Implementation of LED simulated traffic lights based on 51 microcontroller

Specific function implementation:

The north and south red lights are on, and the east and west green lights are on; the north and south green lights are on, and the east and west red lights are on; during the traffic light conversion process, the yellow light flashes 5 times.

Devices used:

Several resistors, 4 red LED lights, 4 green LED lights, 4 yellow LED lights, AT89C51 chip

Proteus simulation schematic diagram:

Simulation test:

Knowledge introduction:

Proteus wiring

In order to make the entire schematic look concise and clear, we label the wires of the components instead of directly connecting them to the chip.

LED active low level

The characteristic of LED is one-way conduction. It can only conduct when the voltage of the anode is greater than the voltage of the cathode. In the simulation diagram, the anode of the LED is connected to the power supply, so we set the cathode to 0 before it can be turned on.

Main code (C language) KEIL5 implementation:

#include

sbit RED_A = P0^0; //east and west

sbit YELLOW_A = P0^1;

sbit GREEN_A = P0^2;

sbit RED_B = P0^3; //north and south

sbit YELLOW_B = P0^4;

sbit GREEN_B = P0^5;

unsigned char type = 1;

unsigned char count=0;

void delay(unsigned int x){

  unsigned char i;

  while(x--){

    for(i=0;i<120;i++);

  }

}

void light(){

  switch(type){

    case 1:  //GREEN_A , RED_B

      RED_A=1;YELLOW_A=1;GREEN_A=0;

      RED_B=0;YELLOW_B=1;GREEN_B=1; 

      delay(2000);

      type=2;

      break;

    case 2:

      delay(300);

      YELLOW_A=~YELLOW_A;GREEN_A=1;

      if(++count!=10) return;

      count=0;

      type=3;

      break;

    case 3: // RED_A,GREEN_B

      RED_A=0;YELLOW_A=1;GREEN_A=1;

      RED_B=1;YELLOW_B=1;GREEN_B=0;

    case 4:

      delay(300);

      YELLOW_B=~YELLOW_B;GREEN_B=1;

      if(++count!=10) return;

      count=0;

      type=1;

      break;      

  }

}

void main(){

  while(1){

    light();

  }

}

FAQ

Q：

Why does port P0 need to be connected to a pull-up resistor?

A：

Because the P0 port is a quasi-bidirectional port, that is, it has an open-drain output. When the P0 port is used as a parallel port, it can only output a low level and cannot output a high level. A pull-up resistor is required to output a high level.

Q：

How to quickly route Proteus?

A：

Press the capital A button, enter the command net=P0.#, then click "Click Object", and finally which wire you want to label is just a click away.