I'm a fan of your fan

it's warm so I ordered some pc-case fans to stack them

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A lot of potential hacks here. First prepare the PWM setup with L293D or ULM2803A, then decide how to generate the pwm. 555? attiny85? ESP8266? Make it spin?

Specifications of the fans

Height120 mm
Width120 mm
Depth25 mm
Voltage range7 - 12 V
Fan speed1,200 rpm
Rated Power1.2 W
Airflow107.9 m³/h
Noise16,0 dBA
Connector3-Pin Molex
Manufacturer numberCT120BW

Cooltek - Silent Fan 120

123dx - 73.66 kB - 08/14/2016 at 17:29


Standard Tesselated Geometry - 364.82 kB - 08/14/2016 at 17:29


Standard Tesselated Geometry - 292.07 kB - 08/14/2016 at 17:28


Standard Tesselated Geometry - 258.33 kB - 08/14/2016 at 17:28


  • 4 × Cooltek - Silent Fan 120 computer case fan
  • 14 × M4 35mm screws
  • 14 × M4 nuts

  • mqtt for the win

    davedarko08/06/2016 at 22:44 2 comments

    I recently played around with mqtt again and used one of my #Ignore this ESP8266 board -s to internet-of-thingify this fan construct. Searching for reasons why the uln2004 wouldn't work with 3.3V I tried pnps and npns until I found that I haven't declared the pins I was using as an output. I might have also connected the 12V with the 3.3V line while experimenting :D but in the end it turned out that I had also connected the fans backwards. Muah. But now it runs and I can control it via MQTT.fx - winning.

    The ESP arduino soft PWM runs at 1kHz and I can hear it, that is kind of annoying.

    Don't forget to set different clientIDs ;)

  • also works as a fume fan

    davedarko08/28/2015 at 08:52 0 comments

    I'm soldering one of the last batches of RFid readers for work, before we skip to a "professionally produced" version. To be honest, I'm a bit relieved that we are replacing the arduino + MC522 modules with something created by guys that actually know stuff about RFid. But on the other hand I can be a bit proud that these readers are working for 2 seasons now and with pretty decent results, knowing that they worked close to water (sometimes even in the water...) and in the sunlight and rain. In a way we are a hardware start up as well, even if we actually don't want to. I will soon release the design files etc. and tell some stories around it - actually looking forward to that.

  • a handle and a base mount

    davedarko08/12/2015 at 19:16 0 comments

    These parts are printing right now - I'll have to find a base worthy thing yet, where I would screw that center piece on to and the controller board as well.

  • first prototype

    davedarko08/10/2015 at 14:57 0 comments

    3D printed parts are ready and I screwed in M3 16mm screws, that are a size too small and about 19mm too short - so I ordered some M4 35mm screws with nuts on eBay and probably payed too much. The fans seem to be not the most powerful fans, what makes sense since they cost about 3 Euros each. I might use some incense sticks and a black background to make a photo project out of it. The humming of 4 fans is noticeable, but hopefully some PWM will bring it down.

  • Fans are here but I'm almost in a plane

    davedarko08/05/2015 at 11:18 0 comments

    shorter text than title.

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Joseph Psaila wrote 08/13/2016 at 20:46 point

I'm curious what software you use for designing 3D parts?

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davedarko wrote 08/13/2016 at 21:33 point

123D Design for macs

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kennycoffin wrote 08/10/2016 at 08:54 point


I want to connect the fans in sequence, stacked on top of one another, with the face plates all facing each other vertically. I want to draw an updraft through the fan blades in a "chimney". Then I want the fan blades to feed the energy into a battery.  Can you build this model and test it for me? My technical hands on is all thumbs. Theory: the output could be high if sufficient temperature differential between base and of top of chimney is sufficiently different. Conjecture: unknown differential, unknown height. Unknown fan types, unknown harness configuration. Consensus: a 12 year old girl in Connecticut claims 1 megawatt of output. Theory: possible. Requires further investigation.

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davedarko wrote 08/10/2016 at 09:11 point

Well, my fans aren't that receptive to turn when blown at, so I'm not sure about that - and I have no chimney(model) ;) What about temperature, won't the fans melt at some point? 

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kennycoffin wrote 08/10/2016 at 19:48 point

Understood! Query: fan stability? Unknown. Melting point? Unknown. Theory: the fan shouldn't melt at high rpms. It is already rotating at high rpms. However, can they operate as mini turbines as claimed? Unknown. Test: stand fans facing each other in a "wind tunnel", push air through and see if they turn. If they don't turn then this is a myth and debunked. If they turn then measurement of minimum wind pushing through would state minimum threshold. Theory: minimal air push should cause fan rotation. Secondary resource: Gerald Bull, University of Toronto, masters dissertation, how to build a wind tunnel 1951.  Key resource: theory of chimney construction

 Such online resources are plentiful. Conclusion: an updraft should be about enough to move any fan system of any size, limits on dimensions and height of chimney effect. Theory: energy generation from computer fans should be feasible if the fans are opened and modified for output instead of input. Conjecture: unknown outweighs known to this one.

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K.C. Lee wrote 08/10/2016 at 23:11 point

Chimney effect relies on external thermal energy (aka heat).

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K.C. Lee wrote 08/10/2016 at 22:39 point

Utterly free energy BS.  The fans use brushless DC motors, so you have to mod them before you can even use them as generators.  You actually trust a 12 years old?

BTW what is the size of battery that can handle 1MW and what is the diameter of wire required for the current?

