verbose mustafa said:
25,000,000 mcd per square meter is what we're looking at. Cool. Let's do some math.
That means 25 mcd per square millimeter (divide by 1000*1000)
Assume each LED is a 5 mm square (it at least takes up that much space in a line)
So 25*5*5 = 625 mcd
With this math, you could say that a CCFL is equivalent to a row of 5mm LED's with each LED having a luminescence of 625 mcd.
Going to a 9,000 mcd LED would give you 9000/625 = 14.4 times the brightness.
That definately hits our high-end goal of 8x brightness.
Alvaius, I feel like we're two people doing a homework problem, and I do the problem one way and get one answer, and you do the problem another way and get a different answer, and we check each other's work and they both make sense and seem to be right, but they're completely different. 🙂
*sigh* I keep wibble-wobbling about this issue. I think I'll just have to go ahead and order these LED's, and when my roommate gets back his laptop will be so incredibly bright he won't know what to do. 🙂 He'll turn it on and it'll be like plugging in the sun. lol
Thanks alot for all your help guys. 🙂 I really appreciate everyone's input.
--Clint
I always argue with idiots who persist in telling people you cant do this and you cant do that. Its such a weak minded attitude. Takes away all the enthusiasm for projects. The guy said he was just going to get a few led not spend a fortune on parts. Havent you done that. And, if you actually read what I said I mentioned it might not work. So its not as if I said it definitely would work.
After my post, here is his reaction.
Thanks for your help Remp, that was very encouraging and it actually helped persuade me to continue in my LED project, as it's somewhat frustrating at times to pioneer, as we all know.
You guys with your fancy get it all down on paper idea had him heading for the door. He was ready to give it up. Thats no way to help a guy. Blind people with science. 90 percent of the Video projection ideas here are never put on paper first. Maybe a sketch of the assembly but I guarantee no one sits down and works out the whole thing and the exact amout of light and how exactly it will perform. Otherwise there would be no point to DIY would there. We would all know before hand.
As far as content goes you have overlooked the technical nformation I gave him regarding brightness enhancment. One smart guy said he expected all lcd to have this already built in but thats not necessarily true. Might have. Might not have. So he could be able to use more of his LED light than expected. He said he was only looking for a small increase. That could have been enough. You got to admit thats a valid point.
You say me trying to give him encouragement contributed nothing to the thread. I think you are totally wrong on that. Personally I dont think you understand anything about the human side of encouraging people to be creative and I take strong exception to you or anyone else saying I contributed nothing to the thread.
After my post, here is his reaction.
Thanks for your help Remp, that was very encouraging and it actually helped persuade me to continue in my LED project, as it's somewhat frustrating at times to pioneer, as we all know.
You guys with your fancy get it all down on paper idea had him heading for the door. He was ready to give it up. Thats no way to help a guy. Blind people with science. 90 percent of the Video projection ideas here are never put on paper first. Maybe a sketch of the assembly but I guarantee no one sits down and works out the whole thing and the exact amout of light and how exactly it will perform. Otherwise there would be no point to DIY would there. We would all know before hand.
As far as content goes you have overlooked the technical nformation I gave him regarding brightness enhancment. One smart guy said he expected all lcd to have this already built in but thats not necessarily true. Might have. Might not have. So he could be able to use more of his LED light than expected. He said he was only looking for a small increase. That could have been enough. You got to admit thats a valid point.
You say me trying to give him encouragement contributed nothing to the thread. I think you are totally wrong on that. Personally I dont think you understand anything about the human side of encouraging people to be creative and I take strong exception to you or anyone else saying I contributed nothing to the thread.
remp said:
Here's an old joke my physics prof likes to tell the incoming freshman class during the main university physics class:
A chicken-processing company was having a serious bottleneck trying to pluck the chickens. So they decided to hire someone to build a machine for it. A whole team of engineers worked for weeks and months to no avail. Chickens came in every shape and size, and you really didn't know how the chicken was going to be oriented when they went into the machine. Finally, after the engineers gave up, they hired a single physicist to see if he could solve the problem. The physicist sat down, and only a few hours later came back claiming he had a solution. The people were dumfounded... "How in the WORLD did you come up with a solution that quickly?" The physicist began, "Well, first assume that all chickens are spherical...."
