Monthly Archives: March 2023

What is I3C Interface Communication

I2C is a popular serial communication protocol, with I3C being an improved version. Embedded systems use this new protocol for achieving significantly higher data throughput and features that are more advanced than what I2C offers. Designers and engineers can use I3C for improving the functioning and performance of their designs while adding more features such as in-band interrupts, hot-join, and high data rate modes. With I3C being backward compatible, it can communicate with legacy targets using the present I2C protocol.

There are some major differences between I3C and I2C. While I2C works on bus speeds of 100 kHz, 400 kHz, or 1 MHz, I3C operates with bus speeds up to 12.5 MHz. The increase is due to I3C using push-pull outputs, which switch between push-pull drivers and open-drain outputs depending on the state of the bus. I3C uses open-drain driving during arbitration or initial addressing where multiple targets are controlling the line at the same time. I3C uses the push-pull driver for unidirectional communication, and no other device is expected to communicate simultaneously.

The voltage range of operation of I2C is between 3.3 and 5 VDC, and I3C operates with supply voltages of 1.2, 1.8, and 3.3 VDC, with the possibility of other voltages in between. Unlike 12C, I3C does not require external pull-up resistors, as the main controller on the bus provides these.

I2C uses static 7-bit and 10-bit addressing of target devices. On the other hand, I3C makes use of dynamic 7-bit addressing, where the active controller designates each target with an unambiguous address to prevent collisions with addressing. In contrast, I2C requires the designer to keep track of the current addresses to prevent assigning the same address to two or more devices. I3C assigns addresses dynamically during bus initialization.

I2C has no mechanism for a target to tell the controller that data is ready unless it uses an extra IO line. However, devices in I3C can signal an interrupt by using the serial data and serial clock lines, thereby making the protocol truly two-wire. I3C also uses this in-band signaling for implementing hot-join functionality. This allows new devices to join once the initial address assignment is over.

I2C allows multi-controller buses. Here, although multiple devices can operate as controllers, only one of them can actively communicate at a time. On the other hand, I3C can have only one active controller, while other capable devices can request to become active controllers on the bus. This device can then become the secondary controller. If the secondary controller is no longer acting as an active controller, it starts functioning as an I3C target.

I3C is backward compatible with I2C. However, for successful communication, the targets in the I2C protocol must have a 7-bit address, and must not use clock stretching. The new protocol suggests the I2C targets contain 50ns filters on their inputs. By meeting these requirements, I2C targets become compatible with the I3C bus. On the other hand, a few I3C devices may also operate as I2C targets, until they have been assigned a dynamic address. When working in the I2C mode, the I3C devices have static communication addresses.

New Graphene Sensors

While more advanced technology sectors have been late in adopting graphene, it finds plenty of interest in both lower- and high-tech applications. One of these applications is sensors based on graphene. Different industry sectors have steadily been using these sensors.

This is because graphene can be the basis of an effective sensing platform. Several interesting applications manifest this in many ways. Of these, the biosensor subsector is especially notable in attracting heavy investment. This trend is likely to continue even beyond 2022.

With graphene properties being exhaustively documented, many are now aware that they can do a lot with graphene and that many applications can benefit from its properties. Although many of these aspects are often subject to some hype, the fundamental properties of graphene make it a superior material of choice. This is primarily of account of graphene being suitable as an active sensing surface in many sensing applications.

The major advantage of graphene is its inherent thinness. This allows sensing devices made from graphene to be far more flexible and smaller in comparison to many other materials. In addition, graphene forms a very high-end active surface area.

In applications involving sensing, a high surface area is beneficial as it allows interaction with a larger range of molecules like different gases, water, biomolecules, and many other molecular stimuli. With graphene being an active surface, it is possible to attach a number of different molecular receptors and molecules to a sheet of graphene. This helps to create sensors that can detect specific molecules.

