Monthly Archives: November 2023

All about Thermoelectrics

TECs or Thermoelectric coolers or Peltier coolers are typically made from semiconductor materials exhibiting good electrical conductivity and thermal insulation. One such material is Bismuth Telluride. It offers the best performance of the above properties at room temperature environments. The development of ceramic-based substrates along with advanced semiconductor processing in the 1960s made thermoelectric devices available in commercial quantities.

TECs are solid-state devices that pump heat from a hot region to a colder region. For this to function properly, a heat transfer mechanism is necessary, a sort of heat exchanger that can absorb and dissipate the heat. TECs typically require DC voltages to operate. When power is applied, current flows through the cooler, carrying electrons from one side of the ceramic to the other. This results in one side of the substrate cooling down, while the other remains hot.

With a standard single-stage TEC, it is possible to achieve a temperature differential of nearly 70 °C at room temperature. That means the temperature difference between the two sides of the TEC can reach a maximum of 70 °C. With more advanced materials, TECs can reach temperature differentials of 74 °C.

Compared to alternate cooling technologies, TECs offer several advantages. One of them is their compact form factor, making them ideal for applications involving low heat loads. As there are no moving parts, TECs operate for extended periods with almost no maintenance necessary.

While cooling with thermoelectric coolers, it is possible to reach temperatures well below the freezing point of water. For instance, with multistage coolers, it is possible to reach temperatures below -90 °C. One major advantage of TECs is their ability to reverse their polarity by reversing the direction of current flow. This property is very useful in enabling thermal cycling, resulting in precise control of temperature, up to ±0.01 °C, maintained under steady-state conditions.

TECs are very efficient for heating purposes as well. In fact, they are more effective compared to conventional resistive heaters. This is because the heat generated by TECs is from the input power in addition to the heat it pumps in from the cold side. As TECs do not emit any HCFCs, they are environmentally friendly.

Depending on their rated capacity, the footprint of a typical TEC can range from 2 x 2 mm to up to 62 x 62 mm. This makes thermoelectric coolers ideal for operating in tight geometric spaces such as in telecom, industrial, analytical, and medical applications. Compared to conventional technologies such as compressor-based systems, TECs are miniscule.

Applications that handle low heat loads, less than 400 W, and those requiring cooling below ambient temperatures are typical applications benefitting from TECs. Where the control temperature is near ambient, passive heat exchanger solutions utilizing a heat sink and a fan may be adequate. Design engineers typically use TECs when their design criteria include such factors as high reliability, precise temperature control, compact form factor, minimal global warming potentials, and low weight requirements. TECs are ideal for various medical, telecom, analytical, and industrial applications that require active cooling.

Hall Effect Sensors for Position Selection

User systems often require the detection of position for operating in a specific switch mode. Such type of On or Off functionality is a straightforward requirement and many devices implement it with Hall-effect switches, including power tools, light switches, safety harnesses, and laptop lids.

The output of the sensor toggles its state as soon as the input magnetic field crosses the operating threshold. Likewise, the output reverts to the idle state when the magnitude of the magnetic field reduces below the release threshold. Hysteresis built into the device prevents the output from toggling rapidly where the magnitude of the magnetic field is close to the operating threshold.

Many applications use this functionality. For typical cases, two output states are adequate, thereby helping to reduce mechanical wear and preventing interference from grease and dust.

Although two positions may be adequate for detection in many applications, others require the detection of additional states. For instance, a tool may require a three-position power switch, denoting Off, Low, and High power modes. Detecting all three states is difficult using a single sensor. Initially, it may seem possible by adding a sensor for every switch position in the system.

A unipolar switch is well-suited for such an application. The designer places the magnet very close—so the air gap is small—thereby ensuring the pole of the magnet facing the sensor will always exceed the worst-case operating point. When the magnet is above the sensor, it results in an upwardly directed field vector. When the magnet has traveled greater than its own width, the sensor will not activate, as the direction of the field is now downwardly directed. Therefore, there can be an array of sensors representing any number of positions, provided the sensor spacing exceeds the full width of the magnet.

While the above arrangement is convenient for a low number of positions, the number of components required gets more difficult to manage as the number of positions increases. For such arrangements, dual-unipolar switches are more convenient.

