Kids Code — Traffic Signal — Lesson 4

3 min readJun 3, 2020

This is lesson 4 in the series of how to teach kids electronics and coding with Arduino and mBlock (block programming).

You can view Lesson 3 here

What will we do

This example uses three LEDs to make a model traffic light signal. You can use all red LEDs if you like, but its more realistic if you use red, yellow and green.

The LEDs cycle around in the sequence red, green, yellow and then back to red again

Parts List

You will need the following parts:

1x arduino uno
1x arduino USB Cable
1x Breadboard
4x Jumper Wire
1x Red LED
1x Green LED
1x Yellow LED
3x Resistor

Wiring it up

To add the extra LEDs and resistors, wire them up as shown in the breadboard layout below.

Ensure that the LEDs are the right way around, with the longer positive leads (anodes) to the left.

How does it work

Think of how a traffic light works.

it starts from RED
then turns to GREEN
then turns YELLOW
and back to RED

Think about the how long the light stays on before it changes to the next colour

This time that it takes before the light changes is called a WAIT in coding. So the program will WAIT for a specific number of seconds before the next light changes to the next colour

In order to turn the light ON or OFF in code, we say that if we want the light on then we need to set it to HIGH and if we want the light OFF we setup it to LOW.

So to change the traffic lights we say