IoT devices come in various forms, and like other ordinary mechanical products, they include input devices to detect user operations and changes in the surrounding environment, as well as output devices that provide certain information or directly interact with the environment, functioning as the brain of the device through a microcontroller.
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Input Devices
To enable devices to gather information about the surrounding environment and user operations, components such as sensors and buttons (electronic devices) must be implemented on the machine.
For example, consider a smartphone. What sensors does this smartphone have? You may have noticed that it is equipped with a touchscreen, buttons, cameras, accelerometers, light sensors, and many other sensing devices. These sensors help users grasp the surrounding situation in more detail and precision. The type and accuracy limits of the sensors largely determine the performance of the machine, so selecting sensors is a crucial step in the device development process.
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Output Devices
The goal of IoT is not just to sense states but to visualize them. The true purpose is to interfere with humans and the environment, controlling the world to develop toward a target state.
When displaying certain information to users, devices such as monitors, speakers, and LEDs that output information play a role. These devices are also referred to as output devices.
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Microcontroller
A microcontroller (Micro Controller) is an IC (Integrated Circuit) chip that serves as a controller. It can execute programs and read terminal states based on descriptions, or output specific signals to the connected circuits.
A microcontroller consists of memory (for storing programs and temporary data), a CPU (for executing computations and control), and peripheral circuits (which include external interfaces and necessary functions like timers). When using a microcontroller, various interfaces such as serial ports and USB, as well as circuits, are required.
4. Sensor Types
Sensors are the main devices in IoT, and they can be classified into various types based on different classification standards. Below is a classification based on what is being measured.
4.1 Temperature Sensors
The function is to detect the hot and cold levels of objects. For instance, thermocouple sensors work based on the Seebeck effect. When two different metal conductors form a closed loop, if the temperatures at the two contact points are different, an electromotive force will be generated in the loop. This type of sensor is widely used in industrial furnace temperature monitoring and environmental temperature measurement. Thermistors are also commonly used temperature sensors, measuring temperature based on the resistance value of metal or semiconductor materials changing with temperature.For instance, platinum resistance temperature sensors are highly accurate and are often used in high-precision temperature measurement scenarios, such as laboratory environmental control and temperature compensation for precision instruments.
4.2 Pressure Sensors
These are primarily used to measure pressure levels. For example, strain gauge pressure sensors change their resistance value when pressure is applied to elastic elements, which causes deformation. This type of sensor is widely used in automotive tire pressure monitoring systems to monitor tire pressure in real-time, ensuring driving safety.
Capacitive pressure sensors measure pressure by detecting changes in the distance between capacitor plates or the dielectric constant of the medium caused by pressure variations. They are used in aerospace to measure parameters such as atmospheric pressure of aircraft.
4.3 Displacement Sensors
These are used to measure changes in the position of objects. For instance, inductive displacement sensors operate based on electromagnetic induction principles. When the displacement of the measured object changes the inductance of the sensor’s coil, the displacement can be converted into an electrical signal through the detection circuit. They are used in machining to measure the relative displacement between tools and workpieces to ensure processing accuracy.
Photoelectric displacement sensors measure displacement using principles of reflection, refraction, or obstruction of light. For example, they are used on automated production lines to detect the position of products on conveyor belts.
4.4 Speed Sensors
These measure the speed of moving objects. For instance, electromechanical speed sensors operate based on electromagnetic induction principles. When a moving conductor cuts through magnetic field lines, it generates an induced electromotive force, which is proportional to speed. This is applied in automotive speedometers to convert wheel rotation speed into vehicle speed display.
Laser Doppler speed sensors use the Doppler effect of laser light. When laser light strikes a moving object, the frequency of the reflected light changes, and the speed of the object can be measured by detecting this frequency change. They are commonly used in fluid speed measurements, such as measuring the flow speed of rivers.