Texas Instruments offers a dual-unipolar switch, DRV5032DU. It has two independently operating outputs. Each output is sensitive to an opposite polarity of the magnetic field. Where one sensor responds as it nears a North pole, the other will respond as it nears a South pole. This functionality allows the detection of three positions with a single magnet.

With the magnet mid-way between the two sensors, there is no component of the magnetic field available to activate the sensors, and therefore, both sensors remain deactivated. When the magnet moves to the left, it activates the N pole-sensitive output. Likewise, when the magnet moves to the right, the S pole-sensitive output activates. However, for this arrangement to function correctly, the magnet must have a length two times the distance of travel between the switch positions. When the magnet moves by one-half its length, one of its poles is directly above the sensor, thereby activating it.

Extending this format makes it possible to sense more than three positions. It requires an array of sensors spaced appropriately for creating additional unique positions.

Matter and Simplicity Studio

So far, home automation has always meant selecting an appropriate ecosystem. Well, that is a thing of the past now, as all IoT or Internet of Things devices can intercommunicate with this new, open-source protocol. Now designers can develop small demo applications that are Matter-compatible, and they can use the new Matter Development board, the SparkFun Thing Plus, and the Simplicity Studio IDE from the Silicon Labs.

Until now, multiple communication protocols have kept IoT devices a rather scattered lot. Developers and consumers were forced to decide how to make their devices communicate and lock them into that environment. With the introduction of Matter, however, those are days of the past, as Matter is a unified, open-source application-layer connectivity standard. Apart from increasing the connectivity among connected home devices, Matter allows the building of reliable and secure ecosystems.

In 2019, major and competing players such as Zigbee Alliance, Google, Apple, Amazon, and a host of other companies such as Nordic Semiconductors got together to develop a single communication protocol. Their aim was to unify the entire world of the Internet of Things. The result was Matter, a royalty-free, open-source protocol that allows devices to communicate over Thread, Bluetooth Low Energy, and Wi-Fi networks. Therefore, Matter-certified devices can communicate with each other regardless of the wireless technology they use, and do so seamlessly.

Now, there is no need for consumers, manufacturers, and developers to have to choose between Google’s Weave, Amazon’s Alexa, or Apple’s Homekit components. While for consumers, this represents increased compatibility, for manufacturers, it means simplified development.

The major benefit of Matter is it simplifies the management and setup of smart home devices. End-users can now set up their smart home systems easily and quickly, using Matter-certified devices. They will not need any technical skills or specialized knowledge. With the protocol supporting end-to-end encryption, safety is in-built, ensuring secure data transmission between devices.

However, this does not mean designers have been relegated to the role of consumers. The Sparkfun Thing Plus Matter Development Board from Sparkfun Electronics combines Matter and the Sparkfun Qwiic ecosystem, thereby providing an agile development and prototyping arrangement for designers of Matter-based IoT devices.

Silicon Labs offers its MGM240P wireless module for a secure 802.15.4 connectivity for both Bluetooth Low Energy 5.3 and Mesh (Thread) protocols. This module is available and ready for integration into the Matter IoT protocol for home automation. Moreover, the Thing Plus development boards are compatible with Feather, and include a Qwiic connector, thereby allowing easy integration for solderless I2C circuits.

Designers can download the latest Simplicity Studio from the Silicon Labs website, for the specific operating system they are using. It may be necessary to create an account for the download. After installing and running Simplicity Studio for the first time, the Installation Manager will come up, and search for any updates available. After updating, the Simplicity Studio will operate as the latest version.

In the next step, the Installation Manager will ask to install the devices by either connecting them or by defining the technology they use. The Installation Manager may want to install additional required packages before proceeding.

Happy Thanksgiving!

To allow our hard-working office staff the ability to spend time with their families during Thanksgiving week, we are closing our office from Monday, November 20 – Friday, November 24. During this time, we will still be shipping orders but phones will not be answered and emails will not be responded to until Monday, November 27th.

We eagerly anticipate serving you again when we reopen on Monday morning, November 27, ready to assist with your electronic component needs. Wishing you a joyous and peaceful Thanksgiving!

West Florida Components Thanksgiving week office hours

Difference Between Power and RF Inductors

In many electronic designs, we have components that consist of only several turns of a wire, with or without a core. These components are inductors. It is customary to find them in many types of electronic devices, including voltage and power conversion circuits to high-frequency microwave and RF circuits. Typically, inductors resist any change in the current flowing through them, by producing an electromagnetic field.

