The Internet of Things

February 9, 2023    Article    3289 words    16 mins read

The Internet of Things (IoT) describes physical objects (or groups of such objects) with sensors, processing ability, software and other technologies that connect and exchange data with other devices and systems over the Internet or other communications networks. Internet of Things has been considered a misnomer because devices do not need to be connected to the public internet, they only need to be connected to a network and be individually addressable.


Hardware platforms are the integral part of IoT applications, with the help of these devices you can quickly build your DIY project or prototype. Here are some of the popular hardware platforms used in IoT projects.


Arduino is an open-source electronics platform based on easy-to-use hardware and software. Arduino boards are able to read inputs - light on a sensor, a finger on a button, or a Twitter message - and turn it into an output - activating a motor, turning on an LED, publishing something online. You can tell your board what to do by sending a set of instructions to the microcontroller on the board. To do so you use the Arduino programming language (based on Wiring), and the Arduino Software (IDE), based on Processing. Homepage

Raspberry Pi

The Raspberry Pi is a Single Board Computer developed by Raspberry Pi Foundation and it is widely popular as a small, inexpensive computing board among experimenters, hobbyists, educators and technology enthusiasts. Homepage


The ESP8266 is a low-cost Wi-Fi microchip, with built-in TCP/IP networking software, and microcontroller capability, produced by Espressif Systems in Shanghai, China. Homepage


BeagleBone Black is a low-cost, high-expansion, community-supported development platform for developers and hobbyists. Users can boot Linux in under 10 seconds and get started on development in less than 5 minutes with just a single USB cable. Like its predecessors, the BeagleBone Black is designed to address the Open Source Community, early adopters, and anyone interested in a low cost ARM Cortex-A8 based processor. It has been equipped with a minimum set of peripherals to allow the user to experience the power of the processor and also offers access to many of the interfaces and allows for the use of add-on boards called capes, to add many different combinations of features. A user may also develop their own board or add their own circuitry. Homepage


Flutter is a programmable processor core for electronics projects, designed for hobbyists, students, and engineers. Flutter features a fast ARM processor, powerful long-range wireless communication, built-in battery charging, and an onboard security chip, making Flutter an ideal choice for robotics, wireless sensor networks, consumer electronics, and educational platforms. Homepage


Sensors are hardware components that can detect events or changes in their surroundings and then provide a corresponding output. Sensors are the eyes and ears of any IoT (Internet of Things) project. Without sensors there’s no IoT, so lets explore some of the commonly used sensors in IoT applications.



BISS0001 is a PIR (passive infra-red) controller, using analog mixing digital design technique and manufactures by CMOS process. With special noise immunity technique, BISS0001 is the most stable PIR controller you can find on the market. More than this, there are few components needed in its application circuit which can reduce material cost and increase competitive.

  • Name: Micro Power PIR Motion Detector IC
  • Manufacturer: Silvan Chip Electronics
  • Datasheet



The TMP35/TMP36/TMP37 are low voltage, precision centigrade temperature sensors. They provide a voltage output that is linearly proportional to the Celsius (centigrade) temperature. The TMP35/TMP36/TMP37 do not require any external calibration to provide typical accuracies of ±1°C at +25°C and ±2°C over the −40°C to +125°C temperature range.

The low output impedance of the TMP35/TMP36/TMP37 and its linear output and precise calibration simplify interfacing to temperature control circuitry and ADCs. All three devices are intended for single-supply operation from 2.7 V to 5.5 V maxi- mum. The supply current runs well below 50 μA, providing very low self-heating—less than 0.1°C in still air. In addition, a shutdown function is provided to cut the supply current to less than 0.5 μA.

