Retrofitting LCD projectors with high-powered LEDs

highpower_led

[Devon] recently repaired a handful of Phillips LCD projectors which he was quite excited to use. The only problem is that he didn’t want to mess with replacing the bulbs after every 2000 hours of use at $100 apiece. He was pretty confident that he could find a better way to drive the projectors, so he disassembled them once more and started looking around for bulb replacements.

He figured that a high-powered LED would do the trick, so he ordered a handful of parts and went about his first retrofit. Using his oscilloscope, he found that the control board pulses the high voltage board when the projector is powered on, and continues to pulse a signal until the machine is turned off. At this point, the HV board powers down the bulb.

He created a small circuit using a PIC that is used to interpret the initial pulse from the control board as well as watch for the steady “heartbeat” pulses that occur while the projector is powered on. This board is used to control the driver board for the high-powered LED he purchased.

His bulb replacement works well as far as color fidelity is concerned, but is not nearly as bright as he hoped for. He has plans to source some far brighter LEDs or automobile HID lighting in the very near future, and we look forward to seeing if he can match the brightness of the original bulbs.

50 thoughts on “Retrofitting LCD projectors with high-powered LEDs

  1. He doesn’t say what LEDs he is using, but Dealextreme has some nice high power LEDs for cheap, I’ve seen some white ones over 900 lumens.

    Also, if he is using white, could that be the brightness problem? If he used some high power RGB LEDs instead, that would probably help.

  2. I wonder if he could increase the power by instead making an LED source that is not White, but a mix of powerful R/G/B LEDs. You are losing a lot of lumens form the conversion of the UV/blue LED->Phosphor->LCD color filters. Cut the phosphor conversion out of the picture.

  3. I he didn’t have to send anything back, then why did he have to use a PIC?

    Two transistors and a capacitor would have done the job.

  4. Good idea Erik.

    Also even if he ends up resorting to automotive HID lighting, that’s still a big improvement from real projector bulbs in cost. I wonder how much power it would use vs. the stock bulb though.

    The power control system seems unnecessarily overcomplicated, if the LED power system is completely separate, why not just put it on a relay triggered by some other power circuit?

  5. @Erik: The LCD absorbs something like 90% of the visible light passing through regardless whether it is white from phosphors in a white LED or white from a mixture of red, green and blue LEDs.

    There was a nice project in Elektor a while ago where a guy retrofitted a DLP projector with RGB leds but he did away with the spinning oclor filter disk. In theory 100% of the light gets though to the screen, although the duty cycle of each color is still only 33%.

  6. @Erik – If he were to use separate Red Blue and Green LEDs, there would be no reason to cluster them in the same housing. Assuming his projector splits the single source light into three beams which are then filtered with RGB LCDs and then put back together, it would be easier to make three separate reflectors, one for each color. However, in thinking about it, this really depends on whether the LCDs are colored or black. If they are black, then this would work. However, if there is a red, a blue, and a green LCD, putting a colored filter in front a similarly colored light will have no effect, so it would only make sense to begin with a white source.

    That all being said, I believe that this would look HORRIBLE in respect to color rendering. If you have ever mixed Red, Green and Blue LED light to make white, you will know how bad it looks. This is due to LEDs producing only a narrow band of wavelengths. No matter how you mix those narrow bands, you will be missing all the wavelengths in between them, which makes the color look muddy to the human eye (which is actually being tricked into seeing a color that does not exist).

  7. @dax

    the projector controls the light source by giving a 5 second pulse, followed by a square waveform pulse of 1 ms, the high voltage board gives an active low signal to the control board… i wanted the projector for function exactly as it did with a regular bulb, without any extra switches or knobs

    i tried doing this using transistor logic and a 555 as a latch but wasn’t able to get it working the way i wanted to, i went with a pic micro controller simply because i haven’t used them before and wanted to expand the range of micro controllers i could use

    @by_matt i actually used an led emitter, reflector and power supply from dealextreme… i guess i forgot to mention that, the parts can be sourced anywhere really

  8. What about the LEDs? They don’t put out the full spectrum of white light do they? I actually think that LEDs are the WRONG light for this application.

    (Not to mention it’s very foolish to think they would be bright enough)

  9. @by_matt
    This is probably the 25W white 2000 lumen unit. They run about $30 on eBay. !00w 8000 lumen untis are available for ~$75. Basically these are arrays of 1W LED dies. The downside is that UHP lamp based projectors have a limited entendue (i.e.area x angle of emission) which leads to diminishing returns at some point.

    RGB LEDs would be better if they were matched to the interference filters in the light engine.

