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Converting video projectors to LED lamp ?

Discussion in 'Electronic Repair' started by N_Cook, Sep 25, 2012.

  1. N_Cook

    N_Cook Guest

    Like the ink-jet printer nonsense. Loads of nominally working video
    projectors around where the lamp has worn out after its 1000 to 2000 hours
    and a complete new projector is a little more than the cost of a replacement
    discharge lamp .
    Anyone done a conversion to high power LED emitter lamp? tips/pitfalls ?
    Obviously a number of opto-coupler functions need fudging as well as
    disconnecting the original lamp supply and HV ignitor sub-circuit
    lamp supply input side optos , ignitor-on , lamp on, half/full brightness
    output side optos , ignitor cct ok, lamp on (drawing correct current)
    confirmation
    Perhaps should only consider projectors that allow colour temperature
    setting within the menu structures
    any other considerations?
    I just saw reference to this LED lamp cluster , anyone sen the spec of the
    beam angle for it
    http://www.ledengin.com/news-events/2012-08
     
  2. JB

    JB Guest

    Don't even bother. It is totally impossible to retrofit an off the shelf LED
    'light engine' into the existing projector optics. You *will* be wasting
    your time. The original short-arc, ultra-high pressure mercury or metal
    halide lamps will have lumen outputs typically 20-30x the best you could
    achieve with an LED 'cluster'. Even if you got the lumens from the LEDs, the
    optical source 'dimensions' would be far too massive for the existing lens
    system to focus on. The thermal issues would be 'interesting' too as you
    would be looking at at least 200W of LED to achieve anything like the
    original screen brightness, even with an optical system matched to the
    larger LED source.

    JB
     
  3. N_Cook

    N_Cook Guest

    The active window for the colour wheel / light tunnel is usually of the
    order 10 mm diameter. At least with a single LED cluster you can direct the
    majority of its light into that 10mm aperture.
    Compared to discharge lamp , not point source, reflected off non ideal
    dicroic reflector with an open-end diameter of the lamp reflector 60mm or
    larger, how much of the discharge lamp light gets to the 10mm active window
    and how much is wasted. ?
    Off-the shelf current generation of manufacured projectors with LED lamp
    sources rated 200 lumens are sufficiennt for 6 foot diagonal screens in dim
    not dark rooms,(room-light level where you can just read a book)
     
  4. JB

    JB Guest

    Not of homogenous white light you can't.
    These short arc HID lamps with integral ellipsoidal dochroic reflectors are
    about as efficient as it is possible to get for this type of application.
    when you have a bare arc-tube producing 25-35kLm, who cares that your
    optical efficiency is typically <40%. You simply can't get a better source
    which can provide this level of lumen output.
    Comparing apples with oranges. A 200Lm (source lumens) LED projector is in
    no way comparable to the output of an HID projector.

    I'm not on a rant here! I'm trying to save you time and money and
    considerable frustration. I have been working in the lighting industry
    designing luminaires, lamps, and optics for over 30yrs and beleive it or
    not, have gained some valuable experience in this time.


    JB
     
  5. More specs at http://www.ledengin.com/products/emitters/#LZ9

    But 1300 lumens is still a long way from a typical video projector. eg
    the NEC NP64 is supposed to put 3000 lumens on the screen, that includes
    all the optical losses along the way.
     
  6. N_Cook

    N_Cook Guest



    I still cannot find the half-power beam angle. It 15 degrees fine but if 120
    degrees then back to all the optics losses business
     
  7. josephkk

    josephkk Guest

    Wow, a 400 W arc lamp. That is the rating and power input for that many
    lumens for HID lamps. That lamp must power large screen movie theater
    projectors. YCLIU
    I am not believing it.

    ?-)
     
  8. josephkk

    josephkk Guest

    Due to the physics of the bare LED, about 45 to 60 degrees. With the
    fancy lens maybe 20 to 30 degrees, but that is a WAG.

    ?-)
     
  9. N_Cook

    N_Cook Guest

    Due to the physics of the bare LED, about 45 to 60 degrees. With the
    fancy lens maybe 20 to 30 degrees, but that is a WAG.

    ?-)

    ++++


    As that light source can be placed within 2 or 3 mm of the apertured mask
    over the rotating colour wheel then sounds promising. If like a short arc
    lamp , has to be set back 50 to 80mm then that 20 to 40 degrees would be a
    no-no

    I've seen a powerpoint presentation via one of these
    http://www.acerdirect.co.uk/Acer_K11_-_DLP_Projector_-_200_ANSI_lumens_EY.K2
    801.001/version.asp
    in a dim but not dark room and was perfectly acceptable, allowing for the
    poorish resolution.
    Certainly not a jokey gimmick gadget
     
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