Fogscreen Project

[absolom7691]

I wonder if leaving this unit at ground level and improving the vertical throw wouldn't be easier than elevating it.

For laser projection, I might do just that for all of the reasons you mentioned. For Halloween, the idea is that the kids will pass through the fog like a spooky veil to add a bit of reluctance/anticipation when entering.

...heating the water as much as the safe limit the soda straws will permit.... ...The differential velocity of the air as you move out from the axis will cause a pressure gradient. If you adjust the velocity you might thin and extend the screen.

Each fogger has about 200W pumping though it. The water needs to be cool so that the units don't overheat. I can try adjusting the filters to have less resistance in a "gradient" type of orientation. I also have speed controls on the main airflow and also the fog flow. I can adjust it quite a bit. I am probably only running the main fans at about 25%. I can give this a try and see how it looks. The higher velocity would also probably give a little less turbulance in the image because the fog would be moving much faster and also thinner.

Alternatively, what does it look like when the lasers strike the screen from the side? Can you produce a lacework of beam fans?

Interesting! I hadn't thought about that. Linear beam fans and solid fans would probably look great. For that, I may even be able to slow the fog down but lower the amount of fog for a liquid effect. I'll try this out, as well and post pics/vids.

[absolom7691]

Another video. I was really disappointed with how badly the video turned out. I probably need to lower the brightness of my projector and also maybe leave the lights on when I try again. The projection look completely washed out. Ah well. The projections look decent of the fogscreen. This image is about 40" x 40". I think I need to raise the projector so that it is hitting the fogscreen a little more squarely. There are a few other things I am going to try as well. In person, it looked great. The thing that gives a certain wow factor is that when the lights are on or when you can see objects behind the screen, it really gives it a "hologram" look. Anyway, for what it's worth, here is another video.

At the request of the user to whom this show belongs, I have removed the video. I have been excessively busy with work but I will try to get another one up soon with some different content as well as some better camera work!

[Jem]

Whoa... Classic tune

ELP - Hoedown

Loving the project, keep the vid's coming

[buffo]

Nice work on the fog screen! Your results are quite impressive.

Regarding the idea of using a 405 nm diode and some sort of dye...

I would think laundry detergent would probably work but then again, I am not sure if the detergent would make it into the fog. Also, I don't know if the detergent would play nice with the foggers, leaving them in working order.

I would think detergent would tend to foam up. I work at a plant that used to manufacture optical brighteners (phorwhite), which is the stuff they add to detergent that absorbs UV and fluoresces in the blue spectrum to make colors "brighter". Even in the product's raw form, it foams quite a bit. Add a soap base to that, and I think you'd end up with a foam-screen instead of a water screen.

On the other hand, Rhodamine 6G or Fluorescein dye might work. Even in very dilute concentrations, they both fluoresce quite readily. Granted, 405 nm is a bit outside the optimal absorption peak, but given the high irradiance of a collimated beam from a blu-ray diode, it should be enough to excite it.

That was the main thing I built this for; Halloween. I have, in mind, a static video I may loop. Dripping blood or flames or something like that

Eons ago I worked with a neighbor to create a "haunted tunnel" entrance to his yard for Halloween guests. The highlight of the spectacle was a video loop from Walt Disney's "Fantasia". We used the "Night on Bald Mountain" clip, and played it on a projection TV aimed at a white sheet strung up behind my buddy. We had the red and blue component signals disconnected, yielding a poor-man's green-screen monitor that looked downright spooky. I'm thinking it would be even more so if you could project it on your fog screen so it would be floating in mid-air...

I plan to use microwave motion sensor from an automatic door that I may rig up to play a flash clip of The Exorcist or some other flash scare right when the kids are passing through.

Or use it to trigger a small solenoid valve connected to a tank of compressed air. The combination of the sound and the physical sensation of being "touched" by the air flow is enough to make most people yelp with fear, even if only for a second.

One question: What is the CFM rating of your fans? Because I've got a bunch of Patriot-style fans (pulls from old air-cooled argon lasers) that might be up to the task of feeding a unit like this, should I ever lose my mind and try to take on yet another project!

Adam

[planters]

I would stay away from any substance that you will intentionally distribute into an audience. Rhodamine is toxic and The MDS of almost any substance, including distilled water, would be a treasure for a personal injury lawyer.

I actually liked the video and as one who has wrestled with producing good videos of laser projects, I can attest that it is hard to do. One thing you might try in a future video is to slowly move the camera in an arc from one side of the projection to the other. This way the true three dimensional quality of this "very thick" scrim might show itself.

