Memories Of A Mis-Spent Youth: Learnabout Simple Electronics

Heaven, for tech-inclined late-1970s British kids.
Heaven, for tech-inclined late-1970s British kids.

Early last spring, we featured a book review, as part of our occasional Books You Should Read series. Usually these are seminal tomes, those really useful books that stay with you for life and become well-thumbed, but in this case it was a children’s book. Making a Transistor Radio, by [George Dobbs, G3RJV], was a part of the long-running series of Ladybird books that educated, entertained, and enthralled mid-20th-century British kids, and its subject was the construction of a 3-transistor regenerative AM receiver. If you talk to a British electronic engineer of A Certain Age there is a good chance that this was the volume that first introduced them to their art, and they may even still have their prized radio somewhere.

Making a Transistor Radio was a success story, but what’s not so well-known is that there was a companion volume published a few years later in 1979. Simple Electronics was part of the imprint’s Learnabout series, and it took the basic premise of its predecessor away from the realm of radio into other transistor circuits. Transistor timers and multivibrators were covered, Morse code, and finally quite an ambitious project, an electronic organ.

Opening the book it is evident that there has been a slight cultural shift since the first volume was published. The typography is much more modern in feel, and the picture of the child experimenter on the inside of the cover is a photograph of a late-70s young girl in place of the 1950s-style boy wearing a tie building the radio. The practical nature of the writing hasn’t changed though, while it states that some of the background information is not being repeated from Making a Transistor Radio we are taken straight into the deep end with a section on the tools required to work with the series’ signature screw cup on wooden baseboard construction technique.

Construction was so much easier when transistors came with long leads.
Construction was so much easier when transistors came with long leads.

The original book used germanium transistors from the Mullard OC series, OC71s and an OC44. These were some of the earliest British transistors, and as I can attest from building my radio in that period, difficult to obtain by the late 1970s. This book has therefore moved on to a later design, the AC128. Still a germanium PNP device, but this time in a metal can and crucially still available at the time due to having been a part used in more than one mid-70s colour TV set. We’re given a no-nonsense introduction to the device, told about its package, pinout, and schematic diagram. It’s refreshing to see a children’s book in which the child is introduced to such an adult subject as this without being constantly reminded that they are a child.

We then spend a couple of pages looking at a transistor as a switch. A 10K base resistor is used to bias an AC128 with a flashlight bulb as its collector load, and with a flying lead to the negative supply (remember this is a PNP transistor!) the bulb can be turned on and off. In typical form, we’re shown how to make a bulb holder from a paper clip should we not be able to source a dedicated component. The basic switch is then extended with an electrolytic capacitor to make a simple time delay switch, and finally we’re shown how two such circuits combine to make an astable multivibrator and flash a pair of bulbs.

The astable multivibrator, explained for kids.
The astable multivibrator, explained for kids.

For me, circa 1979 or 1980, this was something of an earth-shattering moment. For the first time, I understood how an oscillator worked. That transistor turned on, triggering the other transistor after a delay, which in turn triggered the first transistor after a further delay, and so on and so on. It’s a simple enough circuit, but to a kid who had only recently been introduced to electronics, it was an amazing moment of revelation to have an insight into how it worked. It probably gave me a lifetime bad habit in that the two-transistor astable has become my go-to circuit when I need a quick and dirty square wave. They can be assembled from commonly desolderable scrap components on a bit of PCB or tinplate in a matter of minutes, and I have used them for nasty logic clocks, harmonic-rich signal sources, PWM oscillators, switching power supplies, and many more applications all because of this book.

Enough reminiscences, and time to turn the page. For a bit of fun we’re shown the light flasher as a robot with flashing eyes, before substituting some of the components and adding a crystal earpiece for an audio oscillator. This is the first part of the serious business of the book, because it forms the basis of all the following projects. It’s also the furthest I got with the book as a child, because of a lack of enough AC128s for the complete organ project, and a lack of aptitude for music. I was shown how to use a soldering iron, discovered that scrap TV sets in dumpsters contained a goldmine of parts, and never looked back.

[George Dobbs] is a radio amateur, so of course once he has a legion of British kids with audio oscillators he then leads them into making a Morse Code practice oscillator with a filter and a key made from tinplate. In typical no-nonsense style we’re introduced to amateur radio, code, and basic operating procedure. There are even instructions for making a two-station setup using three-core mains flex, how many kids who built that went on to have callsigns of their own?

The organ project awaits, but before then we have time for a couple more circuits to get used to varying the pitch of the oscillator. A “violin” using a potentiometer, and a photoelectric cell each get their own page, after which you have to wonder: how many kids managed to get their parents to shell out for that ORP12 CdS cell?

Never lose the fascination you gain from your first project!
Never lose the fascination you gain from your first project!

