Resistor to quiet fans

[jriker1]

I have a Dell MD1200 Hard Drive case. It has four fans in it. Two in each power supply. Two fans are screwed into each other I guess for increased pressure to pull air from the front of the case. Below is a pic of the back of the case:

http://www.fvstore.com/i/2012/10/14...20-MV-2010-NAS-Drive-Panel-Kit-NO-DRIVE-2.JPG

I tried removing one fan from each case but the system went into alert mode and kicked the remaining fans into 100% usage. The system in general is a screamer. Below are the specs of the fans:

Company: AVC
Model: DBTB0838B2S
Sub Model: P010
80x80x38 (or 80x80x76 together)
DC12V
2.1A
115CFM
4-pin PWM

I was thinking of putting a resistor on the line assuming the Dell case doesn't get upset by the fan speed not being what it wants and attempt to max them out. Based on the before mentioned specs, can someone give me an idea of what kind/size/color band of resistor I would need to slow down this fan adequately to quiet it up? Still going to have the two fans together in the case as I don't have a lot of choice so trying to slow them down enough not to be noisy or to noisy.

Please don't lecture me on this is a server product so is meant to be noisy. It was in a lab, we lost our lab, and now have it sitting in a cube so don't have a choice here.

I've heard different people say use just whatever resistor to change it from 12V to like 7V to make sure it spins up. Others talk about Ohms compared to the amps and say its more than that because it could burn up if it can't handle the power draw. Any help on what resistor I should be looking at and what cable to put it on would be great. if something like this is already buyable as an extension to the fan even better.

Thanks.

JR

 

[RU482]

you mean something like this - http://www.amazon.com/Computer-Noise-Reduce-Resistor-Adapter/dp/B00880S6KA

 

[jriker1]

you mean something like this - http://www.amazon.com/Computer-Noise-Reduce-Resistor-Adapter/dp/B00880S6KA

Yep, exactly something "like" that. Just trying to understand what resistor would be good for this or what would work without burning out. Also saw these earlier:

http://www.amazon.com/Speed-Noise-Re...m+fan+resistor

but the person I contacted didn't seem to know anything about the specifics of them.

JR

 

[imagoon]

An MD1200 being a server room / rack device will get very upset if you lower fan speeds as it will try to speed them up until it detects it can't and then alarm setting all fans on the device to full power. It also may overheat and trigger a shutdown. Some of the MD devices will also fail to power up if they fail the fan self test at power on. You would be better off moving the device away from where ever it is causing you noise issues, put a noise dampening device behind it etc.. They are not really meant to be sat next to.

 

[jriker1]

An MD1200 being a server room / rack device will get very upset if you lower fan speeds as it will try to speed them up until it detects it can't and then alarm setting all fans on the device to full power. It also may overheat and trigger a shutdown. Some of the MD devices will also fail to power up if they fail the fan self test at power on. You would be better off moving the device away from where ever it is causing you noise issues, put a noise dampening device behind it etc.. They are not really meant to be sat next to.

Yes, you are probably right, but let's have me be the first person to try and document it for the world one way or the other.

Overheating is definitely not a concern for me at this point. If I could get each of these fans to run at 2/3 or 1/2 their current speed would be happy and if it actually works without erroring even better. I know the Dell OpenManage software only shows if it's active or not, doesn't even show fan speed. Two fans I took out show error status so hoping if they are at least running will show OK and not start alerting.

Unfortunately for me it's either reduce the fan noise and be able to still use these devices, or they sit in the corner and collect dust. I'm all for being able to try and make them usable.

JR

 

[ClockHound]

Seems like those tiny bastards are spinning well over 4k to get that high CFM. So...cheapest option is earplugs or noise-canceling headphones.

Or...get a hammer and smash the noisy little bastards - it will feel really good. Once you have cleared the debris field, make your own 180-120mm to 80mm convertor using a plastic sheet/foamboard combo. And install some much, much quieter, larger fans.

Altho, collecting dust silently in the corner is not a bad option either.

 

[imagoon]

Yes, you are probably right, but let's have me be the first person to try and document it for the world one way or the other.

