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Build A Phased-Array Radar In Your Garage That Sees Through Walls

April 7, 2015 by 63 Comments

Until recently phased array radar has been very expensive, used only for military applications where the cost of survival weighs in the balance. With the advent of low-cost microwave devices and unconventional architecture phased array radar is now within the reach of the hobbyist and consumer electronics developer. In this post we will review the basics of phased-array radar and show examples of how to make low-cost short-range phased array radar systems — I built the one seen here in my garage! Sense more with more elements by making phase array your next radar project.

Phased array radar

In a previous post the basics of radar were described where a typical radar system is made up of a large parabolic antenna that rotates. The microwave beam projected by this antenna is swept over the horizon as it rotates. Scattered pulses from targets are displayed on a polar display known as a Plan Position Indicator (PPI).

Block diagram of a conventional radar system using a parabolic dish.
Block diagram of a conventional radar system using a parabolic dish.

In a phased array radar (PDF) system an array of antenna elements are used instead of the dish. These elements are phase-coherent, meaning they are all phase-referenced to the same transmitter and receiver. Each element is wired in series with a phase shifter that can be adjusted arbitrarily by the radar’s control system. A beam of microwave energy is focused by applying a phase rotation to each phase shifter. This beam can be directed anywhere within the array’s field of view. To scan the beam rotate the phases of the phase shifters accordingly. Like the rotating parabolic dish, a phased array can scan the horizon but without the use of moving parts.

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How To Build A Thermocouple Amplifier

April 6, 2015 by 54 Comments

A Thermocouple is a terrific way to measure temperature. The effects of temperature change on dissimilar metals produces a measurable voltage. But to make that measurement you need an amplifier circuit designed for the thermocouple being used.

Linear Technology LTC 1049 Low Power Zero-Drift Operational Amplifier with Internal Capacitors
Linear Technology LTC 1049 Low Power Zero-Drift Operational Amplifier
with Internal Capacitors

While researching “Zero Drift Amplifiers” as a follow-up to my video on Instrumentation Amplifiers I noticed the little schematic the front page of the LTC1049 datasheet which is shown here. I thought it was an ideal example of an analog application where some gain and some “gain helper” were needed to accomplish our useful little application of amplifying a thermocouple probe.

In the video I don’t really talk much about the thermocouples themselves other than the type I see most of the time which is type K. If you’re not already familiar with the construction of these probes you can find an informative write-up on thermocouples and the different types on the Wikipedia page and you might also want to check out the Analog Devices app note if you would like to know more. What I will cover is a reliable and precise way to read from these probes, seen in the video below and the remainder of the post after the break.

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The Raspberry Pi Wearable Revolution

April 1, 2015 by 44 Comments

With the human URL [will.i.am] serving as Chief Creative Director of 3D Systems, and [Martha Stewart] selling her own line of 3D printer filament through MakerBot, more and more celebrities are piling onto the hacker, maker, and DIY revolution. Now, the partnership we’ve all been waiting for: the Raspberry Pi Foundation and [The Artist Formerly Known As Prince_logo] are teaming up to produce a line of Pi-based wearable electronics. The first product from this new, fashionable line of electronics is beyond anything you would expect. It’s called the Raspberry Beret, and it’s shaping up to be a Revolution in wearables.

The wearable Raspberry Beret is exactly what you would expect: a habadasher’s masterpiece that pairs equally well with figure skating costumes and skin-tight cloud print suits. Inside, though, is a new piece of hardware based on the Raspberry Pi compute module. This module includes a Bluetooth module that will sync with any Windows phone. The Raspberry Beret also includes enough sensors that will blow away everything from a Fitbit to the new Apple Watch. The Raspberet will keep track of your heart rate, activity, and exercise routine.

The Raspberry Beret is just the beginning; the Pi Foundation and [The Artist Formerly Known As Prince_logo] are also teaming up with OSH Park to produce a limited, special edition Raspberry Pi 2. This board will be clad in the beautiful OSH Park purple soldermask and sports 4GB of eMMC Flash. This Flash will not be usable; instead it will contain a remastered edition of Purple Rain that will play as a startup chime. There will be no option to skip the chime.

Pancakes.

Arduino SRL To Distributors: “We’re The REAL Arduino”

March 28, 2015 by 200 Comments

Arduino SRL (formerly known as Smart Projects SRL) sent out a letter to its distribution partners yesterday. If you’ve been following along with the Arduino vs Arduino story (we’ve previously published two installments), the content isn’t entirely surprising; it’s essentially a tactical move to reassure their distribution channels that Arduino SRL is the “One True Arduino”. That said, there’s still some new tidbits buried inside. You can skip down to read the full text below, but here’s our take.

