im modifying a dlp projector for use with a high power UV led light source. i appreciate that these big 100w leds are not very good for projector use as the light output is quite poor.. however i also assume that removing the colour wheel will compensate somewhat, i read somewhere that it increases the light output significantly.

anyway my issue is tricking the projector into thinking it has a lamp.

the general method is to locate which of the wires which connects from the main board to the ballast is connected to the optocoupler which tells the mainboard if the lamp is on or not. you find one which goes to 3.3 or 5v when the lamp warning light comes on, and connect that wire to ground.. you can then safely remove the lamp and HV ballast and the projector will run happily..

however in some cases its a bit more complicated.

i have been donated an old-ish optoma hd700 dlp projector to hack to bits.. ive found the wires (5) connected to the optocouplers (3) on the ballast.

ive tried measuring the voltages at various stages of the boot up sequence, located a couple that go high if the lamp is missing. grounding any of these or all of them does not work. the projector still goes into "lamp failure" mode.

by accident i made a discovery though, only having two hands i was juggling probes and power switches, and i connected one of the wires to ground a moment after the projector started up.. bingo! the projector sits happily working.

so i need to take that pin to ground a second or so after the projector starts (maybe even a millisecond, im not sure) .

i have very basic electronic skills. how should i approach this? i was toying with the idea of finding a nice voltage on one of the (16) power leads connecting to the main board, and use that to activate a small relay (i have some) connecting the pin to ground. that would be pretty instantaneous. not sure if there is a larger delay required.. ive tried connecting the pin as quicky as possible after turning on proj and it seems to work with a very short delay but i dont know how to time it.

 

What is the coil voltage of the relays you have, and what voltages are available?

 

What is the coil voltage of the relays you have, and what voltages are available?

well ive measured 12v between a few of the power supply pins and the mainboard groundplane.. no idea if im safe connecting a small 12v relay between one of those pins and ground? there are also some fan headers for the cooling fans and i measure 6v across those. probably a safer bet. i need to check which relays i have to hand.. i know i have some 24v ones but i think i have others.

edit: the fan headers would not be ideal. when the projector shuts down the headers go from 6v to 12, speeding up the fans to cool the lamp.

edit: the proj has a 12v trigger output for a screen, however it appears to activate after the lamp check is completed.

 

This thread seems VERY SIMILAR to one that ran about a year ago.
Ultimately the solution would be to start over with a new lamp drive system

 

This thread seems VERY SIMILAR to one that ran about a year ago.
Ultimately the solution would be to start over with a new lamp drive system

yes I will of course have a new lamp driver. trying to run an led from a hid lamp supply would be suicidal. my only issue is convincing the projector not to switch off. resolved really, just need to sort out grounding that wire a moment after the main board powers up. anyway I've found my box of relays and a have a nice tiny 12v one that might just do it

 

have a nice tiny 12v one that might just do it

Try connecting that to one of the 12V supplies to see if the operate time of the relay provides enough delay.

Otherwise you may have to add a small resistor in series with the relay coil, with a large capacitor to ground, to provide additional delay.

 

This thread seems VERY SIMILAR to one that ran about a year ago.
Ultimately the solution would be to start over with a new lamp drive system

ahaha I've just found that thread. very similar indeed.

 

To create a pull-in delay will take a fair resistor and some capacitor, as "{C" already mentioned.
What other functions does the control system provide that it can't simply be replaced?? I am not familiar with that modelso I am askin.

 

To create a pull-in delay will take a fair resistor and some capacitor, as "{C" already mentioned.
What other functions does the control system provide that it can't simply be replaced?? I am not familiar with that modelso I am askin.

the control system cant be replaced as it is a feature of the main projector motherboard, which is a fairly complex pcb as you might imagine. unless that input is spoofed, the projector switches off after about a minute with a lamp error. im not sure how you would go about replacing the control system, but it would be rather more complicated than pulling the sensor pin to ground