Monthly Archives: April 2022

Illuminating Automotive Displays

In recent years, there has been a substantial improvement in automotive displays. Automotive manufacturers now integrate these displays in various applications within the automobile, such as in mirror replacements, central information displays or CIDs, instrument clusters, entertainment displays for the rear seats, and many more. Sometimes, such displays can total up to twelve per vehicle.

Most of these displays use thin-film transistor or TFT driving liquid crystal displays or LCD for enhanced brightness and reliability at reasonable costs. However, there is an increasing need for better picture quality, as the display must also handle real-time video feed from cameras. In addition, an increase in display size is necessary due to the merging of CID and instrument clusters. With these requirements, the displays consume more power, and often, the timing controller or internal power supply source drivers cannot provide this. Therefore, there is a need for a suitable power supply that can handle these high-quality automotive displays.

Although many solutions exist for such TFT-Bias power supply devices, the display panel options are highly variable, and most have an expanded set of feature requirements. This leads to power supply designers considering a few needs for TFT-LCD display systems—high-quality display, source driving, functional safety, EMI mitigation, fast turn-on time, and low total solution cost.

Manufacturers use several TFT technologies for display panel solutions. However, each of them has its own set of benefits, needs, and limitations. For instance, two very common TFT technologies are the Low-Temperature Polysilicon LTPS and the Amorphous Silicon or A-SI panels. While driving an A-Si panel requires a unipolar source driver, the LTPS panels typically require a bipolar source driver.

Manufacturers bond unipolar A-Si source drivers to the edges of the display panel. Multiple digital to analog converters—one for each display column—drive the sources of the TFTs. Depending on the received video signal, the output voltage of the DACs varies, thereby setting the transmissivity of the LC panels. With the common rail for the display backplane set at approximately half the supply voltage, the source driver voltage is free to alternate between zero and full supply voltage.

Using LTPS technology, manufacturers can implement all the necessary circuits, including the bipolar LTPS source driver, directly on the glass of the display panel. This precludes the requirement of a storage capacitor in parallel with the subpixels, The higher carrier mobility in the transistors leads to higher performance in LTPS panels, and subsequently to advanced features.

Optimal display panel performance differentiates the high display quality necessary and requires support from consistent pixel response. However, imperfections in materials and processes often lead to deviations in parameter performance in physical manifestations of display solutions. These imperfections change the electrical characteristics of materials, which the design must account for while stabilizing the performance of the end product. This requires calibration methods where the voltage of the common rail is set.

The common rail voltage must also be compensated for temperature variations. This is because panel characteristics change over temperature, and the common rail voltage must also adjust for the display panel functionality to remain consistent.

Retail Energy Management through IoT

Most people prefer to visit big stores like Walmart and Costco for buying almost everything from iPhones to ice-creams. But running huge stores is not an easy task, and the superstores are always on the lookout for ways to cut costs by streamlining their operations.

With superstores the size of a city block, streamlining operations is not simple. Substantial resources—time and staff—are necessary to keep store lighting, food court ovens, HVAC systems, and digital displays running at maximum efficiency.

The stores may have hundreds of freezers and refrigeration units operating at the same time. Constantly monitoring them for meeting government regulations, while manually adjusting them, can lead to food safety compromises. A breakdown can halt services and food sales, slashing profits and irritating customers. While the retail sector increasingly adopts sophisticated digital solutions, its inefficient management of energy systems can become an anomaly.

With the recent pandemic causing a worldwide worker shortage and subsequent rise in labor costs, retailers would rather not add people for tracking and monitoring their back-end facility.

Traditional energy management systems available on the market operate in two ways. First, system integrators must build from scratch a software program for managing energy consumption to make the effort feasible, but this is too resource-intensive. The other may require purchasing an off-the-shelf system for building management—such as those that office towers and apartment buildings use. But these systems are usually not customizable, and they do not accommodate retailers. This is where a new platform has become necessary.

IBASE and Novakon have created a new platform for managing energy. They have designed the IBASE platform specifically for retailers. The platform, IBASE IoT Energy Management Platform, can monitor and manage refrigerators, freezers, air conditioning, kiosk signs, food court appliances, and lighting. The IoT system connects everything to the Internet, which allows tracking, monitoring, and controlling them possible in real-time.

