Safety - advice while jumping up in power levels

[MountainGoat]

Hi all,

First, I did search and didn't find a thread quite like what I am looking for. If I missed one, please kindly point me towards it and I'll go explore.

To date, my experience has been up to a ~6-7 watt homemade RGB projector.

I am now considering jumping up in power considerably. I have a new 10 watt RGB and am thinking of 15, 20, or maaaaaybe 30 watts.

Quantifiably this is orders of magnitude of higher power, so I know there are more concerns about reflections, starting fires (unintensionally &#128521, eye protection, etc. Even aligning the optics without accidentally burning things seems challenging.

Any thoughts, advice, suggestions and warnings for people pondering such jumps in power? With power levels increasing and costs decreasing, I imagine more people may find themselves in this position and could use some good advice.

Thanks all!

Ps - it would be awesome of have a dedicated forum here for safety issues.

[danielbriggs]

Even aligning the optics without accidentally burning things seems challenging.

I know this sounds trivial, but align at low power...!
Extend this thinking through both internal projector alignment and scanner / zoning while setting up.

Use the minimum amount of power to do the task you need to do; then once everything is good and you know you're safe, crank the output power to the higher levels.
The same methodology should apply whether you're setting up a 3W or a 30W projector; if not you're doing something wrong IMO.

All the best,
Dan

[MountainGoat]

I know this sounds trivial, but align at low power...!
Extend this thinking through both internal projector alignment and scanner / zoning while setting up.

Use the minimum amount of power to do the task you need to do; then once everything is good and you know you're safe, crank the output power to the higher levels.
The same methodology should apply whether you're setting up a 3W or a 30W projector; if not you're doing something wrong IMO.

All the best,
Dan

Aligning at the lowest power makes plenty of sense.😉

At 20 and at 30 watts, how far away can a full power RGB beam be a fire risk if it is at rest?

I'm certainly familiar with the sting a few watts can give if your arm crosses the beam while aligning optics. How bad of a burn will you get if you briefly cross as a 20 or 30 watt beam (assuming it us a large, ~8mm beam)? (This assumes you cross the beam at full power, I'm not ignoring the "align at lower power" comment.)

[buffo]

At 20 and at 30 watts, how far away can a full power RGB beam be a fire risk if it is at rest?

Too many variables to provide an exact answer. Divergence plays a huge role.

Example: I have a multi-diode array that produces nearly 40 watts (!) of 450 nm blue. At the aperture the beam is pretty damned terrifying. However, because of the massive divergence, the beam has no effect on a sheetrock wall 30 feet away. (By that point the beam has expanded to almost 6 inches in diameter.)
Compare that with a 30 watt RGB projector that I also own. The output beam at the aperture is just as dangerous as the 40 watt blue laser, but the 30 watt RGB projector will also leave a burn spot in that same white sheetrock wall that is 30 ft away if I leave a static beam on for more than 2 or 3 seconds.

To clarify: Both projectors will burn your skin in less than a second at close range. And I'm not talking about a "bee sting". I'm talking about a second-degree burn, with a blister, in less than 1 second. By the time you feel the ouch, it's too late.

Conversely, if you are 30 ft away, you can place the palm of your hand directly in the beam path of the 40 watt blue laser, and after 6 or 7 seconds you will finally start to feel a gentle warmth on your hand. But if you are foolish enough to try that with the beam of the 30 wat RGB projector at the same distance, once again you'll have a blister...

From a regulatory standpoint, NFPA considers the beam from *ANY* class IV laser to be a fire hazard by definition. That being said, I don't think you'll be starting any fires with a 500 mw projector unless you have flammable material within a few feet of the projector (and you hit it with a static beam for several seconds). But I'm confident I could set a pile of leaves on fire with a static beam from one of my 30 watt RGB projectors at a considerable distance (not that I'm in any mood to try).

Adam

[MountainGoat]

That's actually very helpful information.

