Does anyone happen to know how I would go about configuring a 120mm computer fan so I can run it on my projector? I don't necessarily need the specs that also contain the ballast, etc. wiring diagram, but what I would need to do exactly in order to power my fan. I have t screwed on to the back piece of my box along with a hole for the vent for the air flow, so I'm almost ready to go. Before, I connect the back piece of MDF to my projector box, I just need to know how I would go about powering the fan. I was told to cut the ends off of a 120 V AC adapter and connect the wires to the two prongs on the fan; that didn't work, though. In that case, I'm trying to find another way that will actually produce results. Like I said, I just want to know the easiest way possible to get the fan to turn on; no specs or diagrams needed. Is anyone able to help me out? Thanks.

If it's a "computer" fan it is designed to run off of 12 volts, but should work with [shot in the dark]I'd say 6 volts up to about 15 volts[/shot in the dark]. So make sure that your AC adapter is close to 12 volts.

If your AC adapter is indeed 12 volts, then it really should be as easy as you say. If you hook up the wires and nothing happens, try swapping the wires. If that doesn't work there's probably something wrong with either the AC adapter or the fan, try a different fan, or test the AC adapter with a multimeter... or 12 volt bulb from a auto parts store (just ask for the cheapest they have).

("shot in the dark" tag curtisy of tameone)

So, I was hooking it up correctly then? I thought I ran a test on both the fan and the adapter and they both seemed ok. However, it did not start the fan up upon connecting the two wires together.

Make sure the AC/DC converter outputs enough amps to power the fan. The fan should say something like 12V/DC .3 AMP on it. Your AC/DC converter should also say for example 12V/DC 1.25 Amps.

Also, what two wires did you wire up? The yellow wire is not used. Only wire up the red and black wires to the AC/DC converter.

Make sure the two wires don't touch each other when you have wired them together.

Hi there Litherish. I actually set it up exactly how you just indicated and also made sure the voltage for the AC adapter had enough voltage to power the fans. Maybe the fan or adapter just aren't working then, or one is out that I don't know about. That's all I do, though, correct? Just cut the end off of the adapter and take the red and black wires and connect them to the two prongs on the fan, rightt? Then it should power on? Is that how it works? If so, at least I know and I'll just go out and buy a couple of new fans and a new adapter so I know they both work.

Let's be sure we're all talking about the same thing. There is such a thing as a 120mm fan that runs on AC (Lumenlab used to sell them). What voltage is the fan designed to run on? There should be a sticker on the fan telling you. Assuming the fan runs on 12 volts DC, it should have a red wire and a black wire coming from it. If there is a yellow wire, it is not used for this application, as Litherish has said. The red wire should be connected to the positive wire from the adapter, the black to the negative. Some DC fans will not run if the polarity is reversed. Also, be sure the adapter is DC output. There are some out there which are merely a step-down transformer still outputting AC. The output of the adapter should be printed on it somewhere. And, as Litherish has said, the current capacity of the adapter must equal or exceed the amperage rating of the fan. Hope this helps.

Ok, that's what I thought. Since reading your posting, I went back and checked out the voltage on the fan and it indicates 115 volts and 60Hz. I'm assuming this would be why I am experiencing problems. What voltage should I be looking for when purchasing a 120mm fan? I was thinking about stopping by Best Buy today to pick up a couple of fans, since I have heard two fans are more efficient at cooling the box than one is, but want to be sure I know what I am looking for. Thanks for the help, by the way.

Yep, that's the problem. That fan is designed to run off 115 volt AC (standard household power here in North America). If you want to use it, just wire it up like the desk fan you're presently trying to use. DC fans are usually somewhat quieter and move more air than the AC fans., but of course, require a power supply. Most builders use a ball bearing 12 volt DC fan having a high CFM rating (moves more air). Remember though, the more air it moves, the more noise it produces.

Ahh, ok. So, if I purchase a 12 volt DC fan, would I then need a power supply to run it, or could I just connect the red and black wires to the adapter like we were discussing before? In other words, if I purchase the 12 volt, what all would I then need to do to get it up and running; without having to configure the wiring with all of the rest of the components, of course? I just want to find a way to power it, as I just want to simply plug in one plug in order to power it each time I want to use it, rather than having switches and all of that other stuff. That's too electrical for me, if you know what I mean.

The 12 volt DC wall adapter we were talking about is a type of power supply. I would recommend one with a current capacity of at least 500 ma (that's 1/2 amp). That should provide enough to run two fans, if need be.

Perfect. Thanks a bunch! How would I got about connecting two fans to one adapter, though? Would you be able to help me out on that one?

Another question I have is would one vent be enough if I'm using two 120mm fans, or would I need to cut a hole out for another one? The one I currently have is about 4"x4" or so.

2 Reds->Positive Wire on Adaptor
2 Blacks->Negative Wire on Adaptor

You can just cap all three wires together for negative, and then the same for positive and it will work, given you have enough amperage for both. Basically the same as one wire just you add in the two other wires from the 2nd fan.

I'm assuming that you're following the basic lumenlab guide for the cooling system in your setup: a closed box with a 1/2 inch wide slot going the width of the top for an air intake, a 1/2 inch space, the width of your box, beneath the first fresnel, and an opening for an exhaust fan. The box must remain closed to force the fan/s to suck fresh air in and across the lcd, thus cooling it, and blow hot air out the back of the box. If you need two fans, you could mount them side by side, each having their own mounting hole. In this diagram, your lcd is represented by the blue item. The bulb is the yellow circle:
Click to view attachment
If the lcd is not cooled, it will darken, and could eventually be ruined. Hope this is of some help.