I used 16 x 16,000mcd LED's. They were white, though I accidentally overpowered them once, so I'm sure they weren't running at peak performance. They were all wired in parallel with a 5v dc source. I recommend using a resistor between the power supply and circuit card to reduce the current (your LED's should run cooler that way). The coloration really wasn't too terrible, but I did notice that the orientation of the LED's towards the projection lens (when no fresnel was used) made a big difference in the resulting color on my wall. It ranged from a dirty white to a cool blue white (very desirable).
I just wanted to let you know that I will be running some experiments on my own soon. I am very new to the whole lcd projection scene but we'll see what I come up with. I am waiting for 100 11,000mcd leds to come in from Hong Kong. Once I get them and start messing around I will let you know what I find.
Welcome to the party! I think I have a lot of critics that think that you and I are wasting our time with LEDs, but even if they don't work for this, there are a bajillion other places to use them ... LED's are just plain cool
Heya Allan, i see you had trouble with your image, to fix the double image you need light control film by 3M, that will solve the double image problem from the leds. Take a search on the net and you will see what it does as my info is out of a fat optical book.
Trev🙂
Trev🙂
Thanks for the tip. I actually think that I didn't explain the artifact correctly. The film you told me about does indeed work for double images caused by reflection, but my double image is actually due to the light coming from different angles, so I actually had 4 or 5 different images. I think that using an apropriate condenser lens would probably work, but my condenser lenses won't do the trick here. I did notice that I was able to insert the LED cluster into an OTC LCD projector and the image came out fine! The image was on the dark side, of course, but I could easily fit twice as many LED's in there and also use ones that are 4,000 mcds brighter! I think that there is some potential here, especially because this method gave me a sharp picture, though the color was a little green.
"I did notice that I was able to insert the LED cluster into an OTC LCD projector and the image came out fine! The image was on the dark side, of course, but I could easily fit twice as many LED's in there and also use ones that are 4,000 mcds brighter!"
Whatwhatwhaaat...... you got visible image with OTC using 16 LEDS? What size and how visible?! I could easily fit something like 80 leds on my OTC....
HB
Whatwhatwhaaat...... you got visible image with OTC using 16 LEDS? What size and how visible?! I could easily fit something like 80 leds on my OTC....
HB
have you tried looking at Star-O's?
http://www.bit-tech.net/review/82/
http://www.quickar.com/lux.php?session=GuUDfSIy
http://www.bit-tech.net/review/82/
http://www.quickar.com/lux.php?session=GuUDfSIy
How would you deal with taking a large panel of LEDs (large than the display panel) and condensing that to go to the back fresnel? Sorry if this is thread-jacking, I made a topic about it if you want to respond there. Thanks!
That film guides light to the correct angle so there is no double images or artifacts of any kind, its a light guide in a film form, it guides light to paralelle. A condenser lens will never work with multiple light sources either, wheather its leds or not, the only way i can see of this working is using a light guide and to hand make one of them for 400 or so leds is alot of work, thats 400 holes all polished through 400 guides, this would be the only efective and eficient way of preserving the light fron the led and to combine the light. by doing that only then you will have a perfecly square and evenly lit block of light.
Ill see how much time i have maybe ill do 1 guide for you with 1 led to show you just how efectivly that idea works.
Trev🙂
trev, thanks for that - please do try it if it's not too much trouble. Also, I looked into those Star/O lamps and they look like they might be of a lot of help. They are a lot brighter, but also hotter, but manageable heat. Anyways, I'll update about that if I get some.
Have you had a chance to make one of those guides yet, ace?
I'm curious as to what you mean exactly, so if you haven't had a chance to do anything, could you possibly explain a little more clearly? I'm not seeing what you mean.
And thanks for all your help thus far. 🙂
I'm curious as to what you mean exactly, so if you haven't had a chance to do anything, could you possibly explain a little more clearly? I'm not seeing what you mean.
And thanks for all your help thus far. 🙂
I got an 80 lumen LED that runs at 3.9v @1000mA. I haven't yet figured out how to build a regulated power supply to these specifications, but I hope to get that done in the next week. I think that this LED should be about as bright as 15 of the bright LED's that I was using in previous tests, but it will be a point source (though I may end up clustering them if that light aligner that ACE mentioned works). I'll post pics as soon as I complete the circuit.