Therefore, retailers no longer need a staffer to tend to freezers and refrigerators. Instead, they can concentrate on their own activities. The system does the tracking and data recording from multiple sensors that transmit new information all the time.

The new platform allows retailers to review the status of not only the refrigeration system but also the power that all connected devices and appliances consume. Anything going wrong brings up an immediate alert. The same alert also reaches the servicing company, so they can take up repair and maintenance immediately.

Moreover, the IBASE platform also has the capability to automatically turn HVAC and lighting on and off in synchronization with business hours. Retailers can tweak the system to match their special requirements to further save energy and money. Utility companies often offer discounts to businesses that can keep their power consumption below a certain threshold.

The IBASE platform is a real boon for large retailers—they can really save big on resources and energy. For instance, in a retail operation with 250 lighting devices, 36 air conditioners, and 22 power meters, staffers had to monitor each floor with notebooks, noting down appliance information every hour. The IBASE platform has transformed this.

Sensors for Structural Health Monitoring

Public bridges and roads require their structural health to be monitored, and engineers use sensors for continuous measurement. To power these embedded sensors, they exploit several sources of ambient energy. This can include vibrational energy obtained from vehicular traffic, which can generate adequate power for sensor nodes that engineers have built into the infrastructure. Off-the-shelf devices make it easier for engineers to design structural monitoring devices. Many manufacturers now provide such sensors.

Drivers are rather well-acquainted with potholes on the bridges and roads on which they frequently travel. However, apart from the surface damage, there are more insidious structural damages that may be less obvious. One of them is stress corrosion cracks in structural components that may lead to a bridge collapse.

Therefore, engineers are rightly concerned about existing infrastructure developing similar defects. The rise in vehicular traffic over bridges and roads, often going beyond the original design specifications, together with rapid aging from the stress, can lead to their continual wear and tear and deterioration. Engineers use Structural Health Monitoring or SHM based on continuous monitoring of infrastructure. This is critical for identifying structures at risk.

Monitoring the system through wireless means is more practical, as this avoids the expenses of using wired system monitoring. Wireless monitoring also leads to the simpler placement of sensors within the existing infrastructure. Powering the wireless sensors with energy harvesting techniques further enables avoiding the cost and maintenance concerns related to using batteries and their periodic replacement.

Engineers use various ambient sources for powering the nodes of SHM wireless sensors. This includes vibrational, thermal, and solar sources. Ultimately, the optimum choice depends less on the technical requirements but rather on the logistics, cost, and maintenance requirements related to the target structure. For instance, noise barriers may be necessary for roads in urban areas with heavy traffic. These noise barriers may double as solar panels for energy harvesting.

Some situations may offer alternative sources of energy for powering sensors. These could be thermoelectric generators or TECs, which generate power based on the temperature differential across them. Such differentials often exist between the subgrade layers and the pavement surface of a road. Although using TECs in new constructions may be quite effective, retrofitting in existing roads may involve prohibitive costs.

Engineers often use a heavier tip mass to augment the mechanical loading of a piezoelectric device. Such loading helps to reduce the natural frequency of the device, bringing it closer to the predominant frequencies from the ambient vibrational energy source, enabling maximization of power generation.

In some cases, the ambient vibrational energy source may have frequencies well below the tunable range of the piezoelectric devices available. Engineers then turn to alternative low-frequency vibrational energy transducers like electromagnetic generators. The low-frequency vibrations cause a spring-mounted magnetic core to move through a coil, thereby converting the energy of vibrations to a current following Faraday’s law of induction.

Ambient-powered wireless sensors also require power conditioning and management. Power management circuits monitor the energy harvested, regulate the voltage applied to the load, and use the excess energy to charge external energy storage devices like a rechargeable battery or a supercapacitor.

 Important Sensors

Engineers use two important types of sensors—superstar sensors and workhorse sensors. The superstar sensors usually provide information in high-profile applications such as advanced driver assistance systems, and engineers update them regularly for improving their performance. On the other hand, the workhorse sensors are more reliable, providing consistent information on more common applications. These workhorse sensors are simple to use, and meet the necessary performance specifications at reasonable price tags.

