NELEM III --September 11-13, 2015

[buffo]

But then again imagine a cool spaceship drone arising behind my big 8 foot Gort laser monster.

I'm more concerned about WHY you have an 8 ft tall Gort laser monster!

Seriously - you trying to re-shoot your own version of "The Day the Earth Stood Still" or something? (Or are you just trying to scare the piss out of the neighborhood kids? Because if I saw that thing in someone's backyard in the middle of the night, I'd probably shit myself.)

You are right about controlling fog outside, but if it is a quiet night you can get some spectacular effects, as seen in this video:

The video looks good, but it appears that the beams are no more than 10 ft off the ground. Eric was talking about a maximum altitude of 150 feet. That's a big difference. Even 50 feet is probably too high. I think you could work with 20-30 feet though.

How much power did you use for the effects seen in the video?

Adam

[Fearless]

Hi Adam,

We can put smoke machines in the trees if need to. The power on the Gort lasers were, 3 watts green, 3 watts red, and 5 watts blue. I'm now in the process of doubling all the laser outputs, two dual green 3 watts PBS together, 6, 1 watt 638's that are differentially cryo-cooled per Eric's specs, and 9 watts of blue. I'm also using X-Lasers new board for the Scannermax 506's. I'm hoping to get it all done in a few weeks.

[planters]

Adam,
I was anticipating limiting the altitude to no more than 150 feet based on communications and control. I agree that the effects might be best anywhere from ground to just above tree height.
My projectors are extremely heavy. They are much heavier than a similar sized commercial unit for rigidity reasons, mounting flexibility and thermal stability. There is no real optical table either. The enclosure is integral to the deck and the power supplies and amps etc are on another level. A 20K scanner is plenty as almost certainly this will only be projecting beams or color washing a particular area. I would rather go for a small, complete unit that could be powered either directly from a battery or through an inverter. I would compromise power and scan speed to make this workable.

I wonder, but if the haze is at a lower level and does not envelop the drone (not to mention the result of the rotor wash), this might be an impressive effect a distance.

[buffo]

Eric;

Sorry - I didn't realize your projectors were so robustly built. OK, so that's out.

The projector I was thinking about with the removable optical table was the old Alphalite RGB unit I sold to Hank. But it only makes about 1.2 watts of RGB. I don't think that will be enough. Based on Rick's video of the Gort robot prop from last year and the specs of those lasers (11 watts total RGB), I'm thinking you will need at least 8-10 watts to pull this off. That's going to be tough.

For power, I was thinking about a straight DC supply driven off a large LiPo pack and then stepped down with a voltage regulator and pass bank. That's going to be a lot lighter (and a lot more efficient) than trying to power an inverter to generate 110VAC and then using the existing AC-DC supplies to power the lasers. But it means someone would need to build the voltage regulator. Then too, getting the dual-polarity supply for the scanners is tricky. The easy way out is to bring a second LiPo pack, but that adds a lot of extra weight. Using a DC-DC converter is lightweight and efficient, but it gets expensive. Sigh...

Regarding the rotor wash of the drone, I'm thinking there's no way to avoid that. If this drone is big enough to lift 8 lbs or more, it's going to have a tremendous downwash. But that might work to your advantage, since it will tend to push the fog back down towards the ground where the people are. Since fog usually rises (it's hot), this might not be too much of an issue. And especially if you only have the drone hovering, or even just moving around in the distance, then the fog closer to the audience shouldn't be affected.

I don't have anything powerful enough in my arsenal to pull this off. And I don't know anyone who has a 10 watt RGB deck that can be easily removed from a projector. If someone wanted to spend a good chunk of money on the project, they might try one of the pre-built 8 watt optical tables that you can get on E-bay for around $1500.

Adam

[Bradfo69]

they might try one of the pre-built 8 watt optical tables that you can get on E-bay for around $1500.

