Monthly Archives: October 2015

What Can the Raspberry Pi Do After Dark?

A lot more goes on in the museums of the world at night, after everyone has vacated the premises and the guards have locked up the place, than one can imagine. The situation may not be as dramatic as what Ben Stiller shows us in the movie, “Night at the Museum,” but still, it does warrant a serious investigation. This is what Tate Britain has done with its After Dark project with help from the inaugural IK Prize.

Tate Britain has one of the largest art collections in the world. In August 2014, it organized a project After Dark, where visitors could experience the thrill of a prohibited voyage, without once stepping into the museum. For 25 hours, more than 100,000 viewers across the globe saw live streaming video over the Internet from four robots let loose in the darkness of the museum. Additionally, 500 people could take control of the robots for approximately 12 minutes each, guide them as they like and see what the robots were witnessing.

RAL Space has engineered the robots, which are based on the tiny single board computer, the Raspberry Pi or RBPi. Working alongside the UK Space Agency or UKSA, RAL Space is one of the world’s leading centers for the research and development of space exploration technologies.

RAL Space worked in close collaboration with Tate Britain, and the team behind the project After Dark combined the latest software with the bespoke RBPi hardware. They designed and engineered the robots, creating a world-first, one of a kind experience and attracted audiences from all over. The Workers, a digital product design studio, designed the Web interface for After Dark.

For the late night explorations within the museum, people from all over the world get to guide four robots by taking control of any one of them. RAL Space has designed the robots to select new operators for driving them every few minutes. As long as the event is live, people can request control of a robot from the project website. The robots know you are waiting, and as soon as a slot frees up, will try to take you on a ride. Even while you wait, you can watch the video of the event being streamed live and appearing on the project website, and on Livestream.com.

You can use the on-screen buttons on the web-based control interface or the arrow keys on your keyboard for controlling the robot. You can make the robot move forward or turn, and even make it look up or look down. The robot senses obstacles around it, feeding this information back to you. Therefore, even though it is nearly dark, you, the navigator, can operate the robot easily.

If you take the robot too close to an object, it will stop moving and inform you through the web-based control interface. Once that happens, you still have control over the robot, as you can make it turn on the spot and let it move forward, continuing with the journey, provided the path ahead is clear.

Synthetic Diamond Manages Power

Power delivery using semiconductor devices is increasing at a rapid pace. This is evident from different forms of power delivered, whether it is controlled power through power inverters, or RF power through amplifiers. Power is necessary to operate nearly everything, such as for alternative forms of energy generation, electric vehicles, radar systems, cellular base stations and even smartphones. However, semiconductor devices need to dissipate the heat they generate, and this poses a stringent challenge for power and thermal management.

Such high-power semiconductor devices are now using a new technology in the form of GaN-on-diamond wafers and synthetic diamond heat-spreaders. The reason behind this is the excellent thermal conductivity of diamond, the highest of any material. At room temperatures, diamond conducts heat about five times better than copper does.

Any semiconductor material can use diamond heat spreaders and these lower the temperature of the semiconductor gate junction by almost 30 percent. In addition, the use of GaN-on-diamond wafers helps lower the temperatures of GaN devices further. With the gate-junction temperature going down by almost 50 percent, GaN-on-diamond devices can handle more than three times the power density than similar GaN-on-SiC can.

Manufacturers use the technique of plasma-assisted microwave CVD or Chemical Vapor Deposition for synthesizing diamond heat spreaders. With this method of growing the synthetic diamond, manufacturers make freestanding diamond wafers up to 140 mm in diameter and nearly 1 mm thick. The wafers have thermal conductivities higher than 2000W/mK, which is five times that of copper. By using microwave CVD for growing diamonds, manufacturers can engineer the properties of the diamond wafers precisely, giving them a range of thermal conductivities. This allows them to offer different cost to performance ratios for matching the specific needs of any application.

When using metalized diamond heat spreaders, manufacturers attach them to the bottom of the semiconductor die. Since they use as thin a layer of solder as is possible for attaching the heat spreader, the diamond lies within 100 to 300 microns of the gate junctions of the device. The diamond heat spreader distributes the heat equally and effectively in both lateral and vertical directions. Heat spreading in the lateral direction is particularly important for RF power amplifiers, as they typically form hot spots of up to 1 micron in diameter with intense heat density.