[andy_con]

that's really good, well impressed

[absolom7691]

Nice work on the fog screen! Your results are quite impressive.

Thanks!

On the other hand, Rhodamine 6G or Fluorescein dye might work. Even in very dilute concentrations, they both fluoresce quite readily. Granted, 405 nm is a bit outside the optimal absorption peak, but given the high irradiance of a collimated beam from a blu-ray diode, it should be enough to excite it.

It looks like planters already covered this but yes Rhodamine is carcinogenic! I really don't think the 405nm idea would come to fruition. It sounds cool but there are too many factors, the biggest is the safety of any aerosol material.

We used the "Night on Bald Mountain" clip, and played it on a projection TV aimed at a white sheet strung up behind my buddy. We had the red and blue component signals disconnected, yielding a poor-man's green-screen monitor that looked downright spooky. I'm thinking it would be even more so if you could project it on your fog screen so it would be floating in mid-air...

I LIKE THIS!!!!!!!! I could wash it through After Effects for color and other effects.

Or use it to trigger a small solenoid valve connected to a tank of compressed air. The combination of the sound and the physical sensation of being "touched" by the air flow is enough to make most people yelp with fear, even if only for a second.

I like this idea too but I only have a little 3 gallon compressor (Harbor freight) and it is VERY noisey! if I had a larger one that didn't need to cycle very much, I would go that route. Maybe something for next year.

One question: What is the CFM rating of your fans? Because I've got a bunch of Patriot-style fans (pulls from old air-cooled argon lasers) that might be up to the task of feeding a unit like this, should I ever lose my mind and try to take on yet another project!

Heh, and what a project! This monopolized a good chunk of time to put together and I still see nothing but improvements that I would love to incorporate or even add to a new one, should I ever lose my mind and build another!

The fans top out at 220cfm. I am not running them anywhere near that fast though. Even still, with 14 fans, the filtering is such that a lot of air doesn't move at least, not at a huge velocity. it is like a steady and constant breeze. It is the strangest air I have ever felt, smooth and constant. Nothing at all like what comes out of a fan. IIRC, those fans from those argons are AC... and loud! If that is the case, you will need to control them via variac, you don't want them running at full speed. If I crank mine all the way up, the fog almost disappears and it sounds like an aircraft powering up.

Good luck, should you you decide to build one!

I actually liked the video and as one who has wrestled with producing good videos of laser projects, I can attest that it is hard to do. One thing you might try in a future video is to slowly move the camera in an arc from one side of the projection to the other....

I was really hoping for better quality video. I'll give your suggestion a try, thanks! My other problem is that my garage is not that big. I wish I had a workshop like yours! You need to give a video tour of that place sometime. Is it a converted barn? That is kind of what it looks like.

that's really good, well impressed

Thanks, Andy!

[buffo]

I would stay away from any substance that you will intentionally distribute into an audience.

Well, we're not talking about a professional venue here. This will be mounted on his front porch... The "audience" (if you can call trick-or-treaters that) will only be exposed for a few seconds tops. And you would be using a very dilute solution.

Rhodamine is toxic

So is chlorine, yet we add that to our drinking water. Rhodamine will still fluoresce even at sub-part-per-million dilutions. (I've put a couple drops into a 20 gallon fish tank with no harm to the fish and still gotten great results when pumping with 532 nm green.)

The MDS of almost any substance, including distilled water, would be a treasure for a personal injury lawyer.

If you are worried about personal injury lawyers, I'd be more concerned about the laser projector than the distilled water, or the Rhodamine. Honestly, we're talking about a Halloween display here. If the design needs to be lawyer-proof, that means no display.

It looks like planters already covered this but yes Rhodamine is carcinogenic!

And toxic, and mildly corrosive as well. All in its concentrated form only. Dilute it enough with water and you can drink it. Even RCRA doesn't consider it a listed waste. (Characteristic waste only; so if you dilute it, it's no longer toxic, just like most chemicals.) I work with stuff like this all the time. (I am employed in the environmental control department of a large multi-facility chemical manufacturing site, and one of the many things we manufacture here are dyes and pigments.)

Sorry to get up on a soap box here, but this really grinds my gears. People freak out when they hear that something causes cancer, yet they have no problem pumping their own gasoline every day, despite the fact that it is quite toxic, and carcinogenic, and flammable to boot! Ever spill gas on your hands? Yeah, me too. Are you worried it will kill you? No? That's my point.