However, graphene has more advantages. Because of the high electrical conductivity of graphene, its high charge transfer properties, and high charge carrier mobility, sensors made from graphene exhibit very high sensitivity. That means, graphene sensors will generate a detectable response even from a small interaction with the environment. This happens because the excellent properties of graphene help in changing the resistivity across the graphene sheet with each small interaction. Therefore, graphene sensor help to detect even the smallest amounts of stimuli from the environment.

Because of their innate thinness, it is possible to make graphene-based sensors in small form factors, while retaining their highly sensitive sensing characteristics. It is also possible to tailor the sensors chemically for detecting a range of stimuli from the environment. This characteristic has led to the generation of much commercial interest in developing various graphene-based sensors for a variety of commercial markets involving many applications.

For instance, Paragraf has a graphene-based Hall-effect sensor that can measure changes in a magnetic field using the Hall effect. Therefore, this has increased the possibility of adding many new and interesting application areas to those that graphene sensors had not ventured into so far.

In the past year, Paragraf has demonstrated that Hall-effect sensors based on graphene are highly sensitive. They can measure currents flowing in batteries within electric vehicles for monitoring their status. Paragraf makes these sensors by depositing single layers of contamination-free graphene directly on a wafer. They repeat this following standard semiconductor manufacturing processes. This has allowed them to make several volume applications possible now, including those for fast and sensitive biosensors for detecting biomarkers within liquid samples.

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Haptic Skin Sensors

Although great technological advances are taking place to engage our eyes and ears in the virtual worlds, engaging other senses like touch is a different ballgame altogether. At City University in Hong Kong, engineers have developed a wearable, thin electronic skin called WeTac. It offers tactile feedback in AR and VR.

At present, there are several wearable devices with designs that allow users to manipulate virtual objects while receiving haptic feedback from them. However, not only are these devices heavy and big but also require tangles of wire and complex setups.

In contrast, the WeTac system is one of the neatest arrangements among all others. The engineers have made it from a rubbery hydrogel that makes it stick to the palm and on the front of the fingers. The device connects to a small battery and has a Bluetooth communications system that sits on the forearm in a 5-square-centimeter patch. The user can recharge the battery wirelessly.

The hydrogel has 32 electrodes embedded in it. The electrodes are spread out all over the palm, the thumb, and the fingers. The system sends electrical currents through these electrodes to produce tactile sensations.

According to the WeTac team, they can stimulate a specific combination of these electrodes at varying strengths. This allows them to simulate a wide range of experiences. They have demonstrated this by simulating catching a tennis ball or generating the feel of a virtual mouse moving across the hand. They claim they can ramp up the sensation to uncomfortable levels, but not to the extent of making them painful. This can give negative feedback, such as a reaction to touching a digital cactus.

According to the researchers, they can pair the system up with either augmented or virtual reality. They can thus simulate some intriguing use cases. For instance, it is possible to feel the rhythm of slicing through VR blocks in Beat Saber, or catch Pokemon while petting a Pikachu in the park in AR.

Using the WeTac system, it may be possible to control robots remotely or transmit to the human operator the tactile sensations of the robot as it grips something.

Syntouch has a new tactile sensor that performs three important functions. First, it measures the impedance using a flexible bladder placed against an array of sensing electrodes fixed in a rigid core. This arrangement helps to measure deformity, somewhat like the human finger, using its ductile skin and flesh against the rigid bone structure inside it. The finger uses its fingernails to cause bulges in the skin for detecting shear forces.

Second, the tactile sensor registers micro-vibrations using a pressure sensor that the sensor core has mounted on its inside. This enables measurements of surface texture and roughness. The fingerprints are very crucial here, as they can interact with the texture.

Third, the sensor has a thermistor. Its electrical resistance is a function of temperature. Just like the human finger can sense heat, the sensor also generates heat, while the thermistor allows it to detect how it exchanges this heat when the finger touches an object.