Available in a variety of package styles depending on their current ratings, inductors are essential components in electronic designs. They function as filters, chokes, and impedance-matching functions. For a practical application, it is essential to understand the important performance parameters of inductors.

Any inductor, whether used for power or RF applications, has the same performance parameters. These include the inductance value, its tolerance, current rating, its DC resistance, SRF or self-resonant frequency, Q or quality factor, and temperature range. However, specific applications may stress more on some of these performance parameters as they have more relevance for that application. For instance, an application involving RF frequencies may give more importance to Q and SRF parameters rather than to the current rating, which is more important for power applications.

The size of an inductor—how big or how small it can be—is usually dependent on the inductance value, its current carrying capacity, and acceptable losses. These are critical parameters when selecting inductors. Selecting an inductor usually begins with the inductance value, typically in nH or in mH, and depends on its function in the circuit. Associated with the nominal inductance value is its tolerance, in %, characterizing the amount of variation of the inductance value, and is determined by the application.

For instance, RF applications typically require inductances closely matched by precise inductance values, and with tight tolerances, such as ±2%. On the other hand, power applications may use inductors with inductance values within a larger band, and with wider tolerances, such as ±20%.

Another important parameter for inductors is their ability to handle current, which can vary greatly by application. This is specifically true for inductors in power circuits such as DC-DC converters, where the current values can change widely, with very high peak-to-average current ratios. Inductors selected on the basis of the application’s highest instantaneous current value may provide an inductor much larger than necessary. On the other hand, selecting an inductor based on the average current value in the circuit may lead to a small inductor resulting in inconsistent performance during peak current deliveries.

The quality of an inductor has more relevance in RF circuits than it has for power applications. Quality or the Q factor is a dimensionless parameter that characterizes the inductor’s bandwidth relative to its center frequency. High Q values are typically matched to narrow bandwidths and low losses, more critical in RF applications.

For power applications, the losses in inductors are more important. Here, the DC losses, characterized by the resistance of the wire, are rather more relevant. Therefore, inductors for power applications tend to be made of wires with larger diameters, so as to increase the area for current travel and thereby reduce the resistance.

Difference Between Chokes and Inductors

Industries typically use chokes and inductors for altering, filtering, and delivering electrical current. However, for using these devices effectively for machinery and devices that rely on electrical power, it is essential to understand the difference between chokes and inductors, as the design of these electrical components must meet specific applications’ requirements.

Despite a choke being a type of inductor, it has a design, functionality, and application that sets it apart from other inductor designs. Physically, this electrical component looks like a donut-shaped core and has an insulated wire wrapped around it.

As its name implies, primarily, a choke restricts or cuts off high-frequency components from alternating currents flowing through it. It allows only low-frequency currents, including direct currents to pass through. Therefore, a choke eliminates most of the high-frequency currents and allows only low-frequency and DC currents to pass through to the load.

Another function of the choke is its ability to restrict a steep rise and fall of current and voltage in circuits. A fast rise in voltage can damage insulation. Conversely, a choke can also generate high voltages such as those necessary to strike an arc for starting fluorescent tubes.

On the other hand, inductors primarily store electrical energy as a magnetic field when current passes through them. For this purpose, inductors typically have a magnetic core wrapped with an insulated coil. Therefore, all chokes are inductors, but the reverse is not true—not all inductors are chokes. Many technologies use inductors for various functions.

For instance, inductors are necessary to filter a band of frequencies by increasing the impedance for these frequencies. Inductors also act as proximity sensors without making physical contact, as the magnetic fields of the inductor and the object can interact. Multiple inductors, using the same magnetic field, constitute a transformer that can effectively transform, or step-up or step-down voltages. Inductors typically arranged circularly around a motor shaft, can interact with other stationary inductors to provide the torque necessary to rotate the motor shaft. Switching power supplies use inductors to temporarily store and supply electrical energy in and from their magnetic fields.

An inductor has a much wider functionality as compared to a choke. For instance, an inductor acts as a choke when filtering high-frequency signals. While the choke’s primary function is to remove high-frequency signals and allow low-frequencies and DC signals to pass through, the primary function of an inductor is to store energy in its magnetic field.

