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Author Topic: Steampunk multi-fan  (Read 1536 times)
flashmasterbrass
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« on: July 26, 2010, 06:42:18 pm »

So, as I was perusing through my boxes full of treasure yesterday, I happened upon a stash of old PC case fans that I have collected over the years. I stared at them blankly for a while, knowing full well that a plan was formulating in my head. That's when it hit me: I was going to wire all of them together and create a steampunk multi-fan!

As far as layout and aesthetics go, I've got it all worked out. However, there is one area that concerns me: the actual electrical work. As it turns out, wiring is the one thing I have never really bothered to study, and as such I am not the best at it. I was hoping that a few of you, who are far more experienced than I, could give me some pointers. Namely, I want some advice on splicing wires and which type of power source I should use. Presently, I count six DC12V fans, for a total of DC72V. Does this mean my power source should supply exactly DC12V, or can it overshoot just a little bit? Also, it should be noted that I am going for outlet power here. No battery power, as it would be extremely tedious to replace the batteries every time they ran out of juice, which would be fairly often.

I'll leave it at that for now. All comments/suggestions/scoldings are welcome, so please put in your two cents! I could use all the advice in the world about this subject. Until later, fare thee well!
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JingleJoe
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« Reply #1 on: July 27, 2010, 01:50:59 pm »

Namely, I want some advice on splicing wires and which type of power source I should use. Presently, I count six DC12V fans, for a total of DC72V.
No that's not quite right, wire each to the power supply separately then you will only need one 12 volt power supply. when you "splice" a wire or divide it into two or three or more, the same voltage goes along each wire, but the amperage divides between them.
Does this mean my power source should supply exactly DC12V, or can it overshoot just a little bit?
Yes that should be alright, better to undershoot though you don't want to burn them out.
Also, it should be noted that I am going for outlet power here. No battery power, as it would be extremely tedious to replace the batteries every time they ran out of juice, which would be fairly often.
Correct, so you will need some sort of transformer/adapter to get from your AC mains voltage to 12 volts DC.

There is an important factor you have overlooked, it seems from lack of knowledge; The amperage! How many mA (milliamps) do these fans require? You need to make sure your power supply can provide enough amps for all of them.
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arcwelder
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« Reply #2 on: July 27, 2010, 05:24:52 pm »

In what way is this steampunk?

Why in the world would you want to do this?

Do you realize that the result will be quite noisy?
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jringling
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« Reply #3 on: July 27, 2010, 05:29:11 pm »

In what way is this steampunk?

Why in the world would you want to do this?

Do you realize that the result will be quite noisy?

1. He hasn't told us yet:
As far as layout and aesthetics go, I've got it all worked out. However...

2. Why not?

3. So it will be a combination fan/ white noise generator! Perfect for the beside to cover the sound of the headboard beating on the wall from the apartment next door!

 Grin

 Cheesy

 Grin
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arcwelder
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« Reply #4 on: July 27, 2010, 05:33:40 pm »

Why not: it doesn't do anything well besides draw current and make noise.

Not white noise either. That would be somewhat useful. This will all be concentrated around the harmonic frequency of the fans with added fun interference effects due to the array format.

I've seen people do this before; it's really not as good of an idea as it might naively seem to be.

On the other hand, if it ends you up learning Ohm's law, that's not a terrible result.
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jringling
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« Reply #5 on: July 27, 2010, 05:40:45 pm »

Why not: it doesn't do anything well besides draw current and make noise.
No... he's not building a television...

 Grin


I will admit to have worked on much sillier things than a fan bank...

Not white noise either. That would be somewhat useful. This will all be concentrated around the harmonic frequency of the fans with added fun interference effects due to the array format.

This statement makes me want to build one...

On the other hand, if it ends you up learning Ohm's law, that's not a terrible result.

Now you're gettin' it!

I was thinkin' you'd be the one to advise on which type of wall box to use for driving the fans... and maybe even suggesting some sort of variable resistor to control speeds...
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arcwelder
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« Reply #6 on: July 27, 2010, 05:59:21 pm »

Okay, 101 time then.

Some fans respond very well to undervolting, some don't (i.e. supplying less than specified voltage in order to make the fans run more slowly). Fortunately, finding out which you have by trial and error tends not to harm the fans.

You *do* need to hook these up in parallel. You can find a discussion of serial vs. parallel circuits here. You may or may not need to back up and read some earlier pages in order to understand what's going on, but this is a great site for learning about the fundamentals of electronics.

This *should* involve some soldering. There are ways around that, but not great ones. You can get started soldering with about $15 in parts, although it will involve putting up with a crappy iron. Lead-based solder is fine, and strongly recommended for hobbyist projects which are not using huge quantities. It is *much* easier to work with than the lead-free alternatives. The Tangent Tutorials are a great resource here.

You should also pick up at least a crappy $10 multimeter. It will let you find out what the current draw per fan is (note that this may vary with supply voltage!) and it will let you perform simple continuity testing (which is going to come up a lot, especially when you're new to soldering).

For a power source, fans are not very particular so you can probably just use a standard AC/DC wall wart. You do NOT want to cut into this though. Pick up a connector which fits the plug, use that. Even for this, a switching adapter will probably be easier to deal with than an unregulated adapter; it will actually give you something around the rated voltage and it will react more predictably to load. You could also just use an old computer power supply, but this would result in a lot of wasted energy and it would be pretty bulky. What you want is something like this provided it meets your amperage requirements (SparkFun also carries most anything else you might need, plus some decent if somewhat pricey practice kits). Note that if it *doesn't* meet your amperage requirements, you are going to have some trouble getting a low-cost supply (600mA is moderately high for a cheap wall wart, the >1A units get more pricey).
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jringling
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« Reply #7 on: July 27, 2010, 06:04:08 pm »

see... that's being constructive! we needs a thumbs up smiley...
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flashmasterbrass
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« Reply #8 on: July 27, 2010, 09:18:43 pm »

Wow. The responses thus far have been far better than I could have hoped for, and I thank you all very much.