Precision RH&T Probe Using Chilled Mirror

The Aosong Electronic Co. Ltd, with a registered trademark ASAIR, is a leading designer and manufacturer in China of MEMS sensors. They focus on the design of sensor chips, the production of wafers, sensor modules, and system solutions. They have designed a sensor AHTT2820, which is a precision relative humidity and temperature probe.

ASAIR has based the design of AHTT2820 on the principles of a cold optical mirror. It directly measures humidity and temperature. Contrary to other methods of indirect measurements of humidity through resistance and capacitance changes, AHTT2820 uses the principles of a cold optical mirror. It can directly measure the surrounding humidity. It is an accurate, intuitive, and reliable sensor.

ASAIR uses a unique semiconductor process to treat the mirror surface of this high-precision humidity and temperature sensor. It uses platinum resistance to measure the temperature by sensing the change in the resistance due to a change in temperature. This gives the high-precision humidity and temperature sensor long-term stability, reliability, and high accuracy of measurement. The sensor features a fast response speed, a short warm-up time, and an automatic balance system.

Users can connect the sensor to their computer through a standard Modbus RTU communication system. It can record data, display the data, and chart curves. The precision RH&T probe provides direct measurement of temperature and dew point. Powered by USB, the split probe is suitable for various scenarios.

The AHTT2820 is a chilled mirror dew point meter that directly measures the dew point according to the definition of dew point. Various industries widely use it. They include food and medicine production industries, the measurement and testing industry, universities, the power electronics industry, scientific research institutes, the meteorological environment, and many others.

The probe uses its optical components to detect the thickness of frost or dew on the mirror surface. It uses the detection information for controlling the temperature of the mirror surface for maintaining a constant thickness of dew or frost. It uses a light-emitting diode to generate an incident beam of constant intensity to illuminate the mirror. On the opposite side, the probe has a photodiode for measuring the reflected intensity of the incident beam from the light-emitting diode.

The probe uses the output of the photodiode for controlling the semiconductor refrigeration stack. Depending on the output of the photodiode, the system either heats up or cools down the semiconductor refrigeration stack. This helps to maintain the condensation thickness of moisture on the surface of the mirror.

As it reaches the equilibrium point, the rate of evaporation from the mirror surface equals the rate of condensation. At this time, the platinum resistance thermometer embedded in the mirror measures the temperature of the mirror, and this represents the dew point.

Under standard atmospheric pressure, it is possible to obtain the related values of absolute humidity, relative humidity, water activity, and humid air enthalpy through calculation after measuring the ambient temperature.

The probe can measure temperatures from -40 to +80 °C, with an accuracy of ±0.1 °C. It measures humidity from 4.5 to 100%RH at 20 °C, with an accuracy of ±1%RH at <90%RH.

A Wheel-to-Leg Transformable Robot

With the general audience preferring to engage in the search for anthropomorphization, the popularity of biped and quadruped robots has been growing. At the Worcester Polytechnic Institute, researchers have innovated a robotic system that they call the OmniWheg—a robotic system that adapts its configuration based on the surrounding environment that it is navigating. They introduced this robot in a paper in the IEEE IROS 2022, and pre-published it on arVix. OmniWheg has its origins in an updated version of whegs, which was a mechanism with a design to transform the wings or wheels of a robot into legs.

Although the researchers would have liked to make the robot capable of going everywhere they go, they found the cost of legs to be very high. While evolution has provided humans and animals with legs, the researchers found that a robot with legs would be highly energy inefficient. While legs could make the robot more human or animal-like, they would not be able to complete tasks quickly and efficiently. Therefore, rather than develop a robot with a single mechanism for locomotion, the team proceeded to create a system that switched between various mechanisms.

The team found that about 95% of the environments at homes and workplaces are flat, while the rest are uneven terrains that require transitioning. Therefore, they went on to develop a robot that performs with a high-efficiency wheel-like arrangement for 95% of the cases, specifically transforming to the lower-efficiency mechanism for the remaining 5%.

