Converting a 200W discharge lamp video projector to LED

Assuming over-riding the opto couplers to falsely confirm to the system micro that the arc is struck and the lamp is lit (maybe requiring a delay) firstly, with the lamp ps disconnected. Then I intend in the first instance to buy 5x 1.2W white LEDs, 3500K, 20 degree, for proof of concept. Assuming that sort of works then get perhaps 10 more, going down to 2700K or 3000K or perhaps (unlikely)

4000K and lenses to colimate to 2 degrees. Set inside a reversed conical silvered glass of an ex-lamp to direct spillover light into the colourwheel/light tunnel aperture. The intended LEDs are 11x10mm footprint so can be mounted quite close to the colourwheel(for 5 anyway) on a spherical back mount. I may as well retain the original fans, perhapps knocked back a bit for less noise intrusion later on.

When coming to scaling up I originally was thinking of using a sectored curvi-linear silvered reflector from PIR units (with faned air cooling) but have since come across 2 degree lens converters for these LEDs so may as well go with them and shine directly from a larger spherical backing mount, directly to the colourwheel aperture.

I'd be interested in any suggestions or comments other than of the I would not bother type of replies. Anyone happen to know what the light wastage proportion is of a non-ideal paraboloid reflector and non-point source discharge lamp is? I'm aware proper LED projectors have active drives to RGB LEDs and not colour wheels but there are a lot of ink-jet-printer-syndrome surplus HD video projectors around with too expensive short-arc lamp costs to replace

Some bods been here before with converting a couple of types of discharge lamp converters

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If anyone is interested, my exploration of inside a standard domestic GU10 LED lamp (to see if they were all in series or mixed series/parallel)

240V,2W. Breaking in:- hold the bulb in a glove and heat the dome cover with "low" temp hot air and prize off with a needle. With old soldering iron destroy the epoxy join between the , not obvious as silvered, pcb to the lamp housing. The slight greeen colouration is due to the reflection of the green dye of the pcb which is not glass fibre reinforced it seems, maybe epoxy substrate only. Prize the pcb away. No glass breakage at any stage. Overlay of this one marked JH-GU10-20 HV ac side 1M//0.33uF 400V dropper and 1/4W resistor size fuse/inductor/fuseable resistor? pink colour with red black brown, or reverse order, colour bands, about 0.4R to small SMD MB6S bridge rectifier. LV quasi-DC side SMD 510R dropper to 20 LEDs in series. White ceramic cap is cemented to the glass of the lamp. Bench ps 50V across LED string and 510R all LEDs just lit 54V and 0.5V over 510R and about 2.6V over each LED some sort of low level brightness. With 75% mains (240V that is) 6.5V DVM dc over 510R or 5.5V DVM ac over 510R 100% mains 9.1V "DC" or 7.2V as "AC" reading over the 510R
Reply to
N_Cook
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Have you calculated whether you can cram enough LEDs into that space to get the same brightness level as the discharge lamp? Or are you expecting to learn from the test?

I'd like to point out that is no such thing as -- nor can there be -- a white LED. LEDs are necessarily limited to a narrow band of wavelengths. * All (???) white LEDs are (I assume) a blue LED with a yellow-fluorescing phosphor. **

This /looks/ white to the eye, but the red and green wavelengths needed for color reproduction aren't present.

Unless your white LEDs contain red, green, and blue LEDs, I don't think this is going to work.

  • This is actually a good thing if one is trying to match a specific color space, and you can manufacture LEDs whose wavelengths correspond to the three primaries.

** I'm thinking of indicator lights and such. Lamps to replace incandescent lighting would necessarily have to put out red and green, or colors wouldn't look right.

Reply to
William Sommerwerck

Its not possible to do any calculation as to brightness because it is impossible to find the true loss of light from a conventional distributed ie not point source discharge lamp source and non ideal reflector, I would guess that 2/3 of the rated light does not get into the apaature and then how to calculat the proportion that is at such an angle to the light tunnel to the active chip and multiple reflections that little of that gets to where it is wanted, axially along the 2 inches or so of narrow diameter light pipe .