Overheating is definitely not a concern for me at this point. If I could get each of these fans to run at 2/3 or 1/2 their current speed would be happy and if it actually works without erroring even better. I know the Dell OpenManage software only shows if it's active or not, doesn't even show fan speed. Two fans I took out show error status so hoping if they are at least running will show OK and not start alerting.

Unfortunately for me it's either reduce the fan noise and be able to still use these devices, or they sit in the corner and collect dust. I'm all for being able to try and make them usable.

JR

In that case you may want to talk to the people that own that MD1200 before you start "hacking" on it. I wouldn't be that thrilled if my employees took it upon themselves to start hacking apart a device that starts at $4000 unloaded.

 

[jriker1]

In that case you may want to talk to the people that own that MD1200 before you start "hacking" on it. I wouldn't be that thrilled if my employees took it upon themselves to start hacking apart a device that starts at $4000 unloaded.

Why do these threads always go this way? Anyway, thanks for the "help?" apparently I'm not going to get an answer to what I'm asking about directly. Even though I am not the "employee" per sea, but the owner. But that shouldn't matter to the point of helping with the original inquiry.

JR

 

[jriker1]

Seems like those tiny bastards are spinning well over 4k to get that high CFM. So...cheapest option is earplugs or noise-canceling headphones.

Or...get a hammer and smash the noisy little bastards - it will feel really good. Once you have cleared the debris field, make your own 180-120mm to 80mm convertor using a plastic sheet/foamboard combo. And install some much, much quieter, larger fans.

Altho, collecting dust silently in the corner is not a bad option either.

ClockHound, you referring to mounting something outside the case? Not sure if you saw the pic of the MD1200 but nothings fitting "inside" other than an 80mm fan.

Unfortunately to the other comment about asking other owners, no one responds to anything in the dell forums.

JR

 

[imagoon]

Why do these threads always go this way? Anyway, thanks for the "help?" apparently I'm not going to get an answer to what I'm asking about directly. Even though I am not the "employee" per sea, but the owner. But that shouldn't matter to the point of helping with the original inquiry.

JR

Fairly simple: Most people here don't own equipment like that and consider it disposable enough risk damaging it. More of them are 16 year "l33t h@ck3r$" that are screwing around with their companies gear.

It is a fairly simple issue:
Those AVC fans are PWM controlled fans with the speed controller on the fan itself with a PWM signal coming from the system itself with as sense wire on the controller. The controller expects 12V on the line with 2.1A available. All a resistor is going to do is cause the unit to ramp the PWM signal to 100% duty cycle and then set the alarm on the unit which will set all fans to 100% and likely fault the speed controller which will fail to 100% anyway.

These are not your normal $1 case fans. They have PCBs and IC's on board that communicate with the management engine on the MD1200. So yes the resistor will cause the fans to run slower with the result of the unit running in fault mode the entire time and possibly overheating and failing.

--
Knock yourself out:
4 ohm, 2 amp resistor isn't exactly small and might need to heatsinked in tight space:

Original fan voltage: 12V

Original fan current: 2.1A

    V=IR (Ohm's Law), so 12 = 2.1R   =>   R = 12 / 2.1   =   5.714

Fan resistance: 5.714 Ohms

Target voltage: 7V

    V=IR (Ohm's Law), so 7 = 5.714I   =>   I = 7 / 5.714   =  1.225

Target current: 1.225A

Voltage drop across resistor: 12V - 7V  =  5V

    V=IR (Ohm's Law), so 5 = 1.225R    =>    R = 5 / 1.225    =  4.082

Target resistance:  4.082 Ohms

Power dissipated by resistor:  5V * 1.225A  =  6.125W

 

[phasseshifter]

so 39 ohm 10 watt resistor from the above calc`s..or 27 ohm and 15 ohm in series10 watt39 should be fine though...don’t use a variable resistor as in a potentiometer there not made for that wattage...there is other ways but i would have to explain in very much detail..this may be easier take the 5 volt power instead of the 12 volt line...

 

[ClockHound]

ClockHound, you referring to mounting something outside the case? Not sure if you saw the pic of the MD1200 but nothings fitting "inside" other than an 80mm fan.

Unfortunately to the other comment about asking other owners, no one responds to anything in the dell forums.

JR

Yes, outside...but from the above posts it appears you can't use the hammer approach to dismount the screaming fans...bummer.