The organ is of the “Stylophone” variety, with notes picked out using a stylus over conductive pads on the keyboard. Skeleton preset potentiometers are used for tuning, with the alternative of filing notches in carbon resistors. This would not have been a cheap project at all on a pocket-money budget in 1979, did any readers build it? If they went for the final two pages, the same 1-transistor loudspeaker amplifier as that used in the transistor radio, and a vibrato circuit using a low-frequency version of the multivibrator, then pocket money would have been in very short supply indeed.

But to look at it this way probably misses the point of the book. Where the previous book was all about presenting a single project in stages, this one is more about teaching some basic transistor circuits in stages. When I was given a copy I had a basic idea about transistors from those OC71s in the radio, but when I’d read this one and built some of the circuits I had a much more varied grasp of solid-state electronics. I knew about RC circuits and oscillators, and the effect of changing the values of an RC circuit on frequency. Some of the things I learned from this book I still use today, and nearly a decade after reading it when I was a 1st year electronic engineering undergraduate I hit the ground running in our course on transistor circuits because of it.

Learnabout Simple Electronics has been out of print for well over three decades now, but if you want a copy you should be able to find it in second-hand book stores online. There’s also at least one PDF version available too, if all you want is a quick look.

Books You Should Read: The 3D Printing Handbook

3D printing was invented in the 80s, twenty years passed, patents expired, and then several diverse uses for 3D printing technology were found. As such, the tips and techniques for 3D printing — especially filament-based printing — have been discussed and documented almost entirely on the Internet, mostly in chat rooms, forums, and YouTube videos. Everything you could ever want to know about 3D printing is available on the Internet, but that doesn’t mean you’ll be able to find it.

There have been dozens of books published as a guidebook to 3D printing over the years, and some of those are even in their second edition. Yes, despite the disappearance of 3D printers from the headlines of TechCrunch, and despite the massive public disillusionment of computer-controlled hot glue guns, there are still people that want to learn about 3D printers. There’s actually a market for 3D printing guidebooks, and people are buying them.

The latest such guidebook for 3D printing is The 3D Printing Handbook from 3D Hubs. 3D Hubs has been around for a while, and can best be described as, ‘3D Printing as a Service’. The usual use case for 3D Hubs is that someone would upload a 3D model to 3D Hubs, and get a quote from someone with a 3D printer. This quote could come from a professional 3D printing outfit with machines that cost more than a house to someone with a LulzBot or Prusa in their garage. 3D Hubs is going to be fantastic when people realize you can do CNC milling on the service as well.

This book was written by Ben Redwood, Filemon Schöffer, and Brian Garret, all employees of 3D Hubs. In one way or another, 3D Hubs has a hand in every conceivable type of 3D printing technology, and this book aims to be an introduction to the uses of these technologies, and a guidebook on how to use 3D printing technology the right way. There’s a question with this book: does it live up to expectations, and for that matter, can any book live up to the expectation of being a ‘guide to 3D printing?’

Continue reading “Books You Should Read: The 3D Printing Handbook”

Bibles You Should Read: PoC || GTFO


For the last few years, Pastor Manul Laphroaig and friends have been publishing the International Journal of PoC || GTFO. This is a collection of papers and exploits, submitted to the Tract Association of PoC || GTFO, each of which demonstrates an interesting exploit, technique, or software toy in the field of electronics. Imagine, if 2600 or Dr. Dobb’s Journal were a professional academic publication. Add some whiskey and you have PoC || GTFO.

This is something we’ve been waiting a while for. The International Journal of PoC || GTFO is now a real book bible published by No Starch Press. What’s the buy-in for this indulgence? $30 USD, or a bit less if you just want the Ebook version. The draw of the dead tree version of PoC includes a leatherette cover, gilt edges, and the ability to fit inside bible covers available through other fine retailers. There are no rumors of a children’s version with vegetable-based characters.

PoC || GTFO, in reality, is an almost tri-annual journal of reverse engineering, computer science, and other random electronic computational wizardry, with papers (the Proof of Concept) by Dan Kaminsky, Colin O’Flynn, Joe FitzPatrick, Micah Elisabeth Scott, Joe Grand, and other heroes of the hacker world. What does PoC || GTFO present itself as? Applied electrons in a religious tract publication. The tongue is planted firmly in the cheek here, and it’s awesome.

Continue reading “Bibles You Should Read: PoC || GTFO”

Books You Should Read: IGNITION!

Isaac Asimov described the business of rocket fuel research as “playing footsie with liquids from Hell.” If that piques your interest even a little, even if you do nothing else today, read the first few pages of IGNITION! which is available online for free. I bet you won’t want to stop reading.

IGNITION! An Informal History of Liquid Rocket Propellants is about how modern liquid rocket fuel came to be. Written by John D. Clark and published in 1972, the title might at first glance make the book sound terribly dry — it’s not. Liquid rocket fuel made modern rocketry possible. But most of us have no involvement with it at all besides an awareness that it exists, and that makes it easy to take for granted.

