micro:bit traffic light example

In this example we will create a simple traffic light system with a micro:bit. This is fairly simple and at a basic level involves switching red, amber and green LEDs on and off at certain time intervals.

We will have blocks, JavaScript, python and an Arduino code example.

Schematic/Layout

I used a little traffic light board which contained all 3 of the LEDs on a module which made it easy to connect to my micro:bit

This is the board that I purchased for anyone interested. It saves a lot of messing about with breadboards, these are low cost.

AliExpress.com Product – WAVGAT LED traffic lights light-emitting module / digital signal output Traffic light module / electronic building blocks

If you were to use a micro:bit, LEDs and resistors you need to create something like this

microbit and traffic light

Traffic lights parts list

This is a list of parts exported from the fritzing layout above

Assembly List

Shopping List

If you buy all the parts separate I have supplied some links to sources – you can buy a pack of LEDs with different colours.

Code Examples

First of all we use blocks.

We will use digital write blocks and set the pins to either 0 or 1.

0 will switch a common cathode LED off and 1 will switch it on.

You need to try and create something like this

microbit screenshot

Javascript Example

Now for the JavaScript code for the example above

Download the hex file and copy it to your micro:bit and watch the traffic light effect on the LEDs

[codesyntax lang=”javascript”]

basic.forever(() => {

    pins.digitalWritePin(DigitalPin.P0, 1)

    basic.pause(4000)

    pins.digitalWritePin(DigitalPin.P0, 0)

    basic.pause(1000)

    pins.digitalWritePin(DigitalPin.P1, 1)

    basic.pause(4000)

    pins.digitalWritePin(DigitalPin.P1, 0)

    basic.pause(1000)

    pins.digitalWritePin(DigitalPin.P2, 1)

    basic.pause(4000)

    pins.digitalWritePin(DigitalPin.P2, 0)

    basic.pause(1000)

})

[/codesyntax]

Python example

We can also do the same in python, I used the online python editor at https://python.microbit.org/v/1.1

Type in the following and then download the hex file to your micro:bit and you should a traffic light sequence

[codesyntax lang=”python”]

from microbit import *
 
red_pin = pin0    # giving the LED pins names by using variables
amber_pin = pin1  # makes it easier to see how the program works
green_pin = pin2
 
while True: 
    # red - turn amber LED off and red LED on
    amber_pin.write_digital(0)
    red_pin.write_digital(1)
    sleep(4000) # delay 4 seconds
    # amber - turn red LED off and amber LED on
    red_pin.write_digital(0)
    amber_pin.write_digital(1)
    sleep(1000)
    # green - turn amber LED off and green LED on
    amber_pin.write_digital(0)
    green_pin.write_digital(1)
    sleep(4000)
    # amber - turn green LED off and amber LED on
    green_pin.write_digital(0)
    amber_pin.write_digital(1)
    sleep(1000)

[/codesyntax]

Arduino Example

If you have your Arduino IDE setup so that you can use it to develop and program your micro:bit then here is an example for you.

Again fairly straightforward

[codesyntax lang=”cpp”]

const int redPin = 0;
const int amberPin = 1;
const int greenPin = 2;
 
void setup() 
{
  pinMode(redPin, OUTPUT);
  pinMode(amberPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
}
 
void loop() 
{
    
    digitalWrite(amberPin, LOW);
    digitalWrite(redPin, HIGH);
    delay(4000);
    
    digitalWrite(redPin, LOW);
    digitalWrite(amberPin, HIGH);
    delay(1000);
    
    digitalWrite(amberPin, LOW);
    digitalWrite(greenPin, HIGH);
    delay(4000);
    
    digitalWrite(greenPin, LOW);
    digitalWrite(amberPin, HIGH);
    delay(1000);
}

[/codesyntax]

There we have it a simple traffic light example for the micro:bit – just choose your preferred development tool and go for it