The Business History of Arduino

arduino_vs_arduino_tnA quick summary of the legal situation. Arduino LLC was formed in April 2008 by the original five founders to provide a corporate entity behind the Arduino project. Smart Projects SRL, controlled by one of the founders, was tasked with the actual production of the boards. It turns out that Smart Projects had trademarked the Arduino brand in Italy in December 2008, before Arduino LLC got around to filing in April 2009 in the USA. But everyone was friends, right? As long as the licensing fees keep flowing.

Fast-forward to September 2014, when Arduino LLC filed a lawsuit in Italy against Smart Projects claiming that they had infringed LLC’s trademark and that they had recently stopped paying licensing fees on their use of the Arduino name. In October, Smart Projects filed with the USPTO to revoke Arduino LLC’s trademark. In late 2014, Smart Projects changed its company name to Arduino SRL (a “Società a responsabilità limitata” is one form of Italian limited-liability company) and hired a new CEO, [Federico Musto].  Around the same time, Arduino SRL opened up the website arduino.org (different from long-existing arduino.cc) but with nearly identical style. In January 2015, Arduino LLC filed a lawsuit in the US, claiming their right on the Arduino name.

The Gist of it

In short, Arduino LLC has been working on developing the Arduino platform, software, and community while Smart Projects / Arduino SRL was the major official producer of the hardware for most boards. Both are claiming to “be” Arduino, and going after each other in court. So it’s not strange that Arduino SRL would like to try to keep its hold on the distribution channels. Which brings us to their letter to distributors.

March 27 Letter

Arduino-Distributor-Update-0A good portion of the letter reads to be a very carefully worded defense of why Arduino SRL is the true Arduino:

“Arduino Srl (aka Smart Projects Srl), as you know has been from the  beginning of the Arduino® project, the place where the ideas were turned into reality and into a business.”

This is of course strictly true — Smart Projects was certainly the largest manufacturer of Arduino boards. But it sidesteps the issue at hand in the trademark suits: whether they were simply a licensed producer of the boards or whether they’re “Arduino”.

Similarly, in the questions section of the letter, they ask if there are actually two “Arduino” product manufacturers, and answer “not really”. Of course, that’s true. Arduino LLC doesn’t manufacture boards, but exists to license their trademark out to fund development.

The only real news in the letter is that Arduino SRL is replacing its old distribution and logistics company, Magyc Now, with a new one named CC Logistics. Both Magyc and CC Logistics are named as defendants in the US lawsuit filed by Arduino LLC, so it’s unlikely that this change is due to legal fallout.

What this Means

In conclusion, Arduino SRL’s letter to its distributors seems to essentially follow the line of reasoning in their trademark lawsuit in the US against Arduino LLC: since Arduino SRL is doing the manufacturing and using the Arduino name, they’re the true Arduino. Whether or not this will stand up in court, or whether Arduino LLC can make its case that SRL was simply a licensed manufacturer, remains to be seen.

We’ve embedded the contents of the letter after the break. You can also download the original PDF.

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Mustachioed Nintendo Virtual Boy Gone Augmented Reality

March 25, 2015 by 14 Comments

Some people just want to watch the world burn. Others want to spread peace, joy and mustaches. [Joe Grand] falls into the latter group this time around. His latest creation is Mustache Mayhem, a hack, video game, and art project all rolled into one. This is a bit of a change from deconstructing circuit boards or designing electronic badges, but not completely new for [Joe], who wrote SCSIcide and Ultra SCSIcide for the Atari 2600 back in the early 2000’s.

Mustache Mayhem is built into a Nintendo Virtual Boy housing. The Virtual Boy itself was broken, and unfortunately was beyond repair. [Joe] removed most of the stock electronics and added a BeagleBone Black, Logitech C920 webcam, an LCD screen and some custom electronics. He kept the original audio amplifier, speakers, and controller connector. Angstrom Linux boots into [Joe’s] software, which uses OpenCV to detect faces and overlay mustaches. Gameplay is simple: Point the console at one or more faces. If you see a mustache, press the A button on the controller! The more faces and mustaches on-screen at once, the more points, or “mojo” the player gets. The code is up on Github, and can be built with Xcode targeted to the Mac, or directly on the BeagleBone Black.

