tripper trapper

All posts tagged tripper trapper

Burning Man is an event which by its nature asks a lot of its participants. If you don’t go with the attitude of “I’ll damn well thrive, come hell bugs or high water winds“, you won’t last long. Art projects don’t just show up — they take determination from the moment of “I’m going to bring this crazy thing to the desert” right up until you dismantle, gift, or burn your project (and if you burn it, you’ve then got ash to deal with… nope).

The Tripper Trapper made a good blocker for the front of our camp, serving to lead people into our bar while simultaneously walling off our shower, greywater evaporation pond and generators (i.e. all the stuff people don’t want near their tents) from the outside world.

The funny thing about things that are shaped like other things is, a lot of the time, they act like the things they are shaped like. This means when your project consists of what amounts to a giant sail, it’s going to catch the wind.
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How the rib was run

The communication line makes a stop at the rib’s intersection with the spine. Here is where the occupancy sensors are positioned. The Cat5e cable continues to the end of the rib, where the LED strip begins.

Making your biggest project to date is a tall order, and is bound to come with all sorts of unforeseen problems. This one was a matter of communication.

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Joke's on them, I was listening to VNV Nation!

Joke’s on them, I was listening to VNV Nation!

The past week for me had the singular focus of assembling the housing for the Tripper Trapper’s power system. It encloses a set of deep-cycle batteries, a busbar each for the battery bank and load distribution, a circuit breaker panel, and a solar charge controller.

Since material in the US is generally only available in English sizes (for some reason, the U.S. saw fit to overthrow their oppressors, but not to abandon England’s ancient system of units), I’ve had to adapt to using inches and feet. It’s odd, but manageable. The box is 21.5″ x 20.5″ x 17″, and its structure is made entirely of scrap material donated by other burners in the community.

Pictured: battery-O-fail, storage busbar, breaker rail.

Pictured: battery-O-fail, storage busbar, breaker rail.

I took some pictures, since watching glue dry is 99.444439% (±0.555561%) as much fun as watching paint dry, and I figured I ought to share that fun.

Wiring the battery array was much more fun. I read what I could find online about using batteries in a parallel configuration, and what I found was that for ideal performance, each battery should see equal series resistance. People have a funny way of making that look hard on the Internet; maybe they just haven’t heard of busbars.

Diagram of how I wired the busbar

Left: 2P configuration with equal series resistance. Centre: 4P configuration with equal series resistance, based on what I’d seen online. Right: 8P configuration used in the Powerhaus.

It looks a little haphazard, but I wanted to keep the layout somewhat symmetrical, so I put the charge and load terminals in the middle. If you trace the current path from the charge controller, through any battery, and back to the charge controller, you’ll see that whichever path you take, you go through the same resistance: the leads to the busbar, four ring terminals, 6 terminal-spacings worth of busbar, two spade terminals, and a constant amount of battery cable (since I kept them the same length). Same goes for the load, which means that this array is kept balanced by design. Since the batteries are AGM lead-acids, there is no need to apply an equaliastion charge, or to balance the cells electrically like in lithium-ion batteries.

This part of the project gave me a lot to research, and I now know a lot more about power systems as a result. The Tripper Trapper has turned out to be the most rewarding thing I’ve built to date.

Dare to fail

Dare to fail

In the early stages of designing the Tripper Trapper, I decided to use 5V addressable LED strip for two reasons: firstly, the mad resolution of 1-LED pixels which would look nice up-close, and secondly because the newer, faster, flicker-free four-wire APA-102C LEDs that I wanted to use didn’t (and still don’t) have a 12V variant.

So I set about finding some point-of-load (POL) DC-DC converters to convert the lead-acid battery voltage (between 10.5V and 14.4V 13.8V) to the 5V needed for the LEDs. I found some quality converters which were rated for a maximum of 14V at 10A continuous output, but would require the fabrication of a PCB with either sockets for these or solder pads for these. Being lazy[1], I kept looking and found some prepackaged BEC modules which HobbyKing were selling for $14.

Bargain, right?

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It's a tarp! Well, okay, it's a bunch of PVC pipe too.

It’s a tarp!
Well, okay, it’s a bunch of PVC pipe too.

This year’s Burning Man festival looked to be an easy one at first: since most of the new toys I had intended to bring to the playa last year didn’t make it there, I’d be able to take it easy and just show them off this year. I didn’t feel any pressure to build anything grand. That was, until our camp mayor got an email from the coordinator of our village stating that we’d be the centrepiece now that another camp had left, and that for us to get favourable placement we’d need something interactive out front, day and night.

Since we already had a daytime activity for this year (an aerialist rig), plus a till-relatively-late activity (the bar), all we needed was something that would be interactive all night. Thus came about…

The Tripper Trapper.

Designs

The basic concept was explained as such:

Sounds like a perfect time to make the Trippy Trap Tunnel. It sits there all nice and glowy with some dull rainbow chases….until the victim gets to the center. All of a sudden, strobes and a klaxon…..How the hell do you get out? Here, have a drink.

The jury’s still out on this thing making noise, but the rest of the idea stuck immediately. We would build the Trapper as a monkeyhut, and attach LED strip to the inside of the ribs. Since this would best be seen up close (people are meant to wander through it, after all), it would use 1-LED pixels (5V strip). Needless to say, it wasn’t long before I was hard at work, calculating how big and bright we could make it with a materials budget of around $1000…