BLUETOOTH CONTROL Through Mobile

Creating a Bluetooth-controlled device with an Arduino Uno and an HC-05 Bluetooth module enables control of lights or even relays to manage AC appliances wirelessly using an Android smartphone.

- HEMAKUMAR K.

Communication between the smartphone and the Arduino Uno is facilitated by the HC-05 Bluetooth module, which provides an easy and cost-effective method to integrate remote control functionality into various devices. By utilising MIT App Inventor, it is possible to develop a custom app that sends commands to the Arduino, allowing complete control over connected devices, such as toggling lights on or off.

Whether controlling an LED or an AC device, this setup demonstrates a simple yet powerful application of Arduino and Bluetooth technology. The author’s prototype is shown in Fig. 1. The list of components required for the device is detailed in the Bill of Materials table. An image of the HC-05 Bluetooth module is shown in Fig. 2.

Circuit diagram

Fig. 3 shows the circuit diagram of the Bluetooth control through mobile. It is built around an Arduino Uno (MOD1), an HC-05 Bluetooth module (MOD2), and a few other components.

In the HC-05, the pin EN stands for enable. This pin, when pulled low, disables the device. When connected to 3.3V or left free, it enables the device. In this setup, it is left free so that it is always enabled. The HC-05 requires a VCC in the range of 3.6V to 6V. Since the Arduino Uno does not provide 3.6V, it is connected to 5V (do not connect to 3.3V as it is too low). The GND of the HC-05 is connected to the GND of the Arduino Uno.

For software serial communication between the HC-05 and the Uno, the library `SoftwareSerial.h` will be used. Pins 2 and 3 of the Uno will act as RX and TX. Connect RX (pin 2) directly to TXD of the HC-05. Since pin 3 cannot be connected to RXD (as the HC-05 expects 3.3V logic levels), a potential divider with 1k and 2k resistors is used to connect RXD to pin 3.