Project tutorial
Traffic light full size for cars

Traffic light full size for cars © GPL3+

Complete design of a traffic light using 250 high brightness LED, learn the electronic circuit and have fun controlling it with your Arduino

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Components and supplies

A000066 iso both
Arduino UNO & Genuino UNO
Original Arduino Uno Atmega 328P.
4415447 jg5sklyzsj
Resistor 220 ohm
Ceramic resistor of 220Ohm and 2W of power.
Resistor 3900 Ohm
Fairchild semiconductor pn2222abu. image
General Purpose Transistor NPN
Kingbright wp7113srd d image
5 mm LED: Red
High brightness led red
Led technology l03r5000q1 image
5 mm LED: Yellow
High brightness led yellow
Kingbright wp7113sgd
5 mm LED: Green
High brightness led green
49ac3715 40
DC Power Connector, Jack

About this project

Learn how to build a traffic light with more than 200 LEDs.

Simple and very productive project, with this project, besides learning to program the Arduino, you will have lessons in Basic electronics, welding and making of printed circuit board.

At the end you will have a traffic light with real size with approximately 250 high brightness LEDs alternating in green, yellow and red.

Traffic Lights with LED's

We will try to make a very complete article explaining part of how this project is, from electronics to programming and assembly.

The components that we will use will be LED, resistor, Transistor, power supply and arduino.

Analyzing the schematic above we have a high power resistor connected right at the source output to the circuit.

The resistor value is 220 Ohm for 2W of power, this resistor was calculated for a 12V and 3A source, if you use another source you need to do the current calculations to guarantee a voltage drop of 4V on the LED and only pass 15mA for each line at most.

Checking the image above we see that the LEDs will be connected in 3 blocks, where each block is driven by a transistor, which we will see in the next image.

Each block has 3 other sub-blocks with 7 LEDs connected in parallel and these 3 sub-blocks connected in series, that is, we have a circuit with 21 LEDs.

This circuit is connected to a transistor as in the image below:

The transistor is the BC548 where, as previously mentioned, one is connected for each LED circuit and these transistors are connected in parallel at the Arduino output protected by a 3900 Ohm 1 / 8W resistor.

The image below represents the complete connection with the Arduino in a more didactic way.

We used the Fritzing LED BARGRAPH component to symbolize the 7 LEDs in parallel and the complete circuit represented by each color by 01 LED would look like this:

Now you can distribute the 63 LEDs of each color so that it is in the original shape of the traffic light, you can draw the circuit above in an electronic circuit software and print to produce your plate, or you can use a perforated copper plate, just like to the one used in this schematic.


Code Traffic LightArduino
int vermelho = 4;
int amarelo =  3;
int verde =    2;

void setup() {
  pinMode(vermelho, OUTPUT);
  pinMode(amarelo, OUTPUT);
  pinMode(verde, OUTPUT);


void loop() {
  digitalWrite(vermelho, HIGH);
  digitalWrite(amarelo,  LOW);
  digitalWrite(verde,    LOW);
  digitalWrite(vermelho, LOW);
  digitalWrite(amarelo,  LOW);
  digitalWrite(verde,    HIGH);
  digitalWrite(vermelho, LOW);
  digitalWrite(amarelo,  HIGH);
  digitalWrite(verde,    LOW);



Full Circuit of Traffic Light


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