It is likely that many of us will at some time have experimented with motion detectors. Our Arduinos, Raspberry Pis, Beaglebones or whatever will have been hooked up to ultrasonic or PIR boards which will have been queried for their view of what is in front of them.
[Connornishijima] has stumbled on a different way to detect motion with an Arduino, he’s polling an ADC pin with a simple length of twisted pair hooked up to it and earth, and reliably generating readings indicating when he (or his cat) is in its vicinity. He’s calling the effect “Capacitive turbulence”, and he’s open to suggestions as to its mechanism. He can only make it work on the Arduino, other boards with ADCs don’t cut it.
Frequent Hackaday featuree [Mitxela] may have also discovered something similar, and we’ve hesitated to write about it because we didn’t understand it, but now it’s becoming unavoidable.
It’s always dangerous in these situations to confidently state your opinion as “It must be…” without experimental investigation of your own. Those of us who initially scoffed at the idea of the Raspberry Pi 2 being light sensitive and later had to eat their words have particular cause to remember this. But this is an interesting effect that bears understanding. We would guess that the Arduino’s fairly high input impedance might make it sensitive to mains hum, if you did the same thing to an audio amplifier with a phono input you might well hear significant hum in the speaker as your hand approached the wire. It would be interesting to try the experiment at an off-grid cabin in the woods, in the absence of mains hum.
If you’d like to give his experiment a try, he’s posted his sketch on Pastebin. And he’s put up the video below the break demonstrating the effect in action, complete with cats.
We like to see people pushing the boundaries of what is possible with their microcontroller I/O lines, it furthers our collective knowledge as a community. We’ve seen people making TV transmitters from ESP8266s, and not so long ago a Raspberry Pi ADC port as further examples. Please, keep them coming!
Electrospinning is a fascinating process where a high voltage potential is applied between a conductive emitter nozzle and a collector screen. A polymer solution is then slowly dispensed from the nozzle. The repulsion of negative charges in the solution forces fine fibers emanate from the liquid. Those fibers are then rapidly accelerated towards the collector screen by the electric field while being stretched and thinned down to a few hundred nanometers in diameter. The large surface area of the fine fibers lets them dry during their flight towards the collector screen, where they build up to a fine, fabric-like material. We’ve noticed that electrospinning is hoped to enable fully automated manufacturing of wearable textiles in the future.
[Douglas Miller] already has experience cooking up small batches of microscopic fibers. He’s already made carbon nanotubes in his microwave. The next step is turning those nanotubes into materials and fabrics in alow-cost, open source electrospinning machine, his entry for the Hackaday Prize.
As always in fundamental research projects, a whole lot of parameters have to be tuned just right. To speed up the process of finding suitable values for the electric potential, dosing feed rate, emitter to collector plate distance, temperature, and humidity, [Douglas] build his machine with a CNC controlled vertical axis and syringe pump, that can dispense even the smallest amounts of a given solutions accurately. Temperature and humidity control will be added as the project progresses. A host software and GUI allows for easy control of all parameters and will also save and recall presets for different spinning solutions once everything has been dialed in. [Douglas] already ran a few tests, spraying saline solution from an old 3D printer nozzle, and we can soon expect first tests with polymer solutions from the better-suited syringe nozzles he installed.
To keep the build affordable and easy to reproduce for other makers, [Douglas] uses available materials and came up with a few design tricks that could also be applied to other projects. The belt-driven vertical axis is based on PVC pipes, on which a 3D-printed bushing block slides up and down, adjusting the distance between the nozzle and the collector plate. An acrylic door with a safety switch prevents the polymer spray from escaping from the spinning chamber. In the heart of the machine sits an Arduino Uno with a gShield, controlling the stepper motors and talking to the host computer. The 3D-printed syringe pump, a custom design, swings out from the side of the machine to allow for easy refilling. Submerged in mineral oil, which may have been chosen to reduce the risk of overheating and arcing, lies a half-wave series voltage multiplier, cranking up the voltage from an AC power supply to a maximum of 30 kV DC.
