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Arduino UNO R3/MEGA 2560 R3 Project 4: Traffic Light

Posted by Fiona Su on


In the previous program, we have done the LED blinking experiment with one LED. Now, it’s time to up the stakes and do a bit more complicated experiment-traffic light. Actually, these two experiments are similar. While in this traffic light experiment, we use 3 LEDs with different color rather than one LED.

Hardware List

  • Arduino uno board/Arduino MEGA 2560 *1
  • USB cable *1
  • Red M5 LED*1
  • Yellow M5 LED*1
  • Green M5 LED*1
  • 220Ω resistor *3
  • Breadboard*1
  • Breadboard jumper wires* 4

Video Tutorial


Connection for REV4:


Connection for 2560 R3:


Sample Code

Since it is a simulation of traffic light, the blinking time of each LED should be the same with those in traffic light system.
In this program, we use Arduino delay () function to control delay time, which is much simpler than C language.

int redled =10; // initialize digital pin 8.
int yellowled =7; // initialize digital pin 7.
int greenled =4; // initialize digital pin 4.
void setup()
pinMode(redled, OUTPUT);// set the pin with red LED as “output”
pinMode(yellowled, OUTPUT); // set the pin with yellow LED as “output”
pinMode(greenled, OUTPUT); // set the pin with green LED as “output”
void loop()
digitalWrite(greenled, HIGH);//// turn on green LED
delay(5000);// wait 5 seconds

digitalWrite(greenled, LOW); // turn off green LED
for(int i=0;i<3;i++)// blinks for 3 times
delay(500);// wait 0.5 second
digitalWrite(yellowled, HIGH);// turn on yellow LED
delay(500);// wait 0.5 second
digitalWrite(yellowled, LOW);// turn off yellow LED
delay(500);// wait 0.5 second
digitalWrite(redled, HIGH);// turn on red LED
delay(5000);// wait 5 second
digitalWrite(redled, LOW);// turn off red LED


When the uploading process is completed, you can see traffic lights of your own design.
Note: this circuit design is very similar with the one in LED chasing effect.
The green light will be on for 5 seconds, and then off, followed by the yellow light blinking for 3 times, and then the red light is on for 5 seconds, repeatedly forming a cycle.
Experiment is now completed. Thank you.


All Tutorial



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