In RF circuits, a choke typically protects against the ingress of high-frequency signals, assuring operational stability. On the other hand, an inductor, in parallel or in series with a capacitor can act as a tuned circuit. Such tuned circuits allow the RF circuit to oscillate at a specific band of frequencies as determined by the inductor and capacitor combination.

Both chokes and inductors are critical in circuits that must conform to EMI/EMC or electromagnetic interference and compatibility standards. They block the generation and reception of unwanted signal frequencies in equipment. They prevent the electromagnetic spectrum of the device from increasing beyond a specified level as directed by the standards.

Gate-Drive and Isolation Transformers

Controlling the current flow between the drain and the source of a MOSFET requires the application of a drive voltage to the gate of the MOSFET. Switching power supplies operate the MOSFET as a current switch by applying a pulsed voltage drive to the gate for turning the drain-source current on and off. Delivering the controlling pulse requires a gate drive transformer to provide isolation between the controlling drive circuit and the MOSFET. Companies like Coilcraft offer off-the-shelf gate drive transformers for the purpose.

Gate drive circuits must provide an isolated or floating bias supply for maintaining the necessary turn-on bias when the MOSFET source rises to the input voltage. While driving the MOSFET gate, not only does the gate drive transformer help in isolating the controlling gate drive circuit from the switch node, it may also scale the output voltage via a suitable turns-ratio between its primary and secondary.

Some applications use optocouplers or digital isolators for driving the MOSFET directly. However, the use of a gate drive transformer is preferable, as it can provide a higher voltage requirement, much lower turn-on and turn-off delay times, and it can scale voltages by the ratio of its turns. These advantages make the simple gate driver transformer the best-performing solution for high-frequency and high-voltage applications that require maintaining accurate and fast signal timing.

Typical low-power applications use a simple single-output, transformer-coupled, high-side gate driver circuit. Additional components like capacitors, resistors, and diodes may be necessary depending on the duty cycle and other circuit conditions. These include preventing the development of a DC voltage across the transformer, as this may cause it to saturate. The additional components also help in the coupling capacitance and magnetizing inductance from resonating with specific duty cycle ratios. For single-ended circuits, the highest duty cycle is preferably 0.5.

Higher power applications may require half-bridge and full-bridge configurations coupled with transformers. Double-ended or DC-coupled bridge configurations may use a theoretical maximum duty cycle of 1.0. Designers use isolation transformers for isolation and voltage scaling in power supply applications. These serve three main purposes.

First, the transformer helps to connect circuits with grounds at different potentials—this prevents ground loop formation. Second, the transformer provides galvanic isolation, thereby preventing any flow of direct current. Lastly, the transformer provides voltage transformation—stepping up or stepping down from one voltage to another.

Isolation transformers may be available as signal transformers, power-supply transformers, communication transformers, data-line transformers, and many others. These are versatile and aptly suited for several industrial and commercial data communications and power supply applications.

Using off-the-shelf gate drive and isolation transformers can simplify the design of the gate drive circuit and significantly reduce the design cycle time. Coilcraft transformers typically use high-permeability ferrite cores for maximizing the inductance and minimizing the magnetizing current.

The designer can determine the required transformer size by the volt-time product of the application. This forms the first selection criterion for a gate drive transformer, as the designer can select the appropriate volt-time or V-µsec rating from the datasheet of the transformer. The rating must be equal to or greater than the highest applicable voltage-time product 

Modern RTD-Based Sensors

The popular belief is to not fix things that aren’t broken. The idea is to not tamper with something performing reliably and proving its worth. This advice aptly applies to circuit designs using RTD sensors that efficiently and quietly measure temperature in industrial manufacturing facilities worldwide.

However, in meeting the requirements of Industry 4.0, where smart factories are the norm, it is now evident that the current RTD sensors in use are not fitting the purpose. Automation engineers today want industrial temperature sensors to be of smaller form factors, flexible with communications, and capable of remote reconfigurability. Incumbent solutions, sadly, are unable to support them. However, it is possible to easily redesign these sensors to equip them with the necessary features to meet the new industrial design.

