Converting a 200W discharge lamp video projector to LED

I now physically have the LEDs and lenses. 2 immediate problems, both active faces of the lenses are dead flat. In the pdfs it looked as though the front faces were surrounded in a ring and I assumed (pdfs not clear pics) the 4 corner holes of the LEDs would mesh with pips on the rear of the lens. They are made for mounting to pcbs not the other way round, so no provisions for that. So I have to find some 12mm or so diameter thinn rings to align the front faces to my 5 inch cistern ball valve float as spherical former, and make some sort of jig for aligning the LEds to the lenses , plus fixing them together

I'm not used to optically pure plastic, I would have sworn that examining the LED side of 2 of the lenses then it was flat faced, but not touched the surfaces, and they contain recesses. I now have some rings for placement. The datasheet does not explain the normal placement. LED soldered to pcb, a non-optical plastic holder placed over the LED, quite loosely. The holder is .4mm undersized so forcing the lens into it, then compresses the other end around the LED with little pip under each corner, but no use made of the 4 holes in the corners. I think I've worked out how to adapt those holders for my purposes.

Supplied in small numbers , the lenses are supplied pushed into the mounts and again they don't say how to remove them without damage to the lens. First one bodged by placing over a couple of metal plates providing the across-flats 12.9mm gap to then push down as detailed below. As stated previously you lock the holder to the pcb in normal use, by pushing the lens into the holder , so first they have to be separate. Then with 1 free holder, place back-to-back castellation to castellation over the next one. Place a flat piece of rubber into the slot part that takes the LED (so not to damage the thin lens wall) and push down quite hard with a rod, until the lens pops the 1mm into the precise recess of the other holder. Remove the second holder by hand and then grip the lens across the pre-existing mold marks and pull out from the first holder with serrated edge pliers. Well that is my method for Osram Golden Dragon lenses made by Polymer Optics Ltd as supplied by RS

The focused 7 cell honeycomb lens came together well. Doing the maths and having a wedge tapering to .3mm seemed ok but trying to adapt plastic to those sorts of dimensions is not practical. Having to mould my own mounts. The 2700K LEDs are noticeably cream yellow colour to the eye and seem to have supressed the blue peak, too much? Relative intensity through a dicroic colourwheel R 340 G 270 B 070 even the reflection off the blue filter, ie complement colour of yellow , is noticeably brighter than the reflections off the R and G sections. I was expecting to add 5mm red LEDs but looks as though it will have to be blue ones. Won't know for sure until the video projector has a reasonable block of time to get inside to mess about.

As my mouldings to fit LED to lens are egg-cup shapes , a 3 part mould required, letting epoxy harden before running off 7 of them, so far so good. I was impressed with just trying one LED at 1/4 power of 90mA (no heatsinks yet) and 5 feet away , bright enough to read by just. Add a lens at the correct position and a neat bright foot by foot "pixel" , of the chip thrown on a screen 5 foot away, probably as bright as the projector showing white (DLP losses unknown). So 7 of them and 4 times as bright would illuminate a 5 x 4 foot screen , with that brightness. If 50% loss in hte projector then add another ring of 6 , room in the "funnel" reflector for them if required. I wonder what a gobo type thing made of a matrix of single RGB LEDs , with lens arranged to throw foot x foot squares with 6 inch overlap , would look like if driven with graphical/animated "video" pulses

any more on this? any luck? would love some pics to see the progress

It had enough light for domestic use but not enough for more than 2m diagonal. I got the 60 or so LEDs and lenses for a Mark 2 version but have been inundated with other work. And as have repaired a number of

600x800 vid projs along the way, I'm not desparate to get the HD one working. The use tends to be just for projecting bullet-point script anyway. I assume you've seen the pics URL'd here. Single compound LED built around a 5 inch ball valve float. Mark2 would be 19-1 built around small christmas bauble as basis. The central lens not having an LED but used to pass light from a similar cluster behind it which also has a cluster behind it. As long as the light falls in the well of one of those lenses then its collimated to about 3x3mm focus, ie within the light tunnel entry aperture

I worked out how to arrange the 19 lenses over a much tighter radius surface. Setting some lifted off the sherical surface a few mm, so not as elegant looking cluster

pics etc on later thread, titled Converting discharge lamp to multi-LED for video projector (maybe)

just saw this thread. back in the 70's while visiting Varian in Palo Alto, CA I met the inventor of the xenon arc light. He was looking for other applications than 'tank' lights for this formidable light producer. He had mounted it inside a 16mm projector to replace the 'hot' bulb presently used. The projector spread the movie images over a 20 ft wide screen in the brightly lit lab, yet the film was easily viewable in that light! and the blues were incredible. and you could freeze frame WITHOUT burning a hole in the film.

That arc light is also used in medical applications down tubes for lighting endoscopy, etc. and in microscope platforms.

I think the arc light is available commercially at several places, incuding those outlets like Edmund Scientific. It's a small cylinder with ring contacts on front and back. I have one somewhere it's approx 1.5 inch long by 1 1/4 diameter has a builtin reflector for throwing the light forward. From memory the arc, once fired runs on something like 10A at

12Vdc, or so. But the light can be used on your off road vehicle to see a mile ahead [again from memory] and having no filament, quite robust.

Not so much to distract your efforts, but worth looking at. Oh, one down side. The light is so bright it creates ozone across the surface of the bulb. and ozone and the aluminum parts in the projector didn't get along so well. But still alternatives to think about.