FPGA Rescues Scope From The Dumpster

I’m always on the lookout for a quality addition to my lab that would respect my strict budget. Recently, I’ve found myself pushing the Hertz barrier with every other project I do and hence desperately wanted a high bandwidth scope. Unfortunately, only recently have 70 MHz to 100 MHz become really affordable, whilst a new quad channel oscilloscope in the 500 MHz to 1 GHz range still costs a fortune to acquire. My only option was to find an absolute miracle in the form of an old high bandwidth scope.

It seemed the Gods of Hand Me Down electronics were smiling upon me when I found this dumpster destined HP 54542C. It appeared to be in fairy good shape and was the Top Dog in its day. But something had to be broken right? Sure enough, the screen was clearly faulty and illegible. Want to know how I fixed it? Four letters: FPGA.

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Interview: Francesco de Comité Makes Math Visually Awesome

Francesco de Comité is an Associate Professor in Computer Science at the University of Sciences in Lille, France, where he researches the 2D and 3D representation of mathematical concepts and objects. He’s presented papers on a variety of topics including anamorphoses, experiments in circle packing, and Dupin cyclides. His current project involves modeling and 3D printing sea shells. He’ll be presenting a paper on the topic at Bridges Conference in July. You can find his projects on Flickr as well as on Shapeways.

Hackaday: One of your recent projects involves creating fractal patterns and warping them into biologically-correct sea shell shapes, which you then print.

FdC: Modeling seashell shapes is an old topic–Moseley, 1838, D’Arcy Thompson beginning of 20th century. A seashell can be defined as a curve turning around an axis, while translating in the direction of this axis (i.e. on a helicoidal trajectory), and growing in size at the same time. This was modeled for computers in the ’60s by David Raup.

Drawing patterns on seashells was described by Hans Meinhardt using a model of chemical reactions (activator-inhibitor), in the same spirit as Turing’s work on morphogenesis. Combining these two works, and using 3D printers instead of 2D renderers, we can build realistic seashells, either by copying existing shells, or inventing new ones. A 3D model is not just a juxtaposition of a huge number of 2D views: manipulating 3D models can help you understand the object, find details, and so on.

I was curious to see if making a 3D seashell was possible. Moreover, I show that this can be done with simple tools — well, except the 3D printer.
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Malduino Elite – First Impressions

A while back, I wrote an article about Malduino, an Arduino-based, open-source BadUSB device. I found the project interesting so I signed up for an Elite version and sure enough, the friendly postman dropped it off in my mail box last Friday, which means I got to play around with it over the weekend. For those who missed the article, Malduino is USB device which is able to emulate a keyboard and inject keystrokes, among other things. When in a proper casing, it will just look like a USB flash drive. It’s like those things you see in the movies where a guy plugs in a device and it auto hacks the computer. It ships in two versions, Lite and Elite, both based on the ATmega32U4.

The Lite version is really small, besides the USB connector it only contains a switch, which allows the user to choose between running and programming mode, and a LED, which indicates when the script has finished running.

Original Malduino Elite sketch and Lite prototype

The Elite version is bigger, comes with a Micro-SD card reader and four DIP switches, which allow the user to choose which script to run from the card. It also has the LED, which indicates when a script has finished to run. This allows the user to burn the firmware only once and then program the keystroke injection scripts that stored in the Micro-SD card, in contrast to the Lite version which needs to be flashed each time a user wants to run a different script.

These are the two Malduinos and because they are programmed straight from the Arduino IDE, every feature I just mentioned can be re-programmed, re-purposed or dropped all together. You can buy one and just choose to use it like a ‘normal’ Arduino, although there are not a lot of pins to play around with. This freedom was one the first things I liked about it and actually drove me to participate in the crowd-funding campaign. Read on for the full review.
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How to Build Your Own Google AIY without the Kit

Google’s voice assistant has been around for a while now and when Amazon released its Alexa API and ported the PaaS Cloud code to the Raspberry Pi 2 it was just a matter of time before everyone else jumped on the fast train to maker kingdom. Google just did it in style.

