Automatic Resistance: Resistors Controlled By The Environment

Resistors are one of the fundamental components used in electronic circuits. They do one thing: resist the flow of electrical current. There is more than one way to skin a cat, and there is more than one way for a resistor to work. In previous articles I talked about fixed value resistors as well as variable resistors.

There is one other major group of variable resistors which I didn’t get into: resistors which change value without human intervention. These change by environmental means: temperature, voltage, light, magnetic fields and physical strain. They’re commonly used for automation and without them our lives would be very different.

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The Healthy Maker: Tackling Vapors, Fumes And Heavy Metals

Fearless makers are conquering ever more fields of engineering and science, finding out that curiosity and common sense is all it takes to tackle any DIY project. Great things can be accomplished, and nothing is rocket science. Except for rocket science of course, and we’re not afraid of that either. Soldering, welding, 3D printing, and the fine art of laminating composites are skills that cannot be unlearned once mastered. Unfortunately, neither can the long-term damage caused by fumes, toxic gasses and heavy metals. Take a moment, read the material safety datasheets, and incorporate the following, simple practices and gears into your projects.

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A Brief History Of ‘Drone’

In the early 1930s, Reginald Denny, an English actor living in Los Angeles, stumbled upon a young boy flying a rubber band-powered airplane. After attempting to help the boy by adjusting the rubber and control surfaces, the plane spun into the ground. Denny promised he would build another plane for the boy, and wrote to a New York model manufacturer for a kit. This first model airplane kit grew into his own hobby shop on Hollywood Boulevard, frequented by Jimmy Stewart and Henry Fonda.

The business blossomed into Radioplane Co. Inc., where Denny designed and built the first remote controlled military aircraft used by the United States. In 1944, Captain Ronald Reagan of the Army Air Forces’ Motion Picture unit wanted some film of these new flying targets and sent photographer David Conover to the Radioplane factory at the Van Nuys airport. There, Conover met Norma Jeane Dougherty and convinced her to go into modeling. She would later be known as Marilyn Monroe. The nexus of all American culture from 1930 to 1960 was a hobby shop that smelled of balsa sawdust and airplane glue. That hobby shop is now a 7-Eleven just off the 101 freeway.

Science historian James Burke had a TV wonderful show in the early 90s – Connections – where the previous paragraphs would be par for the course. Unfortunately, the timbre of public discourse has changed in the last twenty years and the worldwide revolution in communications allowing people to instantaneously exchange ideas has only led to people instantaneously exchanging opinions. The story of how the Dutch East India Company led to the rubber band led to Jimmy Stewart led to remote control led to Ronald Reagan led to Death of a Salesman has a modern fault: I’d have to use the word ‘drone’.

The word ‘propaganda’ only gained its negative connotation the late 1930s – it’s now ‘public relations’. The phrase ‘global warming’ doesn’t work with idiots in winter, so now it’s called ‘climate change’. Likewise, quadcopter pilots don’t want anyone to think their flying machine can rain hellfire missiles down on a neighborhood, so ‘drone’ is verboten. The preferred term is quadcopters, tricopters, multicopters, flying wings, fixed-wing remote-controlled vehicles, unmanned aerial systems, or toys.

I’m slightly annoyed by this and by the reminder I kindly get in my inbox every time I use the dreaded d-word. The etymology of the word ‘drone’ has nothing to do with spying, firing missiles into hospitals, or illegally killing American civilians. People like to argue, though, and I need something to point to when someone complains about my misuse of the word ‘drone’. Instead of an article on Hollywood starlets, the first remote control systems, and model aviation, you get an article on the etymology of a word. You have no one else to blame but yourself, Internet.

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How To Run A Pagekite Server To Expose Your Raspberry Pi

Last time I showed you how to expose a web service on a Raspberry Pi (or, actually, any kind of device) by using a reverse proxy from Pagekite. On your Pi, you just need a simple Python script. However, it also depends on the Pagekite server, which isn’t always convenient. There are limits to the free service, and you don’t control the entire thing. The good news is twofold: the same Python script you use to set up the client-side can also set up a server. The other good news is the entire thing is open source.

In practical terms, then, if you have a computer that is always on and has an IP address that can be found on the public internet, you can run your own Pagekite server (they call it a front end) and service your own backends.

