Circuit design of ultrasonic monitoring and early warning system based on ARM single chip

    With the development of informatization, intelligence and networking, embedded system technology has gained a broad space for development, and the field of industrial control is also undergoing a huge change. Real-time embedded software and hardware technology based on 32-bit high-end processors will be applied in every corner of industrial control. Embedded controllers have been applied to various fields such as industry, agriculture, education, national defense, scientific research and daily life due to their many advantages such as small size, high reliability, strong functions, flexibility and convenience, and have played an extremely important role in promoting technological transformation, product upgrading, accelerating the automation process and improving productivity in various industries.

    Design of obstacle distance detection circuit

    In this system, the ultrasonic distance measurement circuit is designed by MICROCHIP's PIC16C57, and the ultrasonic sensor selected is the T/R40-16 piezoelectric ceramic sensor. During operation, the main controller PIC16C57 sends a signal to make the ultrasonic transducer at the transmitting end send out voltage excitation. After being excited, it emits ultrasonic waves in the form of pulses. When the ultrasonic receiver receives the echo signal, it is transmitted back to the main controller. The timer in the main controller starts timing when the pulse signal starts to be emitted, and stops timing when the echo signal is received. The time interval multiplied by the speed of sound is twice the distance value. Thus, the distance from the obstacle to the transmitting point is calculated. Its circuit diagram is shown in Figure 2.

    The distance value is serially output through the 10th pin of PIC16C57 and connected to the serial port of ARM through the MAX232 chip. The chip MAX232 is an interface circuit designed for the RS232 standard serial port, which completes the conversion between TTL level and RS232 level.

    Design of sound and light alarm circuit

    This system requires a three-level alarm for dangerous conditions based on the critical value of the distance of obstacles that affect the stability of the loader. When in a low-risk situation, only the green indicator light is lit to remind the driver to pay attention; when the danger level increases, the yellow indicator light is lit, accompanied by a soothing buzzer, reminding the driver to take measures; when the highest danger level is reached, the red indicator light is lit, and the buzzer sound changes from soothing to urgent, reminding the driver to brake quickly. In the design, P2.20 (GPIOA4) of LPC2290 is used to drive the green LED, P2.21 (GPIOA5) drives the yellow LED, P2.22 (GPIOA6) drives the red LED, and P2.23 (GPIOA7) drives the buzzer. The designed alarm circuit is shown in Figure 3.

    Through test verification, the system has met the required functional requirements, with a maximum measurement value of 9.99m and an error of ≤0.01m. It is very convenient to install and easy to use. However, there is one shortcoming of the system, that is, when using ultrasonic sensors to detect road information in front of the vehicle, if it is a raised obstacle, it can be effectively detected, but if there is a pit in front, it cannot be detected, so further research is needed .