For instance, sensors have been readily available for detecting particulate matter in a dusty environment. However, in recent times, governments have tightened their regulations and have changed the definition of the acceptable levels of particulate matter. Advancement in technology has led to the development of small commodity dust sensors capable of being incorporated into mobile devices. This makes it easier for air monitors, air conditioners, and air purifiers to detect airborne dust particles in all types of environments.

Sharp Microelectronics offers a compact optical dust sensor, the GP2Y1010AU0F. It consists of an infrared light-emitting diode and a phototransistor placed in a diagonal position within the device. The phototransistor picks up infrared light reflected by dust particles. As the system is based on optical sensing, the device is thin and compact with dimensions of 46 x30 x 17.6 mm. The sensor from Sharp Microelectronics is sensitive enough to detect very fine particles such as those in cigarette smoke.

Honeywell offers their LLE Series of sensors for sensing liquid levels. Their technology uses a phototransistor trigger. The sensor can detect the presence or absence of liquid and presents the output in digital format. The sensor uses an LED and a phototransistor that Honeywell has placed inside a plastic dome at the head of the device. In the absence of liquid, light from the LED reaches the phototransistor after total internal reflections from the dome. As liquid fills up, it covers the dome, changing the refractive index at the liquid-dome boundary. This prevents light from the LED from reflecting back to the phototransistor, instantaneously switching the output and indicating the presence of liquid.

Omron offers their digital differential pressure-type mass-flow sensor, the D6F-PH. The sensor has an I2C output and uses a mass-flow MEMS chip, a proprietary of Omron. The company has redesigned the internal flow path such that it produces a high-velocity low flow for an impedance sensor to produce differential pressure. Users can buy these sensors in three models—for measuring a specific pressure range while being calibrated for several types of gases.

Measurement Specialties offers their compression load cell, the FC22. This is a low-cost, high-performance, medium compression force sensor. The sensor offers normalized zero and span, and thermal compensation for changes in span and zero as the temperature changes. The sensor is based on the Microfused technology of Measurement Specialties. It uses several micromachined piezoresistive strain gauges made of silicon fuzed with high-temperature glass to a stainless-steel substrate. While competitive designs suffer from lead-die fatigue, the FC22 sensor does not and can measure the direct force with unlimited life cycle expectancy, while offering superior resolution, and high over-range capabilities.

SensorTile Wireless Industrial Node

For testing advanced industrial IoT applications, ST Microelectronics offers a wireless industrial node, which they call the STWIN SensorTile. This development kit from ST amplifies prototyping of applications like predictive maintenance and condition monitoring.

The STWIN SensorTile kit has a core system board, using a microcontroller operating at ultra-low power. The microcontroller can analyze vibrations from motion-sensing data across 9 degrees of freedom. The vibrational data may cover a wide range of frequencies. The spectra can cover very high-frequency audio including ultrasound. It is also capable of monitoring local temperature and environmental conditions at high precision.

The user can also tie up the core system board with a wide range of embedded sensors of industrial-grade type. To aid in speeding up design cycles for providing end-to-end solutions, ST compliments the development kit with a rich set of optimized firmware libraries and software packages.

An on-board module on the kit provides BLE wireless connectivity. Users can connect a special plugin expansion board to get Wi-Fi connectivity. Those who require wired connectivity for their projects can use the onboard RS485 transceiver. ST has a host of daughter boards using the STM32 family. This includes the LTE Cell pack. Users can connect these compatible, small form factor, and low-cost daughter boards to the development kit through an on-board STMod+ connector.

Along with the core system board, the wireless industrial node kit also has a protective plastic case, a Li-Po battery rated for 480 mAh, a programming cable, and a STLINK-V3MINI programmer cum debugger for STM32.

Users can employ a comprehensive range of sensors available with the core system board. ST has specifically designed these sensors to enable and support industry 4.0 applications. The microcontroller has various serial interfaces for communicating with these sensors. The interfaces include SPI for communicating with motion sensors with high data rates, and I2C for communicating with environmental sensors and magnetometers. The microcontroller can directly communicate with analog and digital microphones.

