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Thread: "Safe" green laser pointer?

  1. #11
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    Quote Originally Posted by absolom7691 View Post
    My fogscreen just uses water, which is what normal humidifiers use. I have actually been considering doing my personal shows without glycol foggers at this point because of how successful my fogscreen hazes the room.

    Here's an example. You can see the light from the projector in the haze. Even a 5mW pointer would show up brighter than that.

    www.youtube.com/watch?v=vIcHqusLUv8

    Anyway, sorry, I didn't mean to derail your thread regarding laser pointer safety. I just thought it should be mentioned that ultrasonic foggers can haze pretty well in enough numbers.
    Oh wow that looks awesome. Ive seen a mist screen before but yours looks a lot more even. One I've seen has less holes I guess and the output is more uneven.

    Dont worry about hijacking, I think Adam covered pretty much everything I wanted to know.

    Should we discuss, i don't know, the weather these days? : D

  2. #12
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    Quote Originally Posted by absolom7691 View Post
    My fogscreen just uses water, which is what normal humidifiers use.
    With the caveat that you had to use a *shitload* of those little ultrasonic units in the base of your fog-screen unit, right? That is an important detail...

    I didn't mean to derail your thread regarding laser pointer safety.
    Aw - no need to apologize Brian; you aren't derailing anything. Thread topics drift over time, plus we were talking about haze and ultrasonic fog, and you are definitely a recognized expert here when it comes to ultrasonic fog.

    I just thought it should be mentioned that ultrasonic foggers can haze pretty well in enough numbers.
    Just how many units did you have to use for your fog screen anyway?

    Between your comments about trying to do a show without any glycol foggers and the comments about new hazers that use ultrasonics (instead of heaters), I'm wondering if it wouldn't be a worthwhile summer project to try to build one myself...

    Adam

  3. #13
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    Quote Originally Posted by buffo View Post
    With the caveat that you had to use a *shitload* of those little ultrasonic units in the base of your fog-screen unit, right? That is an important detail...

    Actually, not really. To be more accurate, a shitload of transducers, yes but they are concatenated. My current iteration is using 3x ten-head foggers (now under $100 per unit on ebay). Still a lot, I suppose but it isn't too bad!


    Aw - no need to apologize Brian; you aren't derailing anything. Thread topics drift over time, plus we were talking about haze and ultrasonic fog, and you are definitely a recognized expert here when it comes to ultrasonic fog.
    I think you give me too much credit, sir! All of my work has been lucky guesses!!!

    Between your comments about trying to do a show without any glycol foggers and the comments about new hazers that use ultrasonics (instead of heaters), I'm wondering if it wouldn't be a worthwhile summer project to try to build one myself...
    As I mentioned above, they are not cheap but they aren't expensive either. https://www.ebay.com/itm/10-Head-Ult...AAAOSwFytaL1ia

    The stated 3000 - 4500 mL/hr seems a bit exaggerated. I would say it's more like 2000 mL/hr. This weekend, I am going to get a video together of how the fogscreen works because of the multitude of requests I have gotten over at the Halloween Forum. Since I will have the fogscreen out and running, I'll get some video of the hazing capabilities too.
    Attached Thumbnails Attached Thumbnails 20171008_183737.jpg  


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    Quote Originally Posted by Ableton69 View Post
    Oh wow that looks awesome. Ive seen a mist screen before but yours looks a lot more even. One I've seen has less holes I guess and the output is more uneven.
    Thank you! There are a lot of different designs out there. One of the easy ways to make a mist screen is to forgo the laminar air curtain and just concentrate the mist into a slow moving mass. It works and it's easy. I went the full route with laminar curtain. It holds up better outdoors (very light breezes) and the screen of fog stays "collimated" even from heights of 10' (albeit, with some breakdown by the time it hits the floor). I have a pseudo build thread here and at HalloweenForum if interested...

    https://www.halloweenforum.com/hallo...-boogaloo.html . <--- probably more complete than the thread here because I am just too damn lazy!

    Dont worry about hijacking, I think Adam covered pretty much everything I wanted to know.
    He usually does. He and Steve (mixedgas) are the sr people here and their combined knowledge is staggering. I would honestly wager that Steve has touched damn-near every laser in existence. That includes commercial and theoretical!
    Last edited by absolom7691; 05-13-2019 at 08:14.

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    Quote Originally Posted by absolom7691 View Post
    Thank you! There are a lot of different designs out there. One of the easy ways to make a mist screen is to forgo the laminar air curtain and just concentrate the mist into a slow moving mass. It works and it's easy. I went the full route with laminar curtain. It holds up better outdoors (very light breezes) and the screen of fog stays "collimated" even from heights of 10' (albeit, with some breakdown by the time it hits the floor). I have a pseudo build thread here and at HalloweenForum if interested...

    https://www.halloweenforum.com/hallo...-boogaloo.html . <--- probably more complete than the thread here because I am just too damn lazy!



    He usually does. He and Steve (mixedgas) are the sr people here and their combined knowledge is staggering. I would honestly wager that Steve has touched damn-near every laser in existence. That includes commercial and theoretical!
    Nice thread. If it's not a trade secret, how heavy is the whole setup? One I have seen a couple of times (same event equipment provider) has a heavy duty truss system and it looks really bulky. Its an old system I know that, they had it for 8 years at least.

    He usually does. He and Steve (mixedgas) are the sr people here and their combined knowledge is staggering. I would honestly wager that Steve has touched damn-near every laser in existence. That includes commercial and theoretical!
    Yeah, but I am deducting one point because he cant change the laws of physics so I could use a 1 watt green with no regard to safety at all.