In physics, people don't always work out all the math because they can't. Trying to model the magnetic field accelleration problems of an oddly shaped wire with a ramping current in it is INCREDIBLY difficult. However, physicists don't make startling discoveries off of gut-reactions... they do estimation math and see if it's worth doing a more in-depth study.
Yes, it's important to write it out on paper, but when dealing with estimations and guesses, anyone who's taken a higher-order applied physics course knows that if your answer is within an order of magnitude or two of the expected answer, it's probably right (even though it might be 10x or 100x what's expected). That's because the numbers are so fuzzy when dealing with alot of this stuff. When things are this unsure and the numbers this close, the only thing we can do is see how the real world acts and just try it.
So Alvaius, you helped me keep my feet on the ground. Remp, you helped me push for the stars. Both are necessary, for if you only have one you face either disillusionment with unrealistic expectations or you face discouragement from estimation.
I truly think that despite differences, both of you contribute incredible amounts to the board, and that people of all skill levels have found your posts extremely helpful.
Sincerely,
Clint Herron
HanClinto
You put the whole thing very well. Its true I have an abrasive attutude and its true sometimes I speak up without thinking first.
I have learned something from you mate, and I hope your project succeeds as you want it to.
I apologise to verbose mustafa and alvaius and my good old friend Lifter just in case I pissed you guys off.
You put the whole thing very well. Its true I have an abrasive attutude and its true sometimes I speak up without thinking first.
I have learned something from you mate, and I hope your project succeeds as you want it to.
I apologise to verbose mustafa and alvaius and my good old friend Lifter just in case I pissed you guys off.
More math...
Here's another way I just thought of to do the calculations for a MBVP...
Quoting from this website
we see that
I didn't know that about nits, but I think that's extremely cool. 🙂
Okay. So let's say we've got a 14" LCD screen, 8.5"x11" with a normal brightness of about 200 nits. That screen has an area of 93.5 square inches.
Say we want an image of 6 feet by 4 feet. That's 3456 square inches (an increase in area by a factor of about 37)
Assuming that our optics are pretty good, to get a reflected image of 200 nits off the wall, we'd need our backlight to be about 40 times brighter. A far cry from our 14.4 calculated earlier.
However, if laptop screens are 100 nits, those are a pretty nice brightness, and assuming we did our math from a 200 nit-type CCFL, that means that we'd probably be pretty close to being on track with doing a 14.4 brightness modification. I'm not sure if what I calculated would give us a 50 nit image or a 100 nit image, but either way I think it would be watchable.
Thoughts from anyone?
--Clint
Here's another way I just thought of to do the calculations for a MBVP...
Quoting from this website
we see that
I didn't know that about nits, but I think that's extremely cool. 🙂
Okay. So let's say we've got a 14" LCD screen, 8.5"x11" with a normal brightness of about 200 nits. That screen has an area of 93.5 square inches.
Say we want an image of 6 feet by 4 feet. That's 3456 square inches (an increase in area by a factor of about 37)
Assuming that our optics are pretty good, to get a reflected image of 200 nits off the wall, we'd need our backlight to be about 40 times brighter. A far cry from our 14.4 calculated earlier.
However, if laptop screens are 100 nits, those are a pretty nice brightness, and assuming we did our math from a 200 nit-type CCFL, that means that we'd probably be pretty close to being on track with doing a 14.4 brightness modification. I'm not sure if what I calculated would give us a 50 nit image or a 100 nit image, but either way I think it would be watchable.
Thoughts from anyone?
--Clint
haha
i think its great that clint just goes on with his theories, and calulations and all while you all are arguing. Sorry i had no input, just thought it was entertaining.
i think its great that clint just goes on with his theories, and calulations and all while you all are arguing. Sorry i had no input, just thought it was entertaining.