  • Manufacturer: Analog Devices
  • Name: Low Voltage Temperature Sensor
  • Datasheet


The LM35 series are precision integrated-circuit temperature devices with an output voltage linearly- proportional to the Centigrade temperature. The LM35 device has an advantage over linear temperature sensors calibrated in Kelvin, as the user is not required to subtract a large constant voltage from the output to obtain convenient Centigrade scaling. The LM35 device does not require any external calibration or trimming to provide typical accuracies of ±1⁄4°C at room temperature and ±3⁄4°C over a full −55°C to 150°C temperature range. Lower cost is assured by trimming and calibration at the wafer level. The low-output impedance, linear output, and precise inherent calibration of the LM35 device makes interfacing to readout or control circuitry especially easy.

  • Manufacturer: Texas Instruments
  • Name: Precision Centigrade Temperature Sensor
  • Datasheet


The DS18B20 digital thermometer provides 9-bit to 12-bit Celsius temperature measurements and has an alarm function with nonvolatile user-programmable upper and lower trigger points. The DS18B20 communicates over a 1-Wire bus that by definition requires only one data line (and ground) for communication with a central microprocessor. In addition, the DS18B20 can derive power directly from the data line (“parasite power”), eliminating the need for an external power supply.

Each DS18B20 has a unique 64-bit serial code, which allows multiple DS18B20s to function on the same 1-Wire bus. Thus, it is simple to use one microprocessor to control many DS18B20s distributed over a large area. Applications that can benefit from this feature include HVAC environmental controls, temperature monitoring systems inside buildings, equipment, or machinery, and process monitoring and control systems.

  • Manufacturer: Maxim Integrated
  • Name: Programmable Resolution 1-Wire Digital Thermometer
  • Datasheet

Temperature and humidity


DHT11 digital temperature and humidity sensor is a composite sensor that contains a calibrated digital signal output of the temperature and humidity. Application of a dedicated digital modules collection technology and the temperature and humidity sensing technology, to ensure that the product has high reliability and excellent long-term stability. The sensor includes a resistive sense of wet components and an NTC temperature measurement devices, and connected with a high-performance 8-bit microcontroller.

  • Manufacturer: Aosong
  • Name: Temperature and humidity module
  • Datasheet


DHT22 output calibrated digital signal. It utilizes exclusive digital-signal-collecting-technique and humidity sensing technology, assuring its reliability and stability.Its sensing elements is connected with 8-bit single-chip computer.

Every sensor of this model is temperature compensated and calibrated in accurate calibration chamber and the calibration-coefficient is saved in type of program in OTP memory, when the sensor is detecting, it will cite coefficient from memory.

Small size & low consumption & long transmission distance(20m) enable DHT22 to be suited in all kinds of harsh application occasions.

Single-row packaged with four pins, making the connection very convenient.

  • Manufacturer: Aosong
  • Name: Digital-output relative humidity & temperature sensor/module
  • Datasheet

Temperature, humidity and barometric pressure


The BME280 is as combined digital humidity, pressure and temperature sensor based on proven sensing principles. The sensor module is housed in an extremely compact metal-lid LGA package with a footprint of only 2.5 × 2.5 mm2 with a height of 0.93 mm. Its small dimensions and its low power consumption allow the implementation in battery driven devices such as handsets, GPS modules or watches. The BME280 is register and performance compatible to the Bosch Sensortec BMP280 digital pressure sensor.

The BME280 achieves high performance in all applications requiring humidity and pressure measurement. These emerging applications of home automation control, in-door navigation, health care as well as GPS refinement require a high accuracy and a low TCO at the same time.

  • Name: Combined humidity and pressure sensor
  • Manufacturer: Bosch
  • Datasheet

Temperature, altitude and barometric pressure


The BMP180 is the function compatible successor of the BMP085, a new generation of high precision digital pressure sensors for consumer applications.

The ultra-low power, low voltage electronics of the BMP180 is optimized for use in mobile phones, PDAs, GPS navigation devices and outdoor equipment. With a low altitude noise of merely 0.25m at fast conversion time, the BMP180 offers superior performance. The I2C interface allows for easy system integration with a microcontroller.