Few know that the Google Assistant API for the Raspberry Pi 3 has been out there for some time now but when they decided to give away a free kit with the May 2017 issues of MagPi magazine, they made an impression on everyone. Unfortunately the world has more makers and hackers and the number of copies of the magazine are limited.

In this writeup, I layout the DIY version of the AIY kit for everyone else who wants to talk to a cardboard box. I take a closer look at the free kit, take it apart, put it together and replace it with DIY magic. To make things more convenient, I also designed an enclosure that you can 3D print to complete the kit. Lets get started.

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The Tri Rotor Drone: Why Has It Been Overlooked?

A DJI Phantom 3. Zimin.V.G. [CC BY-SA 4.0]
If you are a watcher of the world of drones, or multirotors, you may have a fixed idea of what one of these aircraft looks like in your mind. There will be a central pod containing batteries and avionics, with a set of arms radiating from it, each of which will have a motor and a propeller on its end. You are almost certainly picturing a four-rotor design, such as the extremely popular DJI Phantom series of craft.

Of course, four-rotor designs are just one of many possible configurations of a multirotor. You will commonly see octocopters, but sometimes we’ve brought you craft that really put the “multi” in “multirotor”. If the computer can physically control a given even number of motors, within reason, it can be flown.

There is one type of multirotor you don’t see very often though, the trirotor. Three propellers on a drone is a rare sight, and it’s something we find surprising because it’s a configuration that can have some surprising benefits. To think about why, it’s worth taking a look at some of the characteristics of a three-rotor machine’s flight.

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Ohm? Don’t Forget Kirchhoff!

It is hard to get very far into electronics without knowing Ohm’s law. Named after [Georg Ohm] it describes current and voltage relationships in linear circuits. However, there are two laws that are even more basic that don’t get nearly the respect that Ohm’s law gets. Those are Kirchhoff’s laws.

In simple terms, Kirchhoff’s laws are really an expression of conservation of energy. Kirchhoff’s current law (KCL) says that the current going into a single point (a node) has to have exactly the same amount of current going out of it. If you are more mathematical, you can say that the sum of the current going in and the current going out will always be zero, since the current going out will have a negative sign compared to the current going in.

You know the current in a series circuit is always the same, right? For example, in a circuit with a battery, an LED, and a resistor, the LED and the resistor will have the same current in them. That’s KCL. The current going into the resistor better be the same as the current going out of it and into the LED.

This is mostly interesting when there are more than two wires going into one point. If a battery drives 3 magically-identical light bulbs, for instance, then each bulb will get one-third of the total current. The node where the battery’s wire joins with the leads to the 3 bulbs is the node. All the current coming in, has to equal all the current going out. Even if the bulbs are not identical, the totals will still be equal. So if you know any three values, you can compute the fourth.

If you want to play with it yourself, you can simulate the circuit below.

The current from the battery has to equal the current going into the battery. The two resistors at the extreme left and right have the same current through them (1.56 mA). Within rounding error of the simulator, each branch of the split has its share of the total (note the bottom leg has 3K total resistance and, thus, carries less current).

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On Point: The Yagi Antenna

If you happened to look up during a drive down a suburban street in the US anytime during the 60s or 70s, you’ll no doubt have noticed a forest of TV antennas. When over-the-air TV was the only option, people went to great lengths to haul in signals, with antennas of sometimes massive proportions flying over rooftops.

Outdoor antennas all but disappeared over the last third of the 20th century as cable providers became dominant, cast to the curb as unsightly relics of a sad and bygone era of limited choices and poor reception. But now cheapskates cable-cutters like yours truly are starting to regrow that once-thick forest, this time lofting antennas to receive digital programming over the air. Many of the new antennas make outrageous claims about performance or tout that they’re designed specifically for HDTV. It’s all marketing nonsense, of course, because then as now, almost every TV antenna is just some form of the classic Yagi design. The physics of this antenna are fascinating, as is the story of how the antenna was invented.

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