Are you the hornet's nest?
I don't think so... does that make you the stick? Please don't use sticks in the forum...it's impolite!
zardoz
I don't think so... does that make you the stick? Please don't use sticks in the forum...it's impolite!
zardoz
poohbear said:
poohbear
The stick that stir's the hornets nest, it's not a smart thing to do. The "heated discussion's" have ended with most sides amenable, why add an inflamatory comment?
zardoz
The stick that stir's the hornets nest, it's not a smart thing to do. The "heated discussion's" have ended with most sides amenable, why add an inflamatory comment?
zardoz
I'm really glad that we can end the flames on a good note... but I don't want this discussion to be lost amid the short replies. The thread has gained two pages in just a little over a day, and I don't want people who don't read the forum as religiously as me (like, every few hours... lol) to miss out on giving input to my math equations.
Thanks everyone... I'm still wondering what Alvaius thinks of my equations.
Just to keep everyone updated, I found a good source for 14" LCD monitors for $170 (not including shipping), but as I REALLY want the new Casio Exilim M2 camera... and as I've only got $360 to spend, I think that my money is going towards that instead of the LCD panel for me to dismantle and I'll likely destroy. However I did send in an order for 28 of the 9000 mcd LED's. $1 apiece + $4 shipping off that great site-link (thanks for posting that!), so I'll let everyone know hot my modified laptop backlight turns out if I can take my laptop apart and get it back together again. 🙂
I'm not sure if 28 LED's will be enough... I think it'll be a little on the low side of a projected image, but if it works, holy cow that would be sweet. 🙂 I'm not going to worry about color-mixing just yet, as I like the idea of mixing RGB LED's to get my own white balance.
*sigh* I was talking to my mom today (college students do that from time to time), and she asked me if I really was going to watch TV all that much... if I spent $200 on a flat panel that I was just going to dismantle... not counting the $160 or so that I've already dumped into the project... wait... make that more like $220... and the answer is no. 🙂 I've got a TV in my room that I turn on just because it's more of a novelty for me to have a TV... it's not something I do that much. Nor do I watch that many movies. I think it's really just the fun of making the projector for me... that's just cool. 🙂 I'll turn it on and watch movies on it, more for the fun of just being awed by what I built more than the actual movie. 🙂 I'll probably interrupt everyone with comments like "See that pixel definition" or "My optics were a little sketchy at first, but they worked out nice!" or "You'd never believe how I solved this one projection problem...", then everyone would get mad. lol. Sorry. You just saw a little bit into the workings of my mind there.
If nothing else, this project has definately shown me what I want to do for the next few years after I graduate in a few months.
I think I want to work in research and development for a company that will give me a budget, and let me play to improve products or invent new ones. 🙂 However, I have no idea how things like that work. I just don't want to get stuck in manufacturing. Once I learn something, I'm bored with it and I want to drop it. Like game programming. I wanted to learn that, so that's what I did in high school. I'm pretty confident I could sit down and program a game pretty quickly now... but where's the fun in that? There's nothing new with it for me really. So I skip to some new techy thing and do that. I think that working in R&D would be great for me, as I could learn about new things and work at combining different areas of science and technology in making or improving existing technology. I think that's so cool. 🙂
Anyway, that's just an update of my stuff so that everyone knows where I'm at, and plus because my friends here at college are philosophy or business or computer science, and they don't really care about the techy stuff of soldering and wires and optical lenses... yeah. I bore them if I talk at them about that, so I just talk about normal stuff.
Keep the wheels of imagination turning!
--Clint
P.S. Just in case y'all didn't know, my picture is a shrunk and cropped version of a larger ad I found one time of a guy on a unicycle wearing a lab coat carrying two test tubes and a caption of "Never Sit Still"... I think that guy is incredibly cool. 🙂 (and yes, I ride a unicycle to class)
Thanks everyone... I'm still wondering what Alvaius thinks of my equations.