Aside from the fact that it's from newgazer and chinese cheap.... whoda thunk a couple years ago you could get 8 watts RGB for $1500 - just add scanners. Unbelievable.

Kinda makes me want to get the hell out now, sell everything and get re-interested in about 2019.

[buffo]

Yeah, it's cheap all right. But check the divergence. 2.5 mrad! So the beams will be flashlights. Not anything we'd probably be interested in.

But for a one-off effect at a LEM, I can see it, assuming someone had $1500 eating a hole in their pocket and wanted to do something cool for the event. (That increasingly fictional someone would not be me though!) Right now I'm so broke I can't even pay attention.

Adam

[Fearless]

Why not use the drone as a big bounce mirror and use a very, very small galvo image from one of his large projectors to bounce the image forward. All you would need at that point is a mirror tracking device on the ground that knows where the drone is at all times.

[planters]

This would significantly limit the locations where the drone could operate. It would also limit angles that the beams from the drone could cover.

Two LiPo bats may be the best answer for the scanner. The momentary current draw from the scanner will put a heavy demand on a DC to DC converter.

[Fearless]

Eric, You should check out the X-Laser 506 system that I'm installing on the robot--12 volt operation, 1/2 the weight, only one board for X/Y, and very little current draw. A very small and efficient scanner system.

[buffo]

Re: Bounce mirrors on the drone...
This would significantly limit the locations where the drone could operate. It would also limit angles that the beams from the drone could cover.

It is also amazingly difficult to hold the drone still, assuming you are piloting it yourself. We tried this indoors at FLEM this spring, and it was quite difficult. Granted, we used a much smaller quad (250 series) and we had small mirrors as well, but even so it was a lot more challenging than I thought it would be.

If you had a large enough mirror and a quad with GPS lock and auto-altitude hold, then that would make it easier. Still, I agree that being able to fly the entire projector around is preferable to just flying a bounce mirror.

Two LiPo bats may be the best answer for the scanner. The momentary current draw from the scanner will put a heavy demand on a DC to DC converter.

The problem with two batteries is the added weight. Especially if you plan to run everything off one battery and then use the second one only for the negative rail for the scanners. (I guess you could use different capacities though - that would save some weight, and some money!)

The instantaneous draw from the amps isn't a big deal. A pair of 2200 microfarad caps on the output of the DC-DC converter (one on each rail) will solve that problem handily. After all, nearly all scanner PSU's are only rated for 1 amp continuous draw anyway. They handle the surge current from the amps the same way - output caps.

The issue is finding DC-DC converters that can source a full amp of current and don't cost a fortune. Best bet I found from Mouser.com was a pair of +/- 15 volt units that you'd need to run in parallel to get the full amp (actually 1.1 amps). But that was a $110 solution, which I thought was a bit high. (Then again, if anyone is seriously contemplating buying an entire optical deck just for this effect, then a few hundred bucks on the power supply side of things is trivial.)

The nice thing about the DC-DC converter is that you can use a single (large) LiPo pack (one that is separate from the main pack powering the rotors) for everything related to the lasers and scanners. That saves a lot on weight. It also ensures that when the battery dies, everything dies at the same time (more or less).

Eric, You should check out the X-Laser 506 system that I'm installing on the robot--12 volt operation, 1/2 the weight, only one board for X/Y, and very little current draw. A very small and efficient scanner system.

I had forgotten about those X-laser amps! You're right - they run off a single-rail power supply. So that really simplifies things. Plus the 506 scanners are really nice - they can easily do 30K - so there's no scan-quality trade-off there.

Since they run on 12 volts, we're back to one regulator to power everything (an LM317 combined with a pass-bank to knock the LiPo voltage down to 12 volts). Well, admittedly you might also need +5 volts, which would require a second LM317 with it's own pass-bank. Still, that's cheap to build, even if you need both, and it's far less complicated than using the DC-DC converters or a second battery. Love it!

Now you just need someone to buy (or donate) an 8-10 watt optical table...

Adam