Arduino Workshop-Traffic Lights

We are now going to create a set of traffic lights based on the system that will change from green to red, via amber, and back again, after a set length of time using the four-state system

Parts Required

Arduino Uno

Breadboard

5mm LED

100Ω Resistor

Jumper Wires

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Circuit Diagram

Traffic Lights


Connect your circuit as in Traffic Lights. This time, we have connected three LEDs with the anode of each one going to digital pins 8, 9 and 10, via a 150Ω current-limiting resistor (or whichever value you require) for each. Figure 2-6. The circuit for Project 3 We have taken a jumper wire from the ground of the Arduino to the ground rail at the top of the breadboard. A ground wire goes from the cathode leg of each LED to the common ground rail via a current-limiting resistor (this time, connected to the cathode). For this simple circuit, it doesn’t matter if the resistor is connected between the digital pin and the anode, or between the cathode and ground, as long as it is in series with the LED

Code

	int ledDelay = 10000; // delay in between changes
	int redPin = 10;
	int yellowPin = 9;
	int greenPin = 8;
	void setup() {
	pinMode(redPin, OUTPUT);
	pinMode(yellowPin, OUTPUT);
	pinMode(greenPin, OUTPUT);
	}
	void loop() {
	digitalWrite(redPin, HIGH); // turn the red light on
	delay(ledDelay); // wait 5 seconds
	digitalWrite(yellowPin, HIGH); // turn on yellow
	delay(2000); // wait 2 seconds
	digitalWrite(greenPin, HIGH); // turn green on
	digitalWrite(redPin, LOW); // turn red off
	digitalWrite(yellowPin, LOW); // turn yellow off
	delay(ledDelay); // wait ledDelay milliseconds
	digitalWrite(yellowPin, HIGH); // turn yellow on
	digitalWrite(greenPin, LOW); // turn green off
	delay(2000); // wait 2 seconds
	digitalWrite(yellowPin, LOW); // turn yellow off
	// now our loop repeats
	}
	Figure 2-7. The four states of a traf ic light system (image by Alex43223 from WikiMedia)
	In the next project, we are going

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Previous tutorial

1. Arduino Workshop-LED Flashers