load at up to 50C ambient without derating. 60C requires a 70% derating. This is with the original fan of course. At my load I am reading about 1 to 2 deg C higher at the output than the input. The case of the unit never even feels warm to the touch. We shall see how it does when I increase the load.The lambda supplies with the 30C ambient limit before derating tend to be the older, linear, convection cooled supplies. Those are pretty silent, though (a tad of hum sometimes), but not very efficient.I see where the problem lies. People on this forum are associating Noctua with auiophoolery. I just associate Noctua with quiet, lower CFM fans. I only use them in applications where I need quiet.For instance, all our work computers are in a separate machine room on the other side of a wall. So they all have noisy fans like the Sythe Kaze running 3000RPM (120mm, note this PSU fan is 80mm). They are also abused with 100% load for days or weeks on end (3D rendering).In general I find the Noctua fans to be a little on the low volume side, but they sure are quiet. If there are other quiet fans that provide good datasheets let me know. I would be happy to look at those.Dell and Hp and the like just buy the cheapest parts they can get their hands on for their pre-built systems. Only their top of the line systems take quality into account at all, and even then the power supplies are usually just barely adequate, etc. I gave up on prebuilt computer ages ago, and hand select quality components for every system.

author: alm
author_rank: Super Contributor
timestamp: July 19, 2017, 03:15:57 am
content: For me it is a combination of reports from real users about bad performance with high static pressure (e.g. dense heat sinks), and Noctua refusing to provide detailed technical information about it but replacing it with vague claims. This makes users often treat them as magic 'silence everywhere' fans, because what other information do you have to go on? That makes me suspicious about their claims.Some (low-speed) Papst fans have gotten decent reviews. Papst provides real data sheets.