  • Name: Digital pressure sensor
  • Manufacturer: Bosch
  • Datasheet


The MPL3115A2 is a compact, piezoresistive, absolute pressure sensor with an I2C digital interface. MPL3115A2 has a wide operating range of 20 kPa to 110 kPa, a range that covers all surface elevations on earth. The MEMS is temperature compensated utilizing an on-chip temperature sensor. The pressure and temperature data is fed into a high resolution ADC to provide fully compensated and digitized outputs for pressure in Pascals and temperature in °C. The internal processing in MPL3115A2 removes compensation and unit conversion load from the system MCU, simplifying system design.

MPL3115A2’s advanced ASIC has multiple user programmable modes such as power saving, interrupt and autonomous data acquisition modes, including programmed acquisition cycle timing, and poll-only modes. Typical active supply current is 40 μA per measurement-second for a stable 10 cm output resolution.

  • Name: I2C precision pressure sensor with altimetry
  • Manufacturer: NXP
  • Datasheet



The QRD1113 and QRD1114 reflective sensors consist of an infrared emitting diode and an NPN silicon phototransistor mounted side by side in a black plastic housing. The on−axis radiation of the emitter and the on−axis response of the detector are both perpendicular to the face of the QRD1113 and QRD1114. The phototransistor responds to radiation emitted from the diode only when a reflective object or surface is in the field of view of the detector.

  • Name: Reflective Object Sensor
  • Manufacturer: ON Semiconductor
  • Datasheet



When the target flammable gas exist, the sensor’s conductivity gets higher along with the gas concentration rising. Users can convert the change of conductivity to correspond output signal of gas concentration through a simple circuit.

MQ-2 gas sensor has high sensitivity to propane and smoke, also can detect the natural gas and other flammable steam well. It is with low cost and suitable for different applications of detecting kinds of flammable gases.

  • Name: Flammable Gas Sensor
  • Manufacturer: Zhengzhou Winsen Electronics
  • Datasheet


When the target alcohol gas exist, the sensor’s conductivity gets higher along with the gas concentration rising. Users can convert the change of conductivity to correspond output signal of gas concentration through a simple circuit.

MQ-3 gas sensor has high sensitivity to alcohol gas and can resistant to the interference of gasoline, smoke and vapour. It is with low cost and suitable for various applications of detecting alcohol at different concentration.

  • Name: Alcohol Gas Sensor
  • Manufacturer: Zhengzhou Winsen Electronics
  • Datasheet


When the target flammable gas exist, the sensor’s conductivity gets higher along with the gas concentration rising. Users can convert the change of conductivity to correspond output signal of gas concentration through a simple circuit.

MQ-4 gas sensor has high sensitivity to methane, also has anti-interference to alcohol and other gases.

  • Name: Flammable Gas (Methane) Sensor
  • Manufacturer: Zhengzhou Winsen Electronics
  • Datasheet


When the target flammable gas exist, the sensor’s conductivity gets higher along with the gas concentration rising. Users can convert the change of conductivity to correspond output signal of gas concentration through a simple circuit.

MQ-6 gas sensor can detect kinds of flammable gases, especially has high sensitivity to LPG (propane). It is a kind of low-cost sensor for many applications.

  • Name: Flammable Gas (LPG) Sensor
  • Manufacturer: Zhengzhou Winsen Electronics
  • Datasheet


It make detection by method of cycle high and low temperature, and detect CO at low temperature(heated by 1.5V). The sensor’s conductivity gets higher along with the CO gas concentration rising. At high temperature(heated by 5.0V),it cleans the other gases adsorbed at low temperature. Users can convert the change of conductivity to correspond output signal of gas concentration through a simple circuit.

  • Name: Toxic Gas (Carbon Monoxide) Sensor
  • Manufacturer: Zhengzhou Winsen Electronics
  • Datasheet


When hydrogen gas exists, the sensor’s conductivity gets higher along with the gas concentration rising. Users can convert the change of conductivity to correspond output signal of gas concentration through a simple circuit. MQ-8 gas sensor has high sensitivity to hydrogen gas, also has anti-interference to other gases. This sensor can detect hydrogen, especially city gas. It is a kind of low-cost sensor for kinds of applications.

