A Beacon Suitable For Tracking Santa’s Sleigh?

December 19, 2016 by Anool Mahidharia 8 Comments

High-altitude ballooning is becoming a popular activity for many universities, schools and hacker spaces. The balloons, which can climb up to 40 km in the stratosphere, usually have recovery parachutes to help get the payload, with its precious data, back to solid ground safely. But when you live in areas where the balloon is likely to be flying over the sea most of the time, recovery of the payload becomes tricky business. [Paul Clark] and his team from Durham University’s Centre for Advanced Instrumentation are working on building a small, autonomous glider – essentially a flying hard drive – to navigate from 30 km up in the stratosphere to a drop zone somewhere near a major road. An important element of such a system is the locator beacon to help find it. They have now shared their design for an “Iridium 9603 Beacon” — a small Arduino-compatible unit which can transmit its location and other data from anywhere via the Iridium satellite network.

The beacon uses the Short Burst Data service which sends email to a designated mail box with its date, time, location, altitude, speed, heading, temperature, pressure and battery voltage. To do all of this, it incorporates a SAMD21G18 M0 processor; FGPMMOPA6H GPS module; MPL3115A2 altitude sensor; Iridium 9603 Short Burst Data module + antenna and an LTC3225 supercapacitor charger. Including the batteries and antenna, the whole thing weighs in at 72.6 g, making it perfectly suited for high altitude ballooning. The whole package is powered by three ‘AAA’ Energizer Ultimate Lithium batteries which ought to be able to withstand the -56° C encountered during the flight. The supercapacitors are required to provide the high current needed when the beacon transmits data.

The team have tested individual components up to 35 km on a balloon flight from NASA’s Columbia Scientific Balloon Facility and the first production unit will be flown on a much smaller balloon, launched from the UK around Christmas. The GitHub repository contains detailed information about the project along with the EagleCAD hardware files and the Arduino code. Now, if only Santa carried this on his Sleigh, it would be easy for NORAD to track his progress in real time.

Ask Hackaday: Dude, Where’s My MOSFET?

December 13, 2016 by Elliot Williams 126 Comments

(Bipolar Junction) Transistors versus MOSFETs: both have their obvious niches. FETs are great for relatively high power applications because they have such a low on-resistance, but transistors are often easier to drive from low voltage microcontrollers because all they require is a current. It’s uncanny, though, how often we find ourselves in the middle between these extremes. What we’d really love is a part that has the virtues of both.

The ask in today’s Ask Hackaday is for your favorite part that fills a particular gap: a MOSFET device that’s able to move a handful of amps of low-voltage current without losing too much to heat, that is still drivable from a 3.3 V microcontroller, with bonus points for PWM ability at a frequency above human hearing. Imagine driving a moderately robust small DC robot motor forwards with a microcontroller, all running on a LiPo — a simple application that doesn’t need a full motor driver IC, but requires a high-efficiency, moderate current, and low-voltage-logic compatible transistor. If you’ve been here and done that, what did you use?

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[CNLohr] Reverses Vive, Valve Engineers Play Along

December 12, 2016 by Elliot Williams 11 Comments

[CNLohr] needs no introduction around these parts. He’s pulled off a few really epic hacks. Recently, he’s set his sights on writing a simple, easy to extend library to work with the HTC Vive VR controller equipment, and in particular the Watchman controller.

There’s been a lot of previous work on the device, so [Charles] wasn’t starting from scratch, and he live-streamed his work, allowing others to play along. In the process, two engineers who actually worked on the hardware in question, [Alan Yates] and [Ben Jackson], stopped by and gave some oblique hints and “warmer-cooler” guidance. A much-condensed version is up on YouTube (and embedded below). In the links, you’ll find code and the live streams in their original glory, if you want to see what went down blow by blow. Code and more docs are in this Gist.

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Body Cardio Weighing Scale Teardown

December 5, 2016 by Jenny List 22 Comments

If you weigh yourself by standing on a bathroom scale, not liking the result, then balancing towards one corner to knock a few pounds off the dial, you are stuck in a previous century. Modern bathroom scales have not only moved from the mechanical to the electronic, they also gather body composition measurements and pack significant computing power.

Yet they’re a piece of domestic electronics that sits in our bathroom and rarely comes under scrutiny. How do they work, and what do they contain? The team at November Five tore down a top-of-the-range Withings Body Cardio scale to find out.

