Urban roads are staggered, and traffic lights are an important command system for urban traffic. As an effective means to control traffic flow and improve road traffic capacity, traffic lights have obvious effects on reducing traffic accidents. Programmable controller PLC is an industrial computer and its position in industrial automation is extremely important. It has the characteristics of miniaturization, low price and high reliability, and has been widely used in various industries. This paper is based on PLC's crossroad intelligent traffic light control system, which constitutes the electrical control of the crossroads with countdown display traffic lights and the software and hardware design method of the system. The experiment proves that the system is simple and economical, can effectively divert traffic and improve the traffic capacity of traffic intersections. After the system is powered on, the traffic command signal control system is controlled by two buttons. When the start button is pressed, the traffic command system starts to work according to the normal normal control function, and repeats and reciprocates according to the working sequence shown in FIG. The north-south green light is on for 25s and the light is on 3s. After the yellow light is on for 2s, the north-south red light is on for 30s. The east-west direction is the same as the north-south direction. In normal operation, there are two digital tube countdown display cards in the north-south direction and the east-west direction, and the corresponding remaining time value of the indicator light is displayed. The system mainly realizes two functions of digital display control of crossroad traffic lights and intelligent adjustment of display time. Figure 1 Cross-gate traffic lights normal working sequence FX series PLC has unparalleled speed, advanced functional logic options and positioning control. The FX2N series is the most advanced series in the Mitsubishi PLC's FX family. It features high-speed processing and a wide range of special function modules that can meet a single need. The FX2N is a choice for a wide range of applications from 16 to 256 inputs/outputs. The FX2N-80MR-D basic unit is selected here, with 40-point input/40-point relay output, and the common cathode 25.4cm seven-segment digital tube with rated voltage of 12V and rated current of 25mA (each segment) is selected; Directly powered by a DC12V/25mA power supply. A circular LED dot matrix with a diameter of 200mm is selected. The red, green and yellow lights on the left are rated at DC12V, rated current is 4.2A, rated power is 50W, and DC12V/4.2A power supply is used directly. The description of each control signal is shown in Table 1. When SB2 is pressed, the contact is disconnected and stops working. When SB3 is pressed, the seven-segment display shows "00". Whenever SB4, SB5, SB6 are pressed respectively, in the green-yellow red stage, the seven-segment digital tube is incremented by 1 and the lighting time is increased by 1s, which is used to adjust the working time of each indicator light according to the traffic volume. Table 1 Crossroads traffic light control signal description According to the control requirements, the I/O allocation table based on FX2N-80MR-D is shown in Table 2. Table 2 Programmable Controller Input/Output Assignment According to the traffic light design system control signal description (see Table 1) and the programmable controller input and output distribution table (see Table 2), design the control system electrical control diagram, as shown in Figure 2. Figure 2 Traffic light PLC control system electrical control diagram Load the initialization data, press the start button, and the system starts working. If the system does not need to adjust the data, it will work according to the preset data; if data adjustment is needed, press the stop button to clear the original data and adjust the digital display data in real time. The programming flow is shown in Figure 3. Figure 3 program flow chart
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They are different from traditional cigarettes and work by heating tobacco to a very low temperature. Tobacco is heated to 350 ° C in a heat-incombustible device, while traditional cigarettes burn at up to 900 ° C.
Still, the temperature at which non-combustion products are heated is high enough to vaporize and inhale harmful chemicals.
Although both are electronic devices, heated non-combustible products are also different from e-cigarettes or steam devices. These usually use chemical liquids and do not necessarily contain nicotine. E-cigarettes tend to heat liquids to around 250 degrees Celsius to produce vapor.