Sensors give embedded systems the capability of sensing by identifying and measuring changes in the environment and providing real-time data. Embedded systems with modern sensor technologies ensure a higher level of intelligent services and are sometimes better than humans.
Embedded systems are incorporated with several traditional and existing sensors. The embedded sensor nodes are physically small and relatively inexpensive. Generally, embedded sensors are a basic part of many embedded systems that help interaction with the real-world environment. The development of modern sensing technologies is growing fast with the miniaturization of embedded systems, microprocessors, microcontrollers, and especially micro-electromechanical systems.
SENSORS
A sensor is a device or module (or subsystem) that can sense or detect physical phenomena in the environment, such as light, pressure, temperature, and motion. The input of a sensor can be any physical phenomenon, but the output should be a signal within the human-readable form. A sensor detects the changes or events around it and sends the data to any smart devices or embedded system.
There are many different types of sensors for different purposes. They include but are not limited to vision sensors, motion sensors, position sensors, photoelectric sensors, radiation sensors, temperature sensors, pressure sensors, proximity sensors, particle sensors, metal sensors, level sensors, electrical sensors, humidity sensors, flow sensors, leak sensors, flame sensors, contact sensors, and non-contact sensors.
Generally, the sensors can be divided into two categories—active and passive. An active sensing device requires an external energy source to operate. It emits an energy pulse, and detects the reflection of the energy pulse. The most commonly used active sensor system is RADAR (Radio Detection and Ranging). A passive sensing device does not require an external energy source to operate, and it detects or measures naturally occurring energy. Active sensing systems use a passive sensing device to detect the reflection.
Sensors can also be categorized as analog and digital. Digital sensing devices produce digital signals, where data is digitally converted and transmitted. Some examples of digital sensors are digital accelerometers, digital pressure sensors, and digital temperature sensors. Analog sensing devices produce analog signals. Some examples of analog sensors are light sensors (LDRs), sound sensors, and analog temperature sensors.
SENSORS IN EMBEDDED SYSTEMS
Embedded systems are a combination of microprocessor-based computing hardware and software that is designed for dedicated functions. Today, embedded technologies are becoming necessary for the Internet of Things (IoT), robotics, industrial machines, medical equipment, agricultural devices, driverless vehicles, drones, airplanes, toys, and in all of the areas of our modern tech life.
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Sensors are important for embedded systems to detect changes in the surrounding environment and collect relevant real-time data. An embedded system takes in the relevant data through the sensors, processes them, makes a decision based on the sensors’ data, and takes action based on the decision. Embedded systems and sensors work simultaneously to perform any intelligence operations, such as the IoT, robotics, and AI systems.
CRITICAL APPLICATIONS
Critical applications are the essential factors or services necessary for normal business or organizational operations continuity. Any disruption or failure of those factors could have a serious impact on business operations. The systems in a critical environment are generally built with embedded sensors on wireless networks, to provide real-time and valid data on the surrounding the environments.
Critical applications may include mission-critical, safety-critical, and time-critical applications that require fast detection, timely action, and reliable notifications. Embedded systems with sensors play an important role in the critical environment by ensuring timely, accurate, and scalable monitoring. Embedded sensors are widely used for many critical applications, including medical, autonomous transportation, and nuclear applications.
VISUAL SENSOR SOLUTION
Imaging or visual sensors play the role of eyes for embedded systems. These solutions are deployed across industries, including retail, manufacturing, smart cities, medical, and auto farming.
The Alvium 1800C MIPI CSI-2 camera series from Allied Vision (Figure 1) offers embedded system developers access to Sony’s high-performance image sensors. These sensors provide excellent image quality with resolutions up to 20 megapixels. They also have CMOS global and rolling shutter sensors from Sony, up to 289 frames per second, Bare Board, Open Housing, C-Mount, CS-Mount, or S-Mount. The series offers advanced image corrections. The Alvium 1800 C is designed for low-power or even battery-powered systems, and uses the powerful MIPI CSI-2 interface with up to four lanes.
The Alvium 1800 C MIPI CSI-2 camera series provides excellent image quality, with resolutions up to 20 megapixels, and offer embedded system developers access to Sony’s high-performance image sensors.
DISTANCE SENSOR SOLUTION
Embedded system developers use distance sensors for surface discrimination applications and distance measurement. Distance sensor solutions provide higher accuracy. They are deployed across industries for several purposes, including robotic sensing, stacking height control, and IoT.