Might have to keep the fans to fool the censors, er, sensors and just clip their wings, er, blades. Still doesn't alleviate the shrieking bearing noise at 4800rpm tho. So...

You could build an outside extender isolation box, that uses a double-wall construction for acoustic isolation with an L or W channel to create an indirect audio path. Then mount some large quiet fans on the 'room' side of the isolation box....will require more than foamboard and will take some time and effort. And if you go to that effort, best to just build an isolation chamber for the entire MD1200 box. With indirect intake and exhaust channels and custom audio-isolated i/o ports. Basically a desktop 'server' room. The nice thing about this concept is you'll have a fair sized area on the 'server room' walls for tagging your fav anti-Dell server-fan slogans.

Maybe you could just swap out the fans with quieter 80mm, like these Notua PWMs from the cooler guys. Won't have even half the CFM, so...there's that.

Could check their other 80mm options, probably have some that will be almost as annoying. Oh..wait...

That dusty corner keeps looking better...Good luck!

 

[jriker1]

Thank you everyone for your help on this so far. This was great information.

Few items and excuse me for verbing this instead of properly quoting people.

1. " take the 5 volt power instead of the 12 volt line". Assuming the fans would spin up on 5V, is one of the four pins 5 volt to begin with and could eliminate the 12V from the equation completely? From my understanding on this particular fan it has:

Blue (pin 4)
Yellow (pin 3)
Black (pin 2)
Red (pin 1)

Yellow would be the 12 volt. Blue the ground. Black the sense, and Red the control. Unless Dell switched things around as black is usually ground.

or are you suggesting taking 5 volts from elsewhere on the power supply I'm guessing assuming Dell has any to draw from?

2. With getting other fans, I'm looking at that option, though the 80mm fan options are limited and 38mm deep even less so, however definitely available. I'm trying to prove out first that reducing the fan speed will work at all. If I can use a resistor and slow them down and that works, then know other fans would work to. The resistor route am thinking is, if nothing else, a cheaper initial test to see what the dell management software will do before buying a bunch of fans and finding I can't use them.

3. Brings me to my third one. With "4 ohm, 2 amp" (thanks imagoon for the work on the calculation) or " 39 ohm 10 watt"(thanks phasseshifter for clarifying the wattage for me) resistors, can someone point me to an example of these on the net so I know I'm looking at the right thing? Something like this? http://www.amazon.com/Amico-Fixed-Ce.../dp/B0087YHNVU

I did see some that had heat sync's wrapped around them but not at that specs.

4. OK lied, one more. Is it odd to have a 2.1A fan that is this small? I hear everyone talking about their 0.2A fans and the like when talking resistors but no one ever mentions this much amperage.

Thanks again.

JR

 

[imagoon]

3) "39 ohm" would be a for a much lower current fan. Since those are rated at 2.1 amps, the apparent resistance in the fan is lower so a lower value resistor is required. 39 ohm will give you an apparent ~1.5 volts at the fan. It will likely not start at that value. To be fair it might not start properly on 7 apparent volts either. I don't have anything that large to put on a voltage generator.

4) no. It isn't odd. They are large high volume fans.

Extra note: The 2.1amp is likely when running at full speed. The optimum resistor value (assuming this works at all) may drift if the MD1200 calls for differing speeds which would change the current requirements.

 

[jriker1]

3) "39 ohm" would be a for a much lower current fan. Since those are rated at 2.1 amps, the apparent resistance in the fan is lower so a lower value resistor is required. 39 ohm will give you an apparent ~1.5 volts at the fan. It will likely not start at that value. To be fair it might not start properly on 7 apparent volts either. I don't have anything that large to put on a voltage generator.

4) no. It isn't odd. They are large high volume fans.

Extra note: The 2.1amp is likely when running at full speed. The optimum resistor value (assuming this works at all) may drift if the MD1200 calls for differing speeds which would change the current requirements.

Thanks, so any recommendation of a physical resistor to use? The way these commercial fan makers resistor adapters look understanding this is only a 3-pin (http://www.amazon.com/Zalman-ZM-RC56.../dp/B0015DA0YM), you have 12V, their adapters make it 7V end of story. Understand though it's apparently not that simple with a PWM connector.

