Designer’s guide for deploying sensors in smart cities

Sensors are essential component building blocks in the smart-city environment. The main role of these devices is to sense and gather data, which will ensure that smart cities will function smoothly and safely. Sensors and small systems communicate constantly through gateways and the internet cloud to various city control centers to keep smart-city services running smoothly.

Types of smart-city sensors

Sensors vary widely and can monitor and detect a variety of sources, such as light, heat, motion, moisture, and pressure. Typical sensors used in smart cities can sense temperature, proximity, infrared, pressure, light, smoke, gas, alcohol, touch, color, humidity, tilt, flow, and level.

There is a myriad of applications for sensors in a smart city, ranging from smart meters and smart grids to intelligent traffic systems and environmental monitoring (see Figure 1).

Figure 1: Smart-city sensor applications (Source: Shutterstock)

City-wide sensor nodes

Sensor nodes can be deployed across a city to monitor key parameters like noise, traffic, and pollution levels. Data from these nodes can be transmitted to a central server, which will refine it and make it available to the general public.

Air and noise pollution

Monitoring of air and noise pollution is crucial to the quality of life and health of smart-city citizens. As an example, Flowbird, based in France, developed its “Park & Breathe” system that measures both air and noise pollution in urban areas. The system can measure parameters such as noise (measured in decibels), nitrogen dioxide, and even fine particles.

Parking

Figure 2: PlacePod is an IoT-enabled smart parking sensor. Click for a larger image. (Source: PNI Sensor Corp.)

One example of a smart-parking–sensor system is PNI Sensor Corp.’s PlacePod, an in-ground or surface-mounted sensor. The system communicates with a gateway providing real-time parking data over a low-power wide-area network. This system enables accurate vehicle detection in parking spaces, with up to 10 years of battery life, and is stable over temperature fluctuations, even in harsh environments (see Figure 2).

Traffic monitoring

One example of a cost-effective solution for monitoring traffic in a smart city is Analog Devices Inc.’s multi-channel microwave radar Adaptive Traffic Control Systems (ATCS). The essential sensors are microwave receiver antennas at 24 GHz, with backup video cameras as a redundancy system.

Video and radar detection is also being used in V2X applications. V2X is being deployed in smart cities and their sensors are also microwave antennas.

Environmental pollution

Sensors, which can monitor the environment and especially pollution levels, are critical to a safe, healthy, clean environment. Another great idea is to deploy smart environmental sensors on public buses, which actively cover a large area while traveling through parks, alleys, and side streets.

As an example, Bosch Sensortec offers a variety of environmental monitoring sensors that can be used in smart-city applications. These include pressure, humidity, and gas sensors.

Smart office buildings

Smart-city office buildings use a variety of sensor solutions that can be wireless with very low power technology.

Rooms and zones

Sensors in the smart-city workplace are becoming ubiquitous and many new sensors in buildings are emerging.¹ These include the following:

• Temperature sensors monitor temperature changes and can trigger actions either above or below a specific threshold. These sensors are usually paired with a central thermostat or HVAC components.
• Humidity sensors measure water content in the air and activate once a preset threshold is reached. These sensors are typically linked to an HVAC or dehumidification system.
• Proximity sensors are much like motion sensors and detect the presence of an object and measure how close it is. One of the most familiar uses is reverse-parking sensors in cars.
• Pressure sensors detect pressure and alert the system administrator of any deviation from the standard pressure range — similar to machine monitoring. This is useful in manufacturing as well as in water and heating systems.
• Air- and water-quality sensors monitor the integrity of air or water and activate when contaminants are present. These sensors are often linked to an alert system or reporting program.
• Electrical sensors measure active electrical current, usually in voltage or amperage. These sensors can be linked to an alert system or maintenance ticketing program.
• Status sensors are a diverse kind of sensor that functions as a simple on-off (I/O), changing status from one to the other in the presence of various specific stimuli.
• Motion sensors activate in the presence of movement to trigger a peripheral action, like turning on a light.
• Optical sensors are light-activated devices that trigger an action, usually compliant with on-off (I/O) standards. These are typically used in industries such as health care, energy, and communications to monitor variables including light, radiation, electric, and magnetic field as well as temperature.
• Water-quality sensors are typically employed in environmental management applications to measure chemicals, ions, organic elements, suspended solids, and pH levels in water.
• Chemical sensors can detect the presence of chemicals in water or air. These are used to track air and water quality in cities, monitor industrial processes, and detect harmful chemicals, explosives, and radioactive materials.
• Smoke sensors detect levels of airborne particulates and gases.
• Level sensors determine the level of fluids, liquids, or other substances in an open or closed system. These are typically used to measure fuel levels but are also used to measure sea and reservoir levels and in medical equipment, compressors, and hydraulics.
• Image sensors can be found in digital cameras, medical imaging, and night-vision equipment as well as biometric devices. These are also used in the automobile industry and play an important role in the development of autonomous vehicles.
• Accelerometer sensors detect vibration, tilting, and acceleration in an object. Uses include anti-theft devices, vehicle-fleet monitoring, aircraft and aviation industries, and consumer electronics, including smartphones and pedometers.
• Gyroscope sensors are used together with accelerometers and measure angular velocity, defined as a measurement of speed of rotation around an axis. Their main applications include car navigation systems, game controllers, robotics, and consumer electronics.

TI’s SimpleLink Bluetooth Low Energy and multi-standard sensor tags. Click for a larger image. (Source: Texas Instruments Inc.)

An example of a smart-building–sensor system is Texas Instruments Inc.’s SimpleLink Bluetooth Low Energy and multi-standard sensor tags (see Figure 3). Designed as a solution for rooms and zones, the sensor tags can monitor humidity, occupancy, light, sound, air quality, and temperature. This solution has 10 sensors, including support for light, digital microphone, magnetic, humidity, pressure, accelerometer, gyroscope, magnetometer, object temperature, and ambient temperature.

Passive-infrared sensors can also be used to determine room, desk, and table occupancy as well as cubicle occupancy and people flow. For example, Pressac Communications Ltd. supports these applications and offers a variety of occupancy-, environment-, and energy-monitoring sensors.

Summary

Smart cities are test beds for population health strategies, improved traffic flow, and general sensor implementation to improve city life and leisure activities. Smart cities are reinventing the way we structure and construct buildings and organize cities for the future. Sensors make these things possible. There are also sensors in the background that can be worn and allow biometric data to be collected non-intrusively for health and wellness.

Sensors in a smart-city environment are also in walls, floors, and ceilings of homes and businesses to improve the life and health of the population. Sensors also exist on the roadways to optimize traffic flow and safely move vehicles about the city environment while protecting the city driver, passenger, and pedestrian residents. Smart-city neighborhoods nurture social connectivity as a way of life.

References

¹Smart sensors and connected technology used in millions of businesses and homes worldwide, Pressac