For those of you who stumble upon this instructable, a bit of history is mandatory in order to better understand my goals with this LED projector lamp. Therefore I recommend you first read the LED Projector Lamp v.1.0 instructable I posted a while ago. Check back when you’re done for this second part of my adventure.
For this version of the projector lamp I knew I had to find a way to at least double the amount of light on the projection screen. As high-power LED’s are very expensive parts around here (I live in Sibiu, Romania) I wanted to try making my own LED array. I chose the NS6W183T LEDs from Nichia. For those of you who don’t know, Nichia is a Japanese company that produces high quality LEDs and were the first to invent the high power blue and white LEDs back in the 90’s. These LEDs were available around here and the light output was tempting.
This instructable is not yet finished. Also the timeframe on this project is unspecified. I'm publishing its progress because I need other user's opinion on some matters in order to finish it. If you think you have something truly valuable to add to this project, be my guest and share you opinion in comments. I'll try to answer them all.
Step 1: Bill of Materials
My choice for the NS6W183T LEDs was based mainly on the light output & size. These are SMD components and for their size they put out an amazing 245 lumens each (when powered with If=700mA). I had to settle for an array of 9 LEDs, mainly because of the price involved. My hobby budget is very limited. Even so I paid about 55 Euro or 66 USD on these LEDs. Expensive for Romania, cheap for everyone else. The main goal is filling the entire projector condenser lens with light and the array does just that. There’s a problem though. The SMD LEDs I got have the light beam spread at 120 degrees. I had no choice but to go with that, in hoping that I’ll find a way to focus this light somehow.
The cooler selected (see the Cooling step) was 87 RON, that’s 24.5 Euro or 25.5 USD. I got this one because no matter the outcome of this lamp project I’ll still have a future use for it. The rest are scavenged parts, not really worth mentioning. People in the DIY community knows the importance of dumpster dives.
Final cost of materials so far is around 100 Euro, give or take. One more failed project and I’ll get to hear my wife saying “you know, you could have bought that original lamp already, given the already spent amounts”. Now that’s what I call painful irony.
Step 2: Making the LED Array
The array was made as compact as possible so as to avoid having a too dispersed light generating area. That’s because all the projectors light originates in a single point. With arrays you get several and the challenge is to focus them all in one spot. I will deal with this later, for now it’s a long way until then.
The 9 NS6W183T LEDs are arranged in series, on a custom made PCB board that’s 3x3cm. The LEDs are soldered in the center of this board, inside a 2x2cm square. I could have made it smaller but I can’t solder SMD components using reflow soldering, all had to be done by hand using a soldering iron. Each Led was checked for polarity, glued on the board using Arctic Silver Thermal Compound glue and soldered quickly and carefully. You don’t want to cook the LEDs too much, they are so fragile when it comes to temperatures. My goal is to transfer the LED-generated heat to the PCB and then further to the cooler behind the plate. Four screws will hold the PCB onto the cooler thus avoiding PCB warpage and thermal paste will be used in between the PCB and the cooler.
After all the LEDs were soldered on the board, a quick power check ( a few seconds) proved the array was operating properly and the light output was huge. If you make the mistake of looking into the LEDs (like I did) I guarantee you’ll see nine dots of light for a long time. Hopefully I’ll make good use of this very uniform light.
Step 3: Numbers
9 LEDs like the one I’m using will require 700mA at 31.5V for a total amount of 22.05 Watts of consumed power. Under these parameters I should be getting at least 2025 lumens. Provided I can keep the LEDs temperature under 70 degree (Celsius) I could then try and power them at 800mA and then I’ll be getting 2340 lumens. I assume the light losses inside the projector will cut this output in half. My goal is to use this projector in its original eco-mode, when the lamp output was only 1000 lumens. Hopefully, I’ll now get closer to that than the last time I tried. I’ll be using the same power supply I was using for the lamp v.1.0, it’s a 700mA constant current power supply. It outputs up to about 30V so I will be close to its maximum rated power output. Checking with a multimeter, the current was indeed steady at 700mA but the voltage was only 29.2V. Good enough for initial tests.
