A Design Scheme for Automobile Exhaust Gas Detection System

　　0 Introduction

　　The traditional method of automobile exhaust detection uses chassis dynamometer testing. The working principle of this method is: indoors, combined with chassis dynamometer and gas analyzer, the exhaust emissions of motor vehicles are tested under preset motor vehicle driving conditions. However, since this method must be done indoors and requires the motor vehicle to be tested under fixed driving conditions, it cannot truly reflect the exhaust emissions on the actual road, and the emission test system is too large and difficult to operate. It often takes a lot of time to get the test results for the tested vehicle.

　　The existence of the above-mentioned shortcomings indicates that the traditional automobile exhaust detection system cannot effectively regulate automobile exhaust emissions. It is necessary to develop a system that can detect the exhaust composition of a car when it is driving on an actual road. This system can immediately determine whether the automobile exhaust exceeds the standard based on the test results, effectively saving detection time.

　　Taking advantage of the automatic identification feature of RFID technology, this paper introduces a design scheme of an automobile exhaust detection system based on RFID technology.

　　1. Overall design of the system

　　The automobile exhaust detection system circuit designed in this paper includes a detection module and a judgment module. The automobile exhaust detection system can accurately detect the exhaust components of automobiles traveling on actual roads through the detection module, and send the detection results to the judgment module of the detection section. The judgment module makes a judgment on whether the automobile exhaust exceeds the standard and sends a corresponding signal to the alarm module. Judgment modules can be set up in multiple sections to receive exhaust emission data of automobiles passing through the detection section at any time. It can realize accurate testing of motor vehicle exhaust components without manual operation, greatly reducing the detection time. The schematic diagram of the automobile exhaust detection system is shown in Figure 1.

　　The system is to accomplish the following tasks:

　　(1) The system completes the detection of automobile exhaust and determines whether the automobile exhaust exceeds the standard. The circuit includes a detection module and a judgment module. The detection module is installed on the car, and the judgment module is installed near the detection section.

　　(2) The judgment module completes the control of whether the detection module starts to detect automobile exhaust, and sends a corresponding signal to the alarm module based on whether the detected data exceeds the standard.

　　(3) The detection module completes the detection of vehicle exhaust and sends the detection results and the vehicle license plate number to the judgment module.

　　2. System hardware circuit design

　　According to the functional requirements of the automobile exhaust detection system, an automobile exhaust detection system based on RFID technology was designed.

　　2.1 Detection Module

　　The detection module is composed of a central control module, a sensor module and a detection end RFID reader/writer. The sensor module includes at least a nitrogen oxide sensor, a carbon monoxide sensor and a hydrocarbon sensor. The sensor module is installed inside the exhaust pipe of the car. The central control module is electrically connected to the detection end RFID reader/writer, and the sensor module is electrically connected to the central control module.

　　The partial circuit schematic diagram of the detection module is shown in Figure 2. The central control module uses a single-chip microcomputer STC12C5630AD. The P3.7 port of the single-chip microcomputer is electrically connected to the sensor module to control whether the sensor module is working. The P1.0, P1.1 and P1.2 pins of the single-chip microcomputer are electrically connected to the sensor module to receive the signal collected by the sensor module. The four pins of the SPI interface of the single-chip microcomputer: MISO, SCLK, MOSI and S are electrically connected to the SPI interface of the RFID reader at the detection end, respectively, to receive the UID of the readable and writable tag read by the RFID reader at the detection end, and can send the data collected by the sensor module and the car license plate number to the RFID reader at the detection end.

　　2.2 Judgment Module

　　The judgment module is composed of a judgment end RFID reader/writer, a readable and writable tag, a processing module and an alarm module. The processing module is electrically connected to the judgment end RFID reader/writer, and the processing module is electrically connected to the alarm module. [page]

　　The partial circuit schematic diagram of the judgment module is shown in Figure 3. The processing module uses the single-chip microcomputer Atmega8, and the four pins of its SPI interface: MOSI, SCK, MISO, MOSI and S are electrically connected to the SPI interface of the judgment end RFID reader and writer respectively, and are used to read the data in the judgment end RFID reader and writer. The data is the data stored in the readable and writable tag read by the judgment end RFID reader and writer.

　　The alarm module uses a color LED as an indicator light and a speaker as a generator. The PC3 and PC4 ports of the single-chip Atmega8 are electrically connected to the green indicator light D1 and the red indicator light D2 respectively, and the PC5 port is electrically connected to the speaker U1 through the resistor R5. If the detected automobile exhaust exceeds the standard, the red LED will light up and the speaker will sound an alarm; if it does not exceed the standard, only the green LED will light up.

　　The judgment module can be set up in multiple sections respectively. Different sections can receive and detect the exhaust emission components of cars passing through the section at any time, and can immediately determine whether the car exhaust exceeds the standard, effectively saving detection time.

　　3. System software design

　　When a car passes through a section of road where exhaust gas is to be detected, the RFID reader at the detection end of the system reads the readable and writable tag UID of the judgment module of the detection section through radio waves, and sends the UID to the central control module. The central control module sends a signal to the sensor module. After receiving the signal, the sensor module starts to detect the exhaust gas of the car. The central control module receives the signal detected by the sensor, and sends the collected data and the car license plate number to the RFID reader at the detection end. The RFID reader at the detection end writes the data into the readable and writable tag of the judgment module through radio waves. The RFID reader at the judgment end reads the data of the readable and writable tag and sends it to the processing module. The processing module sends a corresponding signal to the alarm module based on whether the detected data exceeds the standard.

　　4. Summary

　　This paper first introduces the current status of automobile exhaust detection system research, and proposes a design scheme for automobile exhaust detection system. This scheme tests the exhaust composition of automobiles traveling on actual roads through the detection module, and immediately makes a judgment on whether it exceeds the standard through the judgment module of the detection section, realizing the function of accurately testing whether the automobile exhaust composition exceeds the standard without manual operation, effectively reducing the detection time.