Crossroad traffic light controller system based on Multisim 10 simulation software

0 Preface

MulTIsim 10 is a well-known EDA simulation software. The latest version was launched by Canadian IIT and the company in 2007. In the Windows environment, MulTIsim 10 software has a complete integrated design environment, which integrates the creation of schematic diagrams, circuit test analysis, and graphical display of results into the same circuit window. Before the actual circuit is built, the MulTIsim 10 simulation software is used for virtual testing, which can modernize the experimental methods and experimental methods, expand the experimental capacity, make the experimental content more complete, improve the experimental efficiency, and save a lot of experimental resources. The basic steps of MulTIsim 10 software for design simulation analysis are: design and create simulation circuit schematic diagram → setting of circuit diagram options → use simulation instruments → set simulation analysis method → start Multisim 10 simulation.

The following describes the process of designing a crossroad traffic controller system with Muitisiml0 as the platform.

1 System Overview

At crossroads in town streets, in order to ensure traffic order and pedestrian safety, there is generally a set of red, yellow, and green traffic lights on each road. Figure 1 is a schematic plan view of a typical intersection: there are two main roads and branch roads, and each road has a set of red, yellow, and green traffic lights. The vehicles on the main road and the branch road alternately run, and there are more vehicles on the main road. Therefore, the traffic time of the main road is long, and the number of vehicles on the main road is small, so the traffic time of the main road is short. When the main road is running, the green light of the main road is on and the red light of the main road is on for 60 s; when the main road is running, the green light of the main road is on and the red light of the main road is on for 30 s. Each time the green light turns red, the yellow light flashes for 3 s (frequency 5 Hz). At this time, the red light at another intersection remains unchanged. The traffic controller designed based on the above rules controls the state transition of the two sets of red, yellow, and green traffic lights at the intersection, which can easily realize the command of various vehicles and pedestrians to realize the automation of traffic management at the intersection.

2 Traffic controller circuit design and simulation

The traffic controller circuit is divided into three unit circuits according to function: oscillation circuit, counter and decoding display circuit, main control circuit and signal lamp decoding drive.

2.1 Oscillation circuit

The oscillation circuit outputs clock pulses with frequencies of 1 Hz and 5 Hz, and an amplitude of 5 V, respectively. In order to improve accuracy, the design system uses the 555 timer to design a multivibrator with an output frequency of 100 Hz, and then obtains a clock pulse of 1 Hz through a frequency divide by 100 (100-ary counter), and obtains 5 Hz by a frequency divide by 20 Clock pulse.

2.1.1 100 Hz multivibrator composed of 555 timers

555 timer is a multi-purpose analog and digital integrated circuit, which has been applied in many fields such as waveform generation and conversion, control and detection, household appliances and electronic toys. The 555 timer has various functions and is widely used. As long as it is externally equipped with several resistance-capacitance components, it can form circuits such as monostable triggers, Schmitt triggers, and multivibrators.

The circuit diagram of the 100 Hz multivibrator composed of 555 timers is shown in Figure 2. The circuit is composed of a 555 chip, two resistors and two capacitors. The capacitor C is charged and discharged through the resistor to generate oscillation, thereby outputting a rectangular pulse.

2.1.2 Frequency divider composed of 100 and 20 divided by 74LS192

The counter is a timing component used to implement the counting function. It can be used not only to count pulses, but also to be used as the timing, frequency division and digital operations of digital systems and other specific logic functions. It is widely used in circuit design. 74LSl92 is a synchronous decimal reversible counter, which has a dual-clock decimal reversible counter, asynchronous parallel set function, hold function and clear function. CLR is the clear terminal and LOAD is the set control terminal. Two pieces of 74LSl92 can be used to form a second decibel divider, which divides a 100 Hz rectangular wave by 100 to obtain a 1 Hz clock pulse, and obtains a 5 Hz clock pulse by 20 frequency division. The circuit of 100 frequency division and 20 frequency division is shown in Figure 3.

The output QA of the 74LS119 on the right is a 5 Hz clock pulse obtained by frequency division by 20, and the output QD is a 1 Hz clock pulse obtained by frequency division by 100.

2.2 The counter and decoding display circuit composed of 74LSl92

The counter circuit has a 60 s countdown (down counter with a count range of 60 to 1), a 30 s countdown (down counter with a count range of 30 to 1), and a 3 s count function. The realization of these three kinds of counting is mainly composed of two decimal counter 74LSl92 chips, and then the conversion is realized through the main control circuit, and finally the countdown in each direction shares a set of decoding display digital tubes to display. The counter circuit diagram formed by 74LSl92 is shown in Fig. 4: a piece of 74LSl92 chip on the left is the unit bit of the counter, and a piece of 74LSl92 chip on the right is the ten bit of the counter. Tube display. Among them, the CLK of the 74LS192 chip as a single digit is connected with a 1 Hz clock pulse.

2.3 Main control circuit and signal lamp decoding drive

The main control circuit and the signal lamp decoding drive are composed of various gate circuits and T flip-flops, which can realize the conversion of the timing circuit and the control of the signal lamps in all directions. The main control circuit and signal lamp decoding drive circuit are shown in Figure 5. The red light 1, yellow light 1, and green light 1 in Fig. 5 are the three traffic signal lights of the main road, and the red light 2, yellow light 2, and green light 2 are the three traffic signal lights of the branch road. The 8 outputs of the two 74LSl92 in Figure 4 are connected with an OR gate and connected to the LD setting terminal to determine whether the countdown timer is setting or counting.

At the beginning of the work, LD is O and the counter is preset. At this time, the initial state of T flip-flop Q = 0, so the preset number is 30 s. After the setting is completed, LD becomes 1, the counter starts counting down from 30 s, the state of the T trigger flips Q = 1, the red light 1 of the main road and the green light 2 of the branch road turn on. When the counter counts to "03" seconds, the QD2, QC2, QB2, and QA2 of the ten-digit counter in Figure 4 are connected to the QD1 and QC1 of the one-digit counter with a NOR gate to make the signal light switch, and the green light 2 is off , The yellow light 2 flashes at a frequency of 5 Hz within these 3 s, and the red light 1 remains unchanged. When the countdown decreases to "00", the LD becomes 0 again, the counter is preset for 60 s, and then counts down again, and so on.

2.4 Simulation results

By combining the above unit circuits, the overall circuit of the traffic control light can be obtained. Click the "Simulate / Run" button of the Multisim 10 software or directly press the "F5" key to simulate the Traffic Light control circuit. The countdown display of the circuit is first 30 s. The green light 2 of the main road is on, and the vehicles of the main road can pass freely; the red light of the main road is on, and the vehicles of the main road are prohibited. The time indicator decreases from 1 to 30 per second from the preset 30 s. The green light 2 of the branch road changes to a yellow light 2, and the yellow light flashes once at 0.2 s (frequency of 5 Hz), other The lights remain unchanged. When the number is reduced to 1, the display changes to the preset 60 s after 1 s, the yellow light 2 of the branch road is converted to the red light 2, the traffic of the branch road is prohibited, and the red light 1 of the main road is converted to the green light 1, the main road Road vehicles can pass freely, and so on.

3 Conclusion

Using Multisim 10 to design and simulate each unit circuit and the overall circuit of the intersection Traffic Light Controller, just click the mouse to build the circuit conveniently and quickly, and modify the circuit conveniently. After the circuit design simulation is completed, the actual circuit is constructed, thereby reducing costs and greatly improving the efficiency of teaching and professional design.