  • Name: Flammable Gas (Hydrogen) Sensor
  • Manufacturer: Zhengzhou Winsen Electronics
  • Datasheet



The HC-SR04 Ultrasonic Distance Sensor is a sensor used for detecting the distance to an object using sonar. It’s ideal for any robotics projects your have which require you to avoid objects, by detecting how close they are you can steer away from them!

The HC-SR04 uses non-contact ultrasound sonar to measure the distance to an object, and consists of two ultrasonic transmitters (basically speakers), a receiver, and a control circuit. The transmitters emit a high frequency ultrasonic sound, which bounce off any nearby solid objects, and the receiver listens for any return echo. That echo is then processed by the control circuit to calculate the time difference between the signal being transmitted and received. This time can subsequently be used, along with some clever math, to calculate the distance between the sensor and the reflecting object!

  • Name: Ultrasonic Distance Sensor
  • Manufacturer: Kuongshun Electronic
  • Datasheet


GP2Y0A02YK0F is a distance measuring sensor unit, composed of an integrated combination of PSD (position sensitive detector) , IRED (infrared emitting diode) and signal processing circuit. The variety of the reflectivity of the object, the environmental temperature and the operating duration are not influenced easily to the distance detection because of adopting the triangulation method.

This device outputs the voltage corresponding to the detection distance. So this sensor can also be used as a proximity sensor.

  • Name: Distance Measuring Sensor Unit
  • Manufacturer: Sharp
  • Datasheet

Motion, direction, location


The L3G4200D is an is three-axis angular rate sensor, with a digital I2C/SPI serial interface standard output. The device has a full scale of ±250/±500/ ±2000 dps and is capable of measuring rates with a user-selectable bandwidth. The device may be configured to generate interrupt signals by an independent wake-up event. Thresholds and timing of the interrupt generator are programmable by the end user on the fly.

  • Name: Three axis digital output gyroscope
  • Manufacturer: STMicroelectronics
  • Datasheet


The MPU-60X0 is the world’s first integrated 6-axis MotionTracking device that combines a 3-axis gyroscope, 3-axis accelerometer, and a Digital Motion ProcessorTM (DMP) all in a small 4x4x0.9mm package. With its dedicated I2C sensor bus, it directly accepts inputs from an external 3-axis compass to provide a complete 9-axis MotionFusionTM output. The MPU-60X0 MotionTracking device, with its 6-axis integration, on-board MotionFusionTM, and run-time calibration firmware, enables manufacturers to eliminate the costly and complex selection, qualification, and system level integration of discrete devices, guaranteeing optimal motion performance for consumers. The MPU-60X0 is also designed to interface with multiple non- inertial digital sensors, such as pressure sensors, on its auxiliary I2C port. The MPU-60X0 is footprint compatible with the MPU-30X0 family.

  • Name: Three axis digital output accelerometer and gyroscope
  • Manufacturer: InvenSense
  • Datasheet


The ITG-3200 is the world’s first single-chip, digital-output, 3-axis MEMS gyro IC optimized for gaming, 3D mice, and 3D remote control applications. The part features enhanced bias and sensitivity temperature stability, reducing the need for user calibration. Low frequency noise is lower than previous generation devices, simplifying application development and making for more-responsive remote controls.

The ITG-3200 features three 16-bit analog-to-digital converters (ADCs) for digitizing the gyro outputs, a user-selectable internal low-pass filter bandwidth, and a Fast-Mode I2C (400kHz) interface. Additional features include an embedded temperature sensor and a 2% accurate internal oscillator. This breakthrough in gyroscope technology provides a dramatic 67% package size reduction, delivers a 50% power reduction, and has inherent cost advantages compared to competing multi-chip gyro solutions.

