Something to think about with those wall transformers.
Most of them are not switched and their voltage output may vary depending upon load, heat, etc. You need to make sure that the power source that you choose gives you 3.5 volts to each LED all of the time.. 5 volts will shorten the life and probably change the color of the LED, something that we do not want with them costing 1 dollar each.
You might want to look for a voltage regulator that will supply exactly 3.5 volts all of the time, and it has to be able to handle the load of 1.4A that the 28 LEDs will draw,(I think that is right, 28 * 50mA) plus some extra.
Also having 28 LEDs in such a small area is going to generate some heat that could mess up the LCD or shorten the life of the LEDs. When you solder them on a board you may want to figure out some way of connecting them to a heatsink. This probably does not need to be done just for testing but as you work on it have it in mind because it will need to be done sooner or later.. it will not probably take much to get rid of the heat, but it may need to be done. Might have to play it by ear and see if it needs done or not.
Most of them are not switched and their voltage output may vary depending upon load, heat, etc. You need to make sure that the power source that you choose gives you 3.5 volts to each LED all of the time.. 5 volts will shorten the life and probably change the color of the LED, something that we do not want with them costing 1 dollar each.
You might want to look for a voltage regulator that will supply exactly 3.5 volts all of the time, and it has to be able to handle the load of 1.4A that the 28 LEDs will draw,(I think that is right, 28 * 50mA) plus some extra.
Also having 28 LEDs in such a small area is going to generate some heat that could mess up the LCD or shorten the life of the LEDs. When you solder them on a board you may want to figure out some way of connecting them to a heatsink. This probably does not need to be done just for testing but as you work on it have it in mind because it will need to be done sooner or later.. it will not probably take much to get rid of the heat, but it may need to be done. Might have to play it by ear and see if it needs done or not.
Playing with chickens
Assuming we have a LCD that had a 8" CCFL, couldn't we replace the CCFL with ~ 40 leds? I realize they would produce heat but I think it would be nominal.
Clint, do you think that would produce enough nits to have a "quality" image if you used say a semi reflective surface to project onto (silver metalic fabric, maybe)?
I'm curious to know if the 40 leds would be bright enough to suffice.
-HollywoodBob
PS did your 28 leds work ok?
Assuming we have a LCD that had a 8" CCFL, couldn't we replace the CCFL with ~ 40 leds? I realize they would produce heat but I think it would be nominal.
Clint, do you think that would produce enough nits to have a "quality" image if you used say a semi reflective surface to project onto (silver metalic fabric, maybe)?
I'm curious to know if the 40 leds would be bright enough to suffice.
-HollywoodBob
PS did your 28 leds work ok?
Update on the 28 LED's that I got...
Well I got them in the mail... and I also got all the parts needed to make my OTHER projector setup (the OHP and panel one) working... and it honestly kicks butt. 🙂 I'm modifying my OHP with another fresnel so that I can get a 6 foot image with about a 8 foot projection length, and it'll work fantastic in my dorm room. I think I'm just gonna' sell my LED's and my artograph and my 5.6" LCD and all that other wonderful stuff that I sunk money into over the past couple months and find a new project to work on.
I'll prolly keep some of the LED's and modify one of my frisbees for use in Ultimate Frisbee night games... that would look cool. 🙂
I just really can't justify sinking $200 into a LCD flat panel monitor when I don't really even watch TV. I just think the whole engineering aspect is really cool, and that's more of why I'm in the project.
I might still modify my laptop with the 28 LED's, but that's just time that I don't have right now as senior projects have been consuming my time this week.
Just to keep y'all updated.
--Clint 🙂
P.S. The option I get really excited about would be putting 40 CCFL's in place of the backlight, and just running a cooling fan through there (or even casting them in a heat-conductive clear acryllic and cooling that)... and lighting the backlight with that. That would be sweet, and with $2.50 per CCFL, it's more economical than LED's (and better color temperature also).
Well I got them in the mail... and I also got all the parts needed to make my OTHER projector setup (the OHP and panel one) working... and it honestly kicks butt. 🙂 I'm modifying my OHP with another fresnel so that I can get a 6 foot image with about a 8 foot projection length, and it'll work fantastic in my dorm room. I think I'm just gonna' sell my LED's and my artograph and my 5.6" LCD and all that other wonderful stuff that I sunk money into over the past couple months and find a new project to work on.
I'll prolly keep some of the LED's and modify one of my frisbees for use in Ultimate Frisbee night games... that would look cool. 🙂
I just really can't justify sinking $200 into a LCD flat panel monitor when I don't really even watch TV. I just think the whole engineering aspect is really cool, and that's more of why I'm in the project.
I might still modify my laptop with the 28 LED's, but that's just time that I don't have right now as senior projects have been consuming my time this week.
Just to keep y'all updated.
--Clint 🙂
P.S. The option I get really excited about would be putting 40 CCFL's in place of the backlight, and just running a cooling fan through there (or even casting them in a heat-conductive clear acryllic and cooling that)... and lighting the backlight with that. That would be sweet, and with $2.50 per CCFL, it's more economical than LED's (and better color temperature also).
HanClinto,
I am about to work on my projector. Need to select a light source. I am interested in using a LED array. So I am curious about your result with LEDs. Is it bright enough that is comparible to the lamp in OHP? How are the pictures produced by each setup? If you could provied some snap shots for comparison, it would be wonderful. thanks!
I am about to work on my projector. Need to select a light source. I am interested in using a LED array. So I am curious about your result with LEDs. Is it bright enough that is comparible to the lamp in OHP? How are the pictures produced by each setup? If you could provied some snap shots for comparison, it would be wonderful. thanks!
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