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Expose Your Raspberry Pi On Any Network

Everyone’s talking about the Internet of Things (IoT) these days. If you are a long-time Hackaday reader, I’d imagine you are like me and thinking: “so what?” We’ve been building network-connected embedded systems for years. Back in 2003, I wrote a book called Embedded Internet Design — save your money, it is way out of date now and the hardware it describes is all obsolete. But my point is, the Internet of Things isn’t a child of this decade. Only the name is.

The big news — if you can call it that — is that the network is virtually everywhere. That means you can connect things you never would have before. It also means you get a lot of data you have to find a reason to use. Back in 2003, it wasn’t always easy to get a board on the Internet. The TINI boards I used (later named MxTNI) had an Ethernet port. But your toaster or washing machine probably didn’t have a cable next to it in those days.

Today boards like the Raspberry Pi, the Beagle Bone, and their many imitators make it easy to get a small functioning computer on the network — wired or wireless. And wireless is everywhere. If it isn’t, you can do 3G or 4G. If you are out in the sticks, you can consider satellite. All of these options are cheaper than ever before.

The Problem

There’s still one problem. Sure, the network is everywhere. But that network is decidedly slanted at letting you get to the outside world. Want to read CNN or watch Netflix? Sure. But turning your computer into a server is a little different. Most low-cost network options are asymmetrical. They download faster than they upload. You can’t do much about that except throw more money at your network provider. But also, most inexpensive options expose one IP address to the world and then do Network Address Translation (NAT) to distribute service to local devices like PCs, phones, and tablets. What’s worse is, you share that public address with others, so your IP address is subject to change on a whim.

What do you do if you want to put a Raspberry Pi, for example, on a network and expose it? If you control the whole network, it isn’t that hard. You usually use some kind of dynamic DNS service that lets the Pi (or any computer) tell a well-known server its current IP address (see figure below).

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Resistance In Motion: What You Should Know About Variable Resistors

Adjusting the volume dial on a sound system, sensing your finger position on a touch screen, and knowing when someone’s in the car are just a few examples of where you encounter variable resistors in everyday life. The ability to change resistance means the ability to interact, and that’s why variable resistance devices are found in so many things.

The principles are the same, but there are so many ways to split a volt. Let’s take a look at what goes into rotary pots, rheostats, membrane potentiometers, resistive touchscreens, force sensitive resistors, as well as flex and stretch sensors.

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The Bootup Guide To Homebrew Two-Stage Tentacle Mechanisms

What’s not to love about animatronics? Just peel back any puppet’s silicone skin to uncover a cluster of mechatronic wizardry that gives it a life on the big screen. I’ve been hunting online for a good intro to these beasts, but I’ve only turned up one detailed resource–albeit a pretty good one–from the Stan Winston Tutorials series. Only 30 seconds into the intro video, I could feel those tentacles waking up my lowest and most gutteral urge to create physical things. Like it or not, I was hooked; I just had to build one… or a few. This is how you built a very real animatronic tentacle.

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I built this. And you can too!

If you’re getting started in this realm, I’ll be honest: the Stan Winston Tutorial is actually a great place to start. In about two hours, instructor Richard Landon covers the mindset, the set of go-to components, and the techniques for fabricating a tentacle mechanism with a set of garage tools–not to mention giving us tons of real-film examples along the way [1].

We also get a sneak peek into how we might build more complicated devices from the same basic techniques.  I’d like to pick up exactly where he left off: 4-way two-stage tentacles. And, of course, if you’ve picked up on just how much I like a certain laser-cuttable plastic at this point, I’m going to put a modern twist on Landon’s design. These design tweaks should enable you to build your own tentacle and controller with nothing more but a few off-the-shelf parts, some Delrin, and a laser cutter… Ok, fine, a couple 3D printed parts managed to creep their way in too.

bom_graphicIn a good-ol’ engineers-for-engineers fashion, I’m doing something a little different for this post: I’m finishing off this series with a set of assembly videos, a BOM, and the original CAD files to make that beast on the front page come to life. As for why, I figured: why not? Even though these mechanisms have lived in the robotics community and film industry for years, they’re still lacking the treatment of a solid, open design. This is my first shot at closing that gap. Get yourself a cup of coffee. I’m about to give you every bleeding detail on the-how-and-why behind these beasts.

All right; let’s get started.

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