Eureka! *runs naked through the streets*
I just ordered 100 20000mcd LEDs for $25. No, Im not kidding, or full of ****, a factory in hongkong is selling them direct on ebay at about 1/10 the cost of what youd pay if you ordered a similar part from mouser or something. I didnt really belive they where legit at first, but after checking out all the good feedback they have gotten, I have to assume that they are indeed reputable. Just do a search for "20000mcd" to get their listings.
For those who may not be familiar (although I would assume most of you on this forrum probably would be) with what "20000mcd" means; I am told that in order to roughly convert candela to lumens, you multiply by 12.57. So basicly, each LED being 20 candela (or 20000mcd) can put out about 251 lumens. Now, granted, that is their most optimistic rating, their minimum rating is 140000mcd, which would translate to about 175 lemens per LED.
So, just to be conservative, lets assume that you are getting the minimum posible lumens from each LED, and that you will need 5000 lumens to get a good picture from your projector. That would mean that you need about 30 of these pupies to make a projector lamp. Considering that I payed $0.25 each for them, that means you can make a 5000 lumen lamp that will last a very conservative 50,000 hours for arround $7.50.
Is it just me, or is this the bloody freakin holy grail of do it yourself projector building? And to top it all off, I found lots of 10 3v (same voltage as the LEDs) lithium Ion photo batteries with a capacitiy 1300mah each, for as little as $9.00. Crap, I mean, what is to stop us from making completely portable hand held projector for a few hundred dolars?
If somone could point me in the direction of a reasonably priced, decent (aka 1024x768) 2 to 5" inch LCD, and driver, as well as a good source of innexpensive optics, and the plans neccesary make a nice transmissive style projector (I am assuming that a transmissive set up would be optimal in this case, considering I can keep the lcd so close to the lamp without it over heating like an incandecent bulb would do) I would be very greatfull.
-Orochi
I just ordered 100 20000mcd LEDs for $25. No, Im not kidding, or full of ****, a factory in hongkong is selling them direct on ebay at about 1/10 the cost of what youd pay if you ordered a similar part from mouser or something. I didnt really belive they where legit at first, but after checking out all the good feedback they have gotten, I have to assume that they are indeed reputable. Just do a search for "20000mcd" to get their listings.
For those who may not be familiar (although I would assume most of you on this forrum probably would be) with what "20000mcd" means; I am told that in order to roughly convert candela to lumens, you multiply by 12.57. So basicly, each LED being 20 candela (or 20000mcd) can put out about 251 lumens. Now, granted, that is their most optimistic rating, their minimum rating is 140000mcd, which would translate to about 175 lemens per LED.
So, just to be conservative, lets assume that you are getting the minimum posible lumens from each LED, and that you will need 5000 lumens to get a good picture from your projector. That would mean that you need about 30 of these pupies to make a projector lamp. Considering that I payed $0.25 each for them, that means you can make a 5000 lumen lamp that will last a very conservative 50,000 hours for arround $7.50.
Is it just me, or is this the bloody freakin holy grail of do it yourself projector building? And to top it all off, I found lots of 10 3v (same voltage as the LEDs) lithium Ion photo batteries with a capacitiy 1300mah each, for as little as $9.00. Crap, I mean, what is to stop us from making completely portable hand held projector for a few hundred dolars?
If somone could point me in the direction of a reasonably priced, decent (aka 1024x768) 2 to 5" inch LCD, and driver, as well as a good source of innexpensive optics, and the plans neccesary make a nice transmissive style projector (I am assuming that a transmissive set up would be optimal in this case, considering I can keep the lcd so close to the lamp without it over heating like an incandecent bulb would do) I would be very greatfull.
-Orochi
According to the good folks at the University of North Carolina and the scientific dictionary they have .....
millicandela (mcd)
a unit of light intensity equal to 0.001 candela. The intensity of the light-emitting diodes (LEDs) used in electronics are stated in millicandelas.
lumen (lm)
the SI unit for measuring the flux of light being produced by a light source or received by a surface. The intensity of a light source is measured in candelas. One lumen represents the total flux of light emitted, equal to the intensity in candelas multiplied by the solid angle in steradians (1/(4·pi) of a sphere) into which the light is emitted. Thus the total flux of a one-candela light, if the light is emitted uniformly in all directions, is 4·pi lumens. "Lumen" is a Latin word for light.