  6. #16
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    Quote Originally Posted by Ableton69 View Post
    Nice thread. If it's not a trade secret, how heavy is the whole setup? One I have seen a couple of times (same event equipment provider) has a heavy duty truss system and it looks really bulky. Its an old system I know that, they had it for 8 years at least.
    Not entirely a trade secret. I mean, I keep a little bit of it secret because I've gotten messages from people for ALL of my materials... Docs, sketchup files, schematics, list of materials, vendors, even hardware! So, when someone asks me for information and I've decided they aren't just looking to steal my design, then I'll help out with info!

    Empty, my rig weighs about 77Kg. Full, it weighs about 95Kg so, it's a little bulky and heavy but probably not as bad as the pro fogscreens. I don't need "heavy" lighting truss but I do use some lightweight truss. I use Odyssey trussing which I double up on since Odyssey truss is not the best quality. I'm going to shoot some video this week of setup and basic operation. I'll be sure to post it here in my fogscreen thread.

    Yeah, but I am deducting one point because he cant change the laws of physics so I could use a 1 watt green with no regard to safety at all.
    A perfectly acceptable response IMNSHO!!!

  7. #17
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    Quote Originally Posted by absolom7691 View Post
    Not entirely a trade secret. I mean, I keep a little bit of it secret because I've gotten messages from people for ALL of my materials... Docs, sketchup files, schematics, list of materials, vendors, even hardware! So, when someone asks me for information and I've decided they aren't just looking to steal my design, then I'll help out with info!

    Empty, my rig weighs about 77Kg. Full, it weighs about 95Kg so, it's a little bulky and heavy but probably not as bad as the pro fogscreens. I don't need "heavy" lighting truss but I do use some lightweight truss. I use Odyssey trussing which I double up on since Odyssey truss is not the best quality. I'm going to shoot some video this week of setup and basic operation. I'll be sure to post it here in my fogscreen thread.



    A perfectly acceptable response IMNSHO!!!
    Yeah, those hard working Chinese can reverse engineer just about anything.

    Thats not heavy at all. I mean it is, but rigging the beast I saw required a weighted 4 point truss and it wasnt that wide. Maybe 2.5 meters by 40 cm.
    It gave a nice effect when projected on, but after seeing yours, its like watching a 360p video on youtube. You could do it back in the day, but not anymore lol

    Nice idea in using the honeycomb to smooth it out. You think a laminar flow principle would work the same? I know it works for liquids, but probably not for mist.

  8. #18
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    Quote Originally Posted by Ableton69 View Post
    Yeah, those hard working Chinese can reverse engineer just about anything.
    You're not kidding! Most of the correspondence I got was clearly google translated and very broken. Laminar flow isn't easy so this is probably why I was bombarded!

    Nice idea in using the honeycomb to smooth it out. You think a laminar flow principle would work the same? I know it works for liquids, but probably not for mist.
    Any good laminar filter uses honeycomb, mainly for uniformity although a bit for strength (so the center of the fogscreen laminar filter doesn't sag). Technically any viscous substance should be able to achieve laminar uniformity (within practicality, that is). The mist isn't really a substance per se. It's just air that is "dirty" with water particulate. So it would be treated like air.

    You can run the mist through straws which will make it laminar but since it collides with the non-moving air when it exits the straws, it goes from laminar to turbulent really quickly. That's why most of the simple mist walls break down within a few centimeters. If the mist is moving slow enough, the reynolds number is lower and the mist will stay together longer. Because of this, those simple mist walls are really only good indoors and even then, any air movement will play havoc with the mist. They work okay though and for projections, they get the point across.

    The best way is to make the mist laminar and then make a surrounding column of air laminar as well. This protects the mist layer from being disturbed. Since the outer air and inner mist/air are bumping into each other as they travel at the same speed and in the same direction, things stay together longer. Eventually, the turbulence will break it all apart but that is the long and short of it. The good thing with this is, the screen stays relatively thin and the image looks cleaner. The other bit is, there can be less mist needed and this can make the screen almost invisible which makes the image look like it's being projected in mid-air. That's basically how mine and the pro screens work.

  9. #19
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    Quote Originally Posted by absolom7691 View Post
    Not entirely a trade secret. I mean, I keep a little bit of it secret because I've gotten messages from people for ALL of my materials... Docs, sketchup files, schematics, list of materials, vendors, even hardware! So, when someone asks me for information and I've decided they aren't just looking to steal my design, then I'll help out with info!
    Perhaps we can classify this under “imitation is the sincerest form of flattery”!

    Seriously, it is/was a really impressive build. I have wanted to copy it for years, but the project never makes it to the top of my priority list. One day though!

    -David
    "Help, help, I'm being repressed!"

  10. #20
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    Quote Originally Posted by absolom7691 View Post
    Empty, my rig weighs about 77Kg. Full, it weighs about 95Kg so, it's a little bulky and heavy but probably not as bad as the pro fogscreens. I don't need "heavy" lighting truss but I do use some lightweight truss.
    I thought your fog screen was designed to sit on the ground and the fog flowed upward? Are you saying that you can invert it and have a "falling" fog screen too? If so, I must have missed that part of the original thread!


    Quote Originally Posted by ableton69
    I am deducting one point because he cant change the laws of physics so I could use a 1 watt green with no regard to safety at all.
    A perfectly acceptable response IMNSHO!!!
    ROFLCOPTERS!

    Any good laminar filter uses honeycomb <snip>
    You can run the mist through straws which will make it laminar but since it collides with the non-moving air when it exits the straws, it goes from laminar to turbulent really quickly.
    If you used straws for both the mist channel and the surrounding "curtain" air, would there be any difference vs the honeycomb material? I'm wondering what the specific advantage the honeycomb shape has with regard to maintaining the smooth laminar flow.?.

    Adam

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