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Author Topic: bypass fan detection on antminer S9  (Read 977 times)
3ricj
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April 19, 2017, 03:03:02 AM
 #1

I have an external cooling solution (AC squirrel cage fans) which have a higher CFM, designed for higher pressure but also run at a lower RPM.  They are actually much quieter than the factory fans on the S9.

Currently, the default firmware on the S9 is blocking me from being able to test these alternate cooling setups -- if it doesn' detect the fan tach signal it just stops mining.  While I do understand this is important for most users, I need to override this interlock.  

Anybody know how?

If I come up with a clever cooling solution which makes less noise I promise to share details.  Smiley

To be clear, I'm going to profile the thermal performance at various underclocked speeds with the default fans and then retest again with my new cooling system slowly increasing the mhz.

Thanks,
-3ric
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sidehack
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April 19, 2017, 03:19:27 AM
 #2

http://www.electricalbasicprojects.com/simple-555-timer-projects-fixed-and-variable-pulse-waveform-generator/

I'd try something like this, except wired up for about 135Hz. Shouldn't be difficult to find a 555 that'll run off 12V. Tie the output to the tach line (usually the yellow wire) on the fan jack. If I'm remembering right, fan spec says two pulses per rotation so 135Hz means a shade over 4000RPM. 150Hz should detect as 4500RPM. The controller will think it sees a fan present and spinning fast and loud.

Note that I haven't tested this in any way, it's just an idea that I think should work based on what I know about fans.

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NotFuzzyWarm
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April 19, 2017, 03:35:54 AM
 #3

Or mount a proximity sensor or photo-cell near the blower wheel to pick up the blades as they go by. Great airflow and still have fault detection Wink

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3ricj
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April 19, 2017, 05:14:59 AM
 #4

Yes, there are several hardware hacks I could do to fake a fan pulse, but for quick testing there must be a way to disable this in software.  It's a shame these devices are so closed source. 
LanguidLemer
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April 20, 2017, 02:00:37 AM
 #5

3ricj, thank you for starting this discussion. Same problem I am having.

You probably can simply dismount the fans and leave them connected to the controller after having installed the cage fans to test. The controller will be fooled into thinking all is well.

Sidehack, thanks for the 555 idea and basic parms. Hadn't got that far yet, so saves me some time.

I am looking forward to reducing the acoustic foot print of my 4 s9 miners since said foot prints are all over my head right now (ugh).
3ricj
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April 20, 2017, 07:11:14 AM
 #6

My first attempt will be to just install little shitty fans which don't make any noise to keep the controller happy.

https://www.amazon.com/gp/product/B001B2E9EY/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

I'll report back how well they work this weekend.
LanguidLemer
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April 20, 2017, 09:29:04 PM
 #7

I've done a bit of searching and can't find a small, quiet squirrel cage fan that has a lower power demand. (220 CFM)

Are you matching up a cage with a small motor you already have??

I'd like to try this to see how the temps inside the miner do.
NotFuzzyWarm
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April 20, 2017, 10:45:57 PM
 #8

Changing power demand is not the point. The OP wants to reduce noise and a squirrel cage blower can be extremely quiet while delivering high airflow against sizeable back pressure. Of course most run directly off the AC power line.

Think furnace blowers. One with a 1/4hp motor works out to around 300w of power and will probably push well over 1-2k CFM against the back pressure 4-6 miners would have. Since each fan on a s9 pulls a bit over 24w, that's 50w of fan power for the 1 miner. Makes using around 300w to quietly cool several miners look rather good if ya want to make shelves & ducting to do it.

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LanguidLemer
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April 20, 2017, 11:19:27 PM
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Found this unit at $90, which would need some shroud work: http://www.northerntool.com/shop/tools/product_40448_40448

120 VAC 0.51 Amps rated as 40 watts, moves 275 CFM, probably pretty quiet, too, since it is made to install in metal ducting and that would not tolerate much noise at all.
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April 20, 2017, 11:50:24 PM
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Found this unit at $90, which would need some shroud work: http://www.northerntool.com/shop/tools/product_40448_40448

120 VAC 0.51 Amps rated as 40 watts, moves 275 CFM, probably pretty quiet, too, since it is made to install in metal ducting and that would not tolerate much noise at all.
Key point you missed:
Quote
Dependable 40 Watt Fasco motor moves 275 CFM free air, draws .51 Amps. UL listed.
My emphasis on 'free air'.
Why time and again must it be bought up that the densely packed configuration of miners from s7 on up ALL produce substantial resistance to airflow? You know - high back pressure aka Static Pressure? Having to push air against that back pressure is why the fans used in Ants and yes even the Avalons are so loud. It is just the nature of the beast.

Free-air flow ratings of any fan/blower are useless specs for cooling miners and relying on them will always result in very poor real-load performance. Fans/blowers useful to miner cooling will specifically mention using against high back pressure and give a Static Pressure rating usually in Inches of Water or a metric version of that.

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LanguidLemer
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April 21, 2017, 12:06:27 AM
 #11

I am but a lowly, languid lemer. Not sure what your assumptions are in your responses but you seem to think I need educating. I'd appreciate a civil discussion rather than being talked down at. At least that is how you are coming across to me.

NotFuzzyWarm
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April 21, 2017, 12:11:56 AM
 #12

Ok, short and sweet. If someone is going to be tampering with an expensive piece of equipment then they need to have at least a basic understanding of what went into the design of said products. If not - don't mess with the innards.

Learn what needs to be learned then dig in. Just picking up bits and pieces from forums is not learning. Not a bad start, just you better verify technical details and concepts presented. Forum answers are mostly A=B without the how's and why's. Now you know why typical air movers won't work. Bet you will remember it too.

You want a Forum geared to instruction, go to Instructables.com
Seriously, I do highly recommend it. Great site.

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LanguidLemer
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April 21, 2017, 12:38:10 AM
 #13

Squirrel Cage fan blade design as well as volute contour play large roles in efficiency and noise produced by the fan. There are two types of blade orientation: forward facing and reverse facing, each with specific characteristics that relate to air flow, back pressure resistance, etc. Apparently reverse facing blade orientation is used to maximize air volume pass through.

After doing some research it appears that shaded pole induction motors (which are usually used for small, economy blowers) running under light load are terribly inefficient run about 20-25% conversion of power to force. Higher loads result in greater efficiencies, but AC induction motors have lowest range of power use to force produced.

The OP was concerned with reducing noise. Me, too. I am also concerned about power costs.

Not looking for a tutorial, thx.
LanguidLemer
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April 21, 2017, 12:44:33 AM
 #14

OK, have fun with whatever projects you are working on. Sorry for the thread drift. Will find other places to hang out. Looking forward to seeing well engineered and elegant solutions to design problems. Till then ...
NotFuzzyWarm
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April 21, 2017, 12:47:46 AM
 #15

Good answer. So how did you miss the free-air part in the fan description? Rather crucial and Lord knows how many folks have tried using 'quieter' fans and complain/wonder here why they don't work. Driving the point home again gets old...

The R4 is a perfect of using the reverse blades to best effect: The R4 layout has a lot lower airflow resistance so quiet/high flow is a win/win with it. Now if only if Bitmain can get the Vcore power system to behave on the boards, folks would be happy(er)...

-Joshua Zipkin aka Joshua Alexander leaked AMT A1 miner skype chats http://bit.ly/1Qjt6lj
-For bitcoin to succeed the community must police itself.
-Support Sidehacks miner development. Donations to:   1BURGERAXHH6Yi6LRybRJK7ybEm5m5HwTr
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