The LightWare LiDAR SF45/B Scanning MicroLiDAR Sensor from MOUSER (Figure 2) is a small, lightweight scanning sensor. It is an ideal solution for obstacle detection and navigation for autonomous vehicles and drones. The tiny SF45/B weighs only 59g. It has a range capability from 0.2m up to 50m, using a horizontal Field of View (FoV). The FoV adjusts from a few degrees to 320 degrees. The sensor offers a small form factor of 51mm x 48mm x 44mm, and features an update rate of up to 5,000 measurements per second. For communication, it has the Micro USB port, Serial port (3.3V logic level), and I2C port (3.3V logic level).
The LightWare LiDAR SF45/B is an ideal solution for obstacle detection and navigation for autonomous vehicles and drones. It weighs only 59g, and has a range from 0.2m to 50m.
DUST SENSOR SOLUTION
A dust sensor is a device that detects and measures dust in the air. These sensors provide an indication of environmental air quality through the measurement of dust concentration, which helps to understand the level of air pollution. Dust sensors are commonly used in embedded air purifier systems, and they are effective for detecting very fine particles such as smoke.
The AUDIOWELL DL0001 laser dust sensor (Figure 3) uses a laser diode to illuminate the sampling air. It has a lensless design to ensure good consistency and high-accuracy measurement. The laser dust sensor can detect particles as small as 0.3μm in diameter. The measuring ranges of particles are 0.3~1.0, 1.0~2.5, and 2.5~10; and the maximum range of particle mass concentration is 2,000μg/m3. The consistency (PM2.5 standard value) are 0 ~ 100μg/m³: ± 10μg/m³ and 100 ~ 500μg/m³: ± 10%. DC power supply voltage is 5V, and the working temperature ranges between -10°C and +50°C. The DL0001 laser dust sensor applications include ventilation systems, air purifiers, air conditioners, and air quality monitors.
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The AUDIOWELL DL0001 uses a laser diode to illuminate the sampling air. It can detect particles as small as 0.3μm in diameter, and ensures good consistency and high-accuracy measurement.
TEMPERATURE SENSOR SOLUTION
A temperature sensor plays the role of skin that can detect changes of heat, convert the reading into an electrical signal, and help embedded systems understand their surroundings. Temperature sensors are the most commonly used sensors around the world. Temperature sensor solutions are deployed across industries, including railway tracks, data centers, and medical and mobile applications.
The MAX31888 from Maxim Integrated (Figure 4) is a 1-Wire high-precision, low-power digital temperature sensor. It has ±0.25°C accuracy from -20°C to +105°C, and ±0.65°C accuracy from -40°C to +125°C for precision temperature monitoring. The sensors operate at 68μA during measurement and have a 16-bit resolution (0.005º°C). MAX31888 connects a microcontroller through a 1-Wire bus and is available in a 6-pin uDFN package. The power supply voltage ranges between 1.7V and 3.6V for external power supplies, and its operating temperature ranges between -40°C and +125°C. The MAX31888 applications include precision temperature monitoring, RTD replacement, and IoT.
The MAX31888 is a low-power digital temperature sensor that operates at 68μA during measurement, and has a 16-bit resolution (0.005°C). Its accuracy is ±0.25°C from -20°C to +105°C and accuracy ±0.65°C from -40°C to +125°C.
PRESSURE SENSOR SOLUTION
Pressure sensors are commonly used in embedded systems to measure pressure and generate a signal based on the function of the pressure imposed. The sensors are widely used to monitor and control many different fields for different applications, including water level, fluid/gas flow, speed, and altitude.
The FXTH87 Tire Pressure Monitor Sensor Family from NXP (Figure 5) is available with a very small footprint in a 7 mm x 7 mm package and has very low power consumption. The pressure sensors have a very large memory size at 8KB and dual-axis accelerometer architecture. The XZ axis provides motion detection and tire localization capabilities. The FXTH87 family pressure ranges between 100–450kPa and 100–900 kPa. The sensor family has an 8-bit MCU/S08 core with SIM, interrupt and debug/monitor, 512 bytes RAM/16KB flash memory, Internal 315/434MHz RF transmitter, Internal 125kHz low frequency receiver, and six multipurpose GPIO pins, including two A/D inputs.
The FXTH87 Tire Pressure Monitor Sensors range from 100 to 450kPa and 100 to 900kPa, and are available with a very small footprint in a 7mm x 7mm package and very low power consumption.