When interfacing with analog microphones, a low-noise opamp amplifies the signal. An internal 12-bit ADC is available in the microcontroller for sampling the output from the opamp. A digital filter manages the signal output from digital microphones. The microcontroller has a Sigma-Delta modulator interface for signals from digital microphones.

The core system has several sensors on the board. These include a digital MEMS microphone of industrial grade, a wideband MEMS analog microphone, an ultra-low-power 3-axis magnetometer, a high-performance ultra-low-power MEMS motion sensor, an ultra-wide-bandwidth MEMS vibrometer up to 5 kHz, a 3D accelerometer and 3D gyro IMU with a core for machine-learning, a high-output current rail-to-rail dual opamp, a digital low-voltage local temperature sensor, a digital absolute pressure sensor, relative humidity and temperature sensor.

The ultra-low-power microcontroller in the STWIN core system board is a part of the STM32L4+ series of MCUs. The series is based on the ARM Cortex-M4 core, which is of the high-performance 32-bit RISC type. The processors operate up to 120 MHz, and the board has 2 MB Flash memory, along with 640 Kb SRAM. The board has several connectivity options of both wired and wireless types.

3-Axis Digital Output Gyroscope

The I3G4250D is a 3-axis gyroscope with a digital output that STMicroelectronics is offering. This low-power, angular rate sensor provides unprecedented stability over time and temperature and unmatched sensitivity at zero-rate levels. Included in the I3G4250D is a sensing element along with a serial digital interface that transfers the measured angular rate to the application. This data transfer happens over a high-speed digital serial peripheral interface. In addition, the gyroscope comes with an I2C interface as well.

ST manufactures the sensing element in the gyroscope with a unique micromachining process. ST has developed this process for producing inertial actuators and sensors on wafers of silicon.

A CMOS IC provides the interface, allowing a high level of design integration necessary for building a dedicated circuit. Then they trim this to specifically match the sensing element’s characteristics. Users can select the full-scale output of the sensor to be ±245, ±500, or ±2000 DPS. Moreover, the user can also select the bandwidth for measuring the rates.

ST offers this gyroscope as a Land Grid Array or LGA package made of plastic. It is capable of operating within an ambient temperature range of -40 °C to +85 °C. The gyroscope has some unique features. It can tolerate a supply voltage variation of 2.4 VDC to 3.6 VDC. With two digital output interfaces of I2C and SPI, the sensor provides data output for rate value at 16 bits, and data output for temperature at 8 bits. For interfacing with outside circuits, the sensor offers two digital output lines—an interrupt and a data-ready output. Users can select the bandwidth of low- and high-pass filters integrated within the IC. The sensor offers exceptionally stable outputs over time and temperature.

With low-voltage compatible Input/Output lines, the IC can interface with digital signals of 1.8 VDC levels. Along with an embedded temperature sensor, the IC also has an embedded FIFO and also embeds power down and sleep modes. The sensor is ECOPACK, Green, and RoHS compliant, and can survive high shocks.

To evaluate the MEMS devices within the I3G4250D family, ST offers an adapter board— the STEVAL-MKI169V1. This adapter board matches a standard DIL socket, offering an effective solution for speedy system prototyping and evaluation of devices that the user is directly applying.

The user can directly plug in the adapter board in a standard DIL socket with 24 pins and take advantage of the complete I3G4250D pin-outs. The adapter board also comes with the necessary decoupling capacitors mounted on the VDD power supply pins.

ST supports this adapter board with its motherboard, the  STEVAL-MKI109V2. The motherboard has a powerful 32-bit microcontroller to act as a bridge between a PC and the sensor. ST also provides a graphical user interface—the Unico GUI— for the PC, which the user can download and use. They also provide dedicated software routines to customize the applications.

ST has targeted the I3G4250D 3-axis gyroscope with a digital output mainly for industrial applications. However, users can use the gyroscope for applications like navigational systems and telematics. The device is also useful in man-machine interfaces like motion control, and for various appliances like robotics.