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Lamp anomaly

Discussion in 'Hobby Electronics' started by Phil Allison, Feb 10, 2013.

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  1. Phil Allison

    Phil Allison Guest


    I tested a 75W Osram clear lamp & a 70W No Frills halogen (claims
    100W equivalent) - the Osram measured 54ohms and the halogen 56ohms.

    On 240V, the Osram drew 325mA and the halogen 302mA.

    The resistance rises are 13.7 times and 14.2 times = essentially the same
    filament temps.

    However, the filament in the Osram is longer by about 40% plus the wire is
    also slightly thicker.

    Now, light output is proportional to surface area for equal temps, so the
    MUST deliver more light.

    Putting each lamp inside a white, 15cm spherical ceiling fitting and using a
    DSE lux meter - I found the Osram put out fairly even light in all
    while the halogen is uneven and quite poor in the downward direction.

    Dunno which is brighter overall - SFA in it really.

    Except one is banned and the other is legal ......

    .... Phil
  2. Pretty interesting, Phil. Is it possible that different filament composition
    could mean that the filaments are not actually at similar temps though?
    They're double coils aren't they (a coiled coil)? Can you actually see this?
    My eyes aren't good enough to pick it, but with enough magnification it's
    Is all the emission from the metal surface, or does some come from a partial
    plasma around the surface? Because the extent of that plasma would change
    the effective surface area.
    Hmm, right where you're most likely to want light. That's pretty crap.

    Clifford Heath.
  3. **Another good reason why I always avoid dodgy lamps and stick to decent
    manufacturers. The worst I've seen are those Mirabella crap.

    On a related matter, I recently purchased an Ecogem S9041 WW (Warm
    White) 11 Watt LED downlight. Not only does it deliver respectable light
    output (680 Lumen), but the spread of light is similarly impressive (it
    is fitted with a nice diffuser). It is supplied with an electronic
    'transformer' that is suitable for use with dimmers.

    Anyway, a friend is fitting her new home with LED downlights and I
    suggested she examine the Ecogem. Naturally, she reacted with horror at
    the price $46.00 wholesale) and elected to use some $20.00 ones she
    found. Sadly, she finds that she needs more than twice as many to do the
    same job as the Ecogems. More holes, more electricians' time.........
    Reliability is unknown.

    A fool and her money............
  4. Phil Allison

    Phil Allison Guest

    "Clifford Heath"

    ** The colour of the two lamps looks very close, the halogen is a tad

    ** Nope - simple coils that look identical.

    ** The gas ( ie nitrogen or iodine) would be convecting rapidly near the
    filament and AFAIK does not ionise.

    A longer coil at the same temp must deliver more light.

    ..... Phil
  5. felix_unger

    felix_unger Guest

    I've had those incandescents literally explode off the ceiling and
    shatter on the floor!


    "If Julia is the answer, then what was the stupid question!"

    “This election is about trust. The choice before the Australian people could not be clearer. It’s more tax or less. It’s more regulation or less. It’s less competence or more. It’s less freedom or more” - Tony Abbott, Federal Opposition Leader

    Sept 14th. is National Rubbish Collection day..
  6. Phil Allison

    Phil Allison Guest


    ** Errr - like this:

    See half way down the page.


    The other two CFLs were ready to go the exact same way.

    Woolworths " ESSENTIALS " brand 20 watt and 22 watt.

    ..... Phil
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