After a struggle with double-sided sticky pads, the scale revealed its secrets: a simple yet accomplished device. There are four load cells and the electrodes for the body measurement, and the PCB. On the board is a 120 MHz ARM Cortex M4 microcontroller, a wireless chipset, battery management, and the analogue measurement chipset. This last is particularly interesting, a Texas Instruments AFE4300, a specialised analogue front-end for this application. It’s a chip most of us will never use, but as always an obscure datasheet is worth a read.

Finally, the wireless antenna is not the normal simple angular trace you’ll be used to from the likes of ESP8266 boards, but an organic squiggle. It’s a fractal antenna, presumably designed to present a carefully calculated bandwidth to the chipset. A nice touch, though one the consumer will never be aware of.

We’ve shown you quite a few bathroom scales over the years. There was this wisecracking Raspberry Pi scale, this scale reverse engineered to gather weight data, and this one laid bare for use as a controller.

Do You Miss The Sound Of Your Model M?

December 3, 2016 by Jenny List 64 Comments

There is one aspect of desktop computing in which there has been surprisingly little progress over the years. The keyboard you type on today will not be significantly different to the one in front of your predecessor from the 1970s. It may weigh less, its controller may be less power-hungry, and its interface will be different, but the typing experience is substantially identical. Or at least, in theory it will be identical. In fact it might be worse than the older peripheral, because its switches are likely to be more cheaply made.

The famous buckled springs in operation. Shaddim [CC BY-SA 3.0], via Wikimedia Commons. — The famous buckled spring in operation. Shaddim [CC BY-SA 3.0], via Wikimedia Commons.

Thus among keyboard aficionados the prized possessions are not necessarily the latest and greatest, but can often be the input devices of yesteryear. And one of the more famous of these old keyboards is the IBM Model M, a 1984 introduction from the computer behemoth that remains in production to this day. Its famous buckled-spring switches have a very positive action and a unique sound that once heard can never be forgotten.
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Abacus Drive Is A Speed-to-Torque Game-Changer

December 2, 2016 by Sonya Vasquez 34 Comments

Apart from the harmonic drive, the engineering community hasn’t really come up with any clever mechanisms for speed-to-torque conversion in the last few decades. However, recently a few folks at SRI have given us one more transmission to drool over: the Abacus Drive.

The Abacus Drive takes the standard concepts of a cycloidal drive, but takes the eccentric gear tooth pattern that we’re familiar with and converts it to two grooves in which an array of rolling spacers will ride. The benefit with this design is two-fold: it’s both constructed from entirely rigid components (unlike the harmonic drive), and it has a low-backdriving torque, enabling the application to more easily detect changes in load.

Achieving an affordable low-speed, high-torque transmission has been a holy grail among roboticists, where every motor-driven manipulator joint becomes an engineering design headache where the designers fight their application’s backlash, torque, and price constraints to get a functional robot arm. This problem stems from the fact that motors just don’t perform efficiently at low-speeds, where the near-stall conditions cause them to draw vastly larger amounts of torque compared to their full-speed conditions. While the Abacus Drive isn’t hitting the market anytime soon, we’ll let this idea stew in the community and hope to see some budget variants pop up in the near future.

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Flip Dot Displays Appear With Modernized Drivers

November 29, 2016 by Mike Szczys 52 Comments

Admit it, you’ve always wanted to have your own flip-dot display to play with. Along with split-flap displays, flip-dots have an addictive look and sound that hearkens back half a century but still feels like modern technology. They use a magnetic coil to actuate each pixel — physical discs painted contrasting colors on either side. It means that you really only need electricity when changing the pixel, and that each pixel makes a satisfyingly unobtrusive click when flipped. The only problem with the displays is that they’re notoriously difficult to get your hands on.

Breakfast, a Brooklyn-based hardware firm known for creative marketing installations, unveiled their Flip-Disc Display System this morning. Used displays have come up on the usual sites from time to time, but often without a controller. Traditional flip-dot manufacturers haven’t sought out the individual hacker or hackerspace, and a click-to-buy option has been difficult if not impossible to find.

Breakfast’s offering modernizes the driver used to manage all of those electro-mechanical pixels. Whether this will make the displays more accessible is a question that still needs to be answered.
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