The RTD industrial temperature sensor translates temperature, a physical quantity, into an electrical signal. The typical range of such sensors is between -200 °C and +850 °C, with a highly linear response across it. RTDs commonly use metal elements like copper, nickel, and platinum. Among these, PT1000 and PT100 platinum RTDs are the most popular. While an RTD can use either two, three, or four wires, the 3-wire and 4-wire versions are the most popular. Being passive devices, RTDs require an excitation current for producing an output voltage. A voltage reference generates this current, with an operational amplifier acting as a buffer for driving the current into the RTD, which produces an output voltage signal varying in response to changes in temperature. The voltage signal may vary from tens to hundreds of millivolts depending on the type of RTD in use and the measured temperature.

An AFE or Analog Front End conditions and amplifies the low amplitude voltage signal from the RTD before the ADC or Analog to Digital converter digitizes it. A microcontroller runs an algorithm over the digitized signal, compensating for any non-linearity in it. The microcontroller then sends the processed digital output to a communications interface for transmission to a process controller. A typical implementation of the AFE is by a signal chain of components with each performing a dedicated function.

This discrete approach requires a large PCB or printed circuit board for accommodating all the ICs and power and signal routing, setting a minimum size for the sensor enclosure. Rather, modern RTD-based sensors use a superior and more minimal approach—the AD7124-4, an integrated AFE.

The AD7124-4 is a compact IC in a single package. It includes a multiplexer for accommodating multiple-wire RTDs, a voltage reference, a programmable gain amplifier, and an ADC using the sigma-delta operating principles. The IC has the capability to provide the necessary excitation currents for the RTD. The entire arrangement effectively replaces five of the signal-chain components from the traditional setup. Not only does this significantly reduce the amount of board space necessary, but it also enables the sensor to use a much smaller enclosure.

Next comes the communications interface. Modern RTD-based sensors typically use the IO-Link which eliminates the use of expensive ASICs for implementing specific network protocols. IO-Link is a 3-wire industrial communications standard for linking sensors and actuators with all industrial control networks.

Software Defined Electric Vehicles

Around the world, SDVs or software-defined vehicles are one of the two trends driving the design of new vehicles, the other being EVs or electric vehicles. As a result, vehicle design is undergoing a major transformation. From features and capabilities that were so far defined by hardware, they are now changing over to those being defined by software. This opens up newer opportunities resulting in agile developments, fast and continual improvements, and remote maintenance.

SDVs are ushering in a new approach to the development of vehicles. In turn, that is enabling improvements in the vehicle over time, based on in-depth access to the vehicular data in real time. Cloud processing and machine-learning training is leading to updates over the air for improving the software and related machine-learning models. Along with this continuous deployment and integration, engineers are able to use model-based design tools more effectively for improving and developing software algorithms that, in turn, help to run the vehicles more efficiently.

As a result, carmakers over the world are investing hugely in vehicle electrification for helping to reduce greenhouse gases. They are offering their customers vehicles with acceptable driving ranges along with easy access to charging stations. Many are committing to transitioning their fleets from ICE or internal combustion engines to EVs over the next decades. This is resulting in the swift deployment of EVs. Furthermore, the effect of this shift to a more software-centric and electric future is bringing newer challenges to the automobile industry.

The major beneficiary of this change is the EV motor. With the industry moving to the SDV approach, there is faster access to vehicular data that can monitor the aging and performance of the EV motor. Powerful automotive microcontrollers now support newer features over time, while the deployment of software upgrades is available through wireless updates. This makes the software-defined EV motor a dynamic product that keeps evolving and improving over time. It takes advantage of in-vehicle data in real-time, supporting cloud development along with enhancing features.

Changing over to a software-defined EV motor design affects all the stages of development of the control systems of the EV motor. Not only does this enable faster cycles of development, but also helps enhance the performance, while monitoring for maintenance needs, thereby extending the system’s lifetime.

High-level modeling tools are the trend in motor control design. Designers use modeling tools like Simulink and MATLAB for concentrating on using their key expertise in controlling the EV motor and systems, rather than on programming. This is because modeling tools operate at the algorithm level, where the designers can optimize them to improve vehicular performance and efficiency.

Using modeling tools results in three significant advantages—flexibility, safety, and speed. Designers use modeling tools to test algorithms and quickly analyze software, rather than depend on evaluation through hardware integration. Not only does this bring in flexibility, but also speed when designing the control module of EV motors. For designers, developing at the algorithm level is especially useful when developing strategies for the smooth control of a motor.