LED array for a PC with a dimmer

I'm looking at using some LEDs to light my case for a casemod for my PC. Since I'd need quite a bit of light, I'm planning on using an array of at LEAST 20 lights, possibly more. The LEDs I'm using (assuming they're decent for what I want) are rated at 2000 mcd nominal, 3000 mcd max.

Now, one reason for choosing LEDs over a standard cold cathode light like most people choose to use is by having a large array spread out over a larger area, I SHOULD get a more even distribution of light in the case. Secondly, I would like to be able to dim the lights. I don't know of anyone who's specifically done this, but it seems like a worthy project if it works.

My question is how I would go about building a dimmer for the lights. If I did the math right, 20 LEDs running at 30 ma on a 5v line would use something like a 2 ohm resistor. Obviously that would be the lowest value I want for max brightness, then I would like it to go up from there to dim the lights.

Would a simple pot work for that, or would I be better off trying to build some sort of drive circuit for this? If the latter, where could I find said info.

Oh, I'm actually looking at two arrays possibly. One for my blue LEDs and one for some UV ones. Again, I need to get a few of the UV and see how well they work to light up the UV reactive stuff inside my system, but I've heard good things about them.

Any help would be greatly appreciated.

You could use a POT--that's cheap and it works--or you could get a PWM circit. PWM is a little more complex--to dim the LEDs it turns them on and off several times a second (So fast you can't see them turning off, just look dimmer).

PWMs are complex, I'd go with the POT.

I presume you've seen this:

http://www.dansdata.com/caselight2.htm

and this:

http://www.dansdata.com/caselight.htm

Dan writes good stuff....

No, I hadn't actually. The difference, though, is that I'm actually wanting to run the LEDs in a chain around my case window/s (think christmas tree lights) and have them dimmable.

Pot is fine - only argument against just resistoring it down is efficiency which really isnt´t as much of a point when running off the 5V of a PC PS.

A PWM is overkill IMO - unless you would make a SW controlled one - or a SW controlled dimmer of what kind ever - just a SW controlled pot is fine too - how cool having the LEDs of your case mod being able to be set by a small app from your PC itself.

Klaus

That would be cool, if I had any kind of programming ability at all. Actually, you could probably find a way to have the lights respond in patterns and stuff, perhaps to the sound. yeah, I know they have that now, but how many do it with LEDs?

Okay, so let's say I do it like this. Run it on the 12v line. The LEDs are 3.3v I believe, so that gives me 9.9 volts if I run three in series. Depending on the brightness, I run from 4-10 sets of series in parallel to each other. I then have ALL the sets running through a pot in the front of the system that I will use to brighten and dim the lights.

Does that sound like a workable scenario? If the LEDs have too narrow of a beam, is there anything I can do to spread them out and make them more diffuse? What sort of value should I be looking at for the pot? Obviously if it's too high, it won't give me any range to adjust, but if it's too low, it won't do much dimming.