Gentle Electric Eel

It’s no shock that electric eels get a bad rap for being scary creatures. They are slithery fleshy water snakes who can call down lightning. Biologists and engineers at the University of California had something else in mind when they designed their electric eel. Instead of hunting fish, this one swims harmlessly alongside them.

Traditional remotely operated vehicles have relied on hard shells and spinning propellers. To marine life, this is noisy and unnatural. A silent swimmer doesn’t raise any eyebrows, not that fish have eyebrows. The most innovative feature is the artificial muscles, and although the details are scarce, they seem to use a medium on the inside to conduct a charge, and on the outside, the saltwater environment conducts an opposite charge which causes a contraction in the membrane between to the inside and outside. Some swimming action can be seen below the break, and maybe one of our astute readers can shed some light on this underwater adventurer’s bill of materials.

One of our favorite submarines is the 2017 Hackaday Prize winner, The Open Source Underwater Glider. For a more artistic twist on submersibles, the Curv II is one of the most elegant we have seen.

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Using Moiré Patterns To Guide Ships

Moiré screens for arrows
Moiré screens for arrows

[Tom Scott] ran across an interesting visual effect created with Moiré patterns and used for guiding ships but we’re sure it can be adapted for hacks somewhere. Without the aid of any motors or LED animation, the image changes as the user views it from different angles. When viewed straight on, the user sees vertical lines, but from the left they see a right-pointing arrow and from the right, they see a left-pointing arrow. It’s used with shipping to guide ships. For example, one use would be to guide them to the center point of a bridge. When the pilots see straight, vertical lines then they know where to steer the ship.

US patent 4,629,325, Leading mark indicator, explains how it works and how to make one. Two screens are separated from each other. The one in front is vertical but the one behind is split in two and angled. It’s this angle which creates the slants of the arrows when viewed from the left or right. We had to convince ourselves that we understood it correctly and a quick test with two combs showed that we did. See below for the test in action as well as for [Tom’s] video of the real-world shipping one.

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THP Hacker Bio: Rusty Jehangir

[Rusty]’s project for the Hackaday Prize is extremely ambitious. He’s planning on sending an autonomous craft across the ocean, from LA to Hawaii, a distance that will end up being well over 2,500 miles The best part about this project? It’s already had some time in the ocean, cruising off the coast of southern California under its own power for a distance of 20km.

Why is [Rusty] doing this? Partly because he wanted to do something no one had ever done before. For him, this meant developing a cheap underwater thruster, building an autonomous solar-powered surfboard for a months-long voyage halfway across the Pacific. It’s a small step to the goal of exploring the deep ocean with his thruster and mostly off the shelf parts, but already [Rusty] has learned a lot about electronics in a marine environment and being confident enough to let a project go on its own for months at a time.

Interview below.

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Portable audio rig that turned out great

portable-audio-rig

[Michael] wanted a stereo that he could use outside, be it at the beach, beside the pool, or while tailgating. He decided to build this boom box himself, and didn’t cut any corners when it came to a professional looking finish.

Because of the locale in which he plans to use the stereo he went with a set of marine speakers. They’ll have no problem standing up to water, and since they’re used in boats they should also be able to take a beating during transport. To feed it he uses a Lepai T amp which is seen above.

After cutting each piece of the case out of MDF he started working on the openings to receive the components. This involved quite a number of layout lines and some work with a compass to map out the circular openings. He built a recessed panel on the back to interface the power cord for charging. Inside is an 18 Ah battery. A set of switches lets him turn on the charger and choose between powering the amp from battery or from the power cord.

[via Reddit]