Control Board
The control board consists of a pic12f675, a relay, npn transistor, a protection diode for the relay and some resistors... nothing particularly special.
Code
#include <htc.h>
#define _XTAL_FREQ 4000000
__CONFIG(MCLREN & UNPROTECT & BORDIS & WDTDIS & PWRTEN & INTIO);
void main()
{
TRISIO = 0b111100;
ANSEL = 0;
while(1)
{
GPIO = 0b000010;
// wait for power on signal, 5 seconds long
for(int x = 0; x < 2000; x++)
{
__delay_ms(1);
if(GPIO2 == 0) x = 0;
}
GPIO = 0b000001;
// wait for ~1 ms pulses to stop, after 100 ms of nothing turn off
for(int x = 0; x < 100; x++)
{
__delay_ms(1);
if(GPIO2) x = 0;
}
}
}
High Power Led
The led and power supply came in, i wasn't expecting how bright these things would be. Everything came together perfectly somehow...
I mounted the led onto an aluminum heatsink with some screws and some thermal silicone adhesive, to mount the whole thing into the projector i removed the top part of the bulb cage and cut out the section that screwed onto the projector. I happened to have a collimator lens i salvaged from another projector that fit on top of the reflector, with the reflector and lens siliconed down it was ready to install. A note of warning, the power leds tend to have a silicone lens injected over them which is quite fragile and easily peeled off. I almost had this happen when my reflector came off and the silicone i used bonded to the lens!
Its not quite as bright as the uhp bulb but that could easily be fixed with an led with a higher output
Power Supply
The power supply was based on an st micro TSM101I voltage amperage controller, i used a simple hack using a 100k resistor and a 10k potentiometer to fine tune the amperage supply so the led isnt over driven and die prematurely.
At 1.7 amps the heatsink provided (if you can call a thin piece of aluminum one) got quite warm, i found an aluminum heatsink of the perfect dimensions. I siliconed the heatsink down so it wouldn't shift and mounted the power supply using silicone thermal adhesive
Testing
Surprisingly everything worked perfectly, the projector turned on and off just as it would before. A slight disappointment was the fact that the led was not as bright as i hoped it would be, it ended up producing an image about as half as bright as it originally did. This is with the brightness of the projector turned all the way up.
The projected image is a bit brighter and has proper color, my camera sucks for these types of situation.
Conclusion
For about 50 dollars (including consumables) i retrofitted the projector in about 2 hours of solid work and 4 or 5 hours of figuring out the basics of pic micro controllers. For a bit more money a much brighter led can he had that would make this more worthwhile. Considering how much longer an led will last compared to the ~2000 of a uhp lamp and the power savings. Power loss from the conversion taken into account powering the led comes to about 30 watts, one quarter of the power consumed by original bulb.