Manufacturers need to keep the metallization of the die and the heat spreader thin – to the extent of a few hundreds of nanometers. Metallization of the diamond has to be done carefully using a carbide-forming metal as the first layer. The solder layer used to attach the heat spreader must also be thin, preferably lower than 10 microns. With optimal integration into a package, diamond heat spreaders typically help to reduce the gate junction temperatures by nearly 30 percent, when compared to what ceramic packages do that are not using diamond heat spreaders.

The GaN-on-diamond substrates now offer new thermal management tools for GaN semiconductor devices. The reduced thermal resistance of GaN-on-diamond and diamond heat spreaders allows simpler, less expensive thermal management systems. This has a favorable impact on cooling complexity and expenses involved, also leading to better lifetimes of the entire system.

Raspberry Pi Helps Marine Ecology with Autonomous Recordings

The health of marine ecosystems is linked to that of all living beings on Earth. Around the world, people are waking up to this truth and making efforts to find out what goes on in the murky depths of the oceans. One of the foremost indicators of the health of oceans is determining the population size of Cetacean species, which includes porpoises, dolphins and whales.

However, that is easily said than done. Over the centuries, man has recklessly hunted these gentle giants to the point of almost near extinction. Those left over, are in the endangered list. Conservation status and population size of these mostly endangered species is only possible by collecting extensive amounts of data about them.

Researchers are carrying out studies on the ecological impact of industrial activities such as human-generated noise on the coasts. A team from the University of Sao Paulo in Brazil is carrying out underwater acoustic monitoring. They quantify the human-generated noise while studying sound generated by cetaceans. Water being an efficient medium for transmission of sound, such research is useful because water allows easy detection of the tones and clicks cetaceans produce, even when they are hundreds of kilometers away.

The team first went about their research using commercial underwater recorders. However, they found these to be expensive and inflexible. Almost all the underwater recorders had proprietary hardware and software, which they found impossible or difficult to modify. Therefore, the team built a flexible, low-cost autonomous hydrophone recorder based on the Raspberry Pi or RBPi, an affordable single board computer. They published a paper about their effort in the open-access journal PLOS ONE.

The system is an underwater sound recorder. The entire unit consists of a 50 cm PVC case with 9.5 mm thick walls, closed on both ends. One end has a protective cage made of stainless steel, and this houses the actual hydrophone or an underwater microphone. All the other electronics is located within the PVC case, which is sturdy enough to withstand pressures up to 10 bar. Pressure-chamber testing establishes this as equivalent to pressures experienced almost 100 m underwater.

After signal conditioning, the analog output from the hydrophone passes into a USB linked analog to digital converter, which generates the digital data corresponding to the analog signal. The RBPi stores the digital information along with an appropriate time stamp. Five ordinary D-sized Duracell batteries power the RBPi and there is adequate room within the PVC enclosure to add four more such packs in parallel. Power from the batteries reaches the RBPi via a power management module. The RBPi also includes a real-time clock for generating the time stamp.

The team monitored marine traffic including dolphin and whale population on the eastern and southeastern coast of Brazil. They used their own RBPi based hydrophone recorders and these worked satisfactorily. According to the results of their tests, the devices recorded for two weeks continuously when powered with five battery packs. If they recorded for one hour each day, the researchers estimate the five batteries would power the recorder for over four months of recording.

Holograms Can Improve Electronic Devices

Multiplicative use of sensors is generating huge amounts of data calling for ever-increasing storage requirements. Researchers are looking for newer memory devices capable of storing substantially more than the capability of current devices. Now a team of researchers has found new holographic memory devices that can offer unprecedented data storage capabilities in electronic devices.

Devices such as the holographic memory typically use optical beams to store data. The newer devices use spin waves instead. Spin waves are a collective oscillation of spins in magnetic materials and using them is advantageous in two ways. Spin wave devices are compatible with the conventional electronic devices – no need to convert electrons to light. Additionally, these operate at much shorter wavelengths compared to optical devices, which allows for manufacturing smaller electronic devices with greater storage capacity.

