Monthly Archives: March 2016

SLI: Sensing Without Touching

MEMS is revolutionizing technology, causing microminiaturization and increasing the precision of conventional solutions. Ubiquitous MEMS applications are emerging as the next most promising frontier by removing the need for touch in structured light illumination or SLI.

DLPs or digital light processors from Texas Instruments contain millions of mirrors. TI is pioneering SLI that works by projecting moving stripes of light onto objects. It then measures the deformities in the reflected patterns by reconstructing their 3-D shapes using algorithms. The biggest customers so far are OEMs that manufacture touch-free fingerprint scanners.

These scanners are different from the traditional, as they do not require the traditional ink-blotter protocol. Therefore, SLI is revolutionizing biometric, facial, dental and medical scanning by opening up a whole new frontier in DLP applications. That includes the entire range from scientific instrumentation to industrial inspection systems.

So far, TI already has OEM development kits with DLPs and algorithm libraries. These can recognize 3D shapes, contours, surfaces, discontinuities and roughness. Operating on light sources ranging from near-infrared to ultra-violet, they enable accurate, fast and non-contact 3D scanning and recognition systems.

With its new DLP LightCarrier development platform, TI will be using nearly half a million micro-mirrors for illuminating simultaneously almost anything with structured light. That will allow almost instant recognition and characterization of 3D objects without touching them.

For example, TI uses FlashScan3D in DLP technology to capture far greater detail of fingerprints with higher accuracy than any other SLI solution can. That helps in cutting down on the possibilities of technician error and fraud. Moreover, the new DLP LightCrafter can scan faster and store data internally as against on a separate storage device such as a laptop. Therefore, it helps in building even smaller and more portable SLI applications.

YoungOptics Inc. of Taiwan origin manufactures the DLP LightCrafter as a plug-n-play module for TI. YoungOptics also manufactures TI’s DLP Optical Engine for OEMs that make projection televisions. LightCrafter, along with TI’s DLP 0.3 WVGA chipset, is ready to be used by OEMs for research and development. However, it can serve as the main subsystem in their finished end-user products as well.

Along with the DLP chip that contains exactly 415,872 micro-mirrors is an ASIC or Application-Specific Integrated Circuit acting as a second custom controller. There is also a DVP or a DaVinci digital video processor with its own 128MB NAND flash memory for storing patterns, a configurable IO trigger for integrating cameras, sensors and other peripherals needed for SLI.

Users can optionally add an FPGA, thereby speeding up the SLI patterns that LightCrafter displays, making them faster up to 4,000 per second. Finally, LightCrafter is capable of generating 20 lumens of light as it has an integrated light-emitting diode array for generating red, blue and green light.

OEMs can also use embedded Linux for developing their software to run the DaVinci DVP in the LightCrafter. That makes it an evaluation module compact enough for integrating projected light for scientific, medical and industrial applications, creating faster development cycles for end equipment needing high-speed pattern display with a small form factor, intelligent and lower cost.

Microphones Are Going Digital Now

Although we live in an analog world and possess organs that work in ways more analog than digital, it is common to find that we are converting most of the signals we handle to digital forms. This is because working with numbers is more convenient and we can have more uniformity in the digital circuits that process these signals.

However, the human ear does not take kindly to numbers, appreciating music only when it hears it in the analog. Fortunately, converting digital signals to analog is not difficult. Therefore, the entire chain of processing an audio signal can be in the digital domain, except at the extremities. These would be the sensors that collect the sound signals before processing and the transducers that convert the digits to analog sound after it has been processed.

Now, people are trying to convert to digital those entities at the very extremes of the audio processing chain. The humble microphone that has journeyed from the ribbon type to the electret type is now undergoing another makeover. Texas Instruments first introduced the digital microphone as a consumer device that could connect directly to TI’s codecs, bypassing the usual analog-to-digital converter in between. Where analog microphones picked up only 5KHz of the spectrum, digital microphones can now collect information over the entire 20Hz to 20KHz audio band.