Just to keep everyone updated, I found a good source for 14" LCD monitors for $170 (not including shipping), but as I REALLY want the new Casio Exilim M2 camera... and as I've only got $360 to spend, I think that my money is going towards that instead of the LCD panel for me to dismantle and I'll likely destroy. However I did send in an order for 28 of the 9000 mcd LED's. $1 apiece + $4 shipping off that great site-link (thanks for posting that!), so I'll let everyone know hot my modified laptop backlight turns out if I can take my laptop apart and get it back together again. 🙂
I'm not sure if 28 LED's will be enough... I think it'll be a little on the low side of a projected image, but if it works, holy cow that would be sweet. 🙂 I'm not going to worry about color-mixing just yet, as I like the idea of mixing RGB LED's to get my own white balance.
*sigh* I was talking to my mom today (college students do that from time to time), and she asked me if I really was going to watch TV all that much... if I spent $200 on a flat panel that I was just going to dismantle... not counting the $160 or so that I've already dumped into the project... wait... make that more like $220... and the answer is no. 🙂 I've got a TV in my room that I turn on just because it's more of a novelty for me to have a TV... it's not something I do that much. Nor do I watch that many movies. I think it's really just the fun of making the projector for me... that's just cool. 🙂 I'll turn it on and watch movies on it, more for the fun of just being awed by what I built more than the actual movie. 🙂 I'll probably interrupt everyone with comments like "See that pixel definition" or "My optics were a little sketchy at first, but they worked out nice!" or "You'd never believe how I solved this one projection problem...", then everyone would get mad. lol. Sorry. You just saw a little bit into the workings of my mind there.
If nothing else, this project has definately shown me what I want to do for the next few years after I graduate in a few months.
I think I want to work in research and development for a company that will give me a budget, and let me play to improve products or invent new ones. 🙂 However, I have no idea how things like that work. I just don't want to get stuck in manufacturing. Once I learn something, I'm bored with it and I want to drop it. Like game programming. I wanted to learn that, so that's what I did in high school. I'm pretty confident I could sit down and program a game pretty quickly now... but where's the fun in that? There's nothing new with it for me really. So I skip to some new techy thing and do that. I think that working in R&D would be great for me, as I could learn about new things and work at combining different areas of science and technology in making or improving existing technology. I think that's so cool. 🙂
Anyway, that's just an update of my stuff so that everyone knows where I'm at, and plus because my friends here at college are philosophy or business or computer science, and they don't really care about the techy stuff of soldering and wires and optical lenses... yeah. I bore them if I talk at them about that, so I just talk about normal stuff.
Keep the wheels of imagination turning!
--Clint
P.S. Just in case y'all didn't know, my picture is a shrunk and cropped version of a larger ad I found one time of a guy on a unicycle wearing a lab coat carrying two test tubes and a caption of "Never Sit Still"... I think that guy is incredibly cool. 🙂 (and yes, I ride a unicycle to class)
Lesson from photography
HanClinto,
I just thought I'd stir the pot a wee bit...there's another factor to consider in the calculation of light intensity versus area: the distance from the screen to the projector.
As one projects a light, the intensity falls significantly. I cannot recall the formula, but it is like the inverse square laws affecting power....I'll do some searching...
Found it: the light intensity drops as the inverse square of the distance from the source. Essentially, one also must factor the projection distance into the expected intensity at the screen.
Bob
Great stuff folks, keep working on it!
HanClinto,
I just thought I'd stir the pot a wee bit...there's another factor to consider in the calculation of light intensity versus area: the distance from the screen to the projector.
As one projects a light, the intensity falls significantly. I cannot recall the formula, but it is like the inverse square laws affecting power....I'll do some searching...
Found it: the light intensity drops as the inverse square of the distance from the source. Essentially, one also must factor the projection distance into the expected intensity at the screen.
Bob
Great stuff folks, keep working on it!
