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Automated Fixtures Moving Light Surface Temperature

Discussion in 'Lighting and Electrics' started by Diarmuid, Nov 27, 2008.

  1. Diarmuid

    Diarmuid Active Member

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    Hiya,

    Just a quick question that I came across today. Looking at the Mac 250 wash specs, the maximum surface temperature is rated at 160 degrees centigrade. However when I've previously used them, their body surface temperature was nowhere near that hot.

    I was wondering if you knew why this was? is that just a temperature for internal surfaces? Or have I just had very cold fixtures? I also realise that this could be a maximum, that it rarely reaches...?

    Thanks for your help.

    Diarmuid
     
  2. Les

    Les Well-Known Member Premium Member

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    Could be an absolute maximum, with a generous margin of error. It could also assume the fixture is left in one position without moving for an extended amount of time. For example, the measurement could have been taken from the rear of the lamp house after the fixture had been pointing straight down for 3 hours.
     
  3. photoatdv

    photoatdv Active Member

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    I don't know for sure, but I'd certainly be a little concerned if I saw a moving light with a exterior surface temp anywhere near that. That is over 300' F, and the internal temps would be much higher than the surface temp. Are you sure it isn't 160'F? That would make way more sense as a max surface temp.

    I know on one of our shows the ML LD/programmer showed us how the movers worked (I want to say they were Mac 250 spots). The panels were barely warm, and he was playing around with various internal pieces, which obviously weren't very hot since he was touching them. The light had been on until he started the demonstration, so it didn't cool down much.
     
  4. icewolf08

    icewolf08 CBMod CB Mods

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    It is not uncommon for arc lamp fixtures to get very hot. I know that around the exhaust ports on my PowerSpot 700s it gets up to around 200˚F. The rating that is given in the specs though may be for what the case materials can withstand.
     
  5. lightman02

    lightman02 Active Member

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    I believe as well it is what the case can withstand. The cases are usaually always plastic, so they don't conduct heat nearly as much as metal would. Also these lights have a reflector and hot mirror assembly that are designed to keep the heat where the lamp is and expel most of it out the back with the fan. You would notice that you don't feel nearly as much heat out of the front of the light then you would think, this is the hot mirror reflecting the heat back into the rear of the fixture. If the fan were to fail you would definately have a problem with heat and plastic but the light would normally shut down before that temp was reached as they have heat sensors for this purpose.
     
  6. icewolf08

    icewolf08 CBMod CB Mods

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    I believe you mean a cold mirror. I cold mirror only reflects visible light and allows UV and IR wavelengths to pass through it, thus taking much of the "heat" out of beam.
     
  7. lightman02

    lightman02 Active Member

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    No, I mean hot mirror. The hot mirror removes a large amount of the UV light which is why they tell you not to strike an arc lamp while the covers are open and being directly exposed to the unfiltered direct light from the lamp itself. The hot mirror reflects the heat back into the light and filters out the uv so it does not come out the front and expose people to uv. If you open a light the first piece of glass you see in front of the bulb is the hot mirror.
     
    Last edited: Nov 28, 2008
  8. icewolf08

    icewolf08 CBMod CB Mods

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    Ah, yes, I thought you were talking about the reflector. I forgot about that piece of glass. The reflector is a cold mirror, the glass filter is a hot mirror.
     
    Last edited: Nov 28, 2008
  9. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Interesting that the terms are "cold reflector" (metal cold mirror) and "hot mirror" (heat shield), both designed to remove heat from the beam.

    Now does a UV Filter create, or reduce blacklight?;)
     
  10. icewolf08

    icewolf08 CBMod CB Mods

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    In photography, a UV filter removes the UV.
     

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