Design and application analysis of ultrasonic range finder based on single chip microcomputer

【 Abstract 】 Based on the relationship between distance and time in ultrasonic transmission, an ultrasonic range finder which can accurately measure the distance between two points is designed by using AT89C5 1 single chip microcomputer for control and data processing. The rangefinder is mainly composed of ultrasonic transmitting circuit, ultrasonic receiving circuit, single chip microcomputer control circuit, ambient temperature detection circuit and display circuit. Using the designed ultrasonic range finder, different distances are tested and the errors are analyzed in detail.

[Keywords:] ultrasonic ranging single-chip temperature sensor

With the development of society, people have higher and higher requirements for distance or length measurement. Ultrasonic ranging has been paid more and more attention because of its non-contact measurement and relatively high accuracy. The ultrasonic range finder designed in this paper can test different distances and make detailed error analysis.

I. Design principles

Ultrasonic rangefinder is based on the characteristics of ultrasonic reflection when encountering obstacles. The ultrasonic transmitter emits ultrasonic waves in a certain direction and starts timing at the same time. Ultrasonic waves travel in the air and will return immediately when they encounter obstacles on the way. The ultrasonic receiver will stop timing immediately when it receives the reflected wave. By continuously detecting the echo reflected by the obstacle after the generated wave is emitted, the time difference T between transmitting the ultrasonic wave and receiving the echo is measured, and then the distance L is calculated. The basic ranging formula is: l = (△ t/2) * c.

Where l is the distance to be measured.

T—— Time interval between transmitted wave and reflected wave.

C—— the sound speed of ultrasonic wave in air, which is 340m/s at normal temperature.

After the speed of sound is determined, l can be obtained by measuring the round-trip time of ultrasonic wave.

Second, the design goal of ultrasonic range finder

Measuring distance: within 5 meters; LED can correctly display the distance between two points; The error is less than 5%.

Three. Data measurement and analysis

1. Data measurement and analysis

Due to the limitation of actual measurement, six distances less than 1 m, namely, 30cm, 50cm, 70cm, 80cm, 90cm and 100cm, were selected for measurement, and each distance was continuously measured for 7 times to obtain the measurement data (temperature: 29℃), as shown in the table. As can be seen from the data in the table, the measured value is generally several centimeters larger than the actual value, but the accuracy of continuous measurement is still relatively high.

Remove a maximum value and a minimum value from each group of measurement data, then average it as the final measurement data, and finally make a comparative analysis. It is also scientific and reasonable to process data in this way. From the data in the table, although ultrasonic wave has temperature compensation, its relative error is also relatively large in relatively short distance measurement. Especially for the distance measurement of 30cm and 50cm, the relative errors are 5% and 4.8% respectively. But from all the measurement results, the absolute error of this design is relatively small and stable. The blind area of this design is about 22.6cm, which basically meets the design requirements.

2. Error analysis

The ranging error mainly comes from the following aspects:

(1) The ultrasonic transceiver probe has a certain angle with the measured point, which directly affects the accurate value of the measuring distance; (2) The sound intensity of ultrasonic echo is directly related to the distance to be measured, so the actual measurement is not necessarily triggered by the first echo crossing zero; (3) Because the tool is simple, the actual measurement distance also has errors. There are many factors that affect the measurement error, including on-site environmental interference, time-base pulse frequency and so on.

Fourth, the application analysis

Using ultrasonic to measure the ground distance in the atmosphere is a technology that was formally applied with the development of modern electronic technology. Because ultrasonic ranging is a non-contact detection technology, it is not affected by light and the color of the measured object, and it has certain adaptability in harsh environments (such as dust). Therefore, it is widely used. For example, surveying and mapping topographic maps, building houses, bridges, roads, mining, oil wells and so on. Ultrasonic distance measurement and ground distance measurement are realized by photoelectric technology. The advantage of ultrasonic rangefinder is that the instrument cost is lower than that of light wave rangefinder, which is labor-saving and convenient to operate.

Ultrasonic rangefinders are also used in advanced robotics. The ultrasonic source is installed on the robot, which emits ultrasonic waves to the surrounding area, and at the same time receives the echo reflected by obstacles to determine the robot's own position. It is used as a sensor to control the robot's computer and so on. Because of its easy directional emission, good directivity and good intensity control, the application value of ultrasonic wave has been paid more and more attention.

In a word, from the above analysis, we can see that using ultrasonic ranging has many advantages in many aspects. Therefore, the research of this topic has great practical and commercial value.

Verb (abbreviation of verb) conclusion

The measuring distance of this design meets the market requirements, and the measuring blind area is also controlled within 23cm. According to the market demand, this design can also increase the transmission power and make the measurement distance longer. In the aspect of display, the program can also be modified appropriately, so that the LED can display the temperature value when the ultrasonic wave is emitted, and when the distance value is calculated after receiving the ultrasonic echo, the LED can automatically switch to display the distance value, so as to have a more intuitive understanding of the visual effect.

References:

[1] Sun He. Principle and Application of MCS-5 1/96 Series Single Chip Microcomputer (Revised Edition) [M]. Beijing: Beihang University Press

[2] The Book of Jin Wang Zhi Shi Ming. Modern sensor technology [M]. Electronic industry press. 54438+0998+0-330. 100088880805

[3] Sun He. Principle and Application of MCS-5 1/96 Series Single Chip Microcomputer (Revised Edition) [M]. Beijing: Beijing University of Aeronautics and Astronautics Press.2002.46-170

[4] Lu,, Wang,,, Zhao,. Design of ultrasonic range finder [J]. Sensor technology. 2002

For reference only, please learn by yourself.

I hope it helps you.