Sensors are a key component of all IoT systems that are progressively being utilized in Smart City’ designs. Interfaces for most sensors, from temperature and pressure sensors to humidity sensors are simplifying interface to the sensing environment and enhancing the reliability and functionality of systems.
Connecting sensors up to the Internet of Things is sometimes non trivial and needs careful consideration. Improved chip level packaging technology is allowing greater integration so that sensors can provide digital data feeds through protocols that are directly integrated into micro-controllers. These micro-controller enabled edge devices sitting at the edge of the Internet then packetizes the data and ships them to various gateway systems from Microsoft Azure or GE Digital or other proprietary gateways.
The sensors interfaced to the micro-controller are connected to the Internet through a direct Ethernet connection or through a wireless transceiver.
Traditionally sensors with built-in ADCs optimized to its resolution were interfaced to a micro-controller via a serial UART or I²C or GPIO pins. Currently various low-power micro-controllers are available that integrate all of the required functionality by providing a 32-bit processing core and integrated IPv4 stack, with one or more ADCs and various sensors for temperature, pressure, gyroscope, GPS etc. This enables sensors to be added to a system effortlessly, instead of being constrained by the address space of a hub device
Here are some of the more common sensors that are in use by IOT applications.
Temperature Sensor – Used to detect a physical change in temperature from a particular source and converts the physical characteristic to an electrically readable value. This is one of the more ubiquitous values measured by IOT devices. It is used in industrial applications or in Agriculture to measuring Soil temperature for determining optimum conditions for plants.
Proximity Sensor – A device that detects the presence or absence of a nearby object, or properties of that object, and converts it into signal which can be easily read by user or a simple electronic instrument without getting in contact with them. In the retail industry, they can detect and correlate between a customer and products they might be interested in. A user is immediately notified of discounts and special offers of nearby products.
Photoelectric Sensors – This is made up of light-sensitive parts and uses a beam of light to detect the presence or absence of an object.
Ultrasonic Sensors – Ultrasonic sensors are also used to detect the presence or to measure the distance of targets similar to radar or sonar. This makes a reliable solution for harsh and demanding conditions.
Here are a few examples of integrated devices ideal for IOT sensor applications.
- ESP32 – ESP32 WiFi and Bluetooth chip is the latest generation of Espressif products. It has a dual-core 32-bit MCU, which integrates WiFi HT40, Bluetooth/BLE 4.2, 12-bit SAR ADC / DAC, Touch sensors, temp sensors, PWM, Hall sensor, Ethernet MAC etc
- PixyCAM – Pixy2 is the newest version of CMUcam5 smart vision sensor for robotics! You can quickly “teach” objects to Pixy2 with the press of a button. It saves you time by only outputting the object data you’re interested in.
- ADT7320, available from suppliers like DigiKey ia an excellent example of a high-accuracy digital temperature sensor with wide temperature range necessary for IoT applications for a sensor in extremely hostile environments.