Hardware composition and types of ultrasonic sensors
Ultrasonic sensor is a sensor developed using ultrasonic technology. The main component of the ultrasonic sensor is a piezoelectric chip that can both emit and receive sound waves. Ultrasonic sensors used for detection have different structures and can be divided into straight probes, double probes, oblique probes, etc. The materials and thicknesses that make up piezoelectric wafers also vary.
The principle of ultrasonic ranging is to emit sound waves through an ultrasonic transmitter. When the sound wave encounters an obstacle, it returns. The distance between the transmitter and the obstacle is calculated based on the conduction speed of the sound wave and the return time. This is the time difference ranging method. Ultrasound is also a kind of sound wave, and its propagation speed is related to factors such as temperature and pressure. However, when the temperature changes little, the influence of temperature can be ignored. If the requirements for distance measurement are high, temperature compensation should be used for correction.
Ultrasonic sensor hardware components
The hardware composition of the ultrasonic sensor is shown in the figure. The ultrasonic sending circuit is composed of transistors, resistors, T/R40-16 piezoelectric ceramic ultrasonic sensors and transformers. It can be seen from relevant data that ultrasonic waves with a frequency of about 40kHz have the best propagation efficiency in the air. Its working principle is as follows:
When it first starts working, the microcontroller initializes the port through software programming, making the pin RA2 low level. At this time, the ultrasonic transmitting circuit does not work. After the system initialization is completed, the microcontroller controls the RA2 pin to output a high level through software to make the transistor collector change to a low level. Then the transformer increases this voltage and loads it onto both ends of the ultrasonic sensor T40 to generate ultrasonic waves. If there is an object to be measured within the effective ranging direction, the echo from the previous ultrasonic wave should be received before the latter ultrasonic wave is sent out. Otherwise, it is considered that there is no obstacle in front. The maximum measurement distance range of the system is 9.99m, so the pulse interval time is t=2s/v=2×9.99m/340 m/s=59 ms. The ultrasonic circuit consists of an ultrasonic receiving sensor and a three-stage amplification and filter circuit. Figure 4-6 shows the ultrasonic receiving circuit. Its working principle is as follows: Since the echo of the ultrasonic wave will become very weak when the distance is relatively long, the amplitude of the electrical signal converted by the ultrasonic receiving sensor is also small, so the signal needs to be amplified. When the ultrasonic receiving sensor receives the ultrasonic signal, through a three-stage amplification circuit, the R40 pin changes from low level to high level, and the microcontroller stops counting and calculates the distance.
What are the main types of ultrasonic sensors?
Ultrasonic sensor is a commonly used ranging device. According to its working principle and application scenarios, it can be divided into the following types:
1. Ultrasonic ranging module: This is the most common type of ultrasonic sensor. Usually consists of an ultrasonic transmitter and receiver, which can measure the distance between the object and the sensor. An ultrasonic transmitter emits an ultrasonic pulse, and a receiver receives and measures the return time of the pulse to calculate the distance.
2. Ultrasonic dynamic ranging module: Compared with ordinary ultrasonic ranging modules, the ultrasonic dynamic ranging module can provide higher ranging accuracy and fast measurement speed. It is suitable for applications that require frequent measurements or fast moving targets.
3. Sonar sensor: Sonar sensor is mainly used for underwater ranging and obstacle avoidance. It uses the propagation characteristics of sound waves in water to measure the distance and position of underwater targets by sending ultrasonic signals and receiving their echoes.
4. Sonar sensor: Sonar sensor is mainly used for sonar positioning and underwater navigation. It uses the principle of sound wave propagation and reflection in water to determine the position and direction of the target by receiving the intensity and delay of the sound wave signal.
5. Ultrasonic presence measurement sensor: This sensor can detect the presence or absence of an object. When an object enters or leaves the working range of the sensor, the sensor will detect changes in the ultrasonic signal and send it to the control system for corresponding processing.
These are some common types of ultrasonic sensors. Depending on the specific application needs and scenarios, choosing the appropriate ultrasonic sensor can achieve different functions and measurement requirements.
Review Editor: Huang Fei
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