You are correct that the brightness falls significantly... a 200 NIT image on my laptop screen projected would not be 200 NITS on the wall... assuming I had a wonderfully reflective surface I think the brightness of the image on the wall would be:
LCDBrightness * ProjectedImageArea / SourceImageArea
I think that's roughly correct, and might be a decent way to do rough calculations for screen brightness based on your LCD intensity.
Comments anyone? Just at the end of page 3 is where I did the majority of these calculations... you can check my math there. I really have no idea if this is correct.
--Clint
LCDBrightness * ProjectedImageArea / SourceImageArea
I think that's roughly correct, and might be a decent way to do rough calculations for screen brightness based on your LCD intensity.
Comments anyone? Just at the end of page 3 is where I did the majority of these calculations... you can check my math there. I really have no idea if this is correct.
--Clint
Clint,
Your math for projector is accurate. The brightness will drop by the inverse square of the distance. So if you project an image twice as far away, it will be 1/4 as bright (and 4 times bigger).
Compared to a single CCFL, you should be able to achieve higher brightness along a line LEDS than with a CCFL. However, you need to be real careful with LED brightness ratings. Candela is a spot measurement and may not give you a good indication of the Lumens (real LED brightness), even when the illumination angle is given. I would find out from the person supplying the LEDS, who the LED is really made by and get the full data sheet. For 5mm whites, Nichia makes the brightest today under long life drive applications. You will see some competitive products in next few months that are truly comparable. Toshiba is pretty good as well I find. However, you may be able to achive good consistency and much cheaper using a RGB. You may also get better efficiencies through the filters.
I found that paper I was looking for. It should be useful for you. It was in one of my SID books, but I found the link on the Lumileds\Luxeon site:
http://www.lumiled.com/pdfs/techpaperspres/sid2001.pdf
You may find their estimate of the cross-over of LED and CCFL technology for brightness a little optimistic, but probably only by a year or so.
Good Luck,
Alvaius
Your math for projector is accurate. The brightness will drop by the inverse square of the distance. So if you project an image twice as far away, it will be 1/4 as bright (and 4 times bigger).
Compared to a single CCFL, you should be able to achieve higher brightness along a line LEDS than with a CCFL. However, you need to be real careful with LED brightness ratings. Candela is a spot measurement and may not give you a good indication of the Lumens (real LED brightness), even when the illumination angle is given. I would find out from the person supplying the LEDS, who the LED is really made by and get the full data sheet. For 5mm whites, Nichia makes the brightest today under long life drive applications. You will see some competitive products in next few months that are truly comparable. Toshiba is pretty good as well I find. However, you may be able to achive good consistency and much cheaper using a RGB. You may also get better efficiencies through the filters.
I found that paper I was looking for. It should be useful for you. It was in one of my SID books, but I found the link on the Lumileds\Luxeon site:
http://www.lumiled.com/pdfs/techpaperspres/sid2001.pdf
You may find their estimate of the cross-over of LED and CCFL technology for brightness a little optimistic, but probably only by a year or so.
Good Luck,
Alvaius
Sweet!
Interesting read Alvaius.
What is your opinion of my calculations a page or so back... the one where I equivocate a CCFL to a row of LED's 625 mcd in brightness, and find a row of 9000 mcd LED's would make the backlight 14.4x brighter? Is that what you were referring to when you mentioned I should see who manufactures these LED's in order to etermine the accuracy of their brightness claims?
Thanks!
--Clint
Interesting read Alvaius.
What is your opinion of my calculations a page or so back... the one where I equivocate a CCFL to a row of LED's 625 mcd in brightness, and find a row of 9000 mcd LED's would make the backlight 14.4x brighter? Is that what you were referring to when you mentioned I should see who manufactures these LED's in order to etermine the accuracy of their brightness claims?
Thanks!
--Clint
I looked over your calculations again. There is one point that may be missing. The CCFL radiates 360 degrees and when implemented it will have a reflector around it that concentrates the light towards the backlight. That will increase the light output several fold from your calculations I think. However, as remp has pointed out, sometimes you need to just try it. Perhaps you can get access to a dead LCD and start playing around with those LEDS.
