Move Aside Mercury: Measuring Temperature Accurately With An RTD

June 28, 2018 by Sean Boyce 40 Comments

Temperature is one of the most frequently measured physical quantities, and features prominently in many of our projects, from weather stations to 3D printers. Most commonly we’ll see thermistors, thermocouples, infrared sensors, or a dedicated IC used to measure temperature. It’s even possible to use only an ordinary diode, leading to some interesting techniques.

Often we only need to know the temperature within a degree Celsius or two, and any of these tools are fine. Until fairly recently, when we needed to know the temperature precisely, reliably, and over a wide range we used mercury thermometers. The devices themselves were marvels of instrumentation, but mercury is a hazardous substance, and since 2011 NIST will no longer calibrate mercury thermometers.

Luckily, resistance temperature detectors (RTDs) are an excellent alternative. These usually consist of very thin wires of pure platinum, and are identified by their resistance at 0 °C. For example, a Pt100 RTD has a resistance of 100 Ω at 0 °C.

An accuracy of +/- 0.15 °C at 0 °C is typical, but accuracies down to +/- 0.03 °C are available. The functional temperature range is typically quite high, with -70 °C to 200 °C being common, with some specialized probes working well over 900 °C.

It’s not uncommon for the lead wires on these probes to be a meter or more in length, and this can be a significant source of error. To account for this, you will see that RTD probes are sold in two, three, and four wire configurations. Two-wire configurations do not account for lead wire resistance, three-wire probes account for lead resistance but assume all lead wires have the same resistance, and four-wire configurations are most effective at eliminating this error.

In this article we’ll be using a 3-wire probe as it’s a good balance between cost, space, and accuracy. I found this detailed treatment of the differences between probe types useful in making this decision.

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Keep It Close: A Private Git Server Crash Course

June 27, 2018 by Tom Nardi 65 Comments

At this point, everyone has already heard that Microsoft is buying GitHub. Acquisitions of this scale take time, but most expect everything to be official by 2019. The general opinion online seems to be one of unease, and rightfully so. Even if we ignore Microsoft’s history of shady practices, there’s always an element of unease when somebody new takes over something you love. Sometimes it ends up being beneficial, the beginning of a new and better era. But sometimes…

Let’s not dwell on what might become of GitHub. While GitHub is the most popular web-based interface for Git, it’s not the only one. For example GitLab, a fully open source competitor to GitHub, is reporting record numbers of new repositories being created after word of the Microsoft buyout was confirmed. But even GitLab, while certainly worth checking out in these uncertain times, might be more than you strictly need.

Let’s be realistic. Most of the software projects hackers work on don’t need even half the features that GitHub/GitLab offer. Whether you’ve simply got a private project you want to maintain revisions of, or you’re working with a small group collaboratively in a hackerspace setting, you don’t need anything that isn’t already provided by the core Git software.

Let’s take a look at how quickly and easily you can setup a private Git server for you and your colleagues without having to worry about Microsoft (or anyone else) having their fingers around your code.

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Hackers Want Cambridge Dictionary To Change Their Definition

June 26, 2018 by Jenny List 83 Comments

Maybe it’s the silly season of high summer, or maybe a PR bunny at a cybersecurity company has simply hit the jackpot with a story syndicated by the Press Association, but the non-tech media has been earnestly talking about a call upon the Cambridge Dictionary to remove the word “illegal” from their definition of “Hacker”. The weighty tome from the famous British university lists the word as either “a person who is skilled in the use of computer systems, often one who illegally obtains access to private computer systems:” in its learners dictionary, or as “someone who illegally uses a computer to access information stored on another computer system or to spread a computer virus” in its academic dictionary. The cybersecurity company in question argues that hackers in fact do a lot of the work that improves cybersecurity and are thus all-round Good Eggs, and not those nasty computer crooks we hear so much about in the papers.

We’re right behind them on the point about illegality, because while there are those who adopt the hacker sobriquet that wear hats of all colours including black, for us being a hacker is about having the curiosity to tinker with anything presented to us, whatever it is. It’s a word that originated among railway modelers (Internet Archived version), hardly a community that’s known for its criminal tendencies!

Popular Usage Informs Definition

It is however futile to attempt to influence a dictionary in this way. There are two types of lexicography: Prescriptive and Descriptive. With prescriptive lexicography, the dictionary instructs what something must mean or how it should be spelled, while descriptive lexicography tells you how something is used in the real world based on extensive usage research. Thus venerable lexicographers such as Samuel Johnson or Noah Webster told you a particular way to use your English, while their modern equivalents lead you towards current usage with plenty of examples.

It’s something that can cause significant discontent among some dictionary users as we can see from our consternation over the word “hacker”. The administration team at all dictionaries will be familiar with the constant stream of letters of complaint from people outraged that their pet piece of language is not reflected in the volume they regard as an authority. But while modern lexicographers admit that they sometimes walk in an uneasy balance between the two approaches, they are at heart scientists with a rigorous approach to evidence-based research, and are very proud of their efforts.

Big Data Makes for Big Dictionaries

Lexicographic research comes from huge corpora, databases of tens or hundreds of millions of words of written English, from which they can extract the subtlest of language trends to see where a word is going. These can be interesting and engrossing tools for anyone, not just linguists, so we’d urge you to have a go for yourself.