That leads to many further possibilities. With digital microphones or an array of them, not only does audio sound much better than what we are used to, we can have sophisticated noise cancelling and beam forming for tracking a user’s voice.

Conventional electret microphones use a moveable diaphragm to form a capacitor at the gate of a JFET. Sound waves moving the diaphragm cause the capacitance value to change and the charge on it to vary. The JFET converts this varying charge to voltage that is amplified by operational amplifiers before being processed further.

That does not allow the electret microphone to get very much smaller and the signals from the JFET and the operational amplifier are prone to interference and noise. By using MEMS technology, not only can the physical size of the microphone be made more suitable to that demanded by the ever-shrinking digital devices, the ADC can be incorporated within the body of the microphone itself.

Therefore, we have a tiny digital microphone that produces a digital output either in a pulse density modulated (PDM) or in I2S format. The output can directly connect to a digital IC for further processing, eliminating all the issues related to interference and noise pickup.

Among the several types of semiconductor devices, the MEMS microphone package is unique in having a hole for the acoustic energy to travel to the transducer element. Within the package, the MEMS transducer and the ASIC are bonded together, being mounted on a common laminate.

The laminate has a lid over it to enclose the transducer and the ASIC. The laminate is actually a small PCB that routes signals from the electronics to the pins on the outside of the microphone package.

Why Does My Motor Need A Capacitor?

Motor CapacitorIf you are using an AC pump to raise water from a sump to an overhead tank, chances are it uses a squirrel-cage type motor, which needs a capacitor to make it work. This is true for single-phase motors, where the capacitor creates an artificial second phase necessary to generate the rotating magnetic field and make the rotor start spinning. Once the rotor starts rotating, the interaction between the stator and rotor keeps the magnetic field spinning.

A single-phase motor has a primary winding and a secondary winding. If connected to the AC supply without the capacitor, both windings produce magnetic fields of the same phase resulting in zero torque. With a capacitor connected in series to the secondary winding, the magnetic field it produces lags behind the magnetic field generated by the primary winding. This difference in phases creates a starting torque and the motor starts to rotate.

Capacitors that allow a motor to start rotating are called start capacitors. Smaller motors usually have the start capacitor permanently connected in series to the secondary winding. Big motors require a larger capacitor to help them generate the starting torque, but they run more efficiently with a small capacitor in place, called run capacitor. Often both capacitors are housed in the same can, which then has three terminals in place of the customary two. Such motors have a centrifugal switch to disconnect the start capacitor when the motor has reached 70-75% of its full speed. Start capacitors are typically of high value of 100 or more microfarads, while run capacitors are smaller, of about 25-47 microfarads.

You will find motors with large start capacitors being used for several applications where it is necessary to generate considerable torque to begin moving the load. Such applications include mechanical conveyors, belted blowers and commercial garage door openers. These are mostly electrolytic capacitors, housed within a plastic or metal can. Inside the can are two metal foils rolled up with a flexible paper-like insulation separating the sheets. The paper, soaked with an electrolyte, forms the dielectric of the capacitor. The two metal foils are connected to two terminals. The assembly is sealed with epoxy and the two terminals are available for external electrical connection.

Large HVAC units sometimes need two run capacitors, because they have both a fan motor and a compressor motor. To save space, manufacturers combine the two physical capacitors into a single can. Such dual capacitors have three terminals and they are usually marked as Common, Fan and Compressor.

You will find a variety of combinations for dual capacitors, for example, 40 + 5uF, 370V or 100 + 25uF, 440V and others. Their shapes can be cylindrical with a round or oval cross-section. A capacitor’s ability to hold charge is measured in microfarads. As electrolytic capacitors age, their capacity reduces. That results in the motor failing to start or run at less than full speed.

Motors are not fastidious about the capacitance value of the capacitor used for starting. However, when replacing a faulty capacitor, you must never use a replacement that has a lower voltage rating. Always use a part with a voltage rating that is the same or higher than the rating of the capacitor you are replacing. Of course, it’s always preferred to replace a capacitor with another that has the exact electrical specifications for the best results – both in performance and safety.

