Lightsource for DIY LCD Projector

xpndsprt asks: "I'm trying to develop my own projector (i've been reading DIYAudio forums for a while and finaly decided to put together my own), but it seems that people are having problems with light source. The Slashdot crowd seems to always have interesting answers to problems at hand, so to get to the point: Does anyone know of a powerful lightsource (200w+) which would produce a high temperature light (5000K+) and would not heat up too much (ppl seem to be using mag.Hylide bulbs, but those seem to heat up tempreture in the room by about 10F. Xenon lights are out of question, since too hot and not bright or white enough. If someone could help, it would be greatly appreciated."

LCD + OHP

[brejc8]

We got loads of these 640x480 lcd screens for £1 each ($1.50). They work really well when they're placed an OHP. Here [man.ac.uk] are some things we did with them. I am currently thinking of placing four of them in a circle and having a powerful light in the middle. Then a simple GAL or FPGA to control it. then have funky colours shining on your wall. Or the time/wather and so on.
Fat boy Matt made a network controled version [man.ac.uk].

Just stating the obvious

[Mononoke]

Please don't take this the wrong way, but: Don't you think the LCD projector manufacturers are using the best light source for the application?

Having said that...

The only high color temperature light source you'll find suitable for this type of work will be arc lamps. HMI, MRI, HID, etc. In terms of heat:light output ratios, arc lamps put out the most light per btu of heat of any other point source lamp. Point source is important. Light from a diffuse source (flourescent, multiple LED, etc) is nearly impossible to deliver through optics in an orderly fashion.

As you've probably found, getting the lamp is easy. Matching it to a suitable power source is difficult.

Additionally: No matter what lamp you use, your LCD panels and optics will also need some cooling

Once again, I've been of no help.

Three suggestions:

[Russ Nelson]

• White LEDs. Lots of them.
• The sun. It's really bright and it won't heat up your room any more than leaving a window open would.

Suggestions

[adolf]

Light bulbs are generally rated by the power they consume, not by the light they create. An incandescant bulb creates a lot of heat, and a little bit of light, in terms of energy and efficiency. To top it off, unless you've got a window or an open door for that small amount of light to escape through, -all- of it will be turned into heat after some amount of reflection inside the room.

Which is to say: A 200W light bulb may produce various amounts of light at various levels of quality, but will always produce 200W of heat.

Your best bet? I'd vote on hitting a DJ supply store (or a guitar shop, or audio rental place - wherever you find musicians, DJs, or both) either online or locally. Note, however, that if all they have is a collection of PAR cans (glorified coffee cans with common flood lights), you're in the wrong place.

More complicated DJ lights have to deal with the same problems you have: efficiency (heat inside the fixture), color temperature, lifespan, cost, and durability. They need to be close to point-source, so that the gobo patterns they project will be easier to focus. And they need to be extremely bright.

I, once upon a time, had a Martin Robozap mounted on the wall at home. This fan-cooled light weighs 20-25 pounds, IIRC, and has a servo-driven mirror with two 150W overhead projector bulbs aimed at it. Whenever I fired it up, I had to increase air circulation in the room else it would get terribly warm, fairly quickly. I imagine the same would happen with a 300W floor lamp...

Locally, the bulbs were fairly expensive, but I was able to find the type online for ~$10 from some specialty lighting shop that primarily just sold light bulbs. They were a halogen bulb, with an integral reflector. IIRC, it's a pretty common type for overhead projectors.

Speaking of overheads, why not use one? You've appearently got an LCD display - just lay it on top of an overhead projector. Should be cheap, if buying used. Just clean up the optics and re-arrange the innards so that it's concentrating as much light as possible on the LCD display, and things should be peachy.

I hope it's obvious, but it appearently isn't because at least two posters have mentioned it: don't use white LEDs. You'll -never- achieve even satisfactory focus using an array of LEDs, let alone good focus. Now, if it were possible to make them bright enough that you'd only need one for the project, it'd be a different story...

Distributed light via fibre-optic?

[matt_wilts]

If the heat's a problem, how about this? Put the light source (lamp, LED, arc light, whatever) in a box which you can cool and place some distance from the LCD part of the projector - thus keeping noise/heat levels down (water cool it, I dunno?). Then feed the light to the LCD using fibre optics.

I can't take credit for this - I seem to recall seeing a diagram years back suggesting this for a car, with a central light source feeding all the car lights. Google searches bring up these links:

http://www.halfbakery.com/idea/Fibre_20optic-lit_2 0office

http://www.ind-auto.com/news/sept2000.html

Matt

HID Lamps

[bootprom]

I used to use HID (High Intensity Discharge) lamps for growing, uh, tomatoes, in college. I can say that after doing LOTS of research, these lights have the lowest heat/lumens ratio you will find unless you get into some really exotic / expensive stuff.

Advantages of HID lights are: You can mount the ballast remotely - this help because the ballast generates almost as much heat as the bulb. The bulbs are relatively small, though certainly not as small as a halogen. HID's make lots of light for the amount of power they draw - ie: a 400W HPS (High pressure sodium makes 50,000 lumens, while a 100W incandescent makes about 2,000 lumens - that's 125 watt/Watt for the HPS and 20 lumens / Watt for the incandescent).

The three popular types of HID lamps are metal halide, high-pressure sodium, and mercury vapor.

Only drawback here is that the color temp stinks. You will have trouble finding bulbs that do better than 2500k. You might want to look into something called Sun-Argo, which is a HPS / MH hybrid kind of thing. You also might want to look into something called compact fluorescents - these provide a better color temp, but unfortunately, they are florescent, so they are kinda big.

Good Luck.