Step 4: Cooling
Another concern is the dissipated power, each LED is rated at 3.2W of dissipated power. That sums up to 28.8 Watts of heat I need to get rid of. Given the confined space inside the projector (5x5x9cm) I had to find a cooler that would fit inside this space. A very extensive Google image search made clear that the best option for me was the Nexus NHP-2200 chipset cooler. This one is using heatpipe technology to cool down computer chipsets. It’s made entirely out of copper and it fits the space available while the cooling fins are exactly where I wanted them, in front of the projector’s cooling fan. This cooler is truly a beautiful one, I tried handling it with gloves to avoid fingerprints all over it. The cooler base came a bit oxidized already but that won’t affect its performance, just the overall looks. The tricky part will be to make it cool the LEDs as the PCB I’m using should have been made of metal but I don’t have such technology at my disposal. I’m counting on the projector fans, there are two in front and a big one for the backside of the bulb. Hopefully these will help keeping the temperatures under control.
Initial tests proved the LED array is getting hot really fast, without cooling the array the PCB is too hot to touch in under a minute. The temperature probe on my multimeter reached 70 degrees (Celsius) in a few seconds but this was without the projector fan’s cooling. I have no way of checking the array with the projector’s cooling just yet so I’ll just go ahead with it. Hopefully I won’t fry the LEDs too soon. The Nexus cooler works, it also got warm in a minute but the heat transfer between the array PCB and the cooler’s base was slower than expected. By the time this cooler warms up, the LED array is too hot already. Man I wish I had one of those metal PCBs… The three projector fans should help, at least that’s what I’m hoping.
Step 5: Casing
Believe it or not, to me this was the hardest and most labour-intensive part. As the entire LED conversion should be non-destructive and I had no original bulb at all, I had to replicate as best as I could the original frame and mounting points. There are two mounting screws inside the projector and a few plastic pins to be considered. None of them was in line with the others. Therefore I had to measure all I could measure inside that little space inside the projector and try to make a mock-up of my lamp casing out of cardboard at first, to check the measurements. A few cardboard models later I had all the correct distances. The PCB board I used for this casing is a great material to work with as it’s strong, can be soldered in 90 degrees angle easily and will hold firmly in place all I can put inside that frame. The hardest part was to cut the PCB board into the various shapes needed to assemble the casing. I used a tiny jigsaw and all I can say about that is that it was one painful experience.
Step 6: Light Control
As this array is square in shape I have no way of using a round reflector like the one I used on my v.1.0 lamp. So I’ll make a square one out of thin aluminum sheet. It will also control the light spills as that would disturb the projection experience. A second benefit of this aluminum reflector is that it would also double as a heat sink because its base will touch the LEDs thus taking away some of the generated heat. So it’s more a matter of controlling the light spills than directing the light beam, because, as I mentioned before, the LEDs have a 120 degrees light beam, I have no real way of focusing that too much. Lens are useless here because I have 9 separate light sources spread on a 2x2 cm. Fresnel lens are also not available around here. I was thinking of using tiny CD-ROM lens (from the optical heads) for each LED but those tiny lens have a very short focal distance.
This is where this project got stuck. I made a few attempts to use this lamp in the projector. The light output was bad. I have lights spills all over the place. The light output is blinding but I have no way to control it. The projected image is even weaker thant the one I did with the LED projector lamp v1.0. I blame the beam angle. If I can somehow find a way to efficiently focus this square LED array I believe the end result would be a success. But so far nothing worked. Maybe this forum will help me find the answer and this is why I'm posting this unfinished project. (and to get rid of the ones asking about its status) Ok, I'm just joking.
UPDATE: This LED Light bulb version is cancelled. Due to time restraints and the lack of encouraging results, I'm postponing this project until I can come up with something better. When I do, Instructables will be the first place to read about it, so stay tuned. Meanwhile the v.2.0 version is my new bathroom light. :-) Perfect white and high brightness, it's like a operating room in there.