Engineering

603 Articles

Quantum Weirdness In Your Browser

January 24, 2018 by 29 Comments

I’ll be brutally honest. When I set out to write this post, I was going to talk about IBM’s Q Experience — the website where you can run real code on some older IBM quantum computing hardware. I am going to get to that — I promise — but that’s going to have to wait for another time. It turns out that quantum computing is mindbending and — to make matters worse — there are a lot of oversimplifications floating around that make it even harder to understand than it ought to be. Because the IBM system matches up with real hardware, it is has a lot more limitations than a simulator — think of programming a microcontroller with on debugging versus using a software emulator. You can zoom into any level of detail with the emulator but with the bare micro you can toggle a line, use a scope, and hope things don’t go too far wrong.

So before we get to the real quantum hardware, I am going to show you a simulator written by [Craig Gidney]. He wrote it and promptly got a job with Google, who took over the project. Sort of. Even if you don’t like working in a browser, [Craig’s] simulator is easy enough, you don’t need an account, and a bookmark will save your work.

It isn’t the only available simulator, but as [Craig] immodestly (but correctly) points out, his simulator is much better than IBM’s. Starting with the simulator avoids tripping on the hardware limitations. For example, IBM’s devices are not fully connected, like a CPU where only some registers can get to other registers. In addition, real devices have to deal with noise and the quantum states not lasting very long. If your algorithm is too slow, your program will collapse and invalidate your results. These aren’t issues on a simulator. You can find a list of other simulators, but I’m focusing on Quirk.

What Quantum Computing Is

As I mentioned, there is a lot of misinformation about quantum computing (QC) floating around. I think part of it revolves around the word computing. If you are old enough to remember analog computers, QC is much more like that. You build “circuits” to create results. There’s also a lot of difficult math — mostly linear algebra — that I’m going to try to avoid as much as possible. However, if you can dig into the math, it is worth your time to do so. However, just like you can design a resonant circuit without solving differential equations about inductors, I think you can do QC without some of the bigger math by just using results. We’ll see how well that holds up in practice.

Continue reading “Quantum Weirdness In Your Browser” →

Space Escape: Flying A Chair To Lunar Orbit

January 19, 2018 by 56 Comments

In the coming decades, mankind will walk on the moon once again. Right now, plans are being formulated for space stations orbiting around Lagrange points, surveys of lava tubes are being conducted, and slowly but surely plans are being formed to build the hardware that will become a small scientific outpost on our closest celestial neighbor.

This has all happened before, of course. In the early days of the Apollo program, there were plans to launch two Saturn V rockets for every moon landing, one topped with a command module and three astronauts, the other one containing an unmanned ‘LM Truck’. This second vehicle would land on the moon with all the supplies and shelter for a 14-day mission. There would be a pressurized lunar rover weighing thousands of pounds. This wouldn’t exactly be a Lunar colony, instead, it would be more like a small cabin in the Arctic used as a scientific outpost. Astronauts and scientists would land, spend two weeks researching and exploring, and return to Earth with hundreds of pounds of samples.

With this, as with all Apollo landings, came a risk. What would happen if the ascent engine didn’t light? Apart from a beautiful speech written by William Safire, there was nothing concrete for astronauts consigned to the deepest of the deep. Later in the Apollo program, there was a plan for real hardware to bring stranded astronauts home. This was the Lunar Escape System (LESS), basically two chairs mounted to a rocket engine.

While the LESS was never built, several studies were completed in late 1970 by North American Rockwell detailing the hardware that would return two astronauts from the surface of the moon. It involved siphoning fuel from a stricken Lunar Module, flying to orbit with no computer or really any instrumentation at all, and performing a rendezvous with an orbiting Command Module in less than one Lunar orbit.

Continue reading “Space Escape: Flying A Chair To Lunar Orbit” →

Know Your Video Waveform

January 18, 2018 by 84 Comments

When you acquired your first oscilloscope, what were the first waveforms you had a look at with it? The calibration output, and maybe your signal generator. Then if you are like me, you probably went hunting round your bench to find a more interesting waveform or two. In my case that led me to a TV tuner and IF strip, and my first glimpse of a video signal.

An analogue video signal may be something that is a little less ubiquitous in these days of LCD screens and HDMI connectors, but it remains a fascinating subject and one whose intricacies are still worthwhile knowing. Perhaps your desktop computer no longer drives a composite monitor, but a video signal is still a handy way to add a display to many low-powered microcontroller boards. When you see Arduinos and ESP8266s producing colour composite video on hardware never intended for the purpose you may begin to understand why an in-depth knowledge of a video waveform can be useful to have.