Another question with too many variables to answer: ☺️

Would you even advise 30 watts indoors for a venue, let's say the size of a typical high school gymnasium.
For the purposes of the question, lets assume you are doing graphics and beam effects, can modestly darken the gymnasium but not completely dark, and you can take precautions to ensure the beam always terminates safely away from the audience (no reflective materials in the area, projector and projection area is well above the audience, your projector has standard safety mechanisms working as the FDA requires, etc.)

Broad question I know, but I am basically wondering if 30 watts is just over the top and increases risk with little return.

Feel free to entertain my question or take it anywhere you like. This is all good info.

Thanks again!

[buffo]

Would you even advise 30 watts indoors for a venue, let's say the size of a typical high school gymnasium.

Are you asking if it's safe to use a 30 watt projector in a gym? I'd say that it would depend on the materials of construction. The walls in my High School's gym were cinderblock, so I would have no qualms about terminating a 30 watt projector on those walls.

But I've seen gyms with dark wood paneling too. In such an environment, with a short enough throw and a static beam, I'm sure you could leave a scorch mark, at least at full power anyway.

That's not to say that I would refuse to use the projectors though. First, you can always reduce the output power of the projector in your control software. Second, you can normally control your projection direction, so I'd aim for the longest throw possible. (A long throw gives the beam more time to diverge, and having the beams propagate along the long axis of the room also makes it easier to fill the space with beams.) And third, I would be very watchful for any signs of a scanner failure that might lead to an unexpected static beam output, so I could hit the E-Stop.

But all of this assumes that you already have the 30 watt projectors (which I do). Instead, before you buy anything, ask yourself if you ever foresee a *NEED* to use a 30 watt projector in a gym (or similarly-sized venue).

assume you are doing graphics and beam effects, can modestly darken the gymnasium but not completely dark, and you can take precautions to ensure the beam always terminates safely away from the audience (no reflective materials in the area, projector and projection area is well above the audience, your projector has standard safety mechanisms working as the FDA requires, etc.) Broad question I know, but I am basically wondering if 30 watts is just over the top and increases risk with little return.

There are two parts to your question (beams and graphics). For graphics, a 30 watt projector is positively STUPID, unless you're projecting onto the side of a mountain. You would be much better off with a lower power unit (which will also have a smaller beam) for graphics. For an indoor show you really only need a 1 watt projector for graphics. I've used 3 watt projectors for graphics shows outdoors on a 16 x 20 screen, or even on the side of a building, with no problems.

On the other hand, for beam shows the most important factor is fog or haze. If you can use fog (or better yet, haze) and you can control the amount in the air accurately, you can get amazing beam show effects with relatively low power. Yes, the amount of ambient light also plays a role, but the brightness of the room is a secondary concern. But if you can't use fog or haze, you are screwed. I've actually used my 30 watt units ONCE for an indoor show, and it was precisely because they would not allow *ANY* fog or haze in the venue. (Yet they had no issues with people vaping, which seemed hypocritical...) Had they allowed haze, I would have done the show with a pair of 6 watt projectors and been just fine. But without any scattering medium in the air, I had to bring more power. Even so, I didn't need to run them wide open, but if I got much below 40% the effects became hard to see.

30 watt projectors are really designed for outdoor shows. Yes, they can be used indoors, but unless you're doing shows in a huge convention center (basically a room that is 200 ft x 350 ft, with a 40 ft ceiling), it's unlikely that you'll ever need that much power. So if you plan to do mostly indoor shows, you might want to purchase more projectors at a lower power rating, rather than just a few of the 30 watt units.

At the end of the day, the difference in risk between a 15 watt projector and a 30 watt projector is not as big as you might expect. The truth is that BOTH projectors need to be treated with the utmost respect, because both can burn or blind you if you ever get careless. But lower power projectors are more affordable (so you can buy more of them), and lighter (making them easier to set up and take down), so unless you have a dedicated use-case for the 30 watt units, they are probably overkill.

In my case, I purchased my 30 watt projectors with outdoor beam shows in mind. I did have a secondary use case in mind that was an indoor venue, but that actually was a convention center (with the dimensions listed above). Alas, as it turns out, by the time I got my units, the convention center gig had ceased to be an option, so at present my primary use case is back to outdoor shows.

Adam

[MountainGoat]

Thanks. More great practical advice.