Yes, many dyes are downright nasty in their concentrated form, but even so, when was the last time you heard of someone getting cancer because they worked with a dye cell on a laserscope? In fact, I'm pretty sure that Eric (planters) has a dye cell on his laserscope.. So Eric, which do you fear more? The dye, or the many kilowatts of pulsed IR that is in the cavity?

Given that we're talking about concentrations that are 6 to 8 orders of magnitude lower for this project, the threat from the dye pales in comparison to the threat from the laser itself, even if you only use a single blu-ray diode to pump it.

I only have a little 3 gallon compressor (Harbor freight) and it is VERY noisey!

You don't need a lot of air. Regulate it down to around 30 PSI and it will still be enough to scare people without using up all your stored capacity. Then too, you can always pick up some inexpensive hose (again from Harbor Freight - love that store!) and locate the compressor far away from where the air will actually be used. (That's what we did...)

The fans top out at 220cfm. I am not running them anywhere near that fast though.

That's good to know. The fans I have put out a little more than that, but I don't have as many as you do, so it might end up being a wash, assuming I run them a bit faster.

IIRC, those fans from those argons are AC... and loud! If that is the case, you will need to control them via variac, you don't want them running at full speed.

The original Patriot fans are, but these are clones that run off 24 volts AC. (Rather odd, but that's why I got them so cheap.) I could run a bunch of them in series off a variac, but I'd probably just use a Triac instead. (Besides, my variac is currently in use for another project...)

If I crank mine all the way up, the fog almost disappears and it sounds like an aircraft powering up.

Yeah, the noise level would be the main issue I'd be concerned about. Guess I'll have to do some experimenting to see if it's worth heading down this path or not...

Good luck, should you you decide to build one!

Thanks! If I do go down this road, I'll be sure to update the thread here. No promises though. I've already got a ton of work on my plate...

Adam

[absolom7691]

Adam, I get what you're saying about carcinogen warnings, I really do but sometimes you get those crazy, over the top parents who have too much time reading stuff on the internet. I just make it a habit to steer clear. Sure, there are a million things out there that will kill, mame and destroy that we are in contact with every day and when it comes to myself and my own personal safety, I don't worry about nearly as much. When it comes to other's safety or the peice of mind for parents, I try to do what I can to keep things as safe as I can. As such, I actually never use lasers for Halloween. Same with Tesla coils, Jacobs ladders or even dry ice. I love creating something fun for the kids but all it takes is one smart-ass or one over-reacting parent and that's that. As a side, does anyone remember the days when our safety was our own resposibility??? Adam's beef is right up there with mine as far as people are so quick to sue someone over something so trivial and half the time (maybe even more than half) some people/organizations just settle because it is cheaper for them even if the "victim" is lying out their assor don't deserve anything based on stupidity! Anyway....

You don't need a lot of air. Regulate it down to around 30 PSI and it will still be enough to scare people without using up all your stored capacity. Then too, you can always pick up some inexpensive hose (again from Harbor Freight - love that store!) and locate the compressor far away from where the air will actually be used. (That's what we did...)

I am already looking into solenoid valves on ebay for this. I am trying to think of a timer circuit that would work so that it would only send an air blast for a brief second and not keep the valve open the entire time it is getting an activation signal. Maybe a type of ratchet relay.

Yes, Harbor Freight is an awesome store! It is my candy store when I need something to do the job and I need it cheap!

Yeah, the noise level would be the main issue I'd be concerned about. Guess I'll have to do some experimenting to see if it's worth heading down this path or not...

At the speed I run mine at, it isn't too noisy. I would like for it to be a bit quieter but that would require more fans.

If you do decide to build, I can answer any other questions you might have. If time is a villain, I would advise against drinking straws and go with a pre-fabbed laminar filter. Those straws sucked up so much time.

[mixedgas]

I spent a year trying to prove to a Ebay Safety rep that plain old Rhodamine is toxic. Any of the Rhodamine Lakes or Rhodamine Salts, or Rhodamine Perchlorate, yes very toxic and easy to prove that. For plain Rhodamine, well the jury is still out. There was that idiot selling Rhodamine on Ebay for coloring drinks in bars. What was scary was he did not know which salt he was selling.

I know its mutagenic, but proving it is something else. Any dye that initiates the corrosion of aluminum and steel, and stains concrete for decades, I'm not drinking.



Steve