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Converting a 200W discharge lamp video projector to LED

Discussion in 'Electronic Repair' started by N_Cook, Sep 27, 2013.

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  1. N_Cook

    N_Cook Guest

    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
  2. John-Del

    John-Del Guest

    You don't recall correctly...

    RCA color TVs were always the most accurate, with a single exception: the CTC38 (I'm pretty sure about the number, that was over 40 years ago) was a low end toilet made for two years for big stores and buying groups and had a tube lineup distinctly different from the better models, and they were made in the 60s not 70s. By 1971, RCA was running the extremely accurate andreliable XL100, or the mostly transistorized hybrid XL (sweep tubes only),which also was an excellent performer.

    Mid 60s Zeniths were known for crappy color as they aged, but would respondwell to replacing the demodulator transformers and doing a full color alignment.
  3. "John-Del" wrote in message

    Oh, but I do. I might have the decade wrong, but there was a time when RCA
    sets had horrible color. Why, I don't know. My memory is that they were the
    most-common color TV in the motels where I stayed when travelling for Bendix.
    They were invariably tres-lousy.

    I saw a CTC-100 maybe 45 years ago, and I remember it having an excellent
  4. gregz

    gregz Guest

    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.

  5. N_Cook

    N_Cook Guest

    By 5W I supppose you mean co-planar ready-made assembly
    has some cell cluster focusing devices.
  6. chuck

    chuck Guest

    The CTC38s were made from 1969 through 1970. The color demodulator
    had a wide angle in the flesh tone area so flesh tones looked
    "natural" even if the tint shifted slightly. Yellows were reproduced
    as orange because of this feature. The solid state set in 1971,
    except for the hv rectifier, was the CTC40. It wasn't like the
    following XL100 line because the chassis wasn't modular. Some had an
    issue with the color killer circuit killing the color on a normal
    color signal. Chuck
  7. **The largest LED array I've used is a 100 Watt array (approx 25mm X
    25mm). The cooling system is a fan assisted CPU cooler. The whole lot is
    almost double the size of a 250 Watt halide projector lamp (Then there's
    the 33 Volt 3 Amp supply. It occupies another 100cc) and reflector. It
    delivers around half as much light output as the halide lamp. It is
    measurably brighter than a 500 Watt halogen flood lamp. Then there's the
    33 Volt 3 Amp supply. It occupies another 100cc.

    When using RGB LEDs, I've found that it is best to use a translucent
    panel to mix colours.
  8. **Exactly. LEDs are certainly efficient. Far more efficient than any
    incandescent lamp. Discharge lamps, particualarly halides, are a
    different matter entirely. LEDs are (presently) not more efficient than
    halides or sodium vapour lamps. Of course that may change.
    **I disagree. One of my torches uses a 2 Watt halogen bulb. It produces
    excellent light output, though the reflector tends to provide a pretty
    poorly defined pattern. It can be focussed within limited ranges. By
    contrast, one of my 1 Watt LED torches blows it away, in every area. In
    fact last week, I picked up a 1 Watt LED torch for 7 Bucks, which has a
    focus attachment. It is astonishingly good. Except at it's narrowest
    focus setting. The rectangular LED chip is easily seen on a wall at 100
    Metres. At 2 Metres, the 'dot' is 100mm X 100mm. At it's widest focus
    setting, the 'dot' is 2 Metres in diameter. It's so handy I'm buying a
    bunch more. I will avoid incandescent torches in the future.
  9. **BTW: This is the torch I spoke of:

    You may find one locally. It's a bloody rip-snorter.
  10. N_Cook

    N_Cook Guest

    One of those that if you close focus , you can start your campfire
    without having to rub two boyscouts together?
    an example of the focus mechanics shown in here
  11. N_Cook

    N_Cook Guest

    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
  12. N_Cook

    N_Cook Guest

    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.
  13. **What are you going to do? Spelling is not what it once was. One of my
    regular buyng sites is a very large Aussie retailer. It appears they
    employ copywriters whose first language is not English.
    **Indeed. Here is where I get the some really nifty torches:

    A nice aspect of the site are the uncensored reviews of their products.
    Delivery is slow, but free. This is an immensely impressive torch:

    It does us special LiIon batteries though. About 3 Bucks each. The
    special charger is another 6 or 7 bucks.

    These things are astonishingly good:

    Almost twice as bright (measured with a light meter) as an 11 Watt T5
    fluoro lamp. They must be glued to a small flat piece of aluminium heat
    sink, but, even then, they are exceptionally compact. I've purchased
    dozens of these. I cannot recommend them more highly. Awesome product.
    My neighbour uses them in his camping trailer.

    And here is the 100 Watt LED emitter I purchased:

    It requires a separately available 3 Amp, constant current source.
    Easily replaces one of those 500 Watt halogen work lights.
  14. N_Cook

    N_Cook Guest

    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
    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
  15. N_Cook

    N_Cook Guest

    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.
  16. N_Cook

    N_Cook Guest

    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
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