Philo Farnsworth, RCA, And The Battle For Television

July 3, 2018 by Dan Maloney 34 Comments

The parenthood of any invention of consequence is almost never cut and dried. The natural tendency to want a simple story that’s easy to tell — Edison invented the light bulb, Bell invented the telephone — often belies the more complex tale: that most inventions have uncertain origins, and their back stories are often far more interesting as a result.

Inventing is a rough business. It is said that a patent is just a license to get sued, and it’s true that the determination of priority of invention often falls to the courts. Such battles often pit the little guy against a corporate behemoth, the latter with buckets of money to spend in making the former’s life miserable for months or years. The odds are rarely in the favor of the little guy, but in few cases was the deck so stacked against someone as it was for a young man barely out of high school, Philo Farnsworth, when he went up against one of the largest companies in the United States to settle a simple but critical question: who invented television?

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A Cartoon-ifying Camera For Instant Absurdism

July 3, 2018 by Kristina Panos 12 Comments

We take photographs as a way to freeze moments in time and to capture the details that get blurred by our unreliable memories. There is little room for interpretation, and this is kind of the whole point.

[Dan Macnish]’s latest project, Draw This, turns reality into absurdity. It’s a Raspberry Pi-based instant camera that trades whatever passed in front of the lens for a cartoon version of same. Draw This uses neural networks to ID the objects in the frame, and then draws upon thousands of images from Google’s Quick, Draw! dataset to provide a loose interpretation via thermal printer. Seems to us like the perfect camera to take to DEFCON (or any other part of Las Vegas).

If you have a Raspi3, a v2 camera, and a thermal printer, you can make your own crowd-sourced, cartoonified memories using the code in [Dan]’s repo. Still into recording reality? You can use Pi cameras to see in the dark or even explore a body of water.

These Capacitors Are A Cheap Gimmick

July 3, 2018 by Al Williams 31 Comments

If you search through an electrical engineering textbook, you probably aren’t going to find the phrase “gimmick capacitor” but every old ham radio operator knows about them. They come in handy when you need a very small capacitor of unknown value. For example, if you are trying to balance the stray capacitance in a circuit, you might not know exactly what value you need, but you know it won’t be very much. That’s when you want a gimmick capacitor.

A gimmick capacitor is made by taking two strands of insulated wire and twisting them together; the length and the tightness of the twist determine the capacitance. Tightening or loosening the twist, or trimming some of the wire off, makes it tunable.

These are most commonly found in RF equipment or high-speed logic because of the small capacitance involved — usually about 1 to 2 pF per inch of twist or so. The thicker the insulation, the less capacitance you’ll get, so it is common to use magnet wire or something else with a thin insulating layer. You can take this one step further and decrease the spacing by stripping down one wire as long as it isn’t going to touch anything else.

Obviously, the insulation needs to be good enough for the voltage on them, an important consideration in tube circuits, for instance. But other than that, a gimmick capacitor is a straightforward tool to have in your box of design tricks. Can we take this further? Continue reading “These Capacitors Are A Cheap Gimmick” →

Drawing Lines In The Sand: Taking Beach Graffiti To The Next Level

July 3, 2018 by Ben James 39 Comments

When strolling down the beach, there’s always an urge to draw in the sand – it seems compulsory to make your mark by inscribing something. But there’s a dilemma: how do you go about physically drawing it? You could opt to remain standing and attempt to deploy a toe, but that requires a level of dexterity few possess. The only other option is to bend down and physically use your hands. Ultimately, there’s no way to draw anything in the sand without losing your dignity.

The solution? A robot, of course – the brainchild of [Ivan Miranda]. The idea is simple and elegantly executed: make a large linear actuator, place it on wheels, and attach a servo which can position an etching tool to be either in the sand or above it. The whole contraption moves forward one column at a time, making a vertical pass with the marker being engaged or disengaged as required. The columns are quite thin, giving relatively high-resolution text, though this does mean it take a while. Adding another servo and marking two adjacent columns at the same time would be an easy way to instantly double the speed.

