The ultimate beginner's guide to PC FANS

maryjohn · Oct 9, 2009

Heya scrub, nice thread. I have not read it all, so sorry if this has been asked already.

let's say I get a pair of crazy 120mm fans that suck 2.5 amps or so each. you know that super simple stacker I made? would that be too much suction? should I just hook up the one?

also wondering how to control the speed, via voltage or a rheostat. two of them would be 60 watts total. Delta AFB1212GHE.

ScrubNinja · Oct 10, 2009

Hey mj! I can't remember too much about your stacker although I do remember it. But you sort of answered your own question - just slow it down if needed. And trust me, you will want to slow it down. I have a much quieter delta and it's annoying to be around for even brief periods at full speed.

Of course, nothing is ever easy. Not many people use quite such kick-ass fans in their computers, so there is not much call for a speed controller that handles such high wattage. But I did find a couple, and there's no doubt more. I found the Lamptron FC2 (45w per channel) and also Lamptron's FAN-ATIC 5-Port Military Switch Baybus (>60w per channel) so they would be good choices (Edit: I didn't check the maximum wattage of all channels though so please do, just to be sure). I'm fairly certain you will need a PSU to power the controller as I probably discussed. You could also use a 3amp adjustable power supply like I use for my cupboard, except they're expensive and you'd need one for each fan.

maryjohn · Oct 10, 2009

tell me about this adjustable power supply. is it very big? I'm trying to limit the bulk.

ScrubNinja · Oct 10, 2009

Let me tell you, it's the bomb dizzle schnizzle! It cost me $80aud, which was a big outlay compared to wall warts, but I wouldn't hesitate to get another one. It's approx as large as 2.5 of the chunky wall wart style. Dick Smith is an australian electronics store, but I'd assume you can find one easily in any radio shack type place. Seriously, I love mine, it doesn't get hot or do anything except look pretty and power my fan perfectly.

ScrubNinja · Oct 10, 2009

ScrubNinja said:
One important thing he mentioned though - the power supply must be continuous rated. Are any of the wall wart adaptors we use rated for constant load? Is there some way to establish if a particular adaptor is rated continuous?

I notice from the blurb on the box that mine is continuous rated. I would urge you guys to look into your supplies.

maryjohn · Oct 10, 2009

I'm having trouble locating something like that. I am considering one 12V and one lower voltage power supply. I can find adjustables strong enough for one but not for both. on the other hand will I even need both? I get ok cooling now, with 2 x .35 amp fans side by side.

going to use the gamecube adapter, and see if one will do it. But that will leave me with the problem of too much speed. Mind you, I like the sound of small fans like hairdryers and such. I can sleep to them and nothing wakes me up because of the white noise.

ScrubNinja · Oct 10, 2009

I get ok cooling now, with 2 x .35 amp fans side by side.

Frankly I think one will blow you away, bro. Aero often recommends fan power in terms of amperage (as against CFM etc), and it's a good way to do it in general. As we can see you have many times the amperage so thus, many times the cooling power. It's good that you can live with the noise, but be aware you don't want to be sleeping in the same room as one on full song. Well, not close to it anyway. I'm a musician and my dad is deaf as a hammer, so I'm very mindful of stuff like that. If you do want two, just get an adjustable for each.

Edit: also, if you don't slow them down, you may have to increase the layer of carbon in your filter quite dramatically (which I think I remember you use)

maryjohn · Oct 10, 2009

so I can't find an ac adaptor that will work... that leaves me with:
1)use a socket connection and have two sets of power supplies - let's say 5 or 7.5 volt, and a 12 volt. how to choose? at lower voltages, do I need the same amps?
2)use a regulator of some kind. my zalman won't be able to handle the load.

any ideas?

ScrubNinja · Oct 10, 2009

Yes I'd just use a lower voltage "static" power supply. You can also convert a PC's PSU into a lab power supply quite easily, and it gives you a wide range of voltages (more than you probably think) and that should have enough amps and let you set it to *just right* for when you need a nap. A very cheap option too.

If you have 2 x 2.5 amp fans, that equals 5 amps. So if you powered them both at 6v, you'd still have 2.5 amps cooling as total. You can see that if you lower them as far as they'll keep running (vaguely around 3 to 4 volts as a wild guess), you will still probably have far more amps/cfm/mmh2o cooling than your original .7A total from your old fans, and have very stealthy fans in comparison to 12v. Yup we just discovered why high amperage fans are best, even for some stealthy uses. Hope this helps.

maryjohn · Oct 10, 2009

yes thank you that helps! So I only need the adjustable to figure out my desired voltage before ordering up an adapter, or get or make a lab power supply? If I go with the former and just guess, do I need to have 2.5 amps capacity from the adapter at 6 volts, or do I need all 5 amps?

luckily I also have a seperate lid for the scrubber with the single hole. So I can test it that way first before going with both. The determining factor will be noise.

Saftevand · Oct 10, 2009

Check out this fan: http://www.thecoolingshop.com/product_info.php/cPath/98_1_16/products_id/3129

It's an Xilence's Red Wing 120mm. It does a whooping 68cfm with a noise level of no more than 21,2dB, very cheap too! Anyone found a better one?

maryjohn · Oct 10, 2009

not exactly the same ballpark... I'm maxing out at close to 250 scf on this delta fan. crazy shit.