I'm going to see if I have any PWM fans laying around that are small to stick in there just to see if it complains at all or accepts them, however assuming if I only have three pin fans, and assuming dell hasn't switched the pinouts per my other email about location of the black cable, it will probably still send out an alarm when the 4th pin doesn't sense anything.

Thanks.

JR

 

[imagoon]

Something like this should work:

http://www.parts-express.com/4-ohm-10w-resistor-wire-wound-5-tolerance--016-4

So I looked up a bit more about the fans and if you disconnect the PWM wire, the fan should default to full speed. You can then put the resistor inline and still send a sense signal to the controllers. This may work as you want it to. It depends if the MD1200 varies the PWM frequency and then looks for a response on the sense wire or not.

My other concern would be if the fan can start or not with that resistor inline.

Another item for thought:

You may be better off using zenor diodes. As long as the total forward voltage adds up to about a 5volt drop. Make sure to do the math to account for the heat disopation. Zenor Diode 5.1v 10watt would have the same effect as the resistor with better current response (more likely to start the fan to avoid a stall etc.)

 

[jriker1]

Darn. None of my existing fans are 4 pin other than some fans out of my Dell Precision rack servers but those are plug in fans so have proprietary connectors on them already I don't want to mess with. Guess I can't try another PWM fan without ordering one to see what happens. I'm assuming the below is a proprietary pinout from the existing Dell fans?

http://i60.tinypic.com/v4axp3.jpg

Thinking fans are usually:

- Yellow +12VDC
- Black 0 Ground
- Green Tachometer out RPM
- Blue PWM signal in

and This would maybe be from Dell:

- Red +12VDC
- Black 0 Ground
- Yellow Tachometer out RPM
- Blue PWM signal in

Also I went thru and documented a bunch of 80mm fans. Thoughts on which would be a good one for this situation? They are 25mm unless otherwise stated. Can hold up to 2 38mm fans in each power supply.

Silverstone FW81, 1200 ~ 3000 rpm, 12.0 ~ 29.5 CFM, 15.3 ~ 30 dBA
Arctic F8 PWM, 850 ~ 2000 rpm, 31CFM@2000, 12dBA@2000
CoolMaster Blade Master 80, 800 - 3000 rpm, 10.9 - 40.8 CFM, 13.0 - 28 dBA
Nexus 80mm PWM Silent Case Fan, 1000 - 2800 rpm, - 38.0 CFM, 16.2 -
BlackNoise M8-P, 500 - 2000 rpm, - 31.7 CFM, 1.0 - 17.0 dBA
BlackNoise, 500 - 2000 rpm, - 31.7 CFM, - 18.0 dBA
Noctua NF-A8 PWM , 450 - 2200 RPM, - 32.6 CFM, - 17.7 dBA
Mechatronics F8025X-H(25mm), - 4200 RPM, - 53.0 CFM, - 39.0 dBA
Mechatronics G8032E(32mm), - 4500 RPM, - 52.0 CFM, - 46.0 dBA
Mechatronics MC8038M(38mm), - 4200 RPM, - 57.5 CFM, - 44.5 dBA
Mechatronics MC8038H(38mm), - 5000 RPM, - 69.9 CFM, - 48.2 dBA
Mechatronics MQ8038L(38mm), - 4500 RPM, - 61.5 CFM, - 49.0 dBA
CoolJag R128025BU, - 3400 RPM, - 46.2 CFM, - 35.3 dBA
EverCool EC 8025 PWM, 1000 - 3000 RPM, , 10.0 - 33.0 dBA
EverCool EC 8038 PWM(38mm), 2000 - 6500 RPM, , 22.0 - 56.2 dBA

Note this forum kills the tab formatting so hopefully it can be read. Put in commas to see if it would help a bit. Some have both low and high CFM and DBA values and some don't so don't necessarily line up without the tabs anyway. I'm ok with some room noise like take what would be ok in a library and add 10 or 15 DB, but no jet engines. Keep in mind these are two stacked so not sure how that will effect the sound as well. Thinking of if I get 25 or 32mm fans having a slight gap in between them and maybe having a shroud in between them if anyone thinks that's a good idea.

EDIT: Thinking the Arctic F8 (12DB at 2000 rpm??!?!?) or the Noctua. Though the CoolJag at 46.2 CFM and 35.3dBA may be a good trade off of sound and extra CFM.

