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Video projector discharge lamp wattage?

Discussion in 'Electronic Repair' started by N_Cook, May 8, 2009.

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  1. N_Cook

    N_Cook Guest

    Is it simply volts x amps?
    Taken when? at maximum, when heated up, or on some standard standing
    voltage, after start-up?
    Would one maker's 100W bulb be the same light and power draw as some other
    maker's 100w ?
  2. N_Cook

    N_Cook Guest

    I measured a projector that has 300W consumption on the mains plate but no
    info for the bulb consumption.
    Added 0.1R in the supply line to the bulb gives an inferred reading of 2.8
    amp and 80V over the lamp after 10 minutes to warm up , so 224 watts seems
    about right.

    Interesting the brightness setting is just in the DLP chip , not the lamp.
    But selecting "low power" option does reduce the light output but with lamp
    volts staying at 80V , so presumably current draw is less, (0.1R
    disconnected by then). This option for reduced fan noise , if large display
    / high ambient light useage, is not required
  3. Is it simply volts x amps?
    Uh... Ignoring power factor... Power is power. Law of conservation of
    energy, right?
  4. N_Cook

    N_Cook Guest

    I'd forgotten about the hook-up wire volts drop, about 145W, 80 volt, 1.8
    amps for the lamp. DC that is of course
  5. Franc Zabkar

    Franc Zabkar Guest

    It seems to me that your lamp has a constant voltage characteristic
    and that its brightness is determined by a variable current source
    within an electronic ballast.

    I would think that the arc voltage would be determined by the lamp's
    geometry. For example, could it be possible that one maker's 100W lamp
    A may be rated for 1A at 100V, whereas another maker's lamp B may be
    rated for 1.25A at 80V? If so, then a ballast designed for lamp B when
    used with lamp A may try to deliver a constant current of 1.25A,
    causing the lamp to dissipate 125W.

    - Franc Zabkar
  6. Franc Zabkar

    Franc Zabkar Guest

    You may like to read "Sam's and Don's D-Lamp FAQ -- Gas Discharge
    Lamps, Ballasts, and Fixtures".

    Operation of Discharge Lamps on DC:

    "... most discharge lamps are only partially compatible with DC, and
    some are not compatible at all."

    - Franc Zabkar
  7. N_Cook

    N_Cook Guest

    A more complete set of readings for a 2004 Infocus X2

    11,600 lux measuring with probe in the output from the lens. 50mm from the
    with no video and white "blank" screen . With A4 sheet illuminated and a
    light level meter, set for 100 ASA gave f4, 1/60 second reading. With
    of 17 deg C.
    Using diode temperature probes, the parabolic reflector reached 85 deg C and
    88 degree
    after switch off. The light tunnel reached 46 deg C. The housing
    between thermal switch and over the colourwheel reached 26 deg C
    and 47 deg C at switch off.
    Normal power use when warmed up 80V, 1.8 amp (measured with 0.1R
    in line and hookup wire volts-drop). At first striking then drops to about
    20V then increases
    to 80V. If still hot when trying to power up
    then starts at 1300 volts, drops to 64V with no lamp ,
    470V down to 64V etc
    until the fans have cooled it down enough.
    Menu brightness change makes no
    difference to lamp brightness. Changing to low power
    setting does drop the light output, but volts
    stay at 80 V so presumably current drops, used for lower
    fan noise, very large screen display not required.
    Blue screen , no signal, low power setting, with thermometer bulb placed
    at lower left front where most heat is blown out took 10 minutes
    to stabilise at 25 deg C over ambient.
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