I don't know if someone has mentioned this yet here, as I just happened upon the thread, but LED efficiency is not good at all, and is only better than that of incandecent bulbs. All of the HID type lamps are several times as efficient.
Personally I'd like to see some proof for the above, my understanding was that LED's (at least coloured ones) were in the region of 80%+ efficient... I may well be wrong so if anyone has any modern stats then they should post them!
I think that as far as lumens per watt goes, you are probably correct that LED's are about 30% as effecient as HID. The flip side of that is that all of the LED's light comes out of the front at a condensed angle compared to an HID, which makes all of its light in a sphere pattern. I think that when you take that into consideration, an LED setup could be many times more efficient in terms of end lumens vs wattage.
Reflectors can quite make up for that, and they can be quie efficient in the percentage of light reflected. LEDs are below 50 lm/W, and indeed, except for red LEDs, much below that, whereas low pressure sodium has achieved 200 lm/W. Color rendering of the latter is horrible, but high pressure sodium is a good substitute, and still at 140 lm/W.
Considering the amount of LEDs you need, I'm wondering if even price is an advantage with them. The only real advantage LEDs have is long life if they are not overdriven.
Considering the amount of LEDs you need, I'm wondering if even price is an advantage with them. The only real advantage LEDs have is long life if they are not overdriven.
I think your right allan, but looking at it in the terms of a bought of the shelf item. HID lamps are actually more efficient and we can capture the light in a more efective manner than leds, but ofcourse in the diy world not everyone has the money or know how to do this.
Placing a cdm-t lamp in a par reflector with a condenser is the exact same thing as how a led works, its just bigger, my point is that what leds have as in the eficient light path we can certainly do the same with HID, its only different as leds come in a package already optimised where as HID lamps in most cases are bare lamps, and the optimising is left upto us.
The efficiency of a HQI-TSD lamp is in the vicinity of 80 - 90lm per watt.
Trev🙂
MrMike said:
Heya buddy not yet, ive got about 10 other projects going at once which isnt a good thing as its too easy to loose data so ill show you how it works.
Basically all a light guide is, is a mirrored channel, the light guide acts as a mirrored prisim and all of our light is forced forward. This idea will and does work 100% but it will be upto you and your materials properties on how well it will work, bassically u need to do alot of polishing, have you ever polished the edge of some plexi and looked in the sheet so you are looking behind the polished side? notice its a mirror on the inside? thats how prisims work and plexi is by far a perfect chioce for this operation.
Get some 10deg 5mm white leds, get some 8mm square plexi beams, cut to size wich we calculate out to our beam angle, 8cm is a good start, polish all sides and the ends, drill a 5mm hole with a drill bit the same tapper as the taper on the front of the led, notice on normal 5mm led that there is a lip on them? thats the depth you want to go, after the hole polish the hole and your done. Place the led in the hole, turn it on and on the otherside you will have a very bright square of white light, make another 400 of these and you can fill a lcd. Dont glue them together as glue will interact with the plexis polished surface, you need to make a up a clamp that holds the whole lot together (wich is easy enough) and there is your block of light. You should only need the one frensel thus being the top one to guide the light through the projection lens.
Here is a quick pic on how a singular led system works.
Trev🙂
Attachments
Hey, thanks. 🙂 I'll give that a try, pretty sure I understand now.
My calculations (using a viewing angle of +-15 degrees) and a 16, 000 mcd LED bring it to about 50lm/watt. Not nearly as good as a bulb, but there is no worry about heat and such.
As for price, well, yes. That actually is the biggest advantage. You may have to spend around $500 or so for all the LEDs, but then you will NEVER have to replace them, seeing as you could have around 11-12 years of nonstop running time, so long as you're nice to 'em all.
My calculations (using a viewing angle of +-15 degrees) and a 16, 000 mcd LED bring it to about 50lm/watt. Not nearly as good as a bulb, but there is no worry about heat and such.
As for price, well, yes. That actually is the biggest advantage. You may have to spend around $500 or so for all the LEDs, but then you will NEVER have to replace them, seeing as you could have around 11-12 years of nonstop running time, so long as you're nice to 'em all.
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