JR

 

[C1]

In all my computers so far there has been an option in the BIOS (in the power management section) to disable the fan speed sensing. (Ive had to disable fan speed sensing in some situations or else I couldnt boot and there wasnt anything really wrong with the fan.)

Ive actually done what you are trying to do, but dont remember the resistor value used. (I have lots of resistors laying around from electronics home courses taken that I used to get an approximation of the speed desired. I then fine tune by getting some inexpensive resistors from a place like "Gateway Electronics" or "Frys" spaced 50 ohms apart in value. I think a one watt[er] should do for capacity.)

You might want to just go ahead & implement a potentiometer to allow varying the speed. Probably not really cost any more.

http://www.sevenforums.com/tutorials/87295-fan-speed-controller-build-your-own.html

 

[imagoon]

In all my computers so far there has been an option in the BIOS (in the power management section) to disable the fan speed sensing. (Ive had to disable fan speed sensing in some situations or else I couldnt boot and there wasnt anything really wrong with the fan.)

Ive actually done what you are trying to do, but dont remember the resistor value used. (I have lots of resistors laying around from electronics home courses taken that I used to get an approximation of the speed desired. I then fine tune by getting some inexpensive resistors from a place like "Gateway Electronics" or "Frys" spaced 50 ohms apart in value. I think a one watt[er] should do for capacity.)

You might want to just go ahead & implement a potentiometer to allow varying the speed. Probably not really cost any more.

http://www.sevenforums.com/tutorials/87295-fan-speed-controller-build-your-own.html

How we know someone didn't read the thread.
1) It's not a computer
2) 2.1 amp fans require a much larger resistor than a 1W
3) 50ohms would be much to large for these fans
4) Most pots can't do several amps of current.

 

[aigomorla]

Appending to above:

5. its a server case which is PWM'd must be controlled via BMC or some kind of Thermal probe on the board itself inside the case

6. its ramping because the temps are getting too high, and by you reducing the fan's its a quick way to spell disaster inside a server.


Overall i wouldnt recommend it.
Servers are loud for a reason, and they are quiet then they dont need to be loud.


Lastly, a 2.1amp fan is most likely a enterprise class fan, im guessing from either panasonic or sanyo denki or delta.
Are you running actual server parts inside that case? For example do you have ECC Ram, and a heat sink on the cpu which doesnt have a fan?
Because the design of a rack like that is, it uses a wind tunnel for induct air though the front and pull out via rear.
By gimping the fan, reducing it, you will most likely hamper yourself in longivity of said hardware, and on a hot day can lead to possible hardware failure due to it not being able to ramp up to 100% to keep everything in check.

 

[ClockHound]

EDIT: Thinking the Arctic F8 (12DB at 2000 rpm??!?!?) or the Noctua. Though the CoolJag at 46.2 CFM and 35.3dBA may be a good trade off of sound and extra CFM.

JR

First, have a few of the Arctic F8 - they ain't 12dB at 2K - that or my less than exceptional hearing is super sensitive to broadband fan noise. Would peg the F8 closer to 25-28dB at 2K - can pull out the SPL and measure if you want. But they are cheap.

Assume they measure their fans sound pressure in an anechoic chamber at 1M. Which means you only need to mount your box in an anechoic chamber.

Imagine the Cooljags are even louder. As are the other ones in your list. The hideous noise from the EverCool EC 8038 running at 6500rpm will be so much louder than 56dB and annoying when bounced off your office walls.

Since you have 38+38 = 76mm to fill and 3X25mm = 75mm it does make one wonder about a third fan to compensate for the lower individual CFM. The 3rd wheel, er, fan could run off a PWM splitter. With 3 F8s, it's close to the total CFM of the 2 little screamers - assuming perfect summing which is unlikely, but they're cheap. And it's a very cheap experiment, other than time, effort and possible disappointment.

I'm still voting for the server-room in-a-box steamer trunk concept. Or the quiet dusty corner.

 

[Micrornd]

These units are actually quieter than the older 3.5" SCSI units.

These fans are for cooling the power supply AND the enclosure, loss of more than one fan (per PS and some have 4 fans) will shut down the enclosure.
The enclosure itself has temp sensors.
The power supply has temp sensors.
These are all monitored by the enclosure management module (EMM).
Any overtemp and the EMM will shut down the enclosure.

