The UA723 As A Switch Mode Regulator

February 15, 2018 by Jenny List 37 Comments

If you are an electronic engineer or received an education in electronics that went beyond the very basics, there is a good chance that you will be familiar with the Fairchild μA723. This chip designed by the legendary Bob Widlar and released in 1967 is a kit-of-parts for building all sorts of voltage regulators. Aside from being a very useful device, it may owe some of its long life to appearing as a teaching example in Paul Horowitz and Winfield Hill’s seminal text, The Art Of Electronics. It’s a favourite chip of mine, and I have written about it extensively both on these pages and elsewhere.

The Fairchild switching regulator circuit. From the μA723 data sheet in their 1973 linear IC databook, page 194 onwards.

For all my experimenting with a μA723 over the decades there is one intriguing circuit on its data sheet that I have never had the opportunity to build. Figure 9 on the original Fairchild data sheet is a switching regulator, a buck converter using a pair of PNP transistors along with the diode and inductor you would expect. Its performance will almost certainly be eclipsed by a multitude of more recent dedicated converter chips, but it remains the one μA723 circuit I have never built. Clearly something must be done to rectify this situation.

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Create A Discord Webhook With Python For Your Bot

February 15, 2018 by Tom Nardi 22 Comments

Discord is an IRC-like chat platform that all the young cool kids are hanging out on. Originally intended as a way to communicate during online games, Discord has grown to the point that there are servers out there for nearly any topic imaginable. One of the reasons for this phenomenal growth is how easy it is to create and moderate your own Discord server: just hit the “+” icon on the website or in the mobile application, and away you go.

As a long-time IRC guy, I was initially unimpressed with Discord. It seemed like the same kind of stuff we’ve had for decades, but with an admittedly slick UI. After having used it for a few months now and joining servers dedicated to everything from gaming to rocket science, I can’t say that my initial impression of Discord is inaccurate: it’s definitely just a modern IRC. But I’ve also come to the realization that I’m OK with that.

But this isn’t a review of Discord or an invitation to join the server I’ve setup for my Battlefield platoon. In this article we’re going to look at how easy it is to create a simple “bot” that you can plug into a Discord server and do useful work with. Since anyone can create a persistent Discord server for free, it’s an interesting platform to use for IoT monitoring and logging by simply sending messages into the server.

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Hovercraft Of The Future

February 14, 2018 by Al Williams 32 Comments

We think of hovercraft as a modern conveyance. After all, any vision of the future usually includes hovercraft or flying cars along with all the other things we imagine in the future. So when do you think the hovercraft first appeared? The 1960s? The 1950s? Maybe it was a World War II development from the 1940s? Turns out, a human-powered hovercraft was dreamed up (but not built) in 1716 by [Emanuel Swedenborg]. You can see a sketch from his notebook below. OK, that’s not fair, though. Imagining it and building one are two different things.

[Swedenborg] realized a human couldn’t keep up the work to put his craft on an air cushion for any length of time. Throughout the 1800s, though, engineers kept thinking about the problem. Around 1870, [Sir John Thornycroft] built several test models of ship’s hulls that could trap air to reduce drag — an idea called air lubrication, that had been kicked around since 1865. However, with no practical internal combustion engine to power it, [Thornycroft’s] patents didn’t come to much. In America, around 1876 [John Ward] proposed a lightweight platform using rotary fans for lift but used wheels to get forward motion. Others built on the idea, but they still lacked the engines to make it completely practical.

But even 1940 is way too late for a working hovercraft. [Dagobert Müller] managed that in 1915. With five engines, the craft was like a wing that generated lift in motion. It was a warship with weapons and a top speed of around 32 knots, although it never saw actual combat. Because of its physical limitations it could only operate over water, unlike more modern craft.

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Mechanisms: Bearings

February 14, 2018 by Dan Maloney 49 Comments

They lie at the heart of every fidget spinner and in every motor that runs our lives, from the steppers in a 3D printer to the hundreds in every car engine. They can be as simple as a lubricated bushing or as complicated as the roller bearing in a car axle. Bearings are at work every day for us, directing forces and reducing friction, and understanding them is important to getting stuff done with rotating mechanisms.

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OpenSCAD: Tieing It Together With Hull()

February 13, 2018 by Elliot Williams 40 Comments

What’s your favorite OpenSCAD command? Perhaps it’s intersection() or difference()? Or are you a polygon() and extrude() modeler? For me, the most useful, and maybe most often overlooked, function is hull(). Hull() does just what it says on the can — creates a convex hull around the objects that are passed to it as children — but that turns out to be invaluable.

Hull() solves a number of newbie problems: making things round and connecting things together. And with a little ingenuity, hull() can provide a nearly complete modelling strategy all on its own. If you use OpenSCAD and your creations end up with hard edges, or you spend too much time figuring out angles, or if you just want to experience another way to get the job done, read on!

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Mary Somerville: The First Scientist

February 13, 2018 by Brian Benchoff 14 Comments

Science, as a concept, is relatively new. Benjamin Franklin wasn’t a scientist probing the mysteries of amber and wool and electricity and ‘air baths’; he was a natural philosopher. Antonie van Leeuwenhoek was simply a man with a proclivity towards creating new and novel instruments. Robert Hooke was a naturalist and polymath, and Newton was simply a ‘man of science’. None of these men were ever called ‘scientists’ in their time; the term hadn’t even been coined yet.

The word ‘scientist’ wouldn’t come into vogue until the 1830s. The word itself was created by William Whewell, reviewing The Connexion of the Physical Sciences by Mary Somerville. The term used at the time, ‘a man of science’, didn’t apply to Mrs. Somerville, and, truth be told, the men of science of the day each filled a particular niche; Faraday was interested in electricity, Darwin was a naturalist. Mary Somerville was a woman and an interdisciplinarian, and the word ‘scientist’ was created for her.

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Salyut: How We Learned To Make Space Stations

February 12, 2018 by Steven Dufresne 61 Comments

When you think about space stations, which ones come to mind first? You might think Skylab, the International Space Station (ISS), or maybe Russia’s Mir. But before any of those took to the heavens, there was Salyut.

Russia’s Salyut 1 was humankind’s first space station. The ensuing Salyut program lasted fifteen years, from 1971 to 1986, and the lessons learned from this remarkable series of experiments are still in use today in the International Space Station (ISS). The program was so successful at a time when the US manned space program was dormant that one could say that the Russians lost the Moon but won the space race.

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