With the development of the civil aviation industry, the number of aircraft is increasing, the number of ground support vehicles is increasing, and the speed of the airport vehicles is too fast, resulting in the occurrence of unsafe incidents of scraping the aircraft, which directly affects the continued airworthiness of the aircraft. Endangering the operational safety of airlines, but also causing certain economic losses. In order to reduce the occurrence of such unsafe incidents, this design uses a single-chip microcomputer to realize the overspeed alarm of the vehicle to remind the driver to decelerate, and record the overspeed condition in real time as one of the basis for evaluating the driver of the vehicle, so as to facilitate the management of the employee.
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1 system hardware design
1.1 system function
The main functions of the system implementation are as follows:
(1) button adjustment time and real time display time;
(2) Display the speed of the vehicle in real time;
(3) When the vehicle exceeds the specified speed value, the violation is stored in the serial memory in the form of data, and an audible alarm is issued, and the alarm light flashes;
(4) The manager uses the IC card to read the violation of the vehicle and cancel the alarm.
1.2 overall design of the system hardware
The overall structure of the system is shown in Figure 1. It adopts STC89C52 single-chip microcomputer as the main control chip, which mainly includes power supply module, signal acquisition module, clock module, LED display module, button module, alarm module, AT24C64 serial memory module and contact IC card storage module. The STC89C52 mainly completes the control of the peripheral hardware and the information processing function; the power module steps down the 12V vehicle power supply to the 5V single-chip power supply; the signal acquisition module uses the TLP521 photocoupler to convert the collected high-level pulse signal into a 5V pulse signal. The clock module provides real-time time for LED display; the LED display module uses 74HC595 to drive the digital tube to realize time and speed display; the button module is mainly used to adjust the time; the alarm module realizes the sound alarm and flashing warning after overspeed; AT24C64 serial memory The overspeed information is stored; the contact IC card memory can read the data in the AT24C64, and the alarm can be cancelled after reading the data.
1.2.1 main control module
The main control module mainly adopts STC89C52 single-chip microcomputer. The MCU has 4 parallel I/O ports, each port has 8 port lines. P0 port can be used as 8-bit quasi-bidirectional I/O port when there is no external memory. External memory It can be used as an address line/data line; P1, P2 and P3 ports can be used as 8-bit quasi-bidirectional I/O ports. P3 port is very different from other I/O ports, except for general I/O ports. Each pin also has a special function. All external chips can be extended through these ports.
1.2.2 Power Module
The power module uses the LM2596 switching voltage regulator, which is a step-down power management monolithic integrated circuit that can output 3A of drive current with good linearity and load regulation. In this system, the fixed output 5V version is selected, that is, the regulator model is LM2595-5.0. The device integrates a frequency compensation and fixed frequency generator with a switching frequency of 150kHz. Compared to low frequency switching regulators, smaller filter components can be used. Since the device requires only four external components, the design of the switching power supply circuit is greatly simplified. The schematic is shown in Figure 2.
1.2.3 signal acquisition module
At present, the airport vehicle speed sensor mostly uses a Hall sensor, and its output signal is a pulse signal. The high level value of the pulse signal is basically the same as the vehicle power supply voltage value, and needs to be converted into a 5V pulse signal that can be collected by the single chip through the photocoupler. As shown in Figure 3, Signal is the actual output signal of the speed sensor. The converted signal is connected to the INT1/P3.3 pin of the microcontroller. The number of pulses is recorded by the external interrupt function and converted to the speed value by calculation.
1.2.4 Clock Module
The clock module uses the DS1302 trickle charge clock chip, which contains an RTC/calendar and 31B of static RAM. It communicates with the microprocessor through a simple serial interface. The RTC/Calendar provides seconds, minutes, hours, days, dates, months, and years. If the number of days in the month is less than 31 days, the adjustment will be made automatically, including the leap year correction. The clock can work in 24-hour and 12-hour systems, and is indicated by AM/PM in a 12-hour system. The system is designed to use a 24-hour clock.
Synchronous serial communication is used between the DS1302 and the microprocessor. Only three lines are needed to communicate, namely RST (reset), I/O (data line) and SCLK (serial clock), and Vcc1 is connected to the 3V standby power supply.
Guangzhou Ehang Electronic Co., Ltd. , https://www.ehangmobile.com