Fail Of The Week: Ambitious Vector Network Analyzer Fails To Deliver

If you’re going to fail, you might as well fail ambitiously. A complex project with a lot of subsystems has a greater chance of at least partial success, as well as providing valuable lessons in what not to do next time. At least that’s the lemonade [Josh Johnson] made from his lemon of a low-cost vector network analyzer.

For the uninitiated, a VNA is a versatile test instrument for RF work that allows you to measure both the amplitude and the phase of a signal, and it can be used for everything from antenna and filter design to characterizing transmission lines. [Josh] decided to port a lot of functionality for his low-cost VNA to a host computer and concentrate on the various RF stages of the design. Unfortunately, [Josh] found the performance of the completed VNA to be wanting, especially in the phase measurement department. He has a complete analysis of the failure modes in his thesis, but the short story is poor filtering of harmonics from the local oscillator, unexpected behavior by the AD8302 chip at the heart of his design, and calibration issues. Confounding these issues was the time constraint; [Josh] might well have gotten the issues sorted out had the clock not run out on the school year.

After reading through [Josh]’s description of his project, which was a final-year project and part of his thesis, we feel like his rating of the build as a failure is a bit harsh. Ambitious, perhaps, but with a spate of low-cost VNAs coming on the market, we can see where he got the inspiration. We understand [Josh]’s disappointment, but there were a lot of wins here, from the excellent build quality to the top-notch documentation.

Master’s UAV Project Takes Flight

Pushing the maker envelope all the way to the Master level, [Przemyslaw Brudny], [Marek Ulita], and [Maciej Olejnik] from the Politechnika Wroclawska in Poland packed a UAV full of custom sensor boards for their thesis project.

The Skywalker X-8 FPV drone underwent extensive modifications to accommodate the embedded systems as well as upgrading the chassis with carbon glass to withstand the high load and speeds they would need to perform their tests. The ailerons were customized for finer control of the drone. But for our money, it’s all the board design that supports those sensors which is really fun to delve into.

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Extending The Usability Of Touchscreens

Fanboys may be in shock from seeing duct tape applied to the screen of an iPad, but we can assure you it’s in the name of science. [Michael Knuepfel] is working on his thesis for the ITP graduate program at the Tisch School for the Arts. He managed to augment the usability of touchscreen devices by adding hardware to them.

What he’s come up with are devices for both input and output. The output devices generally rely on light and color of light displayed on the screen itself which is picked up by a light sensor. The input devices use conductive material to complete a path between your hand and your screen. This lets the capacitive sensing screen detect the presence of your hand, through the conductor. Some of his example devices include gaming controller overlays, encoder rings, and multiple stylus designs.

After the break we’ve embedded [Michael’s] teaser trailer which jumps through several demonstrations. It’s plenty to get your mind rolling, but if you want to know more you must watch his thesis presentation. It’s available as an MP4 download on this page. Just search for his name, [Michael Knuepfel] for the proper link.

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Irregular Incurve Robotic Instrument

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The Irregular Incurve is a robotic instrument built by [Xiaoyang Feng] as part of his ITP thesis work. It’s a MIDI instrument with an array of 12 strung bows mounted to a curved shower rod. The end of each bow has a tuning key. The strings are each picked using independently mounted arms. One servo controls the downward motion of the pick while the other controls the rotation of the shaft. A damper is also attached to each arm. The string vibrations are transferred to a spruce soundbox under the bridge. Below you can see a video of Gizmodo playing with it at the ITP show. Check out [Xiaoyang]’s Flickr set for images of the build process plus some early videos of the mechanism.

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Tweenbots Rely On Human Help

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[Kacie Kinzer] put together an interesting social experiment: Could a robot navigate purely by the help of strangers? She constructed an inexpensive Tweenbot robot that would drive in a straight line. A flag was attached to the top with a plea for help and a destination. Surprisingly, on the first run it was able to traverse through Washington Square Park in just 42 minutes with the help of 29 people. You can see a video of the first run below. This is part of [Kacie]’s thesis work at ITP and she has many other bots planned. While it’s a great demonstration of human kindness, there’s another lesson: If you don’t think your public project looks innocuous enough, draw a smiley face on it.

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TISCH, Multitouch Framework

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[floe] wrote in to tell us about his multitouch based thesis work. While many projects have focused on the hardware side of multitouch, TISCH is designed to promote the software side. TISCH is a multiplatform library that features hardware abstraction and gesture recognition. This takes a lot of weight off of widget developers since they can specify known library gestures instead of writing the exact motions from scratch. Using TISCH also means a standard set of gestures across multiple widgets, so the learning curve will be much easier when a user tries out a new app. If you’re researching multitouch, check out this project and help improve the codebase.