The fans are needed to cool the drives and PS's and are set up as redundant units, so if one fan is missing or broken, or if the 2 fans will not keep the enclosure within the designed temp range at low rpm, the EMM will speed up the fans to full rpm.
If running the fans at high speed still does not keep the enclosure within the designated temp range of the EMM's firmware, it will shut down the enclosure to prevent damage to the PS's and drives.

Altering the airflow or rpm's of the fans is not really a viable option.
If you are going to mess with something that is engineered to work in a server room, at least take the time to read/download the technical guide for the unit to understand how it works, that's why Dell (and other OEMs) go to the trouble of writing them up.

Enough lecturing
Now for a solution that will work.

A cube enclosure (as you indicate you have) is just too small to effectively quiet servers and HDD enclosures AND allow adequate cooling.

Lacking a server room or closet, a freestanding, full size, fully enclosed rack (46-48u) with a bottom or low air intake and top exhaust is your best option.
Sound absorbing material can be added to them, if needed, and with the top air exhaust above the level of all but NBA player ear heights, the sound level is quite controllable.

You will still have to deal with the heat dumped into whatever room it is in, so plan for that.

You mention you had Dell Precision Rack servers also, so they could go into this free standing enclosure also.

 

[jriker1]

Appending to above:

5. its a server case which is PWM'd must be controlled via BMC or some kind of Thermal probe on the board itself inside the case

6. its ramping because the temps are getting too high, and by you reducing the fan's its a quick way to spell disaster inside a server.


Overall i wouldnt recommend it.
Servers are loud for a reason, and they are quiet then they dont need to be loud.


Lastly, a 2.1amp fan is most likely a enterprise class fan, im guessing from either panasonic or sanyo denki or delta.
Are you running actual server parts inside that case? For example do you have ECC Ram, and a heat sink on the cpu which doesnt have a fan?
Because the design of a rack like that is, it uses a wind tunnel for induct air though the front and pull out via rear.
By gimping the fan, reducing it, you will most likely hamper yourself in longivity of said hardware, and on a hot day can lead to possible hardware failure due to it not being able to ramp up to 100% to keep everything in check.

It's not a computer case it's a hard drive array case so no memory in it. The fan is an AVC fan. I am only using a few hard drives in the case so not concerned with it overheating. As for being quiet when cool, no it's slowest speed it runs at with nothing in it is heard from a long distance.

JR

 

[jriker1]

First, have a few of the Arctic F8 - they ain't 12dB at 2K - that or my less than exceptional hearing is super sensitive to broadband fan noise. Would peg the F8 closer to 25-28dB at 2K - can pull out the SPL and measure if you want. But they are cheap.

Assume they measure their fans sound pressure in an anechoic chamber at 1M. Which means you only need to mount your box in an anechoic chamber.

Imagine the Cooljags are even louder. As are the other ones in your list. The hideous noise from the EverCool EC 8038 running at 6500rpm will be so much louder than 56dB and annoying when bounced off your office walls.

Since you have 38+38 = 76mm to fill and 3X25mm = 75mm it does make one wonder about a third fan to compensate for the lower individual CFM. The 3rd wheel, er, fan could run off a PWM splitter. With 3 F8s, it's close to the total CFM of the 2 little screamers - assuming perfect summing which is unlikely, but they're cheap. And it's a very cheap experiment, other than time, effort and possible disappointment.

I'm still voting for the server-room in-a-box steamer trunk concept. Or the quiet dusty corner.

Thanks. I'm probably going to try some BlackNoise fans. They are willing to send me some to test with so hopefully that will work out.

The three fan concept is an interesting one. May consider that but personally with only a couple hard drives in the system, think two fans in each enclosure is going to be good for basic cooling in a standard climate controlled building.

Originally per the other comment, I was talking full rack. The systems are actually in an APC rack, however that rack has a honeycomb pattern front and back door completely see-thru so would have to close it off and install some kind of fan system. Then as mentioned, I started scratching my head if having the top of the rack just vent out hot air with a bunch of fans into the room would work or not as there is no good way to duct it outside.

JR

 

[piasabird]

They make things like tri-speed fans also.