Researchers from the Russian Academy of Science and the Riverside Bourns College of Engineering, University of California, demonstrated the experimental feasibility of applying holographic techniques. They created a device, a magnonic holographic memory, by applying holographic techniques they developed in optics to magnetic structures. They were able to combine the advantages of wave-based information transfer with the magnetic data storage capabilities.

According to Alexander Khitun, the lead researcher and a research professor at UC riverside, the results of the experiment has thrown open a new field of research. This could profoundly affect the development of new memory and logic devices. The researchers have submitted a paper describing their findings to the journal Applied Physics Letters for publication.

Most people know of holography as being associated with driver’s license or paper currency where images are made from light. This technique is based on the wave nature of light. It uses interfering waves such as those between the object beam and the coherent background. However, this is only a small application of holography.

In 1940s, electron microscopes were the first to use holograms. After about a decade, optical holographic images became popular with the advent of lasers. Since then, wave interference techniques to produce holograms have significantly advanced. This includes microwave holography used in radar systems and acoustic holography used in seismic applications.

Research work related to holography has revealed it as a future data storing technology with enormous capacity for storing data along with the ability to read and write huge amounts of data simultaneously. For nine years, Khitun was trying to develop spin wave based logic circuits similar to those used in computers.

However, last year, Khitun finally decided it might not be necessary for the new device to replace the electronic circuits in a computer. Rather, the device could be made to complement the circuits. This was a critical moment for Khitun.

As outlined in their paper, the researchers conducted an experiment using a prototype device consisting of a 2-bit holographic memory. They aligned a pair of magnets symbolizing the memory elements, in various positions on the magnetic waveguides.

The magnetic field from the magnets affects the spin waves that propagate through the waveguide. At room temperature, when the researchers applied spin waves interference they got a clear picture, in which they were able to recognize the magnetic states of the magnets.

Graphene Metal Sandwich Improves Electronics

Heat conducting properties of the metal Copper are well known. However, scientists have been able to improve this property even further. By creating a sandwich of graphene with copper, scientists have found that the heat conducting properties of copper are strongly enhanced. Expectedly, this discovery could lead to further downscaling of electronic products.

This pioneering discovery is the work of two professors – Alexander A. Balandin and Konstantin S. Novoselov. Balandin is a professor of electrical engineering at the Bourns College of Engineering at the University of California, Riverside. Novoselov is a professor of physics at the University of Manchester in the United Kingdom. Both are corresponding authors for the paper they have published in the journal Nano Letters.

In their experiments, the researchers added a one-atom thick graphene layer on both sides of a copper film. The graphene layer had highly desirable mechanical, thermal and electrical properties. The researchers found that the addition of graphene layers on the two sides of the copper film increased the heat conducting properties of the sandwich by up to 24 percent.

According to Balandin, who initially discovered the unusual heat conducting properties of graphene in 2013, the enhancement of the ability of copper to conduct heat was an important discovery. Hybrid copper-graphene interconnects in electronic chips could now be made much smaller.

Copper is the most popular metal used for semiconductor interconnects and it replaced aluminum because of its better electrical conductivity. Layering copper with graphene and increasing the heat conducting properties of copper, therefore, became an important factor for the electronic industry.

Manufacturers tend to downscale the size of interconnects and transistors in computer chips with the intention of increasing the number of transistors therein. This puts an enormous strain on the performance of the copper interconnects they use. Downscaling had reached a point where there is little room for further improvement. Therefore, manufacturers were actively seeking improved interconnect structures with better conduction properties for current and heat.

Initially, even the researchers were surprised at the significant improvement in the thermal conduction properties of copper film despite the thickness of the graphene coating being only one atom thick. However, they soon realized that the improvement was not from the graphene acting as an additional heat-conducting channel. Rather, the improvement came about as changes occurred in the copper’s Nano- and microstructure because of the graphene layer deposition.

Researchers used microscopes to examine the grain sizes within the copper film both before and after adding graphene. They found that the high temperature deposition of graphene, in vapor form, stimulated the growth of grain sizes in the copper film. Ultimately, it was found the larger grain sizes in the copper coated with graphene that caused the improvement in heat conduction.

Another finding of the research was the improvement in heat conduction of copper was limited to thin copper films alone. This is a significant find since the future copper interconnects will be scaling down to the nanometers range. A nanometer is one-thousandth of a micrometer. Balandin and his team will be researching the heat conduction properties in copper films of nanometer thickness coated with graphene.