As for colour rendition it is unlikely to be any worse than the current situation of having to place a rose-pink filter over the projector lens to get some red into the image as the lamp must be too far into the blue end of the spectrum tio be compensated for in the setable timing of the colourwheel.

So in both cases very much a suck it and see, seat-of-ones pants situation, but worth a go, if you've seen the price of these supposed replacement discharge lamps

Reply to
N_Cook

I've had another look at the product data and the 2 degree lenses are 4 degree , in normal terminology

I don't know what chromaticity means but for the 3500 deg K version a Cx of about .4 and Cy of about .39 A bit more graphic the spectrum is continuous and smooth "bell curve" peak shifted 40nm from 550nm of the standard eye response curve to 590nm and the 50% points broader apart at 150nm compared to 100nm of the eye and a 50% down peak at 460nm which I suppose is the potential bugbear for such a lamp conversion

Reply to
N_Cook

I don't know what chromaticity means but for the 3500 deg K version a Cx of about .4 and Cy of about .39 A bit more graphic the spectrum is continuous and smooth "bell curve" peak shifted 40nm from 550nm of the standard eye response curve to 590nm and the 50% points broader apart at 150nm compared to 100nm of the eye and a 50% down peak at 460nm which I suppose is the potential bugbear for such a lamp conversion

Could you send me the data sheet, or its URL? I'd like to take a look.

Reply to
William Sommerwerck

LEDs, I did not find a uk/us URL

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lenses
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Reply to
N_Cook

I've done this with marginal sucess. The problem is focus. The original light has all the light coming from roughly a single point. An array of 5 LED's will distribute the light over a much larger area. It will work well with light from the central LED using the original reflector, but the outer LED's will be wasted and splattered all over the room.

You don't really need the original reflector if the light source has its own forward facing reflector. Try cramming an MR16 bulb in place of the projector bulb and reflector. The smaller size MR16 lamps might fit.

More:

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

I'm not an expert on this subject (though I do know a little). My gut reaction is this...

The color reproduction index is only 80. That's poor. That doesn't mean that the LED won't work -- but it will probably need appropriate filtering that won't be easy to achieve.

The spectral emission (p11) isn't particularly flat -- and definitely not smooth -- no doubt one of the reasons for the poor CRI.

I don't think you're going to get pleasing results.

Reply to
William Sommerwerck

All the discharge lamps in video projectors , I/ve seen have an electrode and squashed , not optically conductive glass, axial exactly in line to where you want the light to go. With directional 20 degree central LEDs, and lensed 4 degree ones off-axis. will direct most of the energy directly to the half inch aperature , without any reflectors . Reflectors just to mop up spill over . I can see some high power red LEDs being added to counter the blue sub=peak

Reply to
N_Cook

True. However, the lamp I was replacing originally looked like these:

Note that some LED projectors use RGB LED's with three PWM modulators to control the output level of each color LED in order to get a better looking "white". In particular, the micro DLP projectors use RGB LED's. Some use white LED's but methinks they look awful on the screen.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

Intended use in the main part is for projecting text and graphics so as long as there is a colour difference, any colour difference almost, rather than correct colour rendering that is all that is required , a rare pic with a green flesh tone or something does not really matter too much

Reply to
N_Cook

**What a waste of time and effort. The best LEDs are approximately similar efficiency to that of halide lamps. As others have stated, the big problem will be that you are substituting a compact light source with a rather diffuse one. The optics are not designed for such use.
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Trevor Wilson www.rageaudio.com.au
Reply to
Trevor Wilson

But the lamps used in video projectors are ,in effect, not compact. The direct light path from the reasonably compact source is blocked by an electrode and non optical structural glass lump, relying on the mirror surface of the light tunnel / light pipe to average out/balance-up the light coming in at all sorts of angles, off the parabaloid reflector

Reply to
N_Cook

**NO. By the time you try to shove 200 Watts of LEDs into the enclosure (including apprpriate heat sinking) You're not going to be able to focus the whole thing properly. It's a daft idea, unless you are prepared to use MUCH less LED power (say 15 Watts) and a consequent huge drop in Lumens.

