Recently during one of my Ebay window shopping sessions I came across a listing for an 'as is' Epson projector missing a lamp. It was sold as is because it would turn on and then simply flash a lamp error and since the lamp is much more expensive than the projector as a whole, the seller undoubtedly decided to sell just the projector rather than purchase a new bulb. The best part was that he was willing to part with it for $25 with free shipping. As far as I could tell nothing else was wrong with the projector so I took the plunge.
While waiting for it to ship I read up on the control systems that these projectors use in order to control the ballast and lamp assembly. It looked like nothing more complicated than tricking an input to the main board to make the projector think a real lamp was inserted while in reality I would use a high power LED but more on that later.
A week later it arrived in a huge box and as I hurried back to my dorm room I tore it open in excitement. It has three lcds, one for red, blue, and green. These three images are added together with the help of a lens to create the final image. The next step was to remove the ballast and figure out how which two wires from its control cable sent the lamp ok indication. I noticed that the ballast (the circuit board on the bottom left in the picture below), had a digital control circuit mounted vertically with three optoisolators near the i/o cable. These chips are necessary to insure that the digital low voltage i/o dont mix with the high voltages present in the rest of the ballast or else this projector might release its magic smoke. In addition two of the optos were facing left while only one was facing right. This hinted to me that the one lone opto was the output sent to the main board pictured in the upper right below to tell it that the lamp was operating perfectly fine so that the projector would stay on instead of shutting off and giving an error like it would without a lamp inserted.
So my solution was to short out the two wires that led to this opto (found with the help of my multimeter). I also needed to tape down the lamp door safety open switch so it could operate with the cover off. Now when I shone a flashlight into the lens input on the upper left of the image above I could faintly see an image being projected from the projection lens on the bottom right. Bingo, now I was getting somewhere. Now I needed more POWER!
I had bought a 30W 2000 lumen LED and 2A ac/dc driver in anticipation of this exact purpose a while ago so I dug that out of my parts bin along with some optical lenses to focus the light. I drilled into an old pentium cpu heatsink and attached it to the LED because after a few seconds it got rather hot. The fan came with the heatsink so I just wired it up in parallel with the exhaust fan seen below to the upper right of the picture. Then I used some framing wire to attached the glass lens to the assembly. This ensures that the light is concentrated and evenly dispersed into the small window to the left.
Next I need a way to turn on and off the led because having the light on all the time when the projector was plugged in was no fun. I could have gotten fancy and dug into the buck control circuitry of my LED driver and done it that way but I opted for a more universal approach in case I wanted to upgrade the light source in the future. I patched a ac cable into the power input of the projector's main power supply board to gain access to 120V AC. Then I used a beefy relay pulled from an old computer battery backed ups (uninterpretable power supply). This small beast could handle 5A at 125V so it should be sufficient for the task. I placed out of the way it in a crevice in the bottom left of the projector as seen in the picture below. Normally when the coil is unenergized it opens the circuit so the LED is off. When it receives the signal from one of the other optos (I carefully tested with the projector open to see which control line to the ballast changed when the projector was turned on and off) it sends current through the relay switching the AC voltage into the LED driver thus turning the LED on. This way the hacked on LED would behave exactly like the original lamp: it turns on and off with the projector with no user intervention.
The LED driver in the protective plastic shield on top of the main power supply can be seen above in addition to the small optoisolator and flyback diode circuit I built to handle automatic relay control to allow the projector to turn on and off the LED itself.
I pulled ground and +12V for the relay coil from these two spots on the main board.
Finally a picture of the entire device fully modded to my liking. Its a thing of beauty.
Now for a test I played some video games on it for an hour and measured the internal temperatures to make sure that it would be fine. Here is a projected screen size of about 30" in pitch black room for your enjoyment.
And what game did I test I hear you ask. Only one of my favorites of all time ;-)
These images were about 30-35" diagonal. Not too bad. They look better in person its just that I had to use my phone cameras as I forgot to bring home my nice Sony camera for spring break. I can push the image to 45-50" and still be viewable in a pitch dark room but brightness degrades quickly. I'll see if I can get my hands on a 8000 lumen 100W LED and make this almost as bright as it originally would be with the stock lamp. Here is a quick video of the internals and it operating for those who are interested.
For now I will go ahead and call this hack a success. Now let me get back to beating Castlevania Symphony of the Night for the millionth time ...
If you have any questions feel free to comment below and I will do what I can to help.