The purpose of a video signal is to both convey the picture information in the form of luminiance and chrominance (light & dark, and colour), and all the information required to keep the display in complete synchronisation with the source. It must do this with accurate and consistent timing, and because it is a technology with roots in the early 20th century all the information it contains must be retrievable with the consumer electronic components of that time.

We’ll now take a look at the waveform and in particular its timing in detail, and try to convey some of its ways. You will be aware that there are different TV systems such as PAL and NTSC which each have their own tightly-defined timings, however for most of this article we will be treating all systems as more-or-less identical because they work in a sufficiently similar manner.

Continue reading “Know Your Video Waveform” →

Spectre And Meltdown: How Cache Works

January 15, 2018 by 15 Comments

The year so far has been filled with news of Spectre and Meltdown. These exploits take advantage of features like speculative execution, and memory access timing. What they have in common is the fact that all modern processors use cache to access memory faster. We’ve all heard of cache, but what exactly is it, and how does it allow our computers to run faster?

In the simplest terms, cache is a fast memory. Computers have two storage systems: primary storage (RAM) and secondary storage (Hard Disk, SSD). From the processor’s point of view, loading data or instructions from RAM is slow — the CPU has to wait and do nothing for 100 cycles or more while the data is loaded. Loading from disk is even slower; millions of cycles are wasted. Cache is a small amount of very fast memory which is used to hold commonly accessed data and instructions. This means the processor only has to wait for the cache to be loaded once. After that, the data is accessible with no waiting.

A common (though aging) analogy for cache uses books to represent data: If you needed a specific book to look up an important piece of information, you would first check the books on your desk (cache memory). If your book isn’t there, you’d then go to the books on your shelves (RAM). If that search turned up empty, you’d head over to the local library (Hard Drive) and check out the book. Once back home, you would keep the book on your desk for quick reference — not immediately return it to the library shelves. This is how cache reading works.

Continue reading “Spectre And Meltdown: How Cache Works” →

Local Infrastructure: The Devil Is In The Details

January 11, 2018 by 107 Comments

About two months ago I rode my bike to work like any other day, but on the way home a construction project seemed to have spontaneously started at one of the bridges that I pass over. Three lanes had merged into one which, for a federal highway, seemed like a poorly planned traffic pattern for a such a major construction project. As it happens, about an hour after I biked across this bridge that morning both outside sections of the bridge fell into the water. There was no other physical damage that seemed to explain why parts of a bridge on U.S. 1 would suddenly collapse.

The intriguing thing about this bridge collapse was that the outer retaining wall and about half of the sidewalk on both the northbound side and the southbound side had fallen into the water at the same time. This likely wasn’t caused by something like a boat impact, car accident, or an overweight truck. Indeed, Florida Department of Transportation (FDOT) investigated the incident and found that two post tension wires that held these sections of the bridge together had failed, making it unsafe for pedestrians and bicyclists but also for any boaters below. Continue reading “Local Infrastructure: The Devil Is In The Details” →

First Light: The Story Of The Laser

January 8, 2018 by 36 Comments

Lasers are such a fundamental piece of technology today that we hardly notice them. So cheap that they can be given away as toys and so versatile that they make everything from DVD players to corneal surgery a reality, lasers are one of the building blocks of the modern world. Yet lasers were once the exclusive province of physicists, laboring over expansive and expensive experimental setups that seemed more the stuff of science fiction than workhouse tool of communications and so many other fields. The laser has been wildly successful, and the story of its development is an intriguing tale of observation, perseverance, and the importance of keeping good notes.

Continue reading “First Light: The Story Of The Laser” →

Guide: Why Etch A PCB When You Can Mill?

January 4, 2018 by 83 Comments

I recall the point I started taking electronics seriously, although excited, a sense of dread followed upon the thought of facing the two main obstacles faced by hobbyists and even professionals: Fabricating you own PCB’s and fiddling with the ever decreasing surface mount footprints. Any resistance to the latter proves futile, expensive, and frankly a bit silly in retrospect. Cheap SMD tools have made it extremely easy to store, place, and solder all things SMD.

Once you’ve restricted all your hobbyist designs/experiments to SMD, how do you go about producing the PCBs needed for prototyping? Personally, I dread the thought of etching my own boards. The process is laborious and involves messy chemicals and specially sensitized PCB’s — none of which interest me. I’ve only ever done it a few times, and have promised myself never to do it again. Professional but cheap PCB manufacturing is more like it board pooling services such as OSH park have made this both easy and affordable — if you can wait for the turnaround.

So what are the alternatives? If you are really serious about swift prototyping from your own Lab, I put forth the case of milling your own PCB’s. Read on as I take you through the typical workflow from design to prototype and convince you to put up with the relatively high start up cost of purchasing a PCB mill.

Continue reading “Guide: Why Etch A PCB When You Can Mill?” →