Sadly for us the corpus evidence shows the definition for “Hacker” has very firmly trended toward the tabloid newspaper meaning that associates cybercriminality. All we can do is subvert that trend by doing our best to own the word as we would prefer it to be used, re-appropriating it. At least the other weighty tome from a well-known British university has a secondary sense that we do agree with: “An enthusiastic and skilful computer programmer or user“.

Disclosure: Jenny List used to work in the dictionary business.

LEGO: The Kristiansen Legocy

June 26, 2018 by Lauren Faris 75 Comments

Whether you are young, old, or a time traveling Vulcan, something unites all of us globally: the innocent LEGO blocks that encourage creativity over spoon-fed entertainment. Have you noticed the excess of zombified children and adults alike drooling over their collective screens lately? Back in the ancient times, all a child needed to create hours of joy were plastic interlocking bricks and a place for their parents to trip over them. The LEGO Group harbored the inspiration of our childhood inventiveness, and none of it would have been possible without the founder, Ole Kirk Kristiansen (or Christiansen). The humble carpenter from Denmark forever made his mark on the little Scandinavian country, one brick at a time.

Well, maybe not at first. You see the plastic LEGO bricks we all know and love were initially made of wood. And they were also not actually bricks.

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Putting Crimpers To The Test: How Good Are Our Crimp Tools?

June 26, 2018 by Jenny List 90 Comments

Almost every project of mine from the last quarter century, if it has contained any wiring, has featured somewhere at least one crimp connector. There are a multiplicity of different types of crimp, but in this case I am referring to the ubiquitous variety with a red, blue, or yellow coloured plastic sleeve denoting the wire size they are designed for. They provide a physically robust and electrically sound connection that is resistant to wire fatigue due to vibration, and that can carry hefty currents at high voltages without any problems.

You might expect this to now head off into the detail of crimp connection, but my colleague Dan has already detailed what makes a good or a bad crimp. Instead recently my constant searches for weird and wonderful things to review for your entertainment led me to a new crimp tool, and thence to a curiosity about the effectiveness of different styles of tool. So I’m going to evaluate the three different crimping methods available to me, namely my shiny new ratchet crimp pliers, my aged simple crimp pliers, and for comparison an ordinary pair of pliers. I’ll take a look at the physical strength of each crimping method followed by its electrical effectiveness, but first it’s worth looking at the tools themselves.

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Lost In Space Gets 3D Printing Right

June 25, 2018 by Tom Nardi 100 Comments

When it has become so common for movies and television to hyper-sensationalize engineering, and to just plain get things wrong, here’s a breath of fresh air. There’s a Sci-Fi show out right now that wove 3D printing into the story line in a way that is correct, unforced, and a fitting complement to that fictional world.

With the amount of original content Netflix is pumping out anymore, you may have missed the fact that they’ve recently released a reboot of the classic Lost in Space series from the 1960’s. Sorry LeBlanc fans, this new take on the space traveling Robinson family pretends the 1998 movie never happened, as have most people. It follows the family from their days on Earth until they get properly lost in space as the title would indicate, and is probably most notable for the exceptional art direction and special effects work that’s closer to Interstellar than the campy effects of yesteryear.

But fear not, Dear Reader. This is not a review of the show. To that end, I’ll come right out and say that Lost in Space is overall a rather mediocre show. It’s certainly gorgeous, but the story lines and dialog are like something out of a fan film. It’s overly drawn out, and in the end doesn’t progress the overarching story nearly as much as you’d expect. The robot is pretty sick, though.

No, this article is not about the show as a whole. It’s about one very specific element of the show that was so well done I’m still thinking about it a month later: its use of 3D printing. In Lost in Space, the 3D printer aboard the Jupiter 2 is almost a character itself. Nearly every member of the main cast has some kind of interaction with it, and it’s directly involved in several major plot developments during the season’s rather brisk ten episode run.

I’ve never seen a show or movie that not only featured 3D printing as such a major theme, but that also did it so well. It’s perhaps the most realistic portrayal of 3D printing to date, but it’s also a plausible depiction of what 3D printing could look like in the relatively near future. It’s not perfect by any means, but I’d be exceptionally interested to hear if anyone can point out anything better.

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Linux Fu: The Great Power Of Make

June 22, 2018 by Al Williams 76 Comments

Over the years, Linux (well, the operating system that is commonly known as Linux which is the Linux kernel and the GNU tools) has become much more complicated than its Unix roots. That’s inevitable, of course. However, it means old-timers get to slowly grow into new features while new people have to learn all in one gulp. A good example of this is how software is typically built on a Linux system. Fundamentally, most projects use make — a program that tries to be smart about running compiles. This was especially important when your 100 MHz CPU connected to a very slow disk drive would take a day to build a significant piece of software. On the face of it, make is pretty simple. But today, looking at a typical makefile will give you a headache, and many projects use an abstraction over make that further obscures things.

In this article, I want to show you how simple a makefile can be. If you can build a simple makefile, you’ll find they have more uses than you might think. I’m going to focus on C, but only because that’s sort of the least common denominator. A make file can build just about anything from a shell prompt.

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