Alvaius
Alvaius
Ah, so having a reflector can double (or maybe more) the effective output of the CCFL... that would mean instead of 14.4 it might be closer to 7x brighter... still not bad, but nothing as bright as I would want it to be.
When the LED's come in the mail, I'll wire them up and modify my laptop with them to see how it all works. I'll keep everyone posted.
--Clint
When the LED's come in the mail, I'll wire them up and modify my laptop with them to see how it all works. I'll keep everyone posted.
--Clint
Clint, how do you plan to power 28 leds? I belive each should be around 3 volts, but I'm not exact. Keep in mind these are low current too.
http://www.exabytesystems.com/produ...id=29&osCsid=ede039008d758c005f177de91cd8e253
Size: 5mm
Forward Voltage: 3.5V
Reverse Voltage: 5V
Current: 50mA
Viewing Angle: 20
Brightness: 8000-9000mcd
Most high-brightness LED's have a viewing angle of 15 degrees, 20 degrees isn't a whole lot more but makes for more light output in the LED overall.
3.5 volts... wonder what combinations I would have to do to make a good circuit with 28 of them...
--Clint
Size: 5mm
Forward Voltage: 3.5V
Reverse Voltage: 5V
Current: 50mA
Viewing Angle: 20
Brightness: 8000-9000mcd
Most high-brightness LED's have a viewing angle of 15 degrees, 20 degrees isn't a whole lot more but makes for more light output in the LED overall.
3.5 volts... wonder what combinations I would have to do to make a good circuit with 28 of them...
--Clint
I was going to do a combination of both and try to fit it into one of the wall-transformer voltages for the various ones I have laying around. Probably try and do 12 volts, as I have a nice 1 amp power supply that's extra for that.
Equal voltage drops in parallel halve the voltage, equal voltage drops in series double the voltage. Put 3 in parallel and it thirds the voltage drop, put 7 it's 1/7th, etc.
3.5 * 7 = 24.5 volts
24.5 volts / 4 = 6.125 volts
Wonder if I have an extra 6 volt souce... that would be 4 strings of 7 in parallel with each other.
I could do 3.5 * 4 / 7 and have 7 strings of 4 in parallel, and that would need 2 volts, but I like the 6 volt option better.
I *could* order another set of 28 and wire them in series, then run it off a 12 volt source.
50 ma * 3.5 volts = .175 watts per LED
28 LED's * .175 watts = 4.9 watts
4.9 watts / 6 volts = 817 mA draw
Not too bad. Quite alot for a light source... now I see what everyone was talking about when they said LED's suck for effeciency compared to CCFL's... but I'm plugged into a wall. What do I care? 🙂 (I don't have an electric bill in the dorm either... I could run a full-size coin-op video game or huge pop-machine in my room and not pay a dime more than I do now)
--Clint
Equal voltage drops in parallel halve the voltage, equal voltage drops in series double the voltage. Put 3 in parallel and it thirds the voltage drop, put 7 it's 1/7th, etc.
3.5 * 7 = 24.5 volts
24.5 volts / 4 = 6.125 volts
Wonder if I have an extra 6 volt souce... that would be 4 strings of 7 in parallel with each other.
I could do 3.5 * 4 / 7 and have 7 strings of 4 in parallel, and that would need 2 volts, but I like the 6 volt option better.
I *could* order another set of 28 and wire them in series, then run it off a 12 volt source.
50 ma * 3.5 volts = .175 watts per LED
28 LED's * .175 watts = 4.9 watts
4.9 watts / 6 volts = 817 mA draw
Not too bad. Quite alot for a light source... now I see what everyone was talking about when they said LED's suck for effeciency compared to CCFL's... but I'm plugged into a wall. What do I care? 🙂 (I don't have an electric bill in the dorm either... I could run a full-size coin-op video game or huge pop-machine in my room and not pay a dime more than I do now)
--Clint
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