A Universal Antenna for Wireless Charging

Skin effect is a physical phenomenon that limits the amount of high frequency current flowing through a wire. What happens is AC current flowing through the wire sets up local magnetic fields that impede the flow of current. Therefore, current is forced out from the central core of the wire to its periphery, increasing the current density there. Effectively, the current now flows through a smaller cross sectional area of the wire, and thereby faces more resistance. To keep the wire from heating up, it is necessary to reduce the amount of current through the wire.

Companies producing wireless chargers for mobile devices follow specific standards such as Qi, Association for Wireless Power (A4WP) and Power Matters Association (PMA) standards. Since they operate at different frequencies, battery-charging circuits have to handle different skin effects or skin temperatures. This may sometimes cause the batteries to get too hot, missing a full charge by several watts in a cycle of recharge. This happens because the high frequency currents flow only around the outer edges of the charging wire, causing charging times to increase.

To reduce the skin effect, NuCurrent has invented the ML wire. They describe the wire as equivalent to bundling hundreds of straws together for passing liquid through. With several strands of wire in parallel, and each insulated from the others, the current now flows through an optimized conductive area, based on the skin depth of a frequency. Therefore, NuCurrent can pass more current with lower resistance through such a wire.

NuCurrent has over 50 patents in areas such as circumventing the skin effect. They believe this will bring them success in the market for multi-mode wireless charging. NuCurrent produces antennas that support the different standards used by companies making wireless chargers. For this, NuCurrent uses the same coil for resonant PMA (200-300KHz) and inductive Qi (110 & 205KHz) standards. Since A4WP uses 6.78MHz, NuCurrent has to use a second resonant charging on the same board for accommodating A4WP.

NuCurrent produces antennas of higher quality and lower resistance. According to officials at NuCurrent, the higher quality factor is necessary because that achieves the necessary charging efficiency with antennas made of thinner wires. In turn, smaller antennas are useful to keep the phone or device cooler and maintain a good charging speed.

With ML wire, NuCurrent is able to make antennas as thin as 0.08mm and occupy areas as small as 12.7×12.7mm. Endowed with NFC capability, the antennas power mobile devices ranging from 50mW to 2.5W, even going up to 50W. However, these antennas are not meant for charging higher-power devices such as appliances or electric cars. The charging efficiency NuCurrent antennas offer for wearable devices and mobiles can reach up to 80%.

The Efficient Power Corporation or EPC makes transistors with Gallium Nitride instead of silicon. As NuCurrent is involved with EPC, they have used NuCurrent’s ML wire coil and demonstrated wireless power transfer that delivered 35W into a DC load while operating at 6.78MHz. NuCurrent feels the technology from A4WP is more relevant to the market today and is more likely to survive as the dominant standard for wireless charging.

SOUNDBOKS: Batteries to Power the Next Speakers

Your next portable speakers may be able to violate county noise ordinances without the necessity of them being plugged into a vehicle power inverter, a portable generator or even a wall socket. This is what Soundboks is claiming, and their speakers will be battery-powered.

Most portable speakers are limited in their size and their power output. Usually, if you want sizes and power capacity beyond those, it becomes necessary to power the speakers through AC adapters or wall plugs so they can output continuous power. That does not help when catering to outdoor gatherings, where truly wireless music at extreme volumes is the norm. With the battery-operated speakers from Soundboks, you can now expect 30-hours of nightclub-level decibels on a single charge.

In the market, one can find plenty of audiophile-grade boom-box sized speakers such as the Nano HiFi NH1 or the rugged JBL Xtreme suitable for supplying ample amounts of power for pool events, camping, or backyard cookouts. However, the portable speakers from Soundboks beats them hollow, as they house a pair of low-frequency drivers each of 96 dB, and a pair of high-frequency drivers, also of 96 dB SPL or sound pressure level speaker units, along with 42 W digital amplifiers.