    Increasingly, UHP bulbs are the ink cartridges of the projector world serving as the profit center on cheap projectors.

  10. @xeracy the original lamp is a 120watt uhp lamp providing about 1000 ansi lumens at 6500k

    the light passes through a prism, several lenses and an array of polarized beamsplitters and polarized filters to produce discrete rbg sources for each lcd, which is them passed through a polarized combining prism and to the projection lens

    i had though of bypassing the beamsplitters entirely and having a red blue and green led directly illuminate the lcd panels through the polarized filters and collimator lenses

    i might try that at a later date when i get another 3 lcd projector to play with

  11. @dcroy- I wouldn’t recommend using RGB LEDs. The color you get when the three sources are mixed will look GHASTLY. Filter white light, it will look the best, be it LED or not.

  12. Question, since we’re talking about spectrum of blue light + phosphor versus actual rgb sources, would there be any improvement to adding more of the phosphor? Source it from cfl bulbs :D

    Also,@monopole, Dealextreme has recently acquired higher efficiency white LEDs (>80 lumens/watt), which was why I mentioned it. They are still the multi-1W-modules, but with better modules on them.

    I’ve also seen high power red, green, and blue leds for cheap, so if dcroy goes with that idea (bypassing the splitters), I’d definitely like to hear an update.

  13. @GameboyRMH from the blog “powering the led comes to about 30 watts, one quarter of the power consumed by original bulb” To address your power consumption question.

  14. Nice finding the heartbeat pulse, when I tried this I just soldered some wires to the pcb joint where the AC wire attached and added a separate switch in the case.
    On the LCD projector that I’ve worked with, the bulb shines a light down a corridor which uses mirrors to split the light into three different paths, which then shine through 3 lcd screens, and are focused again through the lens as a composite image. I was planning, but haven’t had the time, to remove the colored mirrors and just put three high powered LEDs behind each LCD. The benefit: You have room to fit in 3 LEDs instead of just one, and save on the light lost to the filters. Though you probably should have some sort of diffuser to avoid vignetting.

  15. @xeracy very true, I hadn’t thought about directing them at their respective panels skipping the splitters!

    I understand that LEDs typically only output 1 fixed wavelength, so your colors may be off doing so unless your projector allow you to tweak the individual levels (service menu?). If possible remove the color filters, too…

    I believe some DLP TVs use separate RGB LEDs in place of a color wheel/lamp combo, maybe you could source those somewhere…

  16. i bought a ezpro 550 on ebay for $30, i need to either a: buy a 400 watt, 36 volt bulb for it(under $10 and life from 50-500 hours or b: retrofit, sofar a 50w car headlight produces an acceptable 20-30 inch image but who buys a projector for that?
    thinking chinese car HID retrofit kit($30 or so)
    the nice thing about this projector, the lamp has NOTHING to do with the lcd hardware, as long as a light source is provided it will project
    sadly, full size HID wont work without some fancy lenses(thinking about trying some mirrors and having a “base” the projector sits on containing a 400w metal halide that bends around to the light input(front of the projector)

  17. When I worked at Christie Digital they were just coming out with their LED projectors. They were the one engineers baby. The heatsink for the LED was massive. But at least it didn’t need forced cooling the same way the multi killowatt xenon bulbs did. I wish I knew more about it, but I didn’t have access to its schematics :(

    But LED projectors are a realistic solution. It’s just a matter of multi hundred lumen LEDs and adequate heatsinking.

  18. oh, also, the die up /\ looks like a standard 100w “led” on ebay, they are down to $50/shipped from hond kong actually, anyone know if theres higher wattages available like 150 or 200?
    leds are <3

  19. I did this with a 1000 lumen panel from Dealextreme, and i got about 10 lumen out the other side.

    wound up using the led bank and heatsync as a worklight.

  20. If I may:

    I wouldn’t trust any of the ratings on brandless “High-Brightness” LEDs sold at Deal Extreme and eBay. Its obvious that most ratings are exaggerations.

    Currently, the brightest LED you can buy are those from the PhlatLight series, produced by Luminus (http://www.luminus.com/). Currently, they have 50w, 90w, and even 360w LEDs in production, and they are very popular in the homemade flashlight building community. With proper heatsinking, people have pushed 10+ amps through these LEDs to reach incredible brightnesses.

    While the LEDs from Luminus cost a fair bit more than those from DealExtreme, you will certainly get better performance, and its possible to build a bulb for the same price that would last 5 times as long.

