A Pulse Of Annoyance About Oscillators, Followed By A Flyback Of A Rant

September 26, 2023 by Jenny List 37 Comments

Everyone likes to play with high voltages, right?. Even though the danger of death goes up with every volt, it’s likely that a few readers will have at some time or other made fancy long sparks. You’re reading this so you lived to tell the tale, and we’d only ever counsel only doing so safely, but the point of this piece lies not in the volts themselves but in a touch of frustration at the voltage generators. There’s a circuit I see so often which annoys me every single time, so here if you don’t mind I’m going to deliver both a little rant and a look into flyback converters.

It’s Got Coils, so It’s A Transformer

A power supply with the lid removed, visible is a large transformer — Linear power supplies with a mains transformer are a surprisingly rare sight now. Dilshan Jayakody, CC BY-SA 2.0.

How does a transformer work? An alternating current in a primary winding induces an opposite current in its secondary winding. The voltage out is equal to the turns ratio times the voltage in. Thus if you want to make a high voltage, it’s simply a case of finding a transformer with the right turns ratio, and applying the right AC to the input.

A handy choice for a high voltage transformer has been for years a TV line output transformer, also sometimes known as a flyback transformer. You could find these in CRT displays and TVs, and they consist of a square ferrite core with a big chunky high voltage overwinding for the CRT anode circuit and a load of lower voltage windings. TV designers were always out to save on parts costs, so they often had windings for all the voltage rails inside the set as well as the anode voltage, using the timebase as a crude switching power supply. Continue reading “A Pulse Of Annoyance About Oscillators, Followed By A Flyback Of A Rant” →

You’ve Got Mail: Reading Addresses With OCR

September 20, 2023 by Kristina Panos 14 Comments

Last time I delivered on this column, I told you about the USPS’ attempts to fully automate a post office. Of course, that’s a bit of a misnomer, since it took 1,500 employees to actually operate the place on a daily basis. Although Project Turnkey in Rhode Island and Project Gateway in California were proving grounds for all kinds of mail sorting and processing equipment, the act of actually reading addresses and routing mail to its final destination still required human intervention and hand coding.

Today, the post office processes hundreds of millions of mail pieces each day using various pieces of equipment. One of those important pieces of equipment is the OCR address reader, which manages to make sense of all kinds of chicken scratch.

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You’ve Got Mail: Automatic For The People

September 13, 2023 by Kristina Panos 15 Comments

When we last left the post office, I told you all about various kinds of machinery the USPS uses to move mail around. Today I’m going to tell you about the time they thought they could automate nearly every function inside the standard post office — and no, it wasn’t anytime recently.

By 1953, the post office badly needed modernization. When Postmaster General Arthur Summerfield was appointed that year, he found the system essentially in shambles. Throughout the 1930s and 40s, the USPS had done absolutely no spending beyond the necessary, with little to no investment in the future. But Summerfield was an ideas man, and he had the notion to build a totally automated post office. One of them would be located in Providence, Rhode Island and be known as Project Turnkey — as in a turnkey operation. The other would be located in Oakland, California, and serve as a gateway to the Pacific.

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Bringing Da Vinci’s Saw Mill To Life

September 11, 2023 by Al Williams 30 Comments

DaVinci’s notebook — the real one, not the band — was full of wonderous inventions, though many were not actually built and probably weren’t even practical with the materials available at the time (or even now). [How To Make Everything] took one of the Master’s drawings from 1478 of a sawmill and tried to replicate it. How did he do? You can see for yourself in the video below.

There are five different pieces involved. A support structure holds a water wheel and a saw. There’s a crank mechanism to drive the saw and a sled to move the wood through the machine. It sounds simple enough, although we were impressed and amused that he made his own nails to be authentic. No Home Depot back in the 1470s, after all.

Watching him produce, for example, castle joints, makes us think, “Hey, we could do that!” But, of course, we probably can’t, at least not by hand. We must admit we are pretty dependent on CNC tools and 3D printing, but we admire the woodwork, nevertheless. There’s some pretty cool metal working, too.

We thought the waterwheel would be the easy part, but it turned out to be a bit of a problem. Things worked, but it was slower than you would think. We’ve seen sawmills put together before. Da Vinci worked for money, and there was always money in weapons so he did design a lot of them, too.

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You’ve Got Mail: Straining The Limits Of Machine And Man

September 5, 2023 by Kristina Panos 10 Comments

When we last left this subject, I told you all about Transorma, the first letter-sorting machine in semi-wide use. But before and since Transorma, machines have come about to perform various tasks on jumbled messes of mail — things like distinguishing letters from packages, making sure letters are all facing the same way before cancelling the postage, and the gargantuan task of getting huge piles of mail into the machines in the first place. So let’s dive right in, shall we?

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On Vim, Modal Interfaces And The Way We Interact With Computers

September 1, 2023 by Maya Posch 65 Comments

The ways in which we interact with computers has changed dramatically over the decades. From flipping switches on the control panels of room-sized computers, to punching holes into cards, to ultimately the most common ways that we interact with computers today, in the form of keyboards, mice and touch screens. The latter two especially were developed as a way to interact with graphical user interfaces (GUI) in an intuitive way, but keyboards remain the only reasonable way to quickly enter large amounts of text, which raises many ergonomic questions about how to interact with the rest of the user interface, whether this is a command line or a GUI.

For text editors, perhaps the most divisive feature is that of modal versus non-modal interaction. This one point alone underlies most of the Great Editor War that has raged since time immemorial. Practically, this is mostly about highly opiniated people arguing about whether they like Emacs or vi (or Vim) better. Since in August of 2023 we said our final farewell to the creator of Vim – Bram Moolenaar – this might be a good point to put down the torches and pitchforks and take a sober look at why Vim really is the logical choice for fast, ergonomic coding and editing.

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The 2003 Northeast Blackout And The Harsh Lessons Of Grid Failures

August 29, 2023 by Maya Posch 87 Comments

The grid failure in 2003 which reverted much of the eastern US and Canada back to a pre-electrification era may be rather memorable, yet it was not the first time that a national, or even international power grid failed. Nor is it likely that it will be the last. In August of 2023 we mark the 20th anniversary of this blackout which left many people without electricity for up to three days, while costing dozens of people their lives. This raises the question of what lessons we learned from this event since then.

Although damage to transmission lines and related infrastructure is a big cause of power outages – especially in countries where overhead wiring is the norm – the most serious blackouts involve the large-scale desynchronization of the grid, to the point where generators shutdown to protect themselves. Bringing the grid back from such a complete blackout can take hours to days, as sections of the grid are reconnected after a cascade scenario as seen with the 2003 blackout, or the rather similar 1965 blackout which affected nearly the same region.

With how much more modern society relies today on constant access to electrical power than it did twenty, let alone fifty-eight years ago, exactly how afraid should we be of another, possibly worse blackout?

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