With high-efficiency custom-designed amplifiers, Soundboks speakers enhance the life of the driving batteries while optimizing the sound for outdoor usage. They have designed the speakers for dual-phase boost function and these can belt out a maximum of 119 dB of sound. You can easily get an experience of a live concert, simply by turning up the volume dial on the speaker to position 11.

Weighing in at 14.5 Kg (32 lb.), the 66x43x32 cm (26x17x13 in) Soundboks speaker is not much different from other carry-on luggage used. The low weight is because of the wood and aluminum construction of the case and that makes it shockproof, weather proof and temperature resistant. The case has an integrated side handle that makes it easy to carry about on the beach as easily as a cooler filled with beverages and ice. Wireless and wired connectivity are offered. Bluetooth 3.0 with extended range allows you to connect wirelessly while a 3.5 mm audio input provides the wired connectivity.

The truly remarkable thing about the Soundboks speaker is its ability to play music for 30 hours at 113 dB. That easily violates the county noise ordinance and that too without any help from a vehicle power inverter, portable generator, or wall socket. Each speaker comes with two external batteries, which you can swap and that gives the capability to play for a total 60 hours continuously.
The batteries are special, as they are not the usual lithium-ion type. Rather, Soundboks uses LiFePO4 or lithium-Ferro phosphate batteries that need only three hours to charge, can meet power demands and are safe. Therefore, you only need six hours of charging time, and then enjoy a full weekend-long festival program or a complete week with the volume toned down. Shipments are scheduled to start this April, as Soundboks has already raised 174% of its Kickstarter goal in one day.

What is Buck-Boost Charging?

With Apple unveiling their new MacBook on April 10, 2015, they also opened up a new era in power management for computing devices. The USB-C port in the new MacBook features a true all-in-one port. It is capable of delivering power and bi-directional data at the same time. The technology eliminates a separate charging port, as it integrates the charging functions into the USB-C port.

Intel has released their 6th generation processors, and very soon, a new generation of ultrabook computers, 2-in-1s, tablets, and external devices are expected in the market, ready with the USB-C port. However, with USB-C, fundamental changes are necessary in the existing power delivery architecture. This presents a new challenge to the system designers.

Power Delivery at Present

At present, almost all electronic devices charge through USB-A/B in low power applications. The traditional USB-A/B port offers 5 V DC at up to 2 A current capabilities, but this is insufficient when charging high-power devices. At present, such high-power devices require a separate AC adapter with tens of watts power rating for charging.

For instance, ultrabook computers use different battery stacks ranging from a single-cell battery to 4-cell batteries. Since each Li-ion battery has a typical operating voltage of 2.5 to 4.3 V, from discharge to fully charged status, the ultrabook may have a battery voltage ranging from 2.5 to 17.2 V. Ultrabook computers generally come with a hefty AC adapter with a 20V output.

Therefore, the charger within the ultrabook battery stack has to step down the 20 V DC to make it suitable to charge the battery. This is done through a buck topology. Again, the ultrabook has to provide 5 V on its USB-A/B port for charging an external USB device. To generate this 5 V USB power rail, the ultrabook may have to apply a boost topology if it is using a single-cell battery pack. If it has battery stack of more than one cell, the ultrabook may use a similar buck topology as it does for charging.

Moving to USB-C

USB-C is a standard interface to connect anything to anything. Even though the default is 5 V, the USB-C port is capable of negotiating with a plugged-in device to raise the port voltage to 12 V, 20 V, or any other mutually agreed voltage and mutually agreed current level. Therefore, the maximum power a USB-C port can deliver is 20 V at 5 A, or 100 W. This is more than what most ultrabooks require – about 60 W.

The main consideration involving the use of USB-C technology lies in the absence of input-to-output relationship, which would warrant the use of buck technology when using a 5-20 V adapter voltage to charge a 2.5-17.2 V battery. Likewise, there is no definite output-to-input relationship either, for which a boost topology would be suitable.

This is where the buck-boost approach finds its merit. This operates in buck mode when there is an input-to-output connection and in boost mode when there is an output-to-input connection – the USB-C port being bi-directional. This flexibility allows for a more efficient design using the smallest solution size. It offers the best design solution, achieving all the requirements of a system designer.