Neo Smartpen N2 Connects with Bluetooth

Although computers and keyboards have taken out much of the efforts of writing, some situations still demand we keep this skill alive. Then, some people are unwilling to give up the feeling of writing with a pen to pounding on a keyboard. Engineers have tried to modernize the humble writing instrument with the Bluetooth pen of Livescribe. Now, an improved Smartpen N2 is in the market.

Neo Smartpen N2 has a sleeker design compared to that of Livescribe. According to the manufacturer, the pen has a shape users will find more comfortable and it is lighter than most smartpens in the market. Without the cap, Neo Smartpen N2 is only 22gms as against the Livescribe, which weighs 34gms. Although the difference is not much, to someone who writes extensively with a pen, this could count for a lot.

An ARM 9 dual-core Processor powers the Smartpen N2, which sports a built-in 90MB NAND flash drive. The pen connects via Bluetooth to a tablet or phone. However, it works even without them. N2 has a built-in camera that captures 120 pictures-per-second while recording about 1,000 pages of notes to store in its memory. Later, you can synchronize this content over to another device.

To conserve battery, Smartpen N2 turns itself off automatically when it detects idle time and turns on to be ready for writing. This convenient feature helps to conserve battery and the pen can write for about five continuous hours before it has to be recharged. A full recharge takes about two hours.

The entire Smartpen N2 writing system has three parts. The first is the pen itself, to be followed with the special paper, which records the motion of the pen. Then there is the app, which translates these motions into an image on the tablet’s screen. The app can also send the notes to popular services such as Dropbox or Evernote. Neo Notes app is available for free for Android and iOS phones and tablets.

Both Livescribe 3 and Smartpen N2 translate their ink notes scrawled on special paper for capturing them in digital form. However, the Equil Smartpen 2 uses a sensor that you can clip onto the top of any kind of paper you are writing on. While both Equil and Neo N2 are cross-platform compatible, apps available for Android and iOS, Livescribe 3 remains an iOS-only device.

Apart from recording written notes in the form of images, Neo N2 can also record voice memos in real-time, simultaneously as you write. Other features of this amazing pen include translating features that convert handwritten notes into text, after you have selected the language. Additionally, you only have to draw a check mark on the mail icon in the corner of your page and the app will email the page attached as a PDF. At the same time, the app will synchronize any new notes you make automatically to your Evernote account.

The only thing limiting the appeal of Neo Smartpen N2 is its need for special paper. Therefore, this is a device for serious writers only and not meant for scribblers.

Very Clean Recordings with Olympus VP-10

Recording voices at press conferences can be very disappointing. Sometimes, the voices registered on the handheld audio recorder are not loud enough or they are muffled because of clothes rustling. According to Olympus, their pocket-friendly, portable audio recorder takes care of both issues.

Olympus VP-10, weighing only 37gms and with dimensions of 12.7×1.7×1.7cms, has 4GB of internal memory. According to the company, this tiny portable recorder can store 1,620 hours of audio. On the other end of VP-10 is a full-sized USB plug with a dual function – to transfer the recording to a computer as well as charge the AAA-sized NiMH battery within the recorder. The full-sized USB plug also means no special USB cable is necessary to be carried in the travel bag.

While recording, the VP-10 uses a voice balancer function. This works like an ALC or automatic level control to record quiet speakers with clarity in multiple speaker situations, while lowering the levels for those with a strong voice. In addition to the noise-cancellation algorithm, Olympus has provided the VP-10 with an Anti-Rustle Filter technology.

Interviewers use a portable microphone recorder during conferences. When placed inside a pocket or under a coat lapel, the microphone produces annoying brushing sounds as it rubs against clothing. Olympus claims its Anti-Rustle Filter technology has the intelligence to cut out the rustling sounds and record only the voice of the speaker.

Although you can turn off the power separately, the VP-10 has a special one-touch recording mode to start recording immediately at the beginning of an important conversation. When taking notes from the device, you can use the handy transcription mode to start or stop the playback. This allows you to automatically playback the last 3 seconds of what you have captured.

The VP-10 comes with four recording scenes and you can easily tweak the audio capture to match a specific recording environment. For example, use the Pocket mode for recording a wide range of voices with the recorder inside your jacket or shirt breast pocket. The other three are Dictation, Conference and Meeting modes and they help to achieve flawless, high-quality recordings in respective conditions.

