Video summary

HC-05 Bluetooth Module with Arduino-MIT App Inventor

Main summary

Key takeaways

Technology

What the video teaches (overall)

A step-by-step guide to control an LED on an Arduino Uno using a HC-05 Bluetooth module, with a mobile UI built using MIT App Inventor. The mobile app sends simple characters ("1" / "0") over Bluetooth; the Arduino reads the serial data and turns the LED ON or OFF.

1) HC-05 module overview + pin usage

The HC-05 includes labeled pins: EN, VCC, GND, TX, RX, and STATE.

The tutorial specifies only the following connections for communication:

  • VCC → Arduino 5V
  • GND → Arduino GND

  • HC-05 TX → Arduino RX (Arduino RX corresponds to digital pin 0)

  • HC-05 RX → Arduino TX (Arduino TX corresponds to digital pin 1)

Wiring note: uses male-to-female jumper wires to cross-connect TX ↔ RX.

2) LED wiring on Arduino

  • LED longer leg → Arduino pin 13
  • LED shorter leg → GND

This matches the Arduino code behavior using:

  • pinMode(13, OUTPUT)
  • digitalWrite(13, HIGH) / digitalWrite(13, LOW)

3) Arduino code logic (Bluetooth serial @ 9600 baud)

Key code concepts

  • Uses a character/integer-like variable: incoming value (initialized to 0)
  • Serial configuration:
    • Serial.begin(9600) to match HC-05 serial communication
  • LED setup:
    • pinMode(13, OUTPUT)

Main loop behavior

  • When data is available (Serial.available()):
    • Read it (Serial.read()) into incoming value
    • If incoming value == 1 → turn LED ON (digitalWrite(13, HIGH))
    • If incoming value == 0 → turn LED OFF (digitalWrite(13, LOW))

The tutorial also references a guide: “serial communication with Arduino Uno” (for help, if needed).

4) Uploading the Arduino program (important practical note)

The video warns: when the HC-05 is connected, you may not be able to upload the sketch (because uploading also relies on TX/RX).

Therefore:

  1. Upload the code first
  2. Then connect the HC-05 afterward

5) Building the mobile app in MIT App Inventor

Workflow

  • Go to https://appinventor.mit.edu
  • Create/login to an account (tutorial suggests using Google credentials)
  • Start a new project named “Bluetooth”

MIT App Inventor has:

  • Designer view (drag/drop components)
  • Blocks view (logic)

UI components added

  • ListPicker to show paired/available Bluetooth devices (configured to target hc-05)

  • Bluetooth client component

  • Two buttons:
    • Button “on” → sends "1"
    • Button “off” → sends "0"

The tutorial also updates UI text (for example, changing “LED Bluetooth” to something like “connected” after device selection).

App logic (Blocks view)

  • When selecting a device from the ListPicker, the app connects to the chosen HC-05
  • Button on sends 1 to the Arduino over Bluetooth
  • Button off sends 0 to the Arduino over Bluetooth
  • Result: pressing the buttons toggles the Arduino LED

6) Installing the app to the phone (MIT AI2 Companion)

The tutorial uses MIT AI2 Companion to install the app via QR code.

Notes:

  • Wi‑Fi may or may not be needed; internet can be required for install/download.

After installing/opening the app:

  1. Enable Bluetooth on the phone
  2. Pair with HC-05 using the default password mentioned: "123"
  3. Open the created app, select hc-05, and press on/off to control the LED

Main speakers / sources

  • Single tutorial presenter (referenced as the lesson narrator; no specific name provided in subtitles)
  • Referenced source: MIT App Inventor / MIT AI2 Companion platform documentation and UI flow

Original video