Curated

76 Articles

Hackaday’s finest original content articles curated by the Hackaday editors

Fun With Negative Resistance: Jellybean Transistors

May 8, 2019 by 11 Comments

The concept of negative resistance has always fascinated me. Of course, a true negative resistance is not possible, and what is meant is a negative differential resistance (NDR). But of course knowing the correct term doesn’t do anything to demystify the topic. Negative resistance sounds like an unusual effect, but it turns out to be relatively common, showing up in places like neon lamps and a number of semiconductor structures. Now’s as good a time as any to dig in and learn more about this common principle.

NDR means a portion of a device’s I/V curve where the current falls with increasing applied voltage. The best-known semiconductor device exhibiting negative resistance is the tunnel diode, also known as the Esaki diode after one of the Nobel-Prize-winning discoverers of the quantum tunneling effect responsible for its operation. These diodes can perform at tremendous speeds; the fastest oscilloscope designs relied on them for many years. As the transistor and other technologies improved, however, these diodes were sidelined for many applications, and new-production models aren’t widely available — a sad state for would-be NDR hackers. But, all hope is not lost.

Rummaging through some old notebooks, I rediscovered an NDR design I came up with in 2002 using two common NPN transistors and a handful of resistors; many readers will already have the components necessary to experiment with similar circuits. In this article, we’ll have a look at what you can do with junkbox-class parts, and in a future article we’ll explore the topic with some real tunnel diodes.

So, let’s see what you can do with a couple of jellybean transistors!

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How Art Became Science In Machining

May 7, 2019 by 57 Comments

Machining is one of those fascinating fields that bridges the pre-scientific and scientific eras. As such, it has gone from a discipline full of home-spun acquired wisdom and crusty old superstitions to one of rigorously analyzed physics and crusty old superstitions.

The earliest machinists figured out most of what you need to know just by jamming a tool bit into spinning stock and seeing what happens. Change a few things, and see what happens next. There is a kind of informal experimentation taking place here. People are gradually controlling for variables and getting better at the craft as they learn what seems to affect what. However, the difference between fumbling around and actually knowing something is controlling for one’s own biases in a reproducible and falsifiable way. It’s the only way to know for sure what is true, and we call this “science”. It also means being willing to let go of ideas you had because the double-blinded evidence clearly says they are wrong.

That last part is where human nature lets us down the most. We really want to believe things that confirm our preconceived notions about the world, justify our emotions, or make us feel better. The funny thing about science, though, is that it doesn’t care whether you believe in it or not. So go get your kids vaccinated, and up your machining game with scientific precision. Let’s take a look.

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A Million Zombie Taxis By 2020? It’s Not Going To Happen

May 6, 2019 by 51 Comments

The tech world has a love for Messianic figures, usually high-profile CEOs of darling companies whose words are hung upon and combed through for hidden meaning, as though they had arrived from above to our venture-capital-backed prophet on tablets of stone. In the past it has been Steve Jobs or Bill Gates, now it seems to be Elon Musk who has received this treatment. Whether his companies are launching a used car into space, shooting things down tubes in the desert, or synchronised-landing used booster rockets, everybody’s talking about him. He’s a showman whose many pronouncements are always soon eclipsed by bigger ones to keep his public on the edge of their seats, and now we’ve been suckered in too, which puts us on the spot, doesn’t it.

Your Johnny Cab is almost here

The latest pearl of Muskology came in a late April presentation: that by 2020 there would be a million Tesla electric self-driving taxis on the road. It involves a little slight-of-hand in assuming that a fleet of existing Teslas will be software upgraded to be autonomous-capable and that some of them will somehow be abandoned by their current owners and end up as taxis, but it’s still a bold claim by any standard.

Here at Hackaday, we want to believe, but we’re not so sure. It’s time to have a little think about it all. It’s the start of May, so 2020 is about 7 months away. December 2020 is about 18 months away, so let’s give Tesla that timescale. 18 months to put a million self-driving taxis on the road. Can the company do it? Let’s find out.

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Get To Know The Physics Behind Soldering And The Packaging Of ICs

May 3, 2019 by 22 Comments

Often it feels as if soldering is deemed to be more of an art form than something that’s underpinned by the cold, hard reality of physics and chemistry. From organic chemistry with rosin, to the material properties of fragile gold bond wires and silicon dies inside IC packages and the effects of thermal stress on the different parts of an IC package, it’s a complicated topic that deserves a lot more attention than it usually gets.

A casual inquiry around one’s friends, acquaintances, colleagues and perfect strangers on the internet usually reveals the same pattern: people have picked up a soldering iron at some point, and either figured out what seemed to work through trial and error, or learned from someone else who has learned what seemed to work through trial and error. Can we say something scientific about soldering?

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Twenty Five Years Since The End Of Commodore

May 2, 2019 by 81 Comments

This week marks the twenty-five year anniversary of the demise of Commodore International. This weekend, pour one out for our lost homies.

Commodore began life as a corporate entity in 1954 headed by Jack Tramiel. Tramiel, a Holocaust survivor, moved to New York after the war where he became a taxi driver. This job led him to create a typewriter repair shop in Bronx. Wanting a ‘military-style’ name for his business, and the names ‘Admiral’ and ‘General’ already taken, and ‘Lieutenant’ simply being a bad name, Tramiel chose the rank of Commodore.

Later, a deal was inked with a Czechoslovakian typewriter manufacture to assemble typewriters for the North American market, and Commodore Business Machines was born. Of course, no one cares about this pre-history of Commodore, for the same reason that very few people care about a company that makes filing cabinets. On the electronics side of the business, Commodore made digital calculators. In 1975, Commodore bought MOS, Inc., manufacturers of those calculator chips. This purchase of MOS brought Chuck Peddle to Commodore as the Head of Engineering. The calculators turned into computers, and the Commodore we know and love was born.

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