With an overall recording frequency range of 50Hz to 17KHz, this tiny portable recorder can record in PCM, MP3 or WMA file formats. For monitoring the playback privately, there is an earphone jack conveniently placed at the top of the recorder. Public airing is also possible through an in-built 90mW dynamic speaker.

Two omni-directional stereo microphones embedded within VP-10 capture sound securely from sources surrounding you. You may keep the recorder in your pocket or clipped to your notebook, the recording is high in quality and contains low noise.

VP-10 arranges its recordings by date, which makes it easy and convenient to locate a file. A small LCD allows selection from the menu. The Date Search function when used with the Intro Playback function is a very useful feature – the recorder replays the first few seconds of the file, allowing you to easily search for a specific file.

The RemotePi Board for the Raspberry Pi

If you have designed a mediacenter system around a Raspberry Pi or RBPi, you would also want to control it remotely, just as commercial mediacenters allow. You can do that with the RemotePi Board. Added atop your RBPi, the RemotePi acts as an intelligent infrared remote controlled power switch and remotely controls to power on/off your mediacenter system.

The RemotePi does not need a special IR remote, as it can learn to decipher the IR code of almost any commercial remote – it works with a standard GPIO IR receiver. This allows you to switch off or on the power safely to the RBPi with any TV remote or a pushbutton. The RemotePi is available in two versions, the 2015 version for fitting on older RBPi models A or B, and the Plus 2015 version for fitting on the newer RBPi models A+, B+ or the 2. Two versions of RemotePi are necessary as the RBPi models differ in their physical dimensions as well as in the position of their connectors and mounting holes. For example, the RBPi models A and B have only two mounting holes, while RBPi models A+, B+ and 2 have four mounting holes on each corner.

For both versions of the RemotePi Board, two variants are available. One has the IR LED and receiver integrated on it, while the other has them connected via a cable. The cable-connected variant is useful if you plan to use the RemotePi Board with a non-transparent case or you intend to mount the RemotePi Board and the RBPi out of line of sight. In this case, you only have to keep the extended IR LED and receiver visible to the users. Although you can buy an acrylic case specifically designed to fit the RemotePi Board piggy backing on the RBPi, most of the readily available cases need only minor modifications to accommodate the two.

When using the RemotePi Board with the RBPi, you need to connect the power to the RemotePi Board and not to the RBPi. The RemotePi routes the power to the RBPi, decided by a micro-controller, which switches the power on or off based on the command it receives from a push-button on top of the board or the infrared remote control.

When you command the power to be switched off, the RemotePi first sends a notification to the RBPi via a signal on the GPIO port. The RBPi has a script running in the background that picks up the signal and initiates a clean shutdown of the operating system, avoiding data corruption.

The RemotePi Board cuts off the power to the RBPi completely, after the RBPi has successfully shut itself down. That reduces the power consumption of the duo to a few mA of standby current.

You must teach the RemotePi software to remember the infrared remote control button you want to use for switching power to the RBPi. For this, the RemotePi software has a learning mode and it stores the button information in its flash memory. Of course, you can make it learn a new button any time you like.

Raspberry Pi and the RTK Motor Control Kit

While building robots, many a time you need a simple motor controller for the RBPi or the Raspberry Pi. The RTK Motor Control Kit fits these requirements very well, is budget-friendly, works using the GPIO pins and needs very little coding. The self-assembly kit of the RTK Motor Control Board allows easy control of DC motors with your RBPi.

Once you have soldered the few components correctly on the board, plug the assembly on top of an RBPi. You can control the GPIO pins of the RBPi with a programming software such as Python, Scratch or any other. Connect power to the motors and you can start driving the motors in either direction simply by toggling the GPIO pin on or off. The board supports PWM or Pulse Width Modulation. With PWM, you can control the speed of each motor separately.

To program the board and drive a motor with it is as simple as turning a pin on or off. The tutorial section has an example code in Python, but you could use Scratch or any other compatible language as well. The pins you need to toggle for Motor 1 are 17 & 18 and for Motor 2 are 22 & 23. To control motors with the kit you will need a working RBPi board with its power source, one or two DC motors and 4.5-12VDC power sources for the motors.

