What are the commonly used sensors for the Internet of Things?

In the era of the Internet of Everything, sensors are one of the most critical components.

According to the general division, the Internet of Things is divided into three parts: the sensing layer, the network layer and the application layer. The sensing layer, as the data source of the network layer transmission and the data foundation of the application layer calculation, plays a vital role. The important components that make up the sensing layer are a variety of sensors.

Sensors can be divided into different categories according to different divisions. For example in a non-electrical physical quantity being measured is divided, it can be divided into the pressure sensor and a temperature sensor.

According to the working mode when converting non-electrical physical quantities into electrical physical quantities, it can be divided into energy conversion type (no additional energy access when working) and energy control type (additional energy access when working). In addition, it can be divided into ceramic sensors and integrated sensors according to the manufacturing process.

We start with a variety of different non-electrical physical quantities to measure the sensors that are common in the Internet of Things.

distance sensor

The distance sensor can be divided into optical and ultrasonic according to the pulse signal emitted during ranging. The principle of the two is similar, by sending a pulse signal to the measured object, receiving the reflection, and then calculating the distance of the measured object according to the time difference, the angle difference and the pulse speed.

Distance sensors are widely used in mobile phones and various smart luminaires, and products can vary according to the user's different distances during use.

Light sensor

The working principle of the light sensor is to use the photoelectric effect to convert the intensity of the ambient light into a power signal through the photosensitive material. Depending on the photosensitive material of different materials, the light sensor will have various divisions and sensitivities.

The light sensor is mainly used in the ambient light intensity monitoring of electronic products. The data shows that in general electronic products, the power consumption of the display is as high as 30% of the total power consumption. Therefore, changing the brightness of the display with the change of ambient light has become the most important energy-saving means. In addition, it can intelligently make the display more soft and comfortable.

Temperature Sensor

The temperature sensor can be roughly divided into two types, contact type and non-contact type. The former is to let the temperature sensor directly contact with the object to be tested to sense the temperature change of the measured object through the temperature sensitive element, and the latter is to make the temperature sensor Maintain a certain distance from the object to be tested, and detect the intensity of the infrared radiation emitted from the object to be measured, thereby calculating the temperature.

The main applications of temperature sensors are in areas where temperature is closely related to intelligent insulation and ambient temperature detection.

Smoke sensor

Smoke sensors are commonly used in chemical detection and optical detection depending on the principle of detection.

The former utilizes the radioactive cesium 241 element, and the positive and negative ions generated in the ionized state are directionalally moved by the electric field to generate a stable voltage and current. Once smoke enters the sensor, it affects the normal movement of positive and negative ions, causing corresponding changes in voltage and current. The calculation can determine the strength of smoke.

The latter passes through a photosensitive material, which normally emits light completely on the photosensitive material, producing a stable voltage and current. Once smoke enters the sensor, it will affect the normal illumination of the light, resulting in fluctuating voltage and current. The calculation can also determine the strength of the smoke.

Smoke sensors are mainly used in fire alarms and safety detection.

Heart rate sensor

Commonly used heart rate sensors mainly use the principle of sensitivity of specific wavelengths of infrared light to blood changes. Due to the periodic beating of the heart, the blood in the blood vessel is regularly changed in flow velocity and volume, and the current number of heartbeats is calculated through signal noise reduction and amplification processing.

It is worth mentioning that, depending on the skin color of different people, the infrared rays emitted by the same heart rate sensor are different from the skin and the skin reflection, which causes a certain error in the measurement results.

In general, the deeper the skin color of an individual, the more difficult it is for infrared rays to be reflected back from the blood vessels, and thus the greater the influence on measurement errors.

At present, heart rate sensors are mainly used in various wearable devices and smart medical devices.

Angular speed sensor

Angular velocity sensors, sometimes called gyroscopes, are based on the principle of conservation of angular momentum. A typical angular velocity sensor consists of a rotor that is located at the axis and rotatable. The direction of motion and relative position of the object are reflected by the rotation of the rotor and the change in angular momentum.

A single-axis angular velocity sensor can only measure changes in a single direction, so a typical system requires three single-axis angular velocity sensors to measure changes in the three directions of the X, Y, and Z axes. At present, a general 3-axis angular velocity sensor can replace three single-axis, and it has many advantages such as small size, light weight, simple structure, and good reliability. Therefore, various forms of 3-axis angular velocity sensors are currently the main development. trend.

The most common angular velocity sensor use scene is a mobile phone. For example, the famous mobile game such as Need for Speed ​​is mainly an interactive mode that generates the left and right swing of the car through the action of the angular velocity sensor. In addition to mobile phones, angular velocity sensors are currently widely used in navigation and positioning and AR/VR.

In addition to the sensors mentioned above, air pressure sensors , acceleration sensors, humidity sensors, fingerprint sensors, and fingerprint sensors are common in the Internet of Things. Although their working principles are different, the most basic principles are mentioned above, that is, the light to be measured, converted into electrical quantities by light, sound, materials and chemical principles, but most of them are based on specific fields in general principles. Based on specific upgrades and extensions.

Since the invention of the industrial era, sensors have played a vital role in areas such as production control and probing. Just like human eyes and ears, as a carrier for receiving information from the outside world in the Internet of Things, an important front end of the sensing layer, sensors will usher in a high-speed development period with the popularity of the Internet of Things.