  21. I’m glad to see someone with some reasonable success at this!

    the collimator lens is probably the most critical part of this. Lucky for him to have one on hand!

    great project

  22. The problem with using a bulb like this is even with the reflector, it’s still got a WIDE beam, and most projectors need the light collimated (parallel) and focussed on at most 2-3 square cm, particularly for dlp with a colour wheel.

    The original bulb has a central emitter in a parabolic reflector to create the required light. The LED spits out 180 which gets focussed down a bit, but you still need another collimating lens to REALLY make use of the light coming out, otherwise it’s mostly wasted.

    My projector is dying and when it does, I’ll be doing a 100w retrofit. I will have to use a reflector to get the light into a somewhat conical shape, then a collimator to get it down to the tiny colour wheel hole.

    Lastly, it would be awesome to use an ‘rgb’ source, but they never exceed 10w in my experience, and you need to make sure the dies are close, diffused, and mixed properly before entering the light path or you’ll have uneven lighting of each colour. Then it would be trivial to interpret the colour wheel encoder signal with an mcu to pulse the correct colour while the wheel is physically removed. This is how the pocket projectors work.

  23. “why did he have to use a PIC?
    Two transistors and a capacitor would have done the job.”

    You must be new here.

  24. the collimator lens i had wasn’t perfect but was the right size

    one thing i was thinking of was using a Fresnel lend to get most of the light going in one direction, quite a bit is being wasted by spilling out in all directions even with the reflector and lens, although both helped considerably

  25. Well done!

    I have the same plans for a philips hopper sv10 which is resting somewhere in my storage… I’ve been thinking of HID 4300k kit with 50watts consumption.

  26. i also have a hopper sv10 that i replaced a burnt out polarizer on, and a second one that drove me up the wall trying to align the beam splitters on (really not worth the effort to, quite maddening really)

    the interface should be identical but the hv board is harder to get at and requires taking apart most of it to remove

    the control interface will be a thin bundle of 3 wires going from somewhere on the right side of the lower control board to the hv board

  27. Another, more immediate concern for some projectors I’ve seen out there: the blue filter tends to “burn” or change in opacity due to exposure to UV emitted by typical projector bulbs. I have no idea how much UV is emitted by LEDs, but I would like to think that going full-LED from the start would be a great way to get a lot of mileage out of a new projector.

  28. It is always going to be a compromise, LED’s with good clour rendering have significantly lower light output, so you may need a few more than with something with a low Ra.

  29. Cree has a newish LED, I don;t see it on their website, but managed to get 3 samples from them, The CXA20 is an 11W 42V, 270mA LED pushing 1040lm with a CRI rating of 78, there is also a 900lm version with a CRI rateing of 82, illustrating my earlier comment. These are realy impressive LEDs, I did a test the other night just useing my camera’s light meter, a 15W cfl, required a 1/20s exposure while the LED running at 10W only needed 1/10.

  30. ebay… at least a 50 watt is needed 100 watt bulb will do even better.. it wall all still be cheaper than buying a replacement bulb.. plus why not just make a hole and run the driver out of the shell.. you need a heat sink anyway so why complicate things

  31. Another option (which I’m doing in a project unrelated to this) is to use 3-5W LEDs, with 5 degree optics on each, and build up an array of them. Better heat dispersion, cheaper, and easier to somewhat focus the light. With the “clip on” optics for star mount LEDs (20mm stars), the “lumens” output is multiplied when you only want light going in one direction (small beam angle).

    Just a thought.

  32. I have made an LED lamp for an Eiki 16mm film projector. I used LEDengin’s 40 Watt 9mm “pin point” lamp, which of all the one’s I have tried provides the most illumination from a single point of any high power LED on the market. It comes in 3 color temperatures too. The big issue with retrofitting is the focus of the light. Halogen lamps are pin point sources that can be directed nicely with a simple reflector. LED lamps are arrays of pin-point sources that are much more difficult to focus. They also have to be run at much lower temperatures then halogen, so you need room for a big heat sink. If you are building your own heat sink for a high power LED you need to have a big chunk of solid aluminium right behind the LED (1″ by 2″ by 1″ should do it). This gets the heat away from the LED very quickly. Then you can run your fins off of that. The one I used was custom machined so that if housed the LED and my custom reflector, with the fins in front. I found that using a long reflective columator (made out of tin-foil no less) gave the best results for focusing on to the 16mm gate. The columator was 2.5″ long. One advantage of using tin foil is that you won’t be able to make a perfectly smooth reflector. This helps you out because the LED lamp is made up of several tiny points which will all show up on your screen unless they are blurred together. You can do this by having a slightly crinkly reflector (very slightly), or using ground glass (which eats about 0.5 EV). It should be easier to focus onto a larger gate (such as the ones in video projectors). In the end, the lamp provides 1 EV less light then the original halogen, but at a better color temperature. So not a bad result. Typical lumens out of a 16 mm film projector are 680 for a halogen source. This can be boosted to 840 with some power-supply hacking, and the LED provides about 500 I think (sorry .. could not find my spreadsheet with the final data .. but if you do the EV calculations in reverse if is 1 EV less then 840 lumens).

