The Surface Area to Volume Ratio or Why Elephants Have Big Ears

There are very few things that are so far reaching across many different disciplines, ranging from biology to engineering, as is the relation of the surface area to the volume of a body. This is not a law, as Newton’s second one, or a theory as Darwin’s evolution theory. But it has consequences in a diverse set of situations. It explains why cells are the size they are, why some animals have a strange morphology, why flour explodes while wheat grains don’t and many other phenomena that we will explore in this article.

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Hackaday Prize Entry: There’s An Elephant In The Room

Elephants and people don’t mix as well as you’d hope. Human-elephant conflict causes deaths of both pachyderms and man alike. Elephants raid crops. Elephants are killed by trains. Obviously, where elephants are is useful knowledge. This is the problem [Neil] is solving for his entry into the Hackaday Prize. His project detects elephants, whether they’re on a railroad, in a field gorging on crops, or… in the room.

[Neil]’s goal is simple – he’s building a distributed elephant detection system that can be deployed at railway crossings, between forests and farmland, and along established elephant trails. This gives [Neil] exactly two problems: detecting elephants, and communicating that information to humans.

To detect elephants, [Neil] is relying on a webcam and Raspberry Pi 3 running OpenCV vision processing. He’ll either be comparing histograms, for faster and less resource intensive image processing, or feature matching. Each detector is equipped with a PIR sensor, so at the very least the Pi won’t be looking for elephants all the time.

Notifying humans of the existence of elephants is the next step of the project, and one that might even be harder than finding the elephants in the first place. [Neil] settled on using ZigBees on each Pi to talk to at least one base station. This base station then sends a message to the local human population over a much longer-range radio link. Networking a bunch of Pis in the middle of the African savanna is a hard problem, but by separating the communication aspect of this project into two radio links, [Neil] has a fairly robust solution.

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Cardboard Kinetic Creatures

Browsing around today, I saw this little kit on kickstarter called Kinetic Creatures.  These flat packed models are made from cardboard and can be assembled without tools. Their mechanical legs are operated either by a simple cam that you turn by hand or by a motorized attachment. I love the basic idea here. This is the kind of thing that my 6 year old would really enjoy doing that also serves to get him into making things (he’d probably insist on motorizing it with scraps, he collects dc motors and has quite a collection).

I did notice that they mentioned using it as a robotic platform, adding custom electronics to the empty space allowed in the body of the animal. This initially got me quite excited, thinking that I could, for $30 have a 1 foot tall quadruped platform that looked awesome, then I realized it can’t turn. I guess I’ll have to hack it a little bit to put separate drives in for each side. That would be a cool upgrade they could offer.

Have any of you tried to do turning with a set of only 4 [jansen] legs before?