[Joe’s] goal for the project was to make a ridiculous game that looks like it could have come out in the 90’s. He also used Mustache Mayhem as a fun way to learn some new skills which will come in handy for more serious projects in the future.

We caught up with [Joe] for a quick interview about his new creation.

How did you come up with the idea for Mustache Mayhem?

blockI was selling a bunch of my video game collection at PRGE (Portland Retro Gaming Expo) a few years ago and had a broken Virtual Boy that no one bought. A friend of mine was at the table and said I had to do something with it. I thought “People wear cosplay and walk around at conventions, so what if I could do something with the Virtual Boy that you could walk around with?” That was the seed.

A few months later, Texas Instruments sent me the original production release of the BeagleBone Black (rev. A5A). Eighteen months after that I actually started the project. The catalyst was to do something for an upcoming Portland, OR art show (Byte Me 4.0), which is an annual event that shows off interactive technology-based artwork. I wrote up a little description and got accepted. I had less than 2 months to actually get things working and it ended up taking about a month of full-time work. It was much more work than I expected for such a silly project. I originally was going to do something along the lines of walking around in a Doom-like perspective and shooting people when their faces were detected.

That would be pretty darn cool. How did you get from Doom to Mustaches? 

I saw a TI BeagleBoard demo called “boothstache” which drew mustaches on faces and tweeted the pictures. I thought that doing something non-violent with mustaches would be more suitable (and funny) to actually show my kids. I also secretly wanted to use this project as a way to experiment with Linux, write some code, and learn about face detection and image processing with OpenCV, which I plan to use for some actual computer security research in the future. Mustache Mayhem turned out to be a super cool project and I’m really happy with it. I sort of feel guilty spending so much time on it, since it’s basically just a one-off prototype, but I just got so obsessed with making it exactly as I wanted.

You mentioned on your website that Mustache was “designed to challenge the paradigms of personal privacy and entertainment.” What exactly did you mean there?

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Playing Space Invaders With Real Fire And Lasers

March 25, 2015 by 16 Comments

Making a Space Invaders game is up there on the list of most unconventional things you could do with a laser cutter. In watching the tiny little ships burst into flames, [Martin Raynsford’s] modification has got to be one of the more dangerous looking ones we’ve seen as well.

[Martin] always had the desire to make a tangible version of the classic game. Since his Whitetooth A1 laser cutter already contained the bulk of the moving hardware needed, not to mention an actual high powered laser to “pew pew” with, he decided it was the perfect starting point for such a project. The game is played looking down into the cutter since the laser of course fires in that direction, however a basic webcam is mounted to the laser assembly so that you can view the game on a computer screen at the proper perspective. An Arduino Mini is responsible for stepper control, allowing the player to jog back and forth and fire with a keyboard. [Martin] added an extra gear to the z-axis bed-leveler so that it could drive rows of paper invaders left and right across the bottom. Paperclips wedged into slots along a modified backboard hold each of the paper slips in place. This works ideally since they can be reloaded easily and won’t be maimed during use.

Due to the heat of the laser, landing a well positioned shot will likely nuke all of the nearby invaders as well, making for a theatrical inferno and easy win. Now to step up the difficulty level and figure out how to make them fire back…

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3D Spectrum Analyzer Uses 1280 LEDs

March 23, 2015 by 47 Comments

One of [Dooievriend]’s friends recently pressed him into service to write software for a 3d spectrum analyzer/VU that he made. The VU is a fairly complex build: it’s made up of 1280 LEDs in a 16x16x5 matrix controlled by a PIC32 clocked at 80MHz. [Dooievriend] wrote some firmware for the PIC that uses a variation on a discrete Fourier transform to create a 3D VU effect.

j6v2i When [Dooievriend] set out to design the audio analyzing portion of the firmware, his mind jumped to the discrete Fourier transform. This transform calculates the amplitude in a series of frequency bins in the audio—seemingly perfect for a VU. However, after some more research, [Dooievriend] decided to implement a constant Q transform. This transform is very similar to a Fourier transform, but it takes into account the logarithmic way that the human ear interprets sound.

[Dooievriend] started implementing the constant Q transform using an interrupt-based sampler, but he quickly ran into issues with slow floating-point math on his PIC32 (which doesn’t have a hardware floating-point unit). Thankfully he rewrote his code using fixed-point math, and the transform runs nearly real-time. Check out the video after the break to see the VU in action, and a second video that gives some details on the hardware build.

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