What are Flexible Batteries?

We are accustomed to thinking of batteries as heavy and chunky implements capable of storing energy and powering electronic devices. For long, use-and-throw carbon-zinc batteries along with rechargeable Lead-acid and Nickel-Cadmium batteries dominated.

With the advent of portable devices such as netbooks, ultrabooks, and other hand-held devices, the battery market exploded with various types, of which, the most popular was the Lithium-ion rechargeable battery. However, with electronic gadgets getting slimmer and flexible, it is now necessary for the battery also to shed its rigid form and embrace the curves of the gadget – hence, the market for thin-film flexible battery.

In their new report, market watcher IDTechEx predicts that by 2026, the presently tiny market for thin-film batteries is going to hit $470 million. According to Xiaoxi He, a technology analyst with IDTechEx, this is the reason companies such as TDK, STMicroelectronics, LG, Samsung, Apple, and many others are all becoming increasingly involved. Considering the rate at which the Internet of Things, wearables, and other environmental sensors are being increasingly deployed, replacing traditional battery technologies is becoming imperative. New form factors and designs are urgently required.

For instance, Samsung has a curved battery in their Gear Fit wristband. STMicroelectronics is producing, in limited quantities, thin-film solid-state lithium batteries. Two other companies are now producing printed batteries, according to the report. Therefore, the market now has a variety of flexible batteries vying to power several kinds of devices.

Other companies are trying other strategies as well. For instance, TDK is working on battery-free energy harvesters. The idea is since IoT nodes and wearable devices require extremely low power to operate, these can be operated via energy harvesters rather than batteries. Others such as in South Korea have gone ahead and now TDK is planning to invest heavily in the fiscal years of 2016 and 2017 to ramp up their production of lithium-ion batteries to match.

Other companies such as the Oakridge Global Energy Solutions Inc., plan to ramp up their production capacity in their Brevard County plant at Florida. They will make electrodes and cells for thin-film, solid-state lithium batteries. They acquired this technology in 2002 from Oak Ridge Micro-Energy Inc., and plan to start volume manufacturing in early 2017.

Large varieties of flexible batteries are soon going to be available in the market. Among these will be thin-film batteries, printed batteries, laminar lithium-polymer batteries, micro-batteries, advanced lithium-ion batteries, thin flexible supercapacitors, and stretchable batteries.

Understandably, they will have diverse uses.

For instance, wearables are expected to have the highest potential of high-energy thin-film batteries, followed by printed rechargeable zinc batteries. Printed batteries, in the form of skin patches are already in use in the healthcare industry and the market is steadily increasing. At present, the high cost of printed zinc batteries is preventing widespread use despite having the highest potential for this application. According to the IDTechEx report, there will be rapid expansion in the market for micro-power batteries powering disposable medical devices.

There are additional requirements for batteries to power diverse types of power sources, displays, and flexible sensors. The US Department of Defense has invested $75 million for creating the Flexible Hybrid Electronics Manufacturing Institute in San Jose.

Playing 4-Bot with the Raspberry Pi

Sometime or the other we have all played Connect-4 or Four-in-a-row against either a human or a computer opponent. It is a simple game where you and your opponent each try to get four same-color pieces in a row, while trying to prevent the other from doing so. The first one to line up four adjacent pieces of the same color wins the game.

Conventionally, the game board has 42 squares made of six rows and seven columns. Players start with several discs of two colors each, and to be successful, each player has to constantly plan and revise their strategy. Therefore, an SBC or single board computer such as the Raspberry Pi, or RBPi is a suitable candidate for playing Connect-4. Besides enjoying the game, you hone your skills as a DIY enthusiast by building the game. Of course, this project will require some skill in mechanical assembly, and in coding as well.

