# Bluetooth LED

## What will we do

In this lesson we will learn how to switch an LED’s on and off from our Android phone using a bluetooth module.

We will wire up our circuit to include a LED and a Bluetooth module. We will also write some code that will read a character for the Android app that will tell the LED to come on and go off.

we will use character **a** to turn on the LED and character **b** to switch off the LED

The Android app can be downloaded [here](https://kidscode.nyc3.digitaloceanspaces.com/kides_code_arduino_led.apk).

{% hint style="success" %}
Please ensure that you have mBlock setup on you computer. Click [here](/setting-up-mblock.md) to setup mBlock
{% endhint %}

## Parts List

You will need the following parts:

* **1x** arduino uno
* **1x** arduino USB Cable
* **1x** Breadboard
* **7x** Jumper Wire
* **1x** LED (any colour)
* **1x** Resistor
* **1x** HC-05 Bluetooth module.

I purchased my module from this [store](https://www.robofactory.co.za/arduino-modules/88-bluetooth-transceiver-module.html).

{% embed url="<https://www.robofactory.co.za/arduino-modules/88-bluetooth-transceiver-module.html>" %}

## **Wiring it up** <a href="#wiring-it-up" id="wiring-it-up"></a>

![](/files/-M9FDn-c9VcGtR9NM1ZH)

## mBlock IDE

Launch the mBlock IDE (<https://ide.mblock.cc/#/>) and select the Arduino Uno Device and install the [Kids Code Extension](https://docs.kidscode.co.za/arduino-kids-lessons/blinking-an-led#install-the-kidscode-extension)&#x20;

## Block Coding <a href="#block-coding" id="block-coding"></a>

![](/files/-M9FEIyxew4kOY2eX9oh)

You can find the green coding blocks under **Bluetooth HC-05** at the bottom of your block list

![](/files/-M9FErs9j2o9vJaJ2Bch)

## Block Coding Explained <a href="#block-coding" id="block-coding"></a>

1. Using the green **Start Bluetooth HC-05** block you initialize the Bluetooth
2. You need to check if the bluetooth is receiving data, using the green  **HC-05 receiving data** block
3. If you receiving data then you will read the data from the Bluetooth using the **read data from HC-05** block.
4. You will then check if your received character **a** and then turn **ON** the LED at pin **D5**.
5. You will also  check if your received character **b** and then turn **OFF** the LED at pin **D5**.

{% hint style="info" %}
Please remove the green RX jumper from the Arduino board before you upload your code. If the jumper is not removed then you will get an error.
{% endhint %}

{% embed url="<https://ide.mblock.cc/#/?cloudProjectId=267234>" %}

## Testing your code <a href="#block-coding" id="block-coding"></a>

* Down the Android app from [here](https://kidscode.nyc3.digitaloceanspaces.com/kides_code_arduino_led.apk).
* Pair the bluetooth with your phone. Search for **HC-05** and pair this device. The password will be **1234**
* Open the app and press the Connect button

![](/files/-M9FHQm45F7axTJ97XMe)

* Select **HC-05** from the list.
* Once connected, press the **ON** button and your **LED** should light up.
* Press the **OFF** button and the LED will go **OFF**

&#x20;


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.kidscode.co.za/arduino-lessons/bluetooth-led.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.