Funny you should mention projecting on the side of a mountain, because that was one thing I considered trying.

This is really just a hobby, though I have considered a variance and doing some commerical gigs. Regardless though, safety that is appropriate for commerical gigs should generally be the same for hobbyists - the physics is the same.

Thanks for sharing your thoughts and experience, especially for my admittedly ambiguous questions.

Steve

Ps - I absolutely welcome more thoughts and ideas if anyone else has stuff to share. I'm getting a lot of out of this and I hope others may too.

[buffo]

Funny you should mention projecting on the side of a mountain, because that was one thing I considered trying.

Where are you located? (It would be helpful if you filled out your user profile with at least a general location.)

If you are in the USA (and for the moment I'm going to assume that you are), projecting graphics onto a mountain can present additional regulatory challenges. True, the current FAA position is that you do NOT need to file for a letter of non-objection for any outdoor laser shows that are fully-terminated, but that also assumes that the beams will be low enough that they can not interfere with the flight paths of any aircraft. (Generally interpreted as the beams will never be above 400 ft.) But depending on the length of your throw, you could easily break this limit when trying to project onto a mountain or cliff face, and if you do that, then technically you do need to file.

Then too, you need to consider the possibility of helicopter traffic in the mountain area, because helicopters are not subject to the minimum safe altitude rule of 500 ft. This also applies to large outdoor shows in major cities that have police, news, or emergency medical helicopters. In cases where you are projecting from one building to another, you need to consider if it's possible for a helicopter to fly between those two points and into the beam path. Even if you don't have to file for a letter of non-objection, if there is any chance of helicopter traffic in the area, you should at least file a Notice to Airmen (NOTAM), and it would also be prudent to have a handheld Aviation radio (VHF, AM) to be able to speak with any aircraft that might approach the show area.

I have been involved in just two shows where we had to file for a letter of non-objection with the FAA, and both gigs were great learning experiences. But after doing those shows, I've pretty much decided that if I get asked to do a show that requires a letter of non-objection, or even just a NOTAM, I'll quietly decline and pass the gig on to one of the bigger companies that do that sort of thing all the time. Too much hassle and risk for the limited rewards of just one show. (I'd rather accept a minimal finder's fee for the gig and let someone else deal with everything.)

This is really just a hobby, though I have considered a variance and doing some commercial gigs.

If you want to do some commercial events, I suggest you start with things like nightclub shows, weddings, proms, and other indoor events. With indoor shows it is easier to control the light level, easier to control the fog or haze level, easier to set up (especially when it comes to electrical power), and doesn't pose a risk to anyone outside of the immediate show environment.

One thing to remember about commercial shows: Yes, you must have your Laser Light Show Variance from the CDRH to legally perform commercial shows, but you must also ensure that the laser projectors you are using have been certified as compliant under a Laser Product Manufacturer's Variance.

You can either purchase a commercial projector that has already been certified by someone else (Kvant, X-Laser, etc), or you can apply for your own Laser Product Manufacturer's Variance and then submit a Laser Product Report to certify your own projectors.

Of these two options, the first one is the path that most people choose. True, it costs a little more, but there's very little hassle involved. Conversely, even if you are granted a Laser Product Manufacturer's Variance from the CDRH, the task of creating a Laser Product Report is quite challenging. The certification process is more than just adding a few safety circuits and some labels to a projector. You must develop a quality control program, a compliance testing procedure, and supporting documentation for each and every performance requirement specified by the CDRH. Most product reports run to at least 100 pages, and some are over 200 pages long!

Obviously, if you are just a hobbyist running shows in your basement, then compliance is not strictly required. But if you're planning to do commercial shows, keep the above in mind.

Regardless though, safety that is appropriate for commercial gigs should generally be the same for hobbyists - the physics is the same.

Ayup! Just keep in mind that once you cross the line into commercial shows, the CDRH now has full jurisdiction, and all of 21 CFR 1040 applies. This means that it's not just about safety; you must also ensure that you comply with the legal certification requirements for both the operator and the projector(s). It's that second part (certified projectors) that often trips people up.

Adam