On Unix — the progenitor of Linux — there was
/bin/sh. It was simple, by comparison to today’s shells, but it allowed you to enter commands and — most importantly — execute lists of commands. In fact, it was a simple programming language that could make decisions, loop, and do other things to allow you to write scripts that were more than just a list of programs to run. However, it wasn’t always the easiest thing to use, so in true Unix fashion, people started writing new shells. In this post, I want to point out a few shells other than the ubiquitous
bash, which is one of the successors to the old
Since the 7th Edition of Unix,
sh was actually the Bourne shell, named after its author, Stephen Bourne. It replaced the older Thompson shell written in 1971. That shell had some resemblance to a modern shell, but wasn’t really set up for scripting. It did have the standard syntax for redirection and piping, though. The PWB shell was also an early contender to replace Thompson, but all of those shells have pretty much disappeared.
You probably use
bash and, honestly, you’ll probably continue to use
bash after reading this post. But there are a few alternatives and for some people, they are worth considering. Also, there are a few special-purpose shells you may very well encounter even if your primary shell is
Continue reading “Linux Fu: Alternative Shells”
Every fisherman has a secret. A secret spot, a secret technique, or a secret bait. Maybe that’s why tying flies is so popular. [Steve] certainly has is own special lures, although he’s not keeping it a secret. (Video, embedded below.) He designs lures in Simplify3D, 3D prints molds, and then casts them.
The 3D printing part is interesting, but it is also kind of neat to see the lures and the natural prey he uses for inspiration. If you want to catch fish, you have to use bait that looks like real food.
Continue reading “3D Printing Fishing Lure Molds”
We love a little outside-the-box thinking around here, and anytime we see robots that don’t use wheels and motors to do the moving, we take notice. So when a project touting robotic fish using soft-actuator fins crossed the tip line, we had to take a look.
It turns out that this robofish comes from the fertile mind of [Carl Bugeja], whose PCB motors and flexible actuators have been covered here before. The basic concept of these fish fins is derived from the latter project, which uses coils printed onto both sides of a flexible Kapton substrate. Positioned near a magnet, the actuators bend when a current runs through them. The video below shows two prototype robofish, each with four fins. The first is a scrap of foam with a magnet embedded; the fins did flap but the whole thing just weighed too much. Version two was much lighter and almost worked, but the tether to the driver is just too stiff to allow it to really flex its fins.
It looks like it has promise though, and we’re excited to see where [Carl] take this. Perhaps schools of tiny robofish patrolling for pollution?
Continue reading “Flexible PCBs Make The Fins Of This Robotic Fish”
We get it. You love your fish, but they can’t bark or gently nip at your shin flesh to let you know they’re hungry. (And they always kind of look hungry, don’t they?) One day bleeds into the next, and you find yourself wondering if you’ve fed them yet today. Or are you thinking of yesterday? Fish deserve better than that. Why not build them a smart fish feeder?
Domovoy is a completely open-source automatic fish feeder that lets you feed them on a schedule, over Bluetooth, or manually. This simple yet elegant design uses a small stepper motor to drive a 3D-printed auger to deliver the goods. Just open the lid, fill ‘er up with flakes, and program up to four feedings per day through the 3-button and LCD interface. You can even set the dosage, which is measured in complete revolutions of the auger.
It’s built around an ATMega328P, but you’ll have to spin your own board and put the feeder together using his excellent instructions. Hungry to see this feeder in action? Just swim past the break.
Can’t be bothered to feed your fish automatically? Train them to feed themselves.
Continue reading “Don’t Flake On Your Fish—Feed Them Automatically”
Here’s a Big Mouth Billy Bass with extra lip thanks to Alexa. If you’re not already familiar, Big Mouth Billy Bass is the shockingly popular singing animatronic fish designed to look like a trophy fish mounted to hang on your wall. In its stock condition, Billy uses a motion sensor to break into song whenever someone walks by. It’s limited to a few songs, unless you like to hack things — in which case it’s a bunch of usable parts wrapped in a humorous fish! Hackaday’s own [Bob Baddeley] combined the fish with an Amazon Echo Dot, connecting the two with an ATtiny84, and having Billy speak for Alexa.
[Bob] had a few problems to solve, including making Billy’s mouth move when there was audio playing, detecting when the Echo was on, moving the motors and playing the audio. After a bit of research and a lot of tweaking, a Fast Fourier Transform algorithm designed for the ATtiny was used was used to get the mouth moving. The mouth didn’t move a lot because of the design of the fish, and [Bob] modified it a bit, but there was only so much he could do.
It’s all well and good for the fish to lie there and sing, but [Bob] wanted Billy to move when Alexa was listening, and in order the detect this, the best bet was to watch for the Dot’s light to turn on. He tried a couple of things but decided that the simplest method was probably the best and ended up just taping a photo-resistor over the LED. Now Billy turns to look at you when you ask Alexa a question.
With a few modifications to the Dot’s enclosure, everything now fits inside the original mounting plaque and, after some holes were drilled so the Dot could hear, working. Billy has gone from just a few songs to an enormous entire library of songs to sing!
We’ve seen Alexa combined with Big Mouth Billy Bass before, but just demos and never an excellent guide like [Bob’s]. The nice thing about this guide is that once you’ve hacked the hardware, it’s a breeze to add new functionality using Alexa skills.
Continue reading “Big Mouth Billy Bass Channels Miley Cyrus”
Larval zebrafish, Drosophila (fruit fly), and Caenorhabditis elegans (roundworm) have become key model organisms in modern neuroscience due to their low maintenance costs and easy sharing of genetic strains across labs. However, the purchase of a commercial solution for experiments using these organisms can be quite costly. Enter FlyPi: a low-cost and modular open-source alternative to commercially available options for optogenetic experimentation.
One of the things that larval zebrafish, fruit flies, and roundworms have in common is that scientists can monitor them individually or in groups in a behavioural arena while controlling the activity of select neurons using optogenetic (light-based) or thermogenetic (heat-based) tools.
FlyPi is based on a 3D-printed mainframe, a Raspberry Pi computer, and a high-definition camera system supplemented by Arduino-based optical and thermal control circuits. FlyPi features optional modules for LED-based fluorescence microscopy and optogenetic stimulation as well as a Peltier-based temperature simulator for thermogenetics. The complete version with all modules costs approximately €200 with a layman’s purchasing habits, but for those of us who live on the dark side of eBay or the depths of Taobao, it shouldn’t cost more than €100.
Once assembled, all of the functions of FlyPi can be controlled through a graphical user interface. As an example for how FlyPi can be used, the authors of the paper document its use in a series of “state-of-the-art neurogenetics experiments”, so go check out the recently published open access paper on PLOS. Everything considered the authors hope that the low cost and modular nature, as well as the fully open design of FlyPi, will make it a widely used tool in a range of applications, from the classroom all the way to research labs. Need more lab equipment hacks? Don’t worry, we’ve got you covered. And while you’re at it, why not take a spin with the RWXBioFuge.
[Eric Dirgahayu] wanted to explore underwater with some sensors and cameras. First, he needed a platform to carry them. That led to his Arduino-controlled swimming fish. The fish is made from PVC and some waterproof servos. From the video (see below) it isn’t clear how much control the fish has, but it does swim with an undulating motion like a real fish.
Continue reading “The Arduino Sleeps With The Fishes”