Control an Led using Android App

Required materials

You can download the .apk file for the app here. Or you can also create the file from scratch by following tutorials on the https://appinventor.mit.edu/explore/ai2/tutorials .

Here's how the app will look:

Download the .apk file from the link below

Arduino Code

#include <SoftwareSerial.h>

SoftwareSerial BT(10, 11);

String state;

void setup() {

  BT.begin(9600);

  Serial.begin(9600);

  pinMode(4, OUTPUT);

void loop() {

  while (BT.available()) {

    delay(10);

    char c = BT.read();

    state += c;

  if (state.length() > 0){

    Serial.println(state);

  if (state == "On") {

    digitalWrite(4, HIGH);

  else if(state == "Off") {

    digitalWrite(4, LOW);

  state = "";

After downloading the .apk file move that file to your smartphone and open it. Follow the installation wizard to install the app.

Turn on your smartphone’s Bluetooth.

Alternatively, you can follow the steps below to generate a QR code and scan it using the MIT AI Companion app on playstore https://play.google.com/store/apps/details?id=edu.mit.appinventor.aicompanion3&hl=en .

Connect your phone to the Arduino HC-05 bluetooth module. the code is 0000 or 1234.

Launch the app and connect. (see video below).

OnOff.mp4

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