Over the past few years, the BeagleBone ecosystem has grown from the original BeagleBone White, followed two years later by the BeagleBone Black. The Black was the killer board of the BeagleBone family, and for a time wasn’t available anywhere at any price. TI has been kind to the SoC used in the BeagleBone, leading to last year’s release of the BeagleBone Green, The robotics-focused BeagleBone Blue, and the very recent announcement of a BeagleBone on a chip. All these boards have about the same capabilities, targeted towards different use cases; the BeagleBone on a Chip is a single module that can be dropped into an Eagle schematic. The BeagleBone Green is meant to be the low-cost that plays nicely with Seeed Studio’s Grove connectors. They’re all variations on a theme, and until now, wireless hasn’t been a built-in option.
This weekend at Maker Faire, Seeed Studio is showing off their latest edition of the BeagleBone Green. It’s the BeagleBone Green Wireless, and includes 802.11 b/g/n, and Bluetooth 4.1 LE.
As all the BeagleBones are generally the same, each with their own special bits tacked on, it’s only fair to do a line by line comparison of each board:
While the BeagleBone Blue is still in the works and due to be released this summer, the BeagleBone Green Wireless fills the WiFi and Bluetooth niche of the BeagleBone ecosystem.
As with any single board computer with a fast ARM chip running Linux, comparisons must be made to the Raspberry Pi. Since this is the first BeagleBone released with wireless connectivity baked into the board, the most logical comparison would be against the recently released Raspberry Pi 3.
The Pi 3 includes an integrated wireless chipset for 802.11n and Bluetooth 4.1 connectivity. The BeagleBone Green Wireless has this, but also adds 802.11 b and g networks. This gives the BBGW the ability to sense when anyone is using a microwave in the vicinity – a boon for that Internet of Things thing we’ve been hearing so much about.
Unlike the Pi 3, the BBGW has connections for additional antennas in the form of two u.FL connectors. While the Pi 3 can be hacked to use external antennas, it’s not a job for the faint of heart. The availability of external antennas in a small, compact, low-power format is the ideal solution for any wireless network connectivity dealing with range or a congested network.
The BeagleBone Green Wireless is a Seeed joint, and as with the original BeagleBone Green, there are Grove connectors right on the edge of the board. These connectors provide one I2C bus and one serial connection each for Seeed Studio’s custom modules.
To be honest, I’m of two minds when it comes to Seeed’s Grove connectors. On one hand, breadboards and DuPont cables already exist, and with the two 46-pin headers on the BeagleBone Black, there was nothing you couldn’t wire into the BeagleBone Black. The addition of Grove connectors seems superfluous, and in the most cynical view, merely an attempt to make a system of proprietary educational electronics.
On the other hand, there really isn’t any system of easy to use, plug-in modules for the current trend of educational electronics. Just a few years ago, people were putting out boards with RS-442 into RJ45 sockets. We don’t have DE-9 connectors anymore, and a smaller, easier to use connector is appreciated, especially when the connectors are a mere $0.15/piece.
Then again, the intelligence of a Grove module is purely dependant on the operator. On the BeagleBone Green, there are two Grove connectors, one for I2C, and another for serial. Apart from some silkscreen, there is no differentiation between these two connectors. On the Grove base cape, there are exactly four different implementations using the Grove connectors: four I2C, four digital I/O, with two GPIOs each, two connectors dedicated to analog input, and two serial ports. This is the simple way to connect a lot of devices via common wires; it is not the most user friendly.
The BeagleBone Green Wireless doesn’t really do anything new. The SoC is the same, and of course the PRUs in every BeagleBone are the killer feature for really, really fast digital I/O. The addition of WiFi is nice, and the inclusion of extra antenna connectors phenomenal, but it’s nothing a USB WiFi dongle couldn’t handle.
If anything, the BeagleBone Green Wireless is a signal for the future of the BeagleBone platform. The number of versions, each with their own small take on connectivity, is the bazaar to the Raspberry Pi’s cathedral. It’s encouraging for any fan of Open Hardware, and at the very least another tool in the shed.
Reflow soldering – setting components on a PCB in blobs of solder paste and heating the whole assembly at once to melt all joints simultaneously – has been the subject of many ingenious hacks. Once it was the sole preserve of industrial users with specialist microprocessor-controlled ovens, now there are a myriad Arduino-controlled toaster ovens, hot air blowers, and hotplates that allow hackers and makers to get in on the reflow act too.