The researchers, therefore, created a wheel that changed its configuration for climbing stairs or for circumventing small obstacles. For this, they utilized the concept of whegs,  wing-legs, or wheel-legs, which is popular in the field of robotics.

In the past few years, the team developed and tested several wheel-leg systems. However, most of them were not successful, as the left and right sides of the wheel-leg system would not coordinate well or align properly when the robot tried climbing stairs.

Finally, the team could solve the coordination issues by using an omnidirectional wheel. This enabled the robot to align on-the-fly, but without rotating its body. Therefore, the robot can move forward, backward, and sideways at high efficiency, and remain in a stable position without expending any energy. At the same time, the robot can also climb stairs swiftly, when necessary.

For correct operation, the wheg system that the team developed requires a servo motor to be added to each wheel and operated with a simple algorithm. As the design is straightforward and basic, any other team can easily replicate it.

According to the researchers, the system has abundant advantages with very few drawbacks. The team feels it can pose a threat to the legged robots, and any robotic application can adopt this design.

The team has evaluated their OmniWheg robot system on a multitude of real-world indoor scenarios. This includes climbing steps of various heights, circumventing obstacles, and moving/turning omnidirectionally. They found the results to be highly promising, and the wheel-leg robot could successfully navigate the common obstacles quite flexibly and efficiently.

Micro 3D Printing for Miniaturization

Engineers have been using additive manufacturing for prototyping for about 30 years now and are also using it for production. However, the biggest value addition from additive manufacturing comes from producing parts that other traditional manufacturing methods find difficult.

Fabricators use additive manufacturing as a valuable and important solution for producing parts such as those including complex design features like internal geometries and cavities that are impossible to achieve by regular machining. Additive manufacturing is helpful in producing structural elements that are too cumbersome or difficult to generate effectively by conventional means.

At present, engineers use 3D printers for printing large parts quickly. These parts may have resolutions around 50 µm and tolerances around 100 µm. However, sometimes, they also need to produce parts with sub-micron resolutions that are smaller than 5 um. Therefore, they needed a system for printing micro-sized parts at a reasonably high print speed.

Smaller parts require a more precise production process. For instance, cell phones and tablets, microfluidic devices for medical pumps, cardiovascular stents, MEMS, industrial sensors, and edge technology components require connectors with high resolution and accuracy. Most standard additive manufacturing machines cannot provide the resolution necessary for micro-sized parts.

BMF or Boston Micro Fabrication designs and manufactures the PµSL or Projection Micro Stereolithography technology-based printers. Using PµSL printers, it is possible to create 3D printed parts with 2 µm resolution at ±10 um scales. These 3D printers incorporate the benefits of both the SLA or stereolithography technologies and the DLP or digital light processing technologies.

Using a flash of ultraviolet light at microscale resolutions, these PµSL printers cause a rapid photopolymerization of an entire layer of resin. This takes place at ultra-high precision, accuracy, and resolution, not possible to achieve with other technologies.

For faster processing, the PµSL technology supports continuous exposure. Other design elements allow additional benefits to the user. For instance, in printers using the standard SLA technology, the bottom-up build method requires a support structure to hold the part to the base, while also supporting the overhanging structures. Conventional SLA systems can typically achieve resolutions of 50 µm, an overall tolerance of ±100 µm, and a minimum feature size of 150 µm. Similarly, standard DLP systems using a similar bottom-up build structure offer 25-50 µm resolution, an overall tolerance of ±75 µm, and a minimum feature size of 50-100 µm.

On the other hand, the PµSL uses a top-down build, thereby minimizing the need for a support structure. It also provides a way to reduce damage while removing bubbles with a transparent membrane. Comparatively, PµSL systems offer resolution down to 2 µm, dimensional tolerances as high as ±10 µm, and minimum feature sizes of 10 µm.

BMF provides this type of quality by properly employing every system component. This includes the resolution of the optics, controlling the exposure and resulting curing, the precision of mechanical components, and the interaction between parts and required support structures. It also depends on the ability to control tolerances across the build and the overall size of the part. Moreover, working with such diverse micro parts requires choosing the right material characteristics.