  33. Car headlights are only about 35 watts. Figure that most of the projectors I have had use a 200 watt lamp you are going to have issues.

    I started playing around with this same concept. I have a small little infocus DLP projector I was messing with to do the same.

    Another issue is matching the LED to the filters. Even white LEDs emit light with a three color (Red, Green, Blue) phosphor mixed to create the desired color. If the filters do not match the peaks of the red, green, and blue wavelengths of the led there will be a good amount of light lost to absorbition.

    Plus with the price of projectors being as cheap as they are (1080 epson under $1000) its really hard to mess around. Also there are guys that offer raw lamps to rebuild your original lamp assembly at a fraction of the cost of new.

  34. My projector uses a 135W NSH lamp. I found I could just use a 150W aquarium metal halide lamp in it. I had to cut the outside glass open, add a reflector and UV filter to it, but it works fine and was only $7 including shipping from ebay. I just hope the power supply is ok with the extra output.

  35. They just lit the Caterpillar plant here in Lafayette with LED’s. It’s the largest setup in the world! They had ugly sodium light before. Energy savings 30%, colour rendering greater for sure.

    Price undisclosed.

  36. I’ve been thinking about replacing the high-powered bulb in my DLP projector with an LED solution for a while now, glad to see someone could pull it off.

    There’s all sorts of crazy LED modules on Dealextreme, including ones that put out like 1500 lumens.

  37. Hi Guys.

    Hay dcroy, love the work so far, especially the control for the projector. i just used the grounding trick on mine and have had no problems during testing so far :)

    I am in the middle of a hack like this and have done nearly the same using a 50w LED.
    The problem is the spot point of the light.

    A standad arc lamp in a projector has a light source of 1-2mm (about 4mm square). The 50W square LED’s have a source in excess of 600MM (25*25mm). focussing this in to a paraell beam about 100mm square is near impossible without some optical design and manufacturing equiptment (i spent a long time looking in to this).

    With LED projectors, there are some ways to cheat.
    1. something big with a small focal point like an SST-90 which will average about 2000 lm on about 25mm square. i have run one of these at about 700-1000lm through my projector, and with the reflector i have (no collominating lens at that time) it gave much better results than the 50W LED. This is the final LED i am using, and i am making the psu now (3.7v @ 9a)

    2. in my projector (Epson EMP74 i think) there is easy access to each LCD, and a coloured lens filter in front of each (as well as the coloured beam splitters). passing white light directly through this gives some good results (and bypasses a butt load of optics). Three of the above SST-90′s should get 50-75% power out this way.

    Even though the SST-90 is less powerful, the ability to focus the beam makes more light get to the end (plus the alignment of the beam through the optics is critical, i have a great pic of this somewhere)

    Unfortunatly these chips heat up, but no where near to a 200W HID bulb. With a good copper heatsink and the projectors own cooling, its possible to keep it all cool.

    I am in the middle of creating the PSU for mine (thats for the help Hackaday forums and the great people there) and when done, hackaday will be the first place i come to lol.

  38. I’m working on retrofitting my Epson Powerlite S3 with an HP LED. so far I’m thinking of buying this http://www.kaidomain.com/product/details.S009871
    but 200 bucks exceeds my budget, so in the meantime I’ll go for this http://www.ebay.com/itm/FREE-SH-1x-100W-Cool-WHITE-LED-Lamp-5500-6000K-Bright-Light-High-Power-KD7-/300645874069?pt=LH_DefaultDomain_0&hash=item45ffe3f995#ht_2846wt_956

    Due to the nature of the lamp case of my projector (it comes with a collimator lens) I’m expecting not to have big problems on the light source focal point issue.

    My only problem will be to fit the right cooling device on the small space that is left on the lamp compartment.

    I’ll keep posting my progress

  39. I have a Epson EX71 and i manged to fix a 2500 lumen 30watt led in the existing bulb housing, but i am having a problem tricking the projector into thinking that the factory bulb is installed. I have tried a dirrect short to the board from the sending opto isolator, anybody have any ideas?

  40. What is the maximum power led we can use, it says they have 50,000 hrs use, and are far more robust as long as they stay cool with the correct heat sink and maybe no fan required if heat pipes used so ultra efficent and quite.

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