METAL SENSOR SOLUTION
A metal sensor/detector is an electronic or electro-mechanical device used to sense the presence of metal. These sensors are used extensively for mineral prospecting and industrial applications, including airport security, detecting land mines, food/drug processing, archaeology, geophysical prospecting, and treasure hunting. Metal sensors are important for developing an embedded system when needed to detect metals. There are many different types of metal sensors available to detect different types of metals.
The AI038 inductive sensor from Autosen (Figure 6) has a robust metal housing (brass, white bronze plated) with an LED switch indicator, M12 thread, and M12 connector (3-pin). The sensor belonging to the high resistance class has a switching output with a normally open function. It has an enhanced sensing range of 4mm and a diameter of M12. The AI038 with high protection ratings of IP65 / IP66 / IP67 / IP68 / IP69K satisfies the highest demands of industrial environments. The AI038 inductive sensor’s operating temperature ranges between -40°C and 85°C.
The AI038 inductive sensor has a robust metal housing (brass and white bronze plating). It belongs to the high resistance class and has an enhanced sensing range of 4mm and a diameter of M12.
MOTION SENSOR SOLUTION
A motion sensor is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area. Motion sensors are widely used for security, home control, automated lighting control, energy efficiency, virtual reality systems, and other embedded systems. The motion sensor device is also an embedded system. It has three basic components—a sensor unit, an embedded computer, and hardware or mechanical components.
Reolink Lumus 1080P high-definition Plug-in Wi-Fi Camera (Figure 7) is used for PIR motion detection, home security, industrial monitoring, and other embedded systems. The sensor device capability includes two-way talk and siren alarm, waterproof, and cloud/micro SD Card storage up to 128GB. Reolink provides full-color videos even when there is no light source, through built-in spotlights. It can detect people, vehicles, and other objects with valuable details. The combination of motion detection and passive infrared (PIR) detection provides reliable motion sensing for embedded systems. It also allows the user to set activity zones or adjust motion sensitivity and schedule to fit any situation.
Reolink Lumus 1080P HD Plug-in Wi-Fi Camera combines motion detection and PIR detection. It provides reliable motion sensing for embedded systems with full-color videos without a light source, through built-in spotlights.
FLOW SENSOR SOLUTION
Flow sensors are used to detect and measure the flow of a fluid. These sensors are utilized with electrical and mechanical subsystems, and the measuring physical attributes depend on the physical attributes of the fluid. Embedded systems may use several digital or analog flow sensors for industrial and medical monitoring.
FL-408 Water Flow Hall Sensor from DIGITEN (Figure 8) is light, small, and easy to install. The integrated magnetic Hall-effect sensor produces an output electrical pulse with every revolution, and it is sealed from the water pipe, allowing the sensor to stay safe and dry. The external thread diameter of the sensor is G1/2” (BSP), and the frequency is 7.5 x Q (L/min). The Water Flow Sensor has an error rate of ±2%. The sensor working voltage range is DC 5V to 18V, with a maximum current of 15mA (DC 5V) and load capacity ≤10mA (DC 5V). The sensors’ flow range is 1-30L/min, and the operating temperature and humidity are ≤80°C and 35% to 90% operating relative humidity, respectively. 
DIGITEN’s FL-408 Water Flow Hall Sensor has a flow range of 1-30L/min and an error rate of ±2%. It is light, small, and easy to install, and its working voltage range is DC 5 to18V.
Sensors give embedded systems the capability of sensing by identifying and measuring changes in the environment and providing real-time data. Embedded systems with modern sensor technologies ensure a higher level of intelligent services and are sometimes better than humans.
RESOURCES
Allied Vision | www.alliedvision.com
Audiowell Sensor Technology | www.audiowellsensor.com
Autosen | autosen.com
Digiten | www.digiten.shop
Maxim Integrated | www.maximintegrated.com
Mouser | www.mouser.com
NXP | www.nxp.com
PUBLISHED IN CIRCUIT CELLAR MAGAZINE • JUNE 2022 #383 – Get a PDF of the issue
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Al Mahmud Al Mamun Former (March 2022-July 2022) Editor-in-Chief — Editor-in-Chief Circuit Cellar magazine. With a background in engineering, research, and publishing and a master’s degree in Computer Science and Engineering. His passions include Robotics, Artificial Intelligence, and Smart technologies.