Standard Connectors for EV Charging

With EVs or electric vehicles becoming a trend for both individuals and commercial operations, more people are opting for them for commuting to work, school, and moving around the town. While there are tax benefits to using EVs, they also reduce our dependence on fossil fuels. Moreover, with the maturing of battery technologies, EV performance is comparable to those of vehicles with traditional internal combustion engines.

With the increasing number of EVs in use, their fundamental and foremost requirement is charging the battery. This aspect has led to a spurt in the growth of electric vehicle charging stations. Manufacturers of electric vehicles produce a range of vehicles that they base on their specific design specifications. However, charging devices need a uniform design so that any make or model of an electric vehicle can hook up for charging. At present, there are two categories of electric vehicle chargers—Level 1 and Level 2.

Level 1 chargers are available with the vehicle. They have adapters that the user can plug into a standard mains 120-Volt outlet. Manufacturers make these chargers common for use in home charging outlets.

Level 2 chargers are standalone types and separate from electric vehicles. They have adapters to plug into a 240-Volt outlet. These chargers are typically available in offices, parking garages, grocery stations, and other such locations. Homeowners may also purchase Level 2 chargers separately.

To allow any model or make of EV to connect to any Level 2 chargers, it is necessary for both the EV and the charger to use a standard connector. At present, the standard charger connector for Level 2 chargers is the SAR J1772. All the latest electric vehicles using plug-in charging use the standard SAE J1772 plug, while the charger connectors use the standard SAE J1772 adapters. These are also known as J plugs. J1772_201710 is the most current revision for the J plug specifications.

While SAE was originally an acronym for the Society of Automobile Engineers, presently they are known as SAE International. They often come up with recommended practices that the entire automobile industry accepts as standards. With the use of the standard SAE J1772 plugs, a customer purchasing an electric vehicle from any manufacturer can charge it using the same charging connector. Public electric charging stations also use the SAE J1772 chargers, and these are compatible with plugs in most vehicles from different manufacturers.

Each SAE J1772 charger has a standard coupler control system consisting of AC and DC residual current detectors, an off-board AC to DC high power stage, an auxiliary power stage, an isolation monitor unit, a two-way communication system over a single wire, contactors, relays, service and user interface, and an energy metering unit. Charging stations with J1772 connectors use a cable for charging the electric vehicle, and the rating of this cable is EVJE for 300 Volts or EVE for 600 Volts.

The EVJE/EVE cable consists of a thermoplastic elastomer jacket and insulation around a center conductor made of copper. The cable usually has two conductors of 18 AWG wire, one conductor of 10 AWG, and another conductor of 16 AWG.

Using Ferrites in Wire Assemblies

The phenomenon of magnetism is prevalent all over the world, along with related concepts like the magnetic field, electromagnetism, and electromotive force. Although these are complex subjects at a higher level, they are easy to understand. However, these are principles on which electric motors operate, the earth’s magnetosphere shields life, and refrigerator doors remain closed.

The wonderful properties of magnetism also help products and applications like cable assemblies. There are well-known magnets like those made of neodymium, and these are permanent magnets with inherent magnetic properties. They comprise elements of Neodymium, Boron, and Iron. Neodymium magnets are among the most powerful permanent magnet types available. In comparison, there are non-permanent magnets also. Typically known as electromagnets, they derive their properties from the passage of an electrical current.

Other types of permanent magnets are also available. The most popular of these is the ferrite magnets, and industries use them for a lesser-known reason. Used in various forms like chokes, cores, and beads, these inexpensive devices greatly help filter electrical noise and get products to comply with EMI/EMC regulations. Countless design applications use them in different form factors and are available from numerous manufacturers. Ferrite magnets comprise a mixture of iron oxide and ceramic magnets. In doughnut-like shapes, they keep control over signal integrity within bundles of wire. For instance, a data cable carrying high-frequency data transmission,  when routed through the magnetic field of a ferrite, can eliminate unwanted electrical noise, as the ferrite acts as a passive EMI filter.

