Generating Power with Wind, Water, and Solar

December 9, 2018 by Al Williams 22 Comments

It is three weeks after the apocalypse. No zombies yet. But you do need to charge your cell phone. How do you quickly make a wind turbine? If you’ve read this project, you might reach for a few empty water bottles. This educational project might not charge your phone without some extra work, but it does illustrate how to use water bottles to make a workable air scoop for turning a crank and possibly generating electricity.

That takes care of the wind and water aspects, but how did we get solar? According to the post — and we agree it is technically true — wind power is a form of solar power since the wind is driven by temperature differences created by the sun. Technically true!

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FPGA used VHDL for Fractals

December 9, 2018 by Al Williams 9 Comments

Over on GitHub, [ttsiodras] wanted to learn VHDL. So he started with an algorithm to do Mandelbrot sets and moved it to an FPGA. Because of the speed, he was able to accomplish real-time zooming. You can see a video of the results, below.

The FPGA board is a ZestSC1 that has a relatively old Xilinx Spartan 3 chip onboard. Still, it is plenty powerful enough for a task like this.

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Crystal Oscillators Explained

December 8, 2018 by Al Williams 13 Comments

We’ve read a lot about oscillators, but crystal oscillators seem to be a bit of a mystery. Hobby-level books tend to say, build a circuit like this and then mess with it until it oscillates. Engineering texts tend to go on about loop gains but aren’t very clear about practice. A [circuit digest] post that continues a series on oscillators has a good, practical treatment of the subject.

Crystals are made to have a natural resonant frequency and will oscillate at that frequency or a multiple thereof with the proper excitation. The trick, of course, is finding the proper excitation.

The post starts with a basic model of a crystal having a series capacitance and inductance along with a resistance. There’s also a shunt or parallel capacitor. When you order a crystal, you specify if you want the resonant frequency in series or parallel mode — that is, which of the capacitors in the model you want to resonate with the inductor — so the model has actual practical application.

By applying the usual formula for resonance on the model you’ll see there is a null and a peak which corresponds to the two resonance points. The dip is the series frequency and the peak is the parallel. You can actually see a trace for a real crystal in a recent post we did on the Analog Discovery 2. It matches the math pretty well, as you can see on the right.

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VexRISC-V Exposed

December 8, 2018 by Al Williams 8 Comments

If you want to use FPGAs, you’ll almost always use an HDL like Verilog or VHDL. These are layers of abstraction just like using, say, a C compiler is to machine language or assembly code. There are other challengers to the throne such as SpinalHDL which have small but enthusiastic followings. [Tom] has a post about how the VexRISC-V CPU leverages SpinalHDL to make an extremely flexible system that is as efficient as plain Verilog. He says the example really shows off why you should be using SpinaHDL.

Like a conventional programming language, it is easy to find niche languages that will attract a little attention and either take off (say, C++, Java, or Rust) or just sort of fade away. The problem is you can’t ever tell which ones are going to become major and which are just flashes in the pan. Is SpinalHDL the next big thing? We don’t know.

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Magic Wand Learns Spells through Machine Learning and an IMU

December 7, 2018 by Al Williams 6 Comments

Jennifer Wang likes to dress up for cosplay and she’s a Harry Potter fan. Her wizarding skills are technological rather than magical but to the casual observer she’s managed to blur those lines. Having a lot of experience with different sensors, she decided to fuse all of this together to make a magic wand. The wand contains an inertial measurement unit (IMU) so it can detect gestures. Instead of hardcoding everything [Jennifer] used machine learning and presented her results at the Hackaday Superconference. Didn’t make it to Supercon? No worries, you can watch her talk on building IMU-based gesture recognition below, and grab the code from GitHub.

Naturally, we enjoyed seeing the technology parts of her project, and this is a great primer on applying machine learning to sensor data. But what we thought was really insightful was the discussions about the entire design lifecycle. Asking questions to scope the design space such as how much money can you spend, who will use the device, and where you will use it are often things we subconsciously answer but don’t make explicit. Failing to answer these questions at all increases the risk your project will fail or, at least, not be as successful as it could have been.

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Fail of the Week: A Candle Caused Browns Ferry Nuclear Incident

December 6, 2018 by Al Williams 109 Comments

A colleague of mine used to say he juggled a lot of balls; steel balls, plastic balls, glass balls, and paper balls. The trick was not to drop the glass balls. How do you know which is which? For example, suppose you were tasked with making sure a nuclear power plant was safe. What would be important? A fail-safe way to drop the control rods into the pile, maybe? A thick containment wall? Two loops of cooling so that only the inner loop gets radioactive? I’m not a nuclear engineer, so I don’t know, but ensuring electricians at a nuclear plant aren’t using open flames wouldn’t be high on my list of concerns. You might think that’s really obvious, but it turns out if you look at history that was a glass ball that got dropped.

In the 1960s and 70s, there was a lot of optimism in the United States about nuclear power. Browns Ferry — a Tennessee Valley Authority (TVA) nuclear plant — broke ground in 1966 on two plants. Unit 1 began operations in 1974, and Unit 2 the following year. By 1975, the two units were producing about 2,200 megawatts of electricity.

That same year, an electrical inspector and an electrician were checking for air leaks in the spreading room — a space where control cables split to go to the two different units from a single control room. To find the air drafts they used a lit candle and would observe the flame as it was sucked in with the draft. In the process, they accidentally started a fire that nearly led to a massive nuclear disaster.

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A Christmas Tree for your Lab

December 6, 2018 by Al Williams 11 Comments

It seems like holiday decorations come up earlier and earlier every year. You might not have room for a full-blown tree in your lab, but if you have an arbitrary waveform generator and a scope, Tektronix has a way for you to show your spirit electronically.

You can see the video below. Naturally, it features Tektronix gear, but we are pretty sure you could make it work with any arbitrary waveform generator that has at least two channels and a scope with an XY mode.

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