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Thread: Safety Opinion

  1. #1
    Join Date
    Aug 2008

    Default Safety Opinion


    I'm drawing closer to doing my event and so wanted som opinions.

    For the 1st time I've tarpaulined the car port in and this is what it looks like (daylight):

    I intend to put the projector just inside the garage at the one end (where the camera is in the photo) then project the image onto the roof somewhere down the other end - exact angle will depend on the logistics of keeping it above everyone's heads (I intend a small exclusion zone).

    Total length of the car port is 27 feet from memory.

    Obvious dangers are:

    1. Bulk head lights - I intend to cover these with cloth to stop reflections as they won't be on anyway. I intend to use weak portable lights and reflected light from the laser to light the carport rather than strong lighting.

    2. Polycarbonate roof - can't do much about this but I doubt much will reflect back down and they're smoked polcarb and the beams will help interrupt some reflection

    3. Tarpaulin sheeting itself - its made of polyester type plastic material and is quite shiny. It does reflect light in the day. I wondering if this will be a problem if the lowest part of the projection passes onto it at the far end (ladder end in the picture). Do you think being woven and uneven, any reflection will be diffuse enough not to matter? Do you also think that with the projector pointing upwards, most reflection will go upwards anyway even though it might be on the down stroke of a pattern? My projector appears not to put out any concentrated pencil beams in auto mode anyway. The nearest it comes is when it shrinks the pattern down to near a point, but this happens quickly and in the projection centre which shouldn't be on the tarp anyway - it will be centerd on the roof, probably I'm guessing on the beam between the 2 visible bulk head lights. The exact centre point will be determined obviously by the extent of the downwards sweep and also the angle of the beams up from the projector - I need to keep the exclusion zone small and reasonable so will need either a steeper angle or higher mounted projector to ensure this. However, adjustments there will affect where I centre it on the top, and thus in turn how far towards / onto the end tarp the downward sweep reaches.

    Finally, I have tested the tarp for flame retardeness. It doesn't burn easily even with a naked flame - it tends just to melt, and the one time I got it to burn, it only had a small weak flame that extinguished after a few seconds when it met the molten blob that formed behind it.

    Reckon this will be safe?
    Last edited by White-Light; 09-20-2008 at 10:09.

  2. #2
    Join Date
    Jul 2007
    Knoxville, TN, USA


    You should be fine - in fact, your "stage" enclosure looks like a great idea!

    With your projector, you would probably have to have a prolonged, stationary, full-power, concentrated beam to cause any damage to the tarps or overhead cover, which isn't likely to happen while the projector is actually in use. Just be cautious of your audience - which we already know you will be - and don't forget to shut down any time you're not there to "supervise".

    Post pictures when you get things up and running - it looks like you'll have a pretty cool "home venue" setup going for you!

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.

  3. #3
    Join Date
    Jan 2006
    Charleston, SC


    At the power levels you're talking about (600 mw total output), I think you'll be just fine. Watch for stray reflections off those light housings, yeah, but otherwise I think you won't have any trouble.

    Any chance a beam could hit one of the windows? If so, you'll want to cover them. Window glass can be quite reflective, especially if the beam strikes the glass at a narrow angle (nearly parallel to the surface).


  4. #4
    Join Date
    Sep 2009
    Brno, CZ / Povazska Bystrica, SK


    I don't want to start a new topic just for one small question that popped in my head so i just ask here as it's about safety anyway. Is there any hazard coming from the laser light projected on the wall? Because when i tested the shows or played with laser i could feel a slight headache, i didn't stare in the beam but on the projected pictures on (white) wall, could this projected light be still so bright it can harm your eyes? Thanks for reply in advance.

  5. #5
    Join Date
    Oct 2006
    Central Florida


    I think that just means your eye are sensitive. My fiance has the same proble; she can't watch them for long. I on the other hand can watch them all day, but I get headaches for other reasons anyway...
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  6. #6
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
    Join Date
    May 2007
    A lab with some dripping water on the floor.


    The past calculations I have seen is a stationary spot of 200 mW of all lines argon at 3 meters for argon is safe for a 8 hour day,but not day after day after day, effects are cumulative in the blue.
    Since the eye is a lot more sensitive to 532, you might want to back down on the peak levels.

    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

  7. #7
    Join Date
    Dec 2008
    Southport, UK


    Maybe the headache is because of the flicker? Since changing to LCD tv several years ago; watching a CRT gives me a headache these days.

    I had to do an exam earlier this year on a touch screen monitor (CRT). The refresh rate must have been 60hz because the flicker drove me crazy.

    Maybe this is hereditary as my mother can't stand fluorescent lighting.

    Doc's website

    The Health and Safety Act 1971

    Recklessly interfering with Darwinís natural selection process, thereby extending the life cycle of dim-witted ignorami; thus perpetuating and magnifying the danger to us all, by enabling them to breed and walk amongst us, our children and loved ones.

  8. #8
    Join Date
    Nov 2007
    Southampton, UK


    The refresh rate must have been 60hz because the flicker drove me crazy.
    I'm with you on that one - I'll happily drive strobes all night, (provided I'm in charge of the speed and duration...) but put me in front of a slow-scan crt monitor and I get a headache in seconds! Fortunately the advent of solid-state screens has made this a rare event these days.

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