Saftevand · Oct 10, 2009

maryjohn said:
not exactly the same ballpark... I'm maxing out at close to 250 scf on this delta fan. crazy shit.

Sure but the Red Wing feels more stealth. I actually never seen a better fan around that noise level. Perhaps it's just marketing, sound too good to be true.

maryjohn · Oct 10, 2009

you are assuming they are being run at 12v. I plan on having 2 running at 6v or less with plenty of amps.

should be stealthy and strong.

ScrubNinja · Oct 11, 2009

maryjohn said:
yes thank you that helps! So I only need the adjustable to figure out my desired voltage before ordering up an adapter, or get or make a lab power supply? If I go with the former and just guess, do I need to have 2.5 amps capacity from the adapter at 6 volts, or do I need all 5 amps?

Personally, I would make a lab supply - a new PSU cost me $20au and that's less than two crappy ebay adaptors that will break before a year. The other reason I would do that, is because I can't accurately answer the amps capacity question. I intend to hit a knowledgeable person up about this next time I see them. You see, I know a little tiny bit, but it's enough to be dangerous and potentially cause injury. My common sense says that the undervolted fan would also need half the amps. But there are formulas which are used for this kind of stuff. All I know is that my smart pal said these formulas are ultimate and cannot be argued with. So basically if you do the sums, you'll see that you need TWICE the amps at 6v. But I'm pretty sure that is just a gap in my own understanding. The watts probably go down with voltage or something. Idunno, it's all a bit too much for me to follow. That's why I just go overboard on amps every time. It's why I bought a PSU for my new project, I can't even work that shit out, so overkill always works. You cannot have too many amps but you can have too little and over the sake of very expensive fans, and a few bucks, I know which I would choose. (Unless a smart person can add here with some info)

Saftevand said:
Sure but the Red Wing feels more stealth. I actually never seen a better fan around that noise level. Perhaps it's just marketing, sound too good to be true.

You are both right really because every fan will probably fit in well in some particular application. When we start talking about true stealth...as in hiding it from your wife or in a room where people frequent and you need absolute silence, there are benefits imo with going with a lower amped fan, as against undervolting a strong one. But long story short, yes, it's marketing. No 0.1 amp fan is going to give you true specs like that. It'll be quiet though. Even the loudest .1A fan would still be pretty silent. Just not performing well.

I would look at Noctua fans in a case of true stealth.

ScrubNinja · Oct 11, 2009

Yo mj, I thought I should clarify something - if I was in your position, I wouldn't actually "make a lab power supply" quite so literally. I'd just use gather the wires and use the same principles so you can test different voltages, and then just wire it to the one you decide on. You don't have to go through the whole rigmarole involved in that link.

420.se gave a really good example a couple pages back

420.se said:
Just a tip for anyone using a PC power supply if stealth is an issue. Using a molex you got two blacks 0v, one red +5v and one yellow +12v.

Putting the fan between the +5v and +12v gives 7 volts reducing the noise while still keeping the airflow higher than if you run the fans on 5v. Connect the negative wire from the fan to the +5v and the positive to +12v.

In the ATX connector there is a 3.3v wire aswell but i would not use it as the load it can take is really small.

The PSU lab power supply is just adding a few more voltage comboes and prettying it up if I understand right (didn't read it in depth) And you probably won't have to do any of that. Just use the 5v from the psu.

maryjohn · Oct 11, 2009

I don't even know what a molex is but I will look it up.

good news! I had my numbers mixed up with a fan that is 2.9 amps. the adaptors I can get are 2.5, just like my fans.

but I also want to make a nice power supply that runs with confidence. gonna have to learn some things but I will hook it up!

ScrubNinja · Oct 11, 2009

The PSU only involves sticking a paper clip stuck into a plug at it's most simple level, but cool :yes:

I did it today so I'm pretty hyped on PSUs at the moment :woohoo:

Well, here are some "pinout" diagrams for the benefit of everybody, and myself. These are the usual molexes (clips) you will deal with working with fans and/or PSUs.

The psu I bought was the cheapest I could find which I sort of regret now. But it should be okay and I'll replace it when I can. It's not overloaded or anything, and I replaced the crappy fan inside it for a better one.

By the way you are making a very wise decision with Delta fans. They are a step above the rest for sure. That xb pro fan was hopeless in this application on full blast. The Delta cleans the floor with it even on minimal speed. It's 1.5 amps on full.

maryjohn · Oct 11, 2009

Ok I want to make one. What tools will I need to make it? I would like to have multiple output voltages.

Man this is cool. Oh and I just picked up a wall adapter that will work. So I can test down to 6v.

ScrubNinja · Oct 12, 2009

Cool bro. Well keep in mind I haven't done it myself. I can only give you the link. Sheeit, I was kinda hoping you would come back and explain it to me.

Here is what the cheapest shittiest PSU I could buy supplies:

Note the different amperages at different voltages. Well that's about all I can tell you really. If you're quick, the last page or three of my cold cathode thread has a lot of illuminating talk on power supplies. You would be wise to read it before spending any money. Peace.

btw which fan/s are you getting exactly?

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