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kennycoffin wrote 08/11/2016 at 06:19 point

Seeing as how there is no such thing as "free energy", only energy transference, heat is gathered in a greenhouse system, or, from a climate controlled house. That issue aside, this one saw a MIT model for application done on small scale, and this one thinks its worth testing on a model scale to see if computer fans can in fact work as mini turbines, otherwise, its neat! This one has a fan inside a natural gas fireplace that starts spinning when the air pressure changes. Fact: a functioning chimney requires an updraft effect to work to draw the smoke from the chimney in order to avoid blow back. The fact that you jumped into the accusatory "free energy" accusation shows your complete lack of knowledge in chimneys. In principle, the chimney updraft effect was designed by Leonardo DaVinci in conjunction with a spit turning a pig apparatus. The 1900 to 1926 theories required higher yields, which yet again falls into fallacy because smaller culmative yields is always cheaper. The 1920s papers show green house with sunlight deflectors, but this one argues that for a functional test model, smaller should show significant proportional change in output greater than 5 watts. Anything greater than plus or minus 5 watts shows differential, therefore it would stand to reason that every physics book is right and hot air rises. And thousands of years in chimney design would be right as well. This isn't a test to find "free energy", the purpose is to see if computer fans can be utilized in an unconventional way to test against a theory that is hundreds of years old. This one sees claims that it can work. Does it? As for cost, she built the model on her front lawn. She also won an award for measuring caffeine in sewage and waste water. She's famous in Connecticut. But her model captured this ones interest. If one wishes to replicate such design, one should know brushless vs. Not brushless. But this revelation is rewarding, in itself you defined the difference. Thus, we can move forward an assume she used a brushlesd motor. Now how did she wire it to work in reverse? If this is possible, then part two of the puzzle is assembled. The third part would be how to measure said output. Would a multi meter be practical? I have no idea. How does one measure electrical output? This is a great puzzle!

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K.C. Lee wrote 08/11/2016 at 11:28 point

P = V * I.  So I = 1MW/12V = 83,333A of current for the average 12V fan.

Largest common wire is AWG 0000 has cross sectional area of 107.22m^2 and it is only rated for 325A.  Let say you make your own cable, you'll need a wire of 27492mm^2 which is at least 187mm (7.36in) in diameter.  

The average 2L pop bottle as 4in diameter.  Copper filling up a coke bottle will weight 8.96g/cm3 * 2l * 1kg/l = 17.9kg (39.5lb)  (The 7.36in diameter wire would be around 3.63 times that. )

Copper price is $2.17 per lb on the commodity market.

I'll let someone else figure out how much that weight and how much the amount of copper will cost at current prices. Let's say a lot.

Your average PC fan which would at most give you around 5-10W if you gone through modding them as generators and spinning them at their rated speed.  So let's say you want to build that out a bunch of car alternators.

>Not long ago, an 80 amp alternator was considered a high output unit. Most late model alternators produce 120 to 155 amps or more.

So 14V*155A = 2170W each.  You'll need around 461 alternators.  I am guessing that many car batteries too.

Average multimeter can hand 20A of current and are safety rated for 600V and can probably measure 1500V.  So at most it can measure is 30,000W if your generator use 1500V output.

Average small apartment has 200A service. So a wattmeter for that can handle 200A * 120V = 24000W

That should give someone an idea the dimensions and scale for things.  

There is something called square-cube law for scaling things for mechanically.

To have fans and a tower that can handle that power rating, the material have to withstand the forces as well as its own weights.  Things can't be scaled easily.

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K.C. Lee wrote 08/10/2016 at 23:32 point

BTW this is what 1MW wind turbine looks like:’s-n1000-1-mw-turbine/

Tower height, weight 60m, or 70 m at 63 tons
>For instance, company figures from 2009 list equipment prices of $1.2 million/MW
>Nordic reports that installations are coming in at less than $2 million per turbine including balance of plant.

I guess the average 12 years old have a couple of million dollars and some cranes to build a 1MW generator in her barbie dream house?

What did she as a test load for the generator and how did she measure power output?

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kennycoffin wrote 08/11/2016 at 06:26 point

There was insufficient data from the news article to extrapolate how she calculated said measurement. The companies building the big systems are flawed in their thinking. Just as you and this one knows, KISS is how you build. When you work for government, you practice spend everything you get and buy that which you don't need. But on a farm, you buy what you need and build the rest.

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K.C. Lee wrote 08/11/2016 at 10:49 point

Those wind turbine tell you the basic size of a fan that is designed for the power by a team of engineers from companies.  That's what the current technology can offer.

Basic knowledge say that the size, material, construction, dimension required for 1MW scale is not attainable for a 12 years old.

Believing something does not make it true.  It fails the smell test in this case.
 This is a failure of your education system to not teach you critical and scientific thinking.

BTW if you want to talk about conspiracy.  The media is the last thing you want to trust from a military–industrial complex.   :P

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Stefan-Xp wrote 08/16/2015 at 21:19 point

Nice Project :) Looks neat!

Once I created a Fan of 2 / 4 Fans at work with the use of Fanguards or carton :-D

Didn't look as nice but works okay ;)

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davedarko wrote 08/18/2015 at 04:18 point

anything that moves the air is better than nothing :) 

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esot.eric wrote 08/04/2015 at 01:19 point

hah, I've an entire box full of old PC fans... why hadn't I thought of that for various needs?

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davedarko wrote 08/04/2015 at 08:15 point

It's also supposed to suck away solder fumes :) there are many ways to use them, I guess.

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frankstripod wrote 08/03/2015 at 22:02 point

I have been looking for something like this. I look forward to see where you get the fans from.

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davedarko wrote 08/03/2015 at 22:08 point

I've bought 4 120x12- fans on - a german online store for 3 Euros a piece. I could have recycled some, but they were that cheap and I wanted them to look a like.. 

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davedarko wrote 08/03/2015 at 22:26 point

oh dear, I just remembered the quadcopter made from pc fans, googled it and found out it was an april fools joke made by ... :D

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