You can have a horizontal board and an X, Y arm mechanism to let the RBPi deliver its pieces to the required square. However, a vertical board makes the mechanism simpler, as the arm then has to travel only in one axis, gravity taking care of the other. The vertical board is actually made of two faces, with a gap in between and separators to mark the columns to allow the discs to be dropped in one of the columnar spaces between the two faces. Both faces have 42 matching circular cutouts, so it is easy to see where each disc is positioned. A claw on the arm mechanism picks up a disc from a stack, positions itself above the required column, and releases the disc, allowing it to fall in the column between the board faces.

The software requires the use of Python Imaging Library for processing the image of the game board. To enhance readability, the image can be down-sampled to 16 colors, and then divided into a grid. It is only required to identify each of the 42 spaces on the board as red, yellow, or empty. This is easily done by reading the RGB value of each space in the grid, and saving this data in the form of an array. This forms the board state after every move and this is passed on to the AI or Artificial Intelligence on the RBPi for calculating the next move.

The AI used is a well-known algorithm known as Minimax – applicable to games of this nature, and there is a Python library for Minimax. Using tree-searching methods, the algorithm looks several steps ahead to calculate the next best move. Getting the RBPi to play effectively can be quite a challenge, as even a small Connect-4 board of 6×7 squares can have 4,531,985,219,092 possible game positions. Therefore, the program tries to trade-off between absolute perfect play and reasonable time for each move. If you can strike a balance between the two, the RBPi can play quite intelligently, but still complete each move in about 25 seconds – this is acceptable for a flowing game.

Using eGaN FETs in Wireless Power Transfer Systems

Highly resonant wireless power transfer systems such as the A4WP use loosely coupled coils operating at the standard 6.68 MHz or 13.56 MHz unlicensed industrial, scientific and medical ISM bands. The popularity of such wireless energy transfer is increasing over the last few years specifically for applications targeting charging of portable devices. Usually, such solutions for wireless energy transfer for portable devices demand features such as lightweight, high efficiency, low profile and robustness to varying operating conditions.

Such features call for efficient designs capable of operating without bulky heat sinks and able to handle a wide range of load variations and couplings. Only a few amplifier topologies can meet such extreme demands and these are the current mode class-D, the voltage mode class-D and class-E. Of these, class-E is the most popular choice for several types of wireless energy solutions, chosen for its ability to operate with very high conversion efficiency.

As compared to regular MOSFETs, eGAN FETs have demonstrated superior performance when using voltage mode class-D topologies in a wireless energy transfer application In fact, eGAN FETs showed higher peak efficiencies of more than four percentage points. At output power levels beyond 12 W, regular MOSFETs required the addition of a heat sink to provide the necessary cooling for the switching devices and their gate drivers.

Moreover, in the traditional class-D topology, the resonant coils needed to be operated above resonance for them to appear inductive to the amplifier. Operating the coils above resonance reduced the coil transfer efficiency resulting in high losses in matching the inductor because of its reactive energy.

Working in class-E topology, eGAN FETs were able to deliver as much as 25.6 W of power to the load while operating at 13.56 MHz. Transferring wireless energy with high load resistance of about 350 ohms made sure the system had a high Q resonance. Measuring the system efficiency gave a figure higher than 73%, which included gate power consumption.

In a single-ended class-E circuit, the series capacitance resonates with the reactive component of the load yielding only the real portion of the coil circuit to the amplifier. The design of the matching network works for a specific load impedance and establishes the necessary conditions of zero voltage and current switching.

In tests comparing the performance of MOSFETS and eGAN FETs, temperatures were kept well below 50C, when operating in an ambient temperature of 25C. No forced-air cooling or heat sinks were used during the tests, which used the same gate driver for driving both the eGAN FET and the MOSFET.

Measurements show the eGAN FET requires significantly lower gate charge for the same operating conditions and this is an important consideration for low power converters. Gate power forms a significant portion of the total power processed by the amplifier. Additionally, as the eGAN FET has a 33% higher voltage rating compared to a MOSFET, it can be operated at higher voltages for higher output power.
Therefore, the simple and efficient class-E topology, coupled with eGAN FETs, is well suited for wireless transfer converters.