First, let me explain my vision for the aesthetics, at least as well as I can do so with words. I happen to have a variety of metal tubing and pipes lying around, and I plan on using these for the main body/arms of the fan, with some sort of metal disk for the base, which I will either find or make myself. As far as layout goes, I either plan on spiraling the fans upward, around the pipe, or placing them back to back, with two sets facing east/west, and the other set facing north/south. Of course, they won't actually be touching back to back, as I plan on using smaller pipes to branch them out from the main one. Not exactly sure any of that cleared anything up, but it was worth a shot.

Second, yes, I lack almost any knowledge in the field of electricity/currents, but a person has to start somewhere, and I figure a small project like this is the best place to start, since I already have most of the supplies lying around. I had actually been thinking about using a computer power supply, because I have four or five lying around the house.

Finally, I know this project seems pointless, but let me just point out that I am not actually naive enough to think this fan is going to provide any useful service. I plan on having it for aesthetic purposes, and when somebody comes over, I can plug it in for a few "Oohs" and "Ahhs." Nothing more, nothing less. Plus, half the fun of the project is the labor and frustration of putting it all together, is it not? Anyway, I thank you all again for your kindred responses, and I'll be checking back to update everybody, or to report any snags I've run into. Now, I'm off to read the material you all suggested!
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arcwelder
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« Reply #9 on: July 28, 2010, 02:09:32 am »

If you just want it to look at, then you should definitely undervolt the tar out of the fans. It will be much quieter.
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flashmasterbrass
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« Reply #10 on: July 28, 2010, 02:33:04 am »

Well, I checked out the individual amperage on my fans, and they vary from 0.14A to 0.27A, with the mean being 0.15A and the total 1.08A. After that, I checked out my power supply unit, and it has an output of 12V at 1.5A. Without having read the links you provided, are these good numbers? The amps seem a little high, but I'm not sure what significance that might hold. Anyway, I'll get to reading those links here in a few hours during my office time at work, but until then, I'll be checking back for more updates. Thanks again for your patience and wisdom!
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flashmasterbrass
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« Reply #11 on: July 28, 2010, 08:54:25 am »

I have an update! After having read the suggested articles, I think I have a much better understanding of these things work. Apparently, I had voltage and amperage mixed up in my head, and now that I have very, very basic understanding of resistor's and Ohm's Law, I think I am ready to tackle this project. However, I have decided to cut back the number of involved fans to four, and I will definitely be scaling back to a smaller voltage to reduce noise. I will update you as the project progresses, and hopefully I'll have some pictures up soon. I cannot begin to thank you for the knowledge you have given me, however basic it may be. I assure you that I'll put it to good use.
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arcwelder
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« Reply #12 on: July 28, 2010, 09:38:06 am »

Voltage is potential difference, current is rate of electron flow. Analogically, voltage is how high I drop a ball from while current is the rate at which I drop balls.

Resistance is exactly what it sounds like - the material has a property such that it resists current flow. A resistor is simply a calibrated length of resisting material which gives a specific total resistance value. If resistance was zero, all the electrons would try to flow at once at an infinite rate, creating infinite current (and frying your circuit). If resistance was infinite (or at least very large), no current would flow despite the voltage difference (this is an "open circuit" condition).

If you actually grok what those three things mean, then Ohm's Law is extremely natural. V/R = I? Why, that just says that more voltage means more current and more resistance means less current.

Also, by ohmic components we mean that Ohm's Law "works" for the circuit elements involved. It's easy to find non-ohmic components - for example, a lamp might display a different effective resistance as it heats up. Your fans may or may not be ohmic components, but if we ignore their transient response (what happens when they're turned on) then their steady state response (what they do once they're running) should be more or less ohmic.

Ohm's Law and Kirchoff's Laws are very nearly everything you need to do basic circuit analysis, so you should probably read up on Kirchoff's Laws as well when you get a chance. For now, the short version is that when you're adding the fans in parallel you're going to want to add the current requirements. BUT, it would be a Very Good Idea to try to pick fans which have the same current requirements, or at least very close (0.14A and 0.15A etc). The reason for this is that the fans with lower current requirements will probably do less to impede the current. What this means in practical terms is that the lower current fans will get EXTRA current, while the higher current fans will get LESS current. This can be Very Not Good, depending, but if you pick fans that are close together to begin with then you should be able to ignore this effect.
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sidecar_jon
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« Reply #13 on: July 28, 2010, 10:18:10 am »

I'll throw in a suggestion in the hope someone does it... ever balanced a pingpong ball on the air from a hair dryer? If you haven't your should as soon as possible, you can lean it over at quite an angle and control height etc, even more fun can be two balls in one air stream they fight!.. now imagine several fans, several balls... dancing ping-pong balls!...
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Der Tinkermann
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« Reply #14 on: July 28, 2010, 05:20:29 pm »

Sounds like a fun idea,although I,m not sure  if computer fans have the same power as a blowdryer......
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sidecar_jon
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« Reply #15 on: July 29, 2010, 12:54:23 pm »

Sounds like a fun idea,although I,m not sure  if computer fans have the same power as a blowdryer......

With suitable venturi tubes....
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