Most of us lack any understanding of the fact that its development was the result of a whole lot of hard scientific work, and that work required brilliance (and bravery) and had many frustrating dead ends. It was also an amazingly dangerous business to be in. Isaac Asimov put it this way in the introduction:

“[A]nyone working with rocket fuels is outstandingly mad. I don’t mean garden-variety crazy or a merely raving lunatic. I mean a record-shattering exponent of far-out insanity.

There are, after all, some chemicals that explode shatteringly, some that flame ravenously, some that corrode hellishly, some that poison sneakily, and some that stink stenchily. As far as I know, though, only liquid rocket fuels have all these delightful properties combined into one delectable whole.”

At the time that the book was written and published, most of the work on liquid rocket fuels had been done in the 40’s, 50’s, and first half of the 60’s. There was plenty written about rocketry, but very little about the propellants themselves, and nothing at all written about why these specific substances and not something else were being used. John Clark — having run a laboratory doing propellant research for seventeen years — had a unique perspective of the whole business and took the time to write IGNITION! An Informal History of Liquid Rocket Propellants.

Liquid rocket propellant was in two parts: a fuel and an oxidizer. The combination is hypergolic; that is, the two spontaneously ignite and burn upon contact with each other. As an example of the kinds of details that mattered (i.e. all of them), the combustion process had to be rapid and complete. If the two liquids flow into the combustion chamber and ignite immediately, that’s good. If they form a small puddle and then ignite, that’s bad. There are myriad other considerations as well; the fuel must burn at a manageable temperature (so as not to destroy the motor), the energy density of the fuel must be high enough to be a practical fuel in the first place, and so on.

The actual process of discovering exactly what materials to use and how precisely to make them work in a rocket motor was the very essence of the phrase “the devil is in the details.” For every potential solution, there was a mountain of dead-end possibilities that tantalizingly, infuriatingly, almost worked.

The first reliable, workable propellant combination was Aniline and Red Fuming Nitric Acid (RFNA). “It had the one – but magnificent – virtue that it worked,” writes Clark. “Otherwise it was an abomination.” Aniline was difficult to procure, ferociously poisonous and rapidly absorbed through skin, and froze at an inconvenient -6.2 Celsius which limited it to warm weather only. RFNA was fantastically corrosive, and this alone went on to cause no end of problems. It couldn’t be left sitting in a rocket tank waiting to be used for too long, because after a while you wouldn’t have a tank left. It needed to be periodically vented while in storage. Pouring it gave off dense clouds of remarkably toxic gas. This propellant would go on to cause incredibly costly and dangerous problems, but it worked. Still, no one wanted to put up with any of it one moment longer than they absolutely had to. As a result, that combination was not much more than a first step in the whole process; there was plenty of work left to do.

By the mid-sixties, liquid rocket propellant was a solved problem and the propellant community had pretty much worked themselves out of a job. Happily, a result of that work was this book; it captures history and detail that otherwise would simply have disappeared.

Clark has a gift for writing, and the book is easy to read and full of amusing (and eye-widening) anecdotes. Clark doesn’t skimp on the scientific background, but always in an accessible way. It’s interesting, it’s relevant, it’s relatable, and there is plenty to learn about how hard scientific and engineering development actually gets done. Download the PDF onto your favorite device. You’ll find it well worth the handful of evenings it takes to read through it.

Books you should read: The Bridge

A few weeks ago, Amazon’s crack marketing AI decided to recommend a few books for me. That AI must be getting better because instead of the latest special-edition Twilight books, I was greeted with this:

“The asteroid was called the Hand of God when it hit.”

That’s the first sentence of The Bridge, a new Sci-Fi book by Leonard Petracci. If you think that line sucks you in, wait until you read the whole first chapter.

The Bridge is solidly in the generation ship trope. A voyage hundreds or even thousands of years long, with no sleep or stasis pods. The original crew knows they have no hope of seeing their destination, nor will their children and grandchildren. Heinlein delved into it with Orphans of the Sky. Even Robert Goddard himself discussed generation ships in The Last Migration.

I wouldn’t call The Bridge hard Sci-Fi — and that’s perfectly fine. Leonard isn’t going for scientific accuracy. It’s a great character driven story. If you enjoyed a book like Ready Player One, you’ll probably enjoy this.

The Bridge Is the story of Dandelion 14, a ship carrying people of Earth to a new planet. At some point during the journey, Dandelion 14 was struck by an asteroid, which split the ship in two. Only a few wires and cables keep the halves of the ship together. The crew on both sides of the ship survived, but they had no way to communicate. They do catch glimpses of each other in the windows though.