  • Name: Three axis digital output gyroscope
  • Manufacturer: InvenSense
  • Datasheet


The Honeywell HMC5883L is a surface-mount, multi-chip module designed for low-field magnetic sensing with a digital interface for applications such as low- cost compassing and magnetometry. The HMC5883L includes our state-of-the- art, high-resolution HMC118X series magneto-resistive sensors plus an ASIC containing amplification, automatic degaussing strap drivers, offset cancellation, and a 12-bit ADC that enables 1° to 2° compass heading accuracy. The I2C serial bus allows for easy interface.

  • Name: 3-Axis Digital Compass IC
  • Manufacturer: Honeywell
  • Datasheet


The GlobalTop FGPMMOPA6C is an ultra‐compact POT (Patch On Top) GPS Module, The module utilizes the MediaTek new generation GPS Chipset MT3339 that achieves the industry’s highest level of sensitivity (‐165dBm ) and instant Time‐to‐First Fix (TTFF) with lowest power consumption for precise GPS signal processing to give the ultra‐precise positioning under low receptive, high velocity conditions.

Up to 12 multi‐tone active interference canceller (ISSCC2011 award), customer can have more flexibility in system design. Supports up to 210 PRN channels with 66 search channels and 22 simultaneous tracking channels, FGPMMOPA6C supports various location and navigation applications, including autonomous GPS, SBAS(note) ranging (WAAS, EGNO, GAGAN, MSAS), AGPS.

  • Name: GPS Standalone Module
  • Manufacturer: GlobalTop Technology
  • Datasheet



The Melexis US1881 is a Hall-effect latch designed in mixed signal CMOS technology. The device integrates a voltage regulator, Hall sensor with dynamic offset cancellation system, Schmitt trigger and an open-drain output driver, all in a single package. Thanks to its wide operating voltage range and extended choice of temperature range, it is quite suitable for use in automotive, industrial and consumer applications.

  • Name: Hall Latch – High Sensitivity
  • Manufacturer: Melexis
  • Datasheet


The split core type sensor is particularly suitable for DIY projects. It can be clipped straight on to either the live or neutral wire coming into the building without having to do any high voltage electrical work. The measured current is alternative, and the sensor is calibrated to measure a max of 100A AC. 100A is the RMS value of the maximum current the sensor can handle.

  • Name: Split-core current transformer
  • Manufacturer: Beijing YaoHuadechang Electronic
  • Datasheet


One of the major aspect of the Internet of Things is the data exchange between sensors, servers, databases and consumers. While there are many protocols available to enable this communication between different classes of endpoints, there are some protocols which are designed keeping IoT specific requirements in mind.

Message Queuing Telemetry Transport (MQTT)

MQTT is a Client Server publish/subscribe messaging transport protocol. It is light weight, open, simple, and designed to be easy to implement. These characteristics make it ideal for use in many situations, including constrained environments such as for communication in Machine to Machine (M2M) and Internet of Things (IoT) contexts where a small code footprint is required and/or network bandwidth is at a premium. The protocol runs over TCP/IP, or over other network protocols that provide ordered, lossless, bi-directional connections.Homepage

Very Simple Control Protocol (VSCP)

VSCP stands for Very Simple Control Protocol. The word “Protocol” may be misleading. VSCP is much more and should probably be called a framework instead. Just as HTML is for browsing the Internet, VSCP is an application level protocol making things interact. It uses CAN, RS-232, Ethernet, TCP/IP, MQTT, 6LowPan or whatever as it’s transport mechanism and work over cable and over the air. Homepage

Advanced Message Queuing Protocol (AMQP)

The Advanced Message Queuing Protocol (AMQP) is an open standard for passing business messages between applications or organizations. It connects systems, feeds business processes with the information they need and reliably transmits onward the instructions that achieve their goals. Homepage

Constrained Application Protocol (CoAP)

The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained (e.g., low-power, lossy) networks. The nodes often have 8-bit microcontrollers with small amounts of ROM and RAM, while constrained networks such as IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs) often have high packet error rates and a typical throughput of 10s of kbit/s. The protocol is designed for machine- to-machine (M2M) applications such as smart energy and building automation. Homepage