To assemble the kit you will need a soldering iron of 35W minimum rating and a reel of 60/40 solder wire. Before starting assembly, it is advisable to read the assembly instructions included with the kit.

On unpacking the kit, you will find it containing the RTK-000-001 PCB, an H-Bridge driver IC SN754410NE, three two-way terminal screw blocks, three two-way pin headers, one 26-way pin GPIO header and one 16-pin IC socket. Ensure all parts of the kit are present before beginning the assembly.

Switch on the soldering iron and ensure it is hot. Place the PCB with the writing RTK RPi M.C.B. facing up and towards the right. Place the IC socket in the PCB at the label IC1, taking care to match the notch of the socket with the gap in the silkscreen. Hold the IC socket in place, turn the PCB around and solder all the pins. Solder the three terminal blocks in their positions J1, J2 and J3, ensuring the terminal blocks face outwards. Place the two pin headers into the PCB at positions J4, J5 and J6, taking care to insert the shorter side of their pins into the board and solder them in place.

Insert the RBPi GPIO connector from the bottom side of the board and solder the pins to the top side of the board. This is important, as the assembled board will sit on the RBPi with this connector engaging the GPIO pins of the RBPi.

Don your ESD wrist-strap and insert the H-Bridge IC into its IC socket, ensuring the notch on the IC matches with the notch on the socket. Connect the motors and their power supply with the correct polarity. Plug in the RTK Motor Control Board to the RBPI, and power on the RBPi first and then the motors.

3D Ultrasonic Fingerprint Scanner for Improved Security

Most people are familiar with the biometric sensors used in offices and other places for checking fingerprints. So far, these fingerprint sensors were flat and sensed only 2D images of the surface of your finger. Now, researchers at the University of California, Davis and Berkeley have an improved ultrasonic 3D fingerprint sensor that measures not only a volumetric image of the ridges on fingers, but also measures the tissues beneath the finger’s skin. That makes it almost impossible to spoof.

Most smartphones now sport a fingerprint sensor to verify the authenticity of its user. Apple first introduced this technology in 2013, when it incorporated the fingerprint scanner in its iPhone 5s. Unless you have just come back from swimming, the sensor was accurate enough, and now, many other smartphones use it.

However, most of these sensors are of the capacitive type, and subject to serious security leaks. For example, you can easily fool it by placing a printed image of your fingerprint on top of the sensor. This is because the sensing is only in two dimensions. That is why the 3D fingerprint sensor is assuming such importance.

Using low-depth ultrasound, Professor David Horsley and his team has now overcome this issue. Ultrasound images the valleys and ridges of the finger’s surface and a part of the tissue under it in three dimensions. The main reasons why portable gadgets manufacturers are interested in this technology is its ultra-compact size and the capability to operate with a supply of only 1.8V.

Inspired by sophisticated medical equipment, the technology for the low-depth ultrasound technology for measuring fingerprints started to come together in 2007. This was when the researchers were working with PMUTs or Piezoelectric Micro-machined Ultrasonic Transducer arrays. Later on, they found this array to be a good fit for sensing fingerprints.

The group built their imager by embedding the PMUT arrays within a chip and integrating it. This technology is similar to the MEMS or micro-electromechanical systems that today’s smartphones already use. Using MEMS is very effective for accelerometers, gyroscopes and microphones.

According to Prof. Horsley, the chip is made from two wafers. One of the wafers contains the ultrasound parts, while the other carries the second circuit to take care of the signal processing. After bonding the two wafers, the MEMs wafer part is shaved off partially to expose the ultrasonic transducers.

The researchers explain that collection of the ultrasonic images follows the same method as that of medical ultrasound. From the chip’s surface, the transducers first emit a pulse of ultrasound and then process the echoes returning from the valleys and ridges on the surface of the finger.

Scanning a finger in 3D makes the mechanism more secure and increases the challenge several folds for those trying to get around it. As the world moves towards mobile payments, such secure systems will assume increasing importance.

When manufactured in high volumes and with modern manufacturing techniques, OEMs can expect the cost of the sensor to dip to very low levels. Apart from making better fingerprint scanners, this technology is likely to find use in personal health monitoring and low-cost ultrasonic medical diagnostics as well.