Much of the story is told in the first person by Horatius, a young man born hundreds of years after the asteroid strike. Horatius’ side of the ship has a population of one thousand, carefully measured at each census. They’ve lost knowledge of how to operate the ship’s systems, but they are surviving. Most of the population are gardeners, but there are doctors, cooks, porters, and a few historians. At four years old, Horatius is selected to become a gardener, like his father was before him. But Horatius has higher aspirations. He longs to become a historian to learn the secrets of the generations that came before him and to write his own story down for those who will come after.

Horatius sees the faces of the people on the other side of the ship as well. Gaunt, hungry, often fighting with knives or other weapons. A stark contrast to the well-fed people on his side of the vessel. The exception is one red-haired girl about his age. He often finds her staring back at him, watching him.

Horatius might have been chosen as a gardener, but he’s clever — a fact that sometimes gets him in trouble. His life takes an abrupt turn when the sleeping ship awakens with an announcement blaring “Systems Rebooting, Ship damage assessed. Reuniting the two halves of the ship and restoring airlock, approximately twenty-four hours until complete.”

The hardest part of writing a book review is not giving too much away. While I won’t tell you much more about the plot for The Bridge, I can tell a bit about how the book came about. You might call this book a hack of the publishing system. Leonard Petracci is also known as leoduhvinci on Reddit. The Bridge started life as Leonard’s response to a post on /r/writingprompts. The prompt went like this:

After almost 1,000 years the population of a generation ship has lost the ability to understand most technology and now lives at a pre-industrial level. Today the ship reaches its destination and the automated systems come back online.

Leonard ’s response to the prompt shot straight to the top, and became the first chapter of The Bridge. Chapter 2 followed soon after. In only a few months, the book was complete. Available on Reddit, and on Leonard’s website. The Bridge is also available on Amazon for Kindle, and on paper from Amazon’s CreateSpace.

The only real criticism I have about The Bridge is the ending. The book’s resolution felt a bit rushed. It would have been nice to have a few more pages telling us what happened to the characters after the major events of the book. Leonard is planning a sequel though, and he teases this in the final pages.

You can start reading The Bridge right now on Leonard’s website. He has the entire book online for free for a few more weeks. If you’ve missed the free period, the Kindle edition is currently $2.99.

Book Review: The Art Of The Patent

In bringing suitable illustrations to our articles, we Hackaday scribes use a variety of sources that offer images featuring permissive licences. Among the usual free image libraries there is one particularly rich source, the line drawings contained within the huge archives of patents granted by the various countries around the world. These are the illustrations used as part of the patent itself to describe the working of the patent being claimed. We use them because though the items they depict are legally protected from copying by the patents they are part of, they as part of the patents themselves are in the public domain. Thus we can easily find detailed hand drawn pictures of all kinds of technical innovations from the last couple of hundred years or so, and from time to time you as our readers reap the benefit.

The beauty in hand-rendered fonts from patent artwork, collected within the book.
The beauty in hand-rendered fonts from patent artwork, collected within the book.

If you spend a while browsing old patents through a search engine such as Google Patents, you can quickly become engrossed in these beautiful images of inventions past. Though their purpose is a functional one to convey the workings of an invention, the anonymous artists have often poured all of their skill into rendering them as considerably more than mere draughtsmanship. In those dusty Government archives lurk masterpieces, just waiting to be found.

It seems we here at Hackaday are not alone in sharing a fascination with these images, for a US patent agent, [Kevin Prince], wrote a fascinating exploration of the medium in his book, The Art of the Patent. Continue reading “Book Review: The Art Of The Patent”

Books You Should Read: Making A Transistor Radio

When a Hackaday article proclaims that its subject is a book you should read, you might imagine that we would be talking of a seminal text known only by its authors’ names. Horowitz and Hill, perhaps, or maybe Kernigan and Ritchie. The kind of book from which you learn your craft, and to which you continuously return to as a work of reference. Those books that you don’t sell on at the end of your university career.

Ladybird books covered a huge range of topics.
Ladybird books covered a huge range of topics.

So you might find it a little unexpected then that our subject here is a children’s book. Making A Transistor Radio, by [George Dobbs, G3RJV] is one of the huge series of books published in the UK under the Ladybird imprint that were a staple of British childhoods for a large part of the twentieth century. These slim volumes in a distinctive 7″ by 4.5″ (180 x 115 mm) hard cover format were published on a huge range of subjects, and contained well written and informative text paired with illustrations that often came from the foremost artists of the day. This one was published at the start of the 1970s when Ladybird books were in their heyday, and has the simple objective of taking the reader through the construction of a simple three transistor radio. It’s a book you must read not because it is a seminal work in the vein of Horrowitz and Hill, but because it is the book that will have provided the first introduction to electronics for many people whose path took them from this humble start into taking the subject up as a career. Including me as it happens, I received my copy in about 1979, and never looked back. Continue reading “Books You Should Read: Making A Transistor Radio”