Looks like Orochi is right.
T.
millicandela (mcd)
a unit of light intensity equal to 0.001 candela. The intensity of the light-emitting diodes (LEDs) used in electronics are stated in millicandelas.
lumen (lm)
the SI unit for measuring the flux of light being produced by a light source or received by a surface. The intensity of a light source is measured in candelas. One lumen represents the total flux of light emitted, equal to the intensity in candelas multiplied by the solid angle in steradians (1/(4·pi) of a sphere) into which the light is emitted. Thus the total flux of a one-candela light, if the light is emitted uniformly in all directions, is 4·pi lumens. "Lumen" is a Latin word for light.
Looks like Orochi is right.
T.
Im not expert, but..
Ok, I think I see where I got confused , mutiplying the candela by 12.57 seems to be a way to convert to lumens when your light source radiates sphericaly or something (or at least I think thats what they meant, still not sure really), where as leds only cast their light at a particular "viewing angle".
After plugging the brightness of my LEDs into the equation on this site....
http://www.ledproductstore.com/measurement_of_leds.htm
It seems that you would be getting about 10 lumens per LED. Which obviously does change things quite a bit, but it doesnt change that these 20000mcd LEDs at $0.25, are still one hell of a deal compared with the 2000mcd LEDs that cost about $5.00 each no more than a year ago.
So I guess it turns out that my 100 20000mcd LEDs are good for about 1000 lumens on a good day, but hey, I only payed $25 for the lot of em. When you think about it, even if I need 300 to get something comprable to a 3000 lumen metal halide lamp, wouldnt it be well worth it? I mean, hell, they would still produce a lot less heat, and last 50,000 hours.
Anyway, Im no engineer, so I would love to have someone who really knows what they are doing take a look at the specs for these LEDs and let me know exactly what is what.
Heres a link to the LEDs Im talking about, it has all their specs twords the bottom of the page....
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=66952&item=3840744077&rd=1
Also, Im very curious about something else I found using LEDs that Lamina calls a "Light Engine". They Claim that one of their 8 caviity light engines (about $40 at mouser.com) can produce 1000 lumens, and they sell a light engine that has 39 cavities (about $165 at mouser). Perhaps that would be the way to go?
In any event, here is a link....
http://www.laminaceramics.com/products.htm
Prices at mouser...
http://www.mouser.com/?Ne=400&handler=data.listcategory&N=59901+59930000
-Thanks
-Orochi
ace3000_1 said:
Try devide lol and thats why we dont use leds, i dont even think devide is right, its somthing like 2lumens per led.
Trev
Ok, I think I see where I got confused , mutiplying the candela by 12.57 seems to be a way to convert to lumens when your light source radiates sphericaly or something (or at least I think thats what they meant, still not sure really), where as leds only cast their light at a particular "viewing angle".
After plugging the brightness of my LEDs into the equation on this site....
http://www.ledproductstore.com/measurement_of_leds.htm
It seems that you would be getting about 10 lumens per LED. Which obviously does change things quite a bit, but it doesnt change that these 20000mcd LEDs at $0.25, are still one hell of a deal compared with the 2000mcd LEDs that cost about $5.00 each no more than a year ago.
So I guess it turns out that my 100 20000mcd LEDs are good for about 1000 lumens on a good day, but hey, I only payed $25 for the lot of em. When you think about it, even if I need 300 to get something comprable to a 3000 lumen metal halide lamp, wouldnt it be well worth it? I mean, hell, they would still produce a lot less heat, and last 50,000 hours.
Anyway, Im no engineer, so I would love to have someone who really knows what they are doing take a look at the specs for these LEDs and let me know exactly what is what.
