Won’t Somebody, Please, Think Of The Transistors!

April 6, 2018 by Jenny List 146 Comments

At what age did you begin learning about electronics? What was the state of the art available to you at the time and what kinds of things were you building? For each reader these answers can be wildly different. Our technology advances so quickly that each successive generation has a profoundly different learning experience. This makes it really hard to figure out what basic knowledge today will be most useful tomorrow.

Do you know the forward voltage drop of a diode? Of course you do. Somewhere just below 0.7 volts, give or take a few millivolts, of course given that it is a silicon diode. If you send current through a 1N4148, you can be pretty certain that the cathode voltage will be that figure below the anode, every time. You probably also have a working knowledge that a germanium diode or a Schottky diode will have a lower forward voltage, and you’ll know in turn that a bipolar transistor will begin to turn on when the voltage between its base and emitter achieves that value. If you know Ohm’s Law, you can now set up a biasing network and without too many problems construct a transistor amplifier.

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Circuit VR: The Dickson Charge Pump

April 6, 2018 by Al Williams 23 Comments

There was a time when taking a low DC voltage — say a single battery — and converting it to a higher voltage was painful. Now, however, cheap and easy-to-use DC to DC converters are readily available. For some small tasks, though, these can seem like overkill. For example, consider a case where you need to supply a higher voltage for a MOSFET gate that doesn’t draw much current. Perhaps you need that higher voltage to trigger a microcontroller’s programming mode and nothing else. The current draw is minimal, and a full-blown DC to DC converter is overkill. For cases like that, it is tempting to use some voltage multiplication scheme. There are many, but for this post, I’m going to take you inside a Dickson charge pump. This is Circuit VR because not only are we going to discuss the circuit, we’ll look at an LT Spice simulation you can try yourself.

The Dickson is interesting because it doesn’t require any AC conversion or transformers. Instead, it uses diodes or other switching elements to transfer charge between capacitors in stages. Each stage will effectively increase the voltage by the supply voltage — in theory. Reality isn’t so kind, though, as we’ll see.

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Mechanisms: Couplings

April 5, 2018 by Dan Maloney 39 Comments

I was splitting wood one day a few years back, getting next winter’s firewood ready on my hydraulic splitter. It normally handled my ash and oak with ease, but I had a particularly gnarly piece of birch queued up, and the splitter was struggling. The 20-ton cylinder slowed as the wedge jammed in the twisted grain, the engine started to bog down, then BANG! I jumped back as something gave way and the engine revved out of control; I figured a hydraulic hose gave out. Whatever it was, I was done for the day.

I later discovered that a coupler between the engine shaft and the hydraulic pump failed dramatically. It was an easy fix once I ordered the right part, and I’ve since learned to keep extras in stock. Couplings are useful things, and they’re the next up in our series on mechanisms.

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The Basics And Pitfalls Of Pointers In C

April 4, 2018 by Sven Gregori 105 Comments

Pointers — you either love them, or you haven’t fully understood them yet. But before you storm off to the comment section now, pointers are indeed a polarizing subject and are both C’s biggest strength, and its major source of problems. With great power comes great responsibility. The internet and libraries are full of tutorials and books telling about pointers, and you can randomly pick pretty much any one of them and you’ll be good to go. However, while the basic principles of pointers are rather simple in theory, it can be challenging to fully wrap your head around their purpose and exploit their true potential.

So if you’ve always been a little fuzzy on pointers, read on for some real-world scenarios of where and how pointers are used. The first part starts with regular pointers, their basics and common pitfalls, and some general and microcontroller specific examples.

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Kapton: Miracle Material With A Tragic History

April 4, 2018 by Dan Maloney 64 Comments

On a balmy September evening in 1998, Swissair flight 111 was in big trouble. A fire in the cockpit ceiling had at first blinded the pilots with smoke, leaving them to rely on instruments to divert the plane, en route from New York to Geneva, to an emergency landing at Halifax Airport in the Canadian province of Nova Scotia. But the fire raging above and behind the pilots, intense enough to melt the aluminum of the flight deck, consumed wiring harness after wiring harness, cutting power to vital flight control systems. With no way to control the plane, the MD-11 hit the Atlantic ocean about six miles off the coast. All 229 souls were lost.

It would take months to recover and identify the victims. The 350-g crash broke the plane into two million pieces which would not reveal their secrets until much later. But eventually, the problem was traced to a cascade of failures caused by faulty wiring in the new in-flight entertainment system that spread into the cockpit and doomed the plane. A contributor to these failures was the type of insulation used on the plane’s wiring, blamed by some as the root cause of the issue: the space-age polymer Kapton.

No matter where we are, we’re surrounded by electrical wiring. Bundles of wires course with information and power, and the thing that protects us is the thin skin of insulation over the conductor. We trust these insulators, and in general our faith is rewarded. But like any other engineered system, failure is always an option. At the time, Kapton was still a relatively new wonder polymer, with an unfortunate Achilles’ heel that can turn the insulator into a conductor, and at least in the case of flight 111, set a fire that would bring a plane down out of the sky.

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Nancy Grace Roman, Mother Of The Hubble

April 3, 2018 by Kristina Panos 25 Comments

When she was four years old, Nancy Grace Roman loved drawing pictures of the Moon. By the time she was forty, she was in charge of convincing the U.S. government to fund a space telescope that would give us the clearest, sharpest pictures of the Moon that anyone had ever seen. Her interest in astronomy was always academic, and she herself never owned a telescope. But without Nancy, there would be no Hubble.

Goodnight, Moon

A view of the Milky Way from Reno, Nevada. Via Lonely Speck

Nancy was born May 16, 1925 in Nashville, Tennessee. Her father was a geophysicist, and the family moved around often. Nancy’s parents influenced her scientific curiosities, but they also satisfied them. Her father handled the hard science questions, and Nancy’s mother, who was quite interested in the natural world, would point out birds, plants, and constellations to her.

For two years, the family lived on the outskirts of Reno, Nevada. The wide expanse of desert and low levels of light pollution made stargazing easy, and Nancy was hooked. She formed an astronomy club with some neighborhood girls, and they met once a week in the Romans’ backyard to study constellations. Nancy would later reminisce that her experience in Reno was the single greatest influence on her future career.

By the time Nancy was ready for high school, she was dead-set on becoming an astronomer despite a near-complete lack of support from her teachers. When she asked her guidance counselor for permission to take a second semester of Algebra instead of a fifth semester of Latin, the counselor was appalled. She looked down her nose at Nancy and sneered, “What lady would take mathematics instead of Latin?”

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What’s The Deal With Transparent Aluminum?

April 3, 2018 by Dan Maloney 139 Comments

It looks like a tube made of glass but it’s actually aluminum. Well, aluminum with an asterisk beside it — this is not elemental aluminum but rather a material made using it.

We got onto the buzz about “transparent aluminum” as a result of a Tweet from whence the image above came. This Tweet was posted by [Jo Pitesky], a Science Systems Engineer at the Jet Propulsion Lab in Pasadena. [Jo] reported that at a recent JPL technology open house she had the chance to handle a tube of material that looks for all the world like a section of glass tubing, but was billed as transparent aluminum. [Jo] tweeted this because it was an interesting artifact that few people get to play with and she’s right, this is fascinating!

The the material itself is intriguing, and I immediately had practical questions like what is this stuff? What is it good for? How is it made? And is it really aluminum rendered transparent by some science fiction process?

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