At present, with the development of China's vehicle industry and traffic roads, cars are also taking on more and more tasks in transportation. When the vehicle fails during driving, according to the relevant regulations of the traffic regulations, it is necessary to place a triangular warning sign at an appropriate distance in the direction of the incoming vehicle. Only when it is placed at a certain safe distance, can it play its due safety role. Generally speaking, during the daytime, the warning sign should be placed 50 meters behind the car on the city road. If it is on the highway, it should be placed about 150 meters behind the car, so as to leave enough for the driver behind the car. Avoidance distance. If it is at night or when the light is dim, the distance to be placed needs to be lengthened accordingly. It is necessary to place a point on the city road about 100 meters away from the faulty vehicle and about 250 meters away on the highway.
The current method of placement is carried out by the driver and the policeman walking to the appropriate position on foot, especially on the expressway, in the process of placing the warning sign, it is easy to have a secondary accident. In response to this situation, in order to avoid the occurrence of secondary accidents, this paper designed a smart triangle warning sign that can be remotely operated.
The main function has a remote walking function, and the driver uses the remote control to control the triangle warning sign to travel. (2) A function with a preset distance. A button is designed on the surface of the control panel to set the distance at which the warning sign is placed, and the set distance is displayed by using a three-digit LED seven-segment digital tube. The set distance value can be changed by repeating the action of the button. When the triangle warning sign moves to the set distance, it can no longer advance, and can only adjust the state or backward. (3) A warning function with flashing lights. High-brightness red and blue LED lights are installed on the warning sign, and the red and blue LED lights flash alternately during normal operation, and a light warning effect is emitted.
The circuit block diagram designed in this paper is as shown. The control core of this circuit uses AT89S52 single-chip microcomputer produced by Atmel Company. This single-chip microcomputer is a low-power, high-performance 8-bit microcontroller with 8KB in system programmable flash memory, which is convenient for process debugging.
2.3 Remote control transmitting and receiving module selection There are two ways to remotely transmit and receive. Firstly, the infrared transmitting and receiving module is adopted. Its characteristic is that it does not interfere with the work of other electrical equipment, nor does it affect the surrounding environment. The circuit debugging is simple. Encoding the transmitted signal can realize multi-channel infrared remote control function, but the control distance of the infrared remote control is about 10 meters, which is difficult to meet the requirements of this design. The other is to use the wireless remote control and receiving module PT2262/PT2272. The encoding chip PT2262 and the decoding chip PT2272 are currently commonly used in wireless communication circuits. The data output digits of the receiving chip PT2272 are 0, 2, 4, 6 digits, etc. The data output has two modes of "temporary storage" and "latch", which is convenient for the user to select and use, and the suffix is ​​M for "temporary storage." Type", the suffix is ​​L is "latch type". In this design, since it is necessary to control the forward, backward, left turn, and right turn of the warning sign, four control signals are required, which requires 4-bit data encoding, so the design uses the M4 model.
The working process is: When the remote control transmitter has a button action, the PT2262 first encodes, and then, after being modulated by the 315 MHz modulation circuit, the power is amplified, and finally the code is output. The receiving circuit sends the received signal to the inside through the 14 pin of the PT2272, and then decodes the received signal. After receiving the signal, PT2272 compares its address code through two comparisons, the VT pin outputs a high level, and the corresponding data pin (D0~D3) corresponding to PT2262 also outputs a high level, and these data are passed through the single chip microcomputer. The P2.4-P2.7 pin is input to the inside of the MCU. After processing, the corresponding MCU pin outputs the corresponding level signal to drive the motor. Therefore, when the remote control has a button press and the receiving module receives the signal, the single chip microcomputer can perform corresponding operations on the remote control warning sign according to the received signal.
The motor drive module motor drive module uses a high-voltage, high-current L298N motor drive chip produced by SGS, which contains two H-bridge circuits that can drive the left and right DC motors of the remote warning sign. When the left motor rotates alone, the remote warning sign turns to the right; when the right motor rotates alone, the remote warning sign will turn to the left. If the left and right motors rotate forward or reverse at the same time, the function of forward and backward of the remote warning sign is realized.
Because no speed regulation is required in this design, all enable terminals ENA and ENB are directly connected to the high level. Its drive circuit diagram is as shown. Intelligent triangle warning sign structure block diagram The setting distance of Henan science and technology machinery and automatic motor drive circuit is set by a button connected with the external interrupt pin P3.2 of the MCU, which is 000050100150250000. When the predetermined distance is 000, the remote control alarm The placement of the cards is controlled entirely by remote control buttons. In the other four cases, when the distance is set, just press the forward button on the remote control, the remote warning sign will automatically drive until the driving stops at the specified distance. During the driving process, the remote control can be used to remotely alert. The direction of the card is adjusted.
The distance measuring circuit adopts the photoelectric measuring method. The specific method is to fix and fix an opaque disc on the motor shaft, and there are N halved holes on the edge, and the photoelectric couple is mounted on both sides of the disc, and the position is aligned. At the hole. When the motor drives the disc to the round hole, the LED illuminates the phototransistor through the circular hole, and the triode is turned on, and the triode is turned off. The motor rotates once a week, according to the P3.4 pin of the single chip microcomputer. N low levels will be generated. Therefore, according to the number of low levels, the number of turns of the motor can be calculated. Combined with the circumference l of the wheel, the relationship between the set distance L and the total number of low levels n can be obtained as follows: The counter T0 controls the running distance by counting the low-level pulses.
The design idea of ​​the system software is to adopt a modular program structure, which mainly includes a main program, an external interrupt program, a timer interrupt program, a display and an LED flashing driver subroutine. In the main program, it is determined whether the preset distance is needed to determine the running of the program. When the preset distance is not required, the motion of the remote warning sign is completely controlled by the remote controller, and according to the action of the remote controller, it is determined what action the warning sign should perform. (including forward, backward, left turn, right turn), thereby controlling the motor drive chip L298, driving the forward and reverse rotation of the corresponding DC motor to realize the function corresponding to the button pressed by the wireless remote controller. If the preset distance is required, the program starts the counter T0 of the single-chip microcomputer to realize the control of the distance. The main program flow chart is as shown.
The system is initialized and shown in the flowchart of the main program of the research and LEO function. Through the comprehensive debugging of the hardware and software of the system, the design task requirements can be completed. The advantages of this design are as follows: Firstly, the powerful functions and remote control technology of the single-chip microcomputer are used to solve the safety hazard problem in the process of placing and retrieving the warning sign. In practical applications, the warning effect is very obvious, especially at night or in the light. It is better for darker occasions. The second is to be able to pre-set the distance, through the actual measurement, on the flat road, when placed to 250 meters away, the error is not more than 10 meters. The design realizes the characteristics of simple circuit, convenient use and stable operation.
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