Heres a link to the LEDs Im talking about, it has all their specs twords the bottom of the page....
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=66952&item=3840744077&rd=1
Also, Im very curious about something else I found using LEDs that Lamina calls a "Light Engine". They Claim that one of their 8 caviity light engines (about $40 at mouser.com) can produce 1000 lumens, and they sell a light engine that has 39 cavities (about $165 at mouser). Perhaps that would be the way to go?
In any event, here is a link....
http://www.laminaceramics.com/products.htm
Prices at mouser...
http://www.mouser.com/?Ne=400&handler=data.listcategory&N=59901+59930000
-Thanks
-Orochi
The 12.57 conversion will never, ever, ever, give you the right data. You will actually be getting 7.65 lumens per LED. I wrote a program in c++ based on the proper conversion method posted below. It's just a simple DOS program but eliminates the need to do the math by hand .
You Can Download It Here
.You Can Download It Here
Yeah, I got the same result..
Yeah, I got the same result once I plugged the correct solid angle into the equation. What a difference 5 degrees makes. It seems that LEDs in general tend to fluctuate between 20 and 25 degrees. At 25 degrees I got about 12 lumens per LED, at 20 I got 7.5. Im guessing that my last assessment of about 300 LEDs would be equivelent to a fairly decent mid range comercial projector. If you think about it though, at $75 it still beats the pants off an incandecent bulb. Yeah, for that price you could get much brighter light sources (I think someone once told me you can get a 10,000 lumen lamp for about $100) but leds will last 50 to 100 times longer, are far more durable, and dont make anywhere near as much heat..
What Im really curious about is that Lamina light engine. If every 7 cavities, really do produce 1000 lumens like they say, then I would more than happily cough up the $160 for a 39 cavity product., 5600 lumens aint to shabby at all, and it would save me the hastle of wiring all those single leds together.
-Orochi
verbose mustafa said:The 12.57 conversion will never, ever, ever, give you the right data. You will actually be getting 7.65 lumens per LED. I wrote a program in c++ based on the proper conversion method posted below. It's just a simple DOS program but eliminates the need to do the math by hand
You Can Download It Here
Yeah, I got the same result once I plugged the correct solid angle into the equation. What a difference 5 degrees makes. It seems that LEDs in general tend to fluctuate between 20 and 25 degrees. At 25 degrees I got about 12 lumens per LED, at 20 I got 7.5. Im guessing that my last assessment of about 300 LEDs would be equivelent to a fairly decent mid range comercial projector. If you think about it though, at $75 it still beats the pants off an incandecent bulb. Yeah, for that price you could get much brighter light sources (I think someone once told me you can get a 10,000 lumen lamp for about $100) but leds will last 50 to 100 times longer, are far more durable, and dont make anywhere near as much heat..
What Im really curious about is that Lamina light engine. If every 7 cavities, really do produce 1000 lumens like they say, then I would more than happily cough up the $160 for a 39 cavity product., 5600 lumens aint to shabby at all, and it would save me the hastle of wiring all those single leds together.
-Orochi
Ok, we are all agreed that a 20,000 mcd led with a 20 degree viewing angle will produce about 7.5 lumens of light. I will keep with the tenths place only to stay simple. With 300 LEDs X 7.5 lumens a peice, we are looking at a total gross of 2,250 lumens. That is assuming you can somehow defuse all of the light from each LED in to one general path with no light loss. That is not going to happen no matter how hard one tries.
Once all the light from the leds has been defused and is essentially ready to shine its way through the lcd, there will be a good amount of light loss. What it all comes down to is how good your light kit is. By that I mean not only all the optics involved, but the way it is put together. Something crude like brute force style will not work. You cannot expect to throw a fresnel in front of some leds and go from there. You will need somthing small, well crafted, with little if not no light leaks, and good quality optics. Anyone will tell you the best light kits are made by ace. If you used a highly modfied version of his designs to fit your application, you may get somthing nice.
