RadiantBee Is A Flying Microwave Antenna Calibration System

Many of the projects we link to here at Hackaday have extensive write-ups, pages of all the detail you could need. Sometimes though we happen upon a project with only a terse description to go on, but whose tech makes it one worth stopping for and unpicking the web of information around it.

Such a project is [F4GKR] and [F5OEO]’s RadiantBee, an attempt to use a beacon transmitter on a multirotor as an antenna calibration platform. (For more pictures, see this Twitter feed.) In this case a multirotor has a GPS and a 10 GHz beacon that emits 250 ms chirps, from which the receiver can calculate signal-to-noise ratio as well as mapping the spatial response of the antenna.

The transmitter uses a Raspberry Pi feeding a HackRF SDR and a 10 GHz upconverter, while the receiver uses an RTL-SDR fed by a 10 GHz to 144 MHz downconverter. The antennas they are testing are straightforward waveguide horns, but the same principles could be applied to almost any antenna.

There was a time when antenna design at the radio amateur level necessitated extensive field testing, physical measurements with a field strength meter over a wide area, correlation of figures and calculation of performance. But with computer simulation the field has become one much more set in the lab, so it’s rather refreshing to see someone producing a real-world simulation rig. If you ever get the chance to evaluate an antenna through real-world measurement, grasp it with both hands. You’ll learn a lot.

We’ve covered very few real-world antenna tests, but there is mention in this write-up of a radar antenna test of a measurement session on a football field.

Via Southgate ARC.

8-Bit Breadboard Computer is up to 8 Hours

[Ben Eater] posted some videos of an 8-bit computer with no CPU chip that he built completely on a breadboard a few years ago. After being asked for schematics, he finally admitted that he didn’t have any. So, instead, he decided to rebuild it and keep a video log of each step in the process. You can see his kickoff video, below, but you can also find 30 more recent videos covering topics from the ALU design and troubleshooting to the decimal LED display. He even uses an Arduino to program a EEPROM that he uses to replace a lot of logic.

You probably want to wait until you have some free time as there are around eight hours of videos so far. The videos start off with a simple 555 timer and work up from there. Each piece gets a test separate from the whole, so with luck you won’t have an impossible job trying to troubleshoot the whole thing at the end.

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Wireless Nunchuck R/C Remote!

[Dan], admirably rose to the occasion when his son wanted a new toy. Being a dedicated father — and instead of buying something new — he took the opportunity to abscond to his workbench to convert a Wiimote Nunchuck into a fully wireless controller for his son’s old r/c car — itself, gutted and rebuilt some years earlier.

Unpacking the nunchuck and corralling the I2C wires was simply done. From there, he combined a bit of code, an Arduino pro mini, and two 1K Ohm resistors to make use of an Aurel RTX-MID transceiver that had been lying around. Waste not, want not.

A TI Stellaris Launchpad is the smarts of the car itself, in concordance with a TB6612FNG motor controller. The two Solarbotics GM9 motors with some 3D printed gears give the car some much needed gusto.

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Wirelessly Charge Your Phone From High Voltage Power Lines

Using nothing more than an antenna, a spark plug, a flyback transformer, a diode, and a car phone charger, [Kreosan] have implemented the world’s most dangerous cell-phone charger: wirelessly charging their phone from high voltage power lines. This is a demonstration of a hack that we thought was just an urban legend, but it’s probably best to leave this as just a demo — this one is probably illegal and definitely dangerous.

The charger works by holding an old TV aerial fairly close to high voltage overhead cables, and passing the resulting tiny current through a spark plug and a flyback transformer to ground. To charge the phone, they tapped the transformer, rectified it through a diode, and fed it into a car-plug phone charger. [Kreosan] claims to harvest enough “free” electricity to charge the phone. (Where by “free”, we mean stolen from the electric grid.)

If you regularly find yourself running out of charge and like a bit of danger why not make a power bank that looks like a bomb instead. Sure we don’t advise you take it on a plane but it seems like a much safer option than using overhead power lines.

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Hackaday Prize Entry: Detecting Adulterated Food Using AI

Adulterated food is food that has a substance added to it to save on manufacturing costs. It can have a negative effect, it can reduce the food’s potency or it can have no effect at all. In many cases it’s done illegally. It’s also a widespread problem, one which [G. Vignesh] has decided to take on as his entry for the 2017 Hackaday Prize, an AI Based Adulteration Detector.

On his hackaday.io Project Details page he outlines some existing methods for testing food, some which you can do at home: adulterated sugar may have chalk added to it, so put it in water and the sugar will dissolve while the chalk will not. His approach is to instead take high-definition photos of the food and, on a Raspberry Pi, apply filters to them to reveal various properties such as density, size, color, texture and so on. He also mentions doing image analysis using a deep learning neural network. This project touches us all and we’ll be watching it with interest.

If all this talk of adulterated food makes you nervous about your food supply then consider growing our own, hacker style. One such project we’ve seen here on Hackaday is Farmbot, an open-source CNC farming robot. Another such is MIT’s OpenAg Food Computer, a robotic control and monitoring growing chamber.

Hackaday Trims Its Own Resistors

There are times when you might want an odd-value resistor. Rather than run out to the store to buy a 3,140 Ω resistor, you can get there with a good ohmmeter and a willingness to solder things in series and parallel. But when you want a precise resistor value, and you want many of them, Frankensteining many resistors together over and over is a poor solution.

Something like an 8-bit R-2R resistor-ladder DAC, for instance, requires seventeen resistors of two values in better than 0.4% precision. That’s just not something I have on hand, and the series/parallel approach will get tiresome fast.

Ages ago, I had read about trimming resistors by hand, but had assumed that it was the domain of the madman. On the other hand, this is Hackaday; I had some time and a file. Could I trim and match resistors to within half a percent? Read on to find out.

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Souped-Up, Next Gen Wearables

The biggest hurdle to great advances in wearable technology is the human body itself. For starters, there isn’t a single straight line on the thing. Add in all the flexing and sweating, and you have a pretty difficult platform for innovation. Well, times are changing for wearables. While there is no stock answer, there are some answers in soup stock.

A group of scientists at Stanford University’s Bao Lab have created a whisper thin co-polymer with great conductivity. That’s right, they put two different kinds of insulators together and created a conductor. The only trouble was that the resulting material was quite rigid. With the help of some fancy x-ray equipment, they discovered that adding a molecule found in standard industrial soup thickeners stops the crystallization process of the polymers, leaving them flexible and stretchy. Get this: the material conducts even better when stretched.

The scientists have used the material to make both simple, transparent electrodes as well as entire flexible transistor arrays with an inkjet printer. They hope to influence next generation wearable technology for everything from smart clothing to medical devices. Who knows, maybe they can team up with the University of Rochester and create a conducting co-polymer that can also shape-shift. Check out a brief demonstration after the break.

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