The wheels are big and chunky, to ensure the horizontal distance travelled does not change between the top and the bottom. Of course, when making big parts like these it always helps if you’ve already built a giant custom 3D printer. If you want to read more of [Ivan]’s large scale 3D printing antics, checkout his tank with suspension, or plus-sized seven-segment clock.

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The A To Z Of Building Your Own Keyboard

July 3, 2018 by Tom Nardi 6 Comments

We’ve featured a number of people who’ve taken the plunge and created their own customized keyboard; at this point it’s safe to say that there’s enough information and source code out there that anyone who’s looking to build their own board won’t have much trouble figuring out how to do so. That being said, it’s nice to have a comprehensive at a process from start to finish. Why sift through forum posts and image galleries looking for crumbs if you don’t have to?

That’s precisely what makes this write-up by [Maarten Tromp] so interesting. He walks the reader through every step of the design and creation of his customized keyboard, from coming up with the rather unique layout to writing the firmware for its AVR microcontroller. It’s a long read, filled with plenty of tips and tricks from a multitude of disciplines.

After looking at other custom boards for inspiration, [Maarten] used OpenSCAD to create a 3D model of his proposed design, and had it printed at Shapeways. His electronics are based around an Atmel ATMega328P using vUSB, and Microchip MCP23017 I/O expanders to connect all the keys. He wrapped it all up by designing a PCB in gEDA PCB and having it sent off for production. As a testament to his attention to detail, everything mated up on the first try.

[Maarten] is happy with the final product, but mentions that in a future revision he would like to add RGB lighting and use a microcontroller that has native USB support. He’d also like to drop the I/O expanders and switch over to Charlieplexing for the key matrix.

From uncommon layouts to diminutive technicolor beauties, it seems there’s no end of custom keyboards in sight. We aren’t complaining.

Using An AI And WiFi To See Through Walls

July 2, 2018 by Steven Dufresne 36 Comments

It’s now possible to not only see people through walls but to see how they’re moving and if they’re walking, to tell who they are. We finally have the body scanner which Schwarzenegger walked behind in the original Total Recall movie.

This is the work of a group at the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL). The seeing-through-the-wall part is done using an RF transmitter and receiving antennas, which isn’t very new. Our own [Gregory L. Charvat] built an impressive phased array radar in his garage which clearly showed movement of complex shapes behind a wall. What is new is the use of neural networks to better decipher what’s received on those antennas. The neural networks spit out pose estimations of where people’s heads, shoulders, elbows, and other body parts are, and a little further processing turns that into skeletal figures.

They evaluated its accuracy in a number of ways, all of which are detailed in their paper. The most interesting, or perhaps scariest way was to see if it could tell who the skeletal figures were by using the fact that each person walks with their own style. They first trained another neural network to recognize the styles of different people. They then pass the pose estimation output to this style-recognizing neural network and it correctly guessed the people with 83% accuracy both when they were visible and when they were behind walls. This means they not only have a good idea of what a person is doing, but also of who the person is.

Check out the video below to see some pretty impressive side-by-side comparisons of live action and skeletal versions doing all sorts of things under various conditions. It looks like the science fiction future in Total Recall has gotten one step closer. Now if we could just colonize Mars.

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Load Bank Teardowns Show Danger

July 2, 2018 by Al Williams 16 Comments

[Syonyk] has been acquiring some large load banks to test power supplies and battery packs. These devices consist of a big current sink, a measurement device, and a fan. He picked up two similar-looking boards from the usual Chinese sources, both rated for 150W, both for about $30. Upon closer examination, though, he found that one was really a bargain and the other was likely to blow up.

The loads are rated for 60V and as you can see from the photos, appear virtually identical at a glance. They offer a configurable cut-off voltage and even use 4-wire measurement to avoid problems with voltage drop through the power cables.

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