BTW: The light from a parabolic reflector does not come off at all sorts of angles.

--
Trevor Wilson www.rageaudio.com.au
Reply to
Trevor Wilson

That Osram with built in lens is discontinued, only came out 3 years ago. I'm getting 7 of the LCW W5SM, white 2700K 120 degree and matching 7 off

6 degree hex shaped lenses. The off the shelf 7 cell hex cluster lens is for parallel , not focused. Using a 5 to 6 inch ball as a jig I'll combine the 7 as a focused cell. With the lenses at 85% transmission, brings the 75 lumen per LED down to 64 lumen, so x 7 =450 lumen. Some heatsinky type protrusions added to the LEDs to catch the fanned air. When new the projector was rated 2000 lumen, although still taking 200W , the light output is now much less. Combined with the poor optics of these lamp setups I suspect fully directed into the light pipe 450 lm is not much different to the present discharge lamp situation. Still plenty of room to add another 6 plus lenses around the periphery to bring up to 900 lm. Playing around with a scrapped colour wheel dicroic disc and assorted white LEDs the red transmission , to eye anyway , is a lot lower than G and B. So I will get a number of red 100mA 5mm , 15 degree standard size LEDs to add red, perhaps 6 at the interstices of the lenses, mounted to the rear and between the SMD LEDs plus maybe another 6 around the periphery to infill. Good progress with the silvered "cone" for mop-up, front of PAR lamp removed and bulb removed, about 3/4 way through grinding through the thick glass with cintrided disc, to remove the barrel part. Previous attempt with thinner glass photoflood failed. If I was brave or had a load of these sort of lamps, I would try the old bottle cutter routine, freezer spray and a ring of "fuse" wire around , fired up for the cut
Reply to
N_Cook

Well that was very successful, a job I've never done before. Not a cone but the nearest I could find with a good silvered internal surface and right sort of dimensions. The thinnest part of the glass 4.5mm thickening to 7mm as 12 flutes around the stem, but a neat ground-glass cut. So I have a spillover reflector with 70mm internal diameter available for the LED assembly, down to 21mm diameter opening for the colour wheel aperature (from memory about 12mm) and 43mm axially. It will be a couple of weeks before I can get some time to convert the projector . But in the meantime anyone any ideas how to measure the intensity of the LED assembly at the axis and focus of the array, with any sort of accuracy (no known "standard candles" etc in my possession)?, for anyone else coming down the same path. My uncalibrated luxmeter , I doubt goes that high plus probably would melt, as would any of the plastic neutral density filter I have and placed in the path of that beam

Reply to
N_Cook

How about some photos of what you are doing, most of what you are describing is WAY over my knowledge of optics and lenses.

Reply to
hrhofmann

Its more bodging than optics. I'll take a few pics along the way. I've just noticed on the LED lens makers datasheet if you put 7 of their

1.2W white light LEDs in a specialised version of one of their lens structures , as I will be doing in a different manner, and directing to a 12mm waist , you end up with 3,000,000 lux there . All I need then is some deuterium pellets. I think I'll need more than neutral density 4 stop Lee Filter , I just tried black silicone rubber sheet and that is more like x0.001 light attenuation with an odd colour cast from white LED
Reply to
N_Cook

One of my projects was making a light source with multiple colored 5 watt LEDs. I was also considering white LEDs. First test was using fiber optics. Problems in getting an even field, trying different lens, diffusors. Second attempt was using reflectors. Since the project required a fairly compact unit, I probably would need fluid cooling. Project stalled, but its still in my mind.

Greg

Reply to
gregz

By 5W I supppose you mean co-planar ready-made assembly

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has some cell cluster focusing devices.

Reply to
N_Cook

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