Public Lab Research note

Make a $25 minimal-helium balloon mapping rig

by natevw | July 03, 2014 23:03 03 Jul 23:03 | #10651 | #10651

natevw was awarded the Basic Barnstar by warren for their work in this research note.

What I want to do

808 keychain mini-camera

I'm going to try out a low-budget/lo-fi balloon rig to see if it's worth anything.

My attempt and results

The basic gist is that by dramatically reducing the weight of the camera the rest of the kit can be significantly cheaper, and the helium usage dramatically less.

So far it's on budget, but still waiting for packages to arrive :-)

Questions and next steps

My biggest concern is actually the string itself. The camera should weigh less than 20g, so the tethering line's weight becomes even more important.

Of course, I'm also assuming that the camera quality is comparable to a smartphone, which could be wishful thinking…

One thing I don't have a plan for (besides "winging it") is how to close this smaller balloon in a reusable fashion without adding much weight. I am fairly good at picking knots out of my kid's balloons (using the dull but sturdy tine of a metal dinner fork), but ideally I can figure out something that lends to even more reuses.

The next steps, once I've got a better sense of how little helium I can get away with using with this line/payload, would be to try with an even smaller 24" balloon. I'm also gonna give the not-recommended — but dirt-cheap! — 6lb monofilament a shot myself, with a dummy payload at least.

One other idea would be to eliminate the tether line completely ;-)

Why I'm interested

I love my "big balloon" kit, but honestly it's not that affordable. Especially if you factor in buying a helium tank and a Canon point-and-shoot camera, and having to replace a popped balloon, and loosing some of the swivels, and a big tarp to help haul the balloon around town, and, and… (Not to mention that helium costs well over $25 per weekend; it's hard not to start eyeing an RC plane or quadcopter again!)

If this yields halfway decent results, there's potential that anyone could get into basic balloon mapping with not much more than a $15 eBay splurge plus an errand to a big box store to pick up a few pre-filled balloons and some fishing line!

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Love it! We've been planning to release a minimal kite kit based on a keychain can but haven't run hard numbers or a test. A slightly higher end one could use the Mobius Action Cam but the #16 version of that keychain can (which the Mobius is based on) looks so great! And so cheap! Please post photos once you test!!

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Nice! John Wells and SNAPS are masters of this. You might enjoy their rigs and strategies:

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Next step: Live streaming data from your balloons to the ground. ;)

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on second thought I think the nylon monofilament will work if you have a good winder for it (I.E. fishing rod). go for at least 10lb.

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I've tried using a small keychain camera for KAP and I basically just used a miniature version of the standard PET Bottle Rig- However, I've got to say the difference in weight affects the stability of the rig considerably. I'd be very interested in getting input from others using small cams like the Mobius on my new research note-

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Thanks for the feedback everyone! I'd been traveling a lot lately and then catching up, so most of the equipment has been just sitting around.

I've done some basic testing of the camera, and to put it bluntly…it's crap. The reason it was so cheap — free now, actually, once I filed a complaint with eBay! — is that it is a much lower-end model than advertised in the listing.

I did pick up a cheap-but-decent reel and rod too, after staring at the fishing line and deciding I didn't want to ever wind it by hand even once :-P

Where I'm at with this:

  • kit cost probably twice as much as hoped (change to $40 for an actually maybe half-decent keychain camera, add $20 for basic reel and rod)
  • have keychain weight: 15.6g total (7.5g for the PCB+battery, 5.1g for the plastic case, 3.0g for the metal "keychain-y" part)
  • haven't actually tried the 2ft ballon rig (well I did test if an even smaller balloon could lift it — nope!)

Going camping for a few days this weekend though and planning to bring the kit, so hopefully more interesting results soon!

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So the good news: the fishing reel (and bottom half of a rod) plus a two foot balloon is a real fun rig! Did not have any trouble with the ~10lb line that came on the reel itself.

The bad news: the camera is every bit as poor quality as expected. It also has a very narrow field-of-view.

Here's a screengrab from a video (there's no intervalometer mode, and video is same resolution anyway, so…), the balloon is a decent ways up:

Sample from lofted keychain camera

In some ways, the narrow FOV may be alright given the poor resolution but would require some serious software to process into something useful.

I think this holds promise, in a few years when Moore's law has had longer to work on these lightweight cameras. It's ultimately more of a $50 kit though ($5 balloon, $20 rod+reel+line, $25+ for a slightly better camera) and still assumes you'll be able to beg/steal/borrow a small helium tank.

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cool flight test!

it looks like its one of those cameras that takes a 640x480 image and upscales it to 1280x960. I've seen several of those. beware! not actually hi-res!

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