So assuming you get this really nice light kit made, you're still bound to get some degree of light loss. I can't really throw out a 100% accurate number, but assuming you loose around 30% of the light from the light kit. That means that there would be 1,575 lumens hitting the back of your LCD panel (Becuase I am assuming there would be no way to loose light between the light kit and the lcd).
Your assuming that you will have 10% of the light hitting the back of the LCD actually pass through. That number is a little high in actuality, but since we have a really nice light kit with low loss and there is no way to loose light between that and the lcd, I'll give it the benifit of the doubt. After, 10% of the light passing through the lcd, you would be left with 157.5 lumens of light on the front side of the lcd.
Not taking into account the light lost by the time the image is projected through the lens, accross your room, and onto your wall, that is very roughly a number you might expect on by the time you hit the wall. So you say you would have the results of a mid range commercial projector? About what you would achive IMHO is the brightness a little less then an old, 150 ANSI lumen nView projector, but with the benefit of a much sharper looking picture from your projector. Also, ANSI lumens is not just the % of light after the lcd. It is measured in relation to the size and brightness of the projected image. So, you go for a smaller image, 157 lumens of light passing the LCD might be just right for you (even if oh lets say 80-100 ANSI is your final result).
So! Will LEDs work? IMHO Yes. Seeing the results from placing my delta lens over an unmoddified lcd with the original backlight installed many years ago and seeing a 5 foot projected image on the wall leads me to belive that yes, LEDs will work to a point. How will they will work is up to your engineering skill and the application you want to use the projector. You will not get commercial quality results. You projector will be cripled in the area of size in relation to brightness. I just wanted to make you realize that your aiming your results too high. There is no doubt it'll work (maybe even well). You just need to build the thing to work with what is reasonable. Having the results of a 500 ANSI lumen projector with LEDs is not. Remember, the projector companies are always a a few years ahead of us in technology.
Good luck and please, don't let me discourage you. I'll probably be building one of the guys too
.Hmm, definetly good to know.
Verbose Mustafa:
No no, I definetly appreciate your input on this. Yeah, I had assumed that the lumen rating of those comercial projectors was a refferance to the light source, I had no idea that the lcd absorbed so much of the light.
I would never have imagined that only 10% of your light gets through to the final image. Damn, that would mean that the metal halide lamps in those commercial projectors, are what, about 20,000 lumens? No wonder they are so expensive, and difficult to keep cool.
In light of this new information, Im thinking those Lamina light engines would no doubt be the way to go if you wanted a solid state light source. The 39 cavity light engine apparently produces about 5500 lumens (yes, they rate it in lumens rather than candela). It would take 4 of them to get that 20,000 lumens, and it wouldnt be cheap at $160 each, but it sure would make for a slick projector.
These things are extremely small too, I think the 5500 lumen product was a little over 2x2 centemetemeters, so youcould probably make it a hand held projector. Which is one of the main attractions to lcds for me anyway. I mean, they are durable, have very low power consumption, and dont produce much heat, which sounds like exactly what youd be looking for in a portable product.
-Thanks
-Orochi
Verbose Mustafa:
No no, I definetly appreciate your input on this. Yeah, I had assumed that the lumen rating of those comercial projectors was a refferance to the light source, I had no idea that the lcd absorbed so much of the light.
I would never have imagined that only 10% of your light gets through to the final image. Damn, that would mean that the metal halide lamps in those commercial projectors, are what, about 20,000 lumens? No wonder they are so expensive, and difficult to keep cool.
In light of this new information, Im thinking those Lamina light engines would no doubt be the way to go if you wanted a solid state light source. The 39 cavity light engine apparently produces about 5500 lumens (yes, they rate it in lumens rather than candela). It would take 4 of them to get that 20,000 lumens, and it wouldnt be cheap at $160 each, but it sure would make for a slick projector.
These things are extremely small too, I think the 5500 lumen product was a little over 2x2 centemetemeters, so youcould probably make it a hand held projector. Which is one of the main attractions to lcds for me anyway. I mean, they are durable, have very low power consumption, and dont produce much heat, which sounds like exactly what youd be looking for in a portable product.
-Thanks
-Orochi
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