For a ferrite to be effective, the cable must pass through the center of the ferrite and its magnetic field. Looping and routing the wire multiple times through the ferrite helps incrementally improve the signal integrity. While a majority of cables have their wires passing through the ferrites only once, some designs require them to make as many as three loops to meet design objectives. Typically, there are two types of ferrites available that are suitable for cable assemblies—snap-on ferrites and doughnut ferrites.

Snap-on ferrites are the easiest to assemble. These are passive suppression devices with two halves. A plastic clamshell case holds the two halves as it snaps close around the wire. Available in a wide variety of sizes for different cable diameters and performance types, these are excellent devices that can mix and match various types of ferrite to help pass an aggressive test requirement. However, snap-on ferrites can be expensive and require accurate sizing to match the wire’s outer diameter to create an interference fit. As their design is like a clamshell, it is easy to remove snap-on ferrites.

Doughnut ferrites are simpler, being in the shape of a ring or a doughnut. The cable must pass through the center of the continuous circle of the ferrite before the wires terminate into a connector. The doughnut ferrite is therefore a permanent fixture, unlike the snap-on ferrite that the user can remove at any time. Overmolding the ferrite helps to fix its position on the cable while protecting the brittle ferrite magnet from damage.

Switches & Latches Based on Hall Effect

Switches and latches based on the Hall effect compare magnetic fields. More correctly, they compare the B-field, or the magnetic flux density with a pre-specified threshold, giving out the comparison result as a single-bit digital value. It is possible to have four categories of digital or on/off Hall sensors—unipolar switches, omnipolar switches, bipolar switches, and latches.

Each of the above switches/latches has a unique transfer function. However, this depends on an important concept—the polarity of the magnetic flux density. The polarity of the B-field makes the Hall effect devices directional. Moreover, it is sensitive only to that component of the magnetic flux density that happens to be along its sensitivity axis.

When a component of the magnetic field applied to a device is in the direction of its sensitivity axis, the magnetic flux density is positive. However, if the component is in the opposite direction of the sensitivity axis, the polarity of the -field is negative at the sensor.

Hall sensor manufacturers follow another convention for the B-field polarity. They consider the magnetic field from the south pole of a magnet as positive, while that from the north pole, as negative. They base their assumption on the branded face of the sensor facing the magnet. The branded face of the Hall sensor is the front surface bearing the device part number.

Therefore, for a sensor with a SOT23 package, the sensitivity axis is perpendicular to the PCB. Whereas for a sensor with a TO-92 package, the sensitivity axis will be parallel to the PCB, provided the sensor is upright after soldering.

A unipolar switch has its thresholds in the positive region of the B-field axis. Its output state changes only when the south pole of a magnet comes near it. Bringing the north pole or a negative field close to the sensor produces no effect, hence the name unipolar.

When the sensor is off, its output is logic high. Gradually bringing a south-pole closer to the sensor causes the device to switch to a logic low as the magnetic field crosses its threshold. The opposite happens when the south pole gradually moves away from the sensor. However, as the threshold of switching for a decreasing magnetic field is different from the threshold of switching for an increasing magnetic field, the device shows a hysteresis effect. Manufacturers create this hysteresis deliberately to allow the sensor to avoid jitter.

An omnipolar switch responds to both—a strong positive field and a strong negative field. As soon as the magnitude of the magnetic field crosses the sensor’s threshold, it changes state. With omnipolar switches, the magnitude of the operating point is the same irrespective of the polarity of the B-field. However, the magnitude of the release point is different from the operating point, but the same for both polarities. Hence, the omnipolar switch also has a hysteresis effect.

A latch device turns on by an adequately large positive field but turns off only by an adequately large negative field. A bipolar switch behaves as a latch device, but its exact threshold values may change from device to device.