PTC heating elements are thermistors with a positive temperature coefficient. As their temperature rises, so does their electrical resistance. By careful selection of materials they can be manufactured with a sharp increase in resistance at a particular temperature. Thus when an electrical current is passed through them they heat up until they reach that temperature, then the current decreases as the resistance goes up, and they do not heat beyond that point. Thus as heaters they are intrinsically self-regulating. From our point of view they have another advantage, they are also cheap. Fitted as they are to thousands of domestic heating products they are readily available, indeed [Analog Two] found his on Amazon.
The heater chosen was a 200W 110V model with a temperature of 230 Celcius to match the solder he was using. They are also available for other mains voltages, and even at 12 and 24V for automotive applications. He reports that the time to reflow was about 90 seconds.
We’ve mentioned the advantages of this heater as its price and regulated temperature. Looking at the pictures though a disadvantage is its size. This is a reflow plate for small boards. There are larger PTC heater elements available though, it would be interesting to hear people’s experiences reflowing with them.
When Hackaday announced winners of the 2014 Hackaday Prize, a bunch of hackers from Greece picked up the grand prize of $196,418 for their SatNOGS project – a global network of satellite ground stations for amateur Cubesats.
The design demonstrated an affordable ground station which can be built at low-cost and linked into a public network to leverage the benefits of satellites, even amateur ones. The social implications of this project were far-reaching. Beyond the SatNOGS network itself, this initiative was a template for building other connected device networks that make shared (and open) data a benefit for all. To further the cause, the SatNOGS team set up the Libre Space Foundation, a not-for-profit foundation with a mission to promote, advance and develop Libre (free and open source) technologies and knowledge for space.
Now, the foundation, in collaboration with the University of Patras, is ready to launch UPSat – a 2U, Open Source Greek Cubesat format satellite as part of the QB50 international thermosphere research mission. The design aims to be maximally DIY, designing most subsystems from scratch. While expensive for the first prototype, they hope that documenting the open source hardware and software will help kickstart an ecosystem for space engineering and technologies. As of now, the satellite is fully built and undergoing testing and integration. In the middle of July, it will be delivered to Nanoracks to be carried on a SpaceX Dragon capsule and then launched from the International Space Station.
A typical Cubesat like this one consists of several sub-systems. The main one being the structural unit that holds it all together. The Electrical Power Subsystem (EPS) module produces, stores, distributes and controls the Cubesat’s electrical power. The Science Unit (SU) is the main payload, consisting of a multi-needle Langmuir Probe instrument which works by measuring the current collected individually from four needle probes, placed in front of the satellite.
The secondary payload is the Image Acquisition Component (IAC) that does terrestrial imagery using a DART4460 Linux embedded board running a custom build of OpenWRT, a Ximea MU9PM-MH USB Camera and a 50mm lens attached to the camera, providing resolution between 11 m to 18 m per pixel depending on the Satellite’s altitude. The Attitude Determination and Control Subsystem (ADCS) stabilizes the satellite and orients it in desired directions during the mission.
The On Board Computer subsystem (OBC) is the brains of the satellite. It facilitates all core flight functionality and implements all major decision-making and monitoring of all subsystems. At its heart is a STM32F4 microcontroller running a customised version of FreeRTOS. Ground communication is implemented using ECSS-CCSDS telemetry and telecommand packet standard as defined by ECSS-E-70. The on-board Communications Subsystem (COMM) is based on the CC1120 RF Transceiver chip, a device that has been employed successfully in previous missions.
All of the extensive project documentation is available on their GitHub Repository, and blog posts on their website record the major milestones along their journey, so do check it all out. And then keep a lookout for announcement of the launch and deployment of the UPsat sometime in July. In the meanwhile, check out this post announcing the winners of the 2014 Hackaday Prize. May the Force be with you, UPsat.
USB C allows data transfer, but also has provisions for transferring data related to power distribution. Of course, where there is data, there is a need to snoop on data for troubleshooting or reverse engineering. That’s the idea behind the open source Type-C/PD Analyzer.
According to the project the features include:
Spec support: USB PD 2.0 and USB Type-C 1.1
Allows pass-through of legacy USB, USB 2.0, USB 3.1, and Alternate mode
Non-intrusive, preserves signal integrity and timing conditions
Transparent interposing on a USB Type-C connection
Displays Packet timing
Monitors USB Type-C state machine
Exporting received packets as CSV and proprietary bin file format
Complete PD packet decoding
Supports Real-time decoding and Error detection
Sniffing PD traffic on both CC lines
Displays the CC packets in a human readable form
Monitors CC and VBus line voltage and displays graphically