Introduction:

Want to control electrical appliances around you right from your Android device remotely? So, you have landed at the right place… !! After reading this article you will be able to develop an embedded system which will make you able to control electrical loads remotely from your Android Mobile/Tablet.

The entire project consist of two parts, Android Application and an electronic controlling circuitry. The Android device communicates with the controlling circuit through Bluetooth channel. So, the distance up to which it works depends upon the range of the Bluetooth Module used in your electronic system. Download the Droid Remote Application from Google Play and install it on your Android device free of charge.

You can develop the android application as per your requirement by modifying the original codes provided in the download link. The electronic circuit can be built easily as per the description provided below

Description:

The circuit consists of a Bluetooth module, a microcontroller, relay driver IC along with relays to switch electrical loads and of course the power supply. The Bluetooth module receives the command sent by the Android device and sends it to the microcontroller through its USART serial interface. On receiving the command, the microcontroller takes the necessary action.

The microcontroller used in this system is Atmel’s ATmega8, a RISC architecture based 8-bit MCU.  It runs on 5V power supply. So to get the desired voltage, the voltage regulator (LM7805 or 78E05) is used. On the other hand, the Bluetooth module runs at 3.3V which is derived by the IC TC1185. The UART of both the devices are in TTL logic, so we can directly connect  Rx  of Microcontroller to  Tx of the Bluetooth Module through a current limiting resistor.

The baud rate of the serial communication is 9600bps. The Microcontroller can’t source sufficient current to drive relays. Hence, the relay driver IC (ULN2803/ULN2003) is used. It is a open collector type darlington transistor pair. All relays are rated at 12V DC. The loads to be controlled are to be connected in between the COM and N/O pins of each relays.

Firmware for the microcontroller ATmega8 is written in CodeVisionAVR compiler. The microcontroller is clocked with the internal crystal at 8MHz. The UART baudrate is set at 9600bps.
Built the circuit in a general purpose PCB and program the microcontroller through the ISP header.

Install the Application “Droid Remote” from Google Play (click) or download the application here. Save the downloaded DroidMot.apk file in your Android Device and Install it. Prior to installation make sure that you have enabled the option to Install Non-market application in your device. (NOTE: To enable this option go to Setting)
After Installation, launch the application, click on the Search button. After the search is complete, it will show the available nearby Bluetooth Device with their MAC address. Click on the bluetooth device address which is attached in the electronic circuit. Once a device is connected, the application will automatically pointed to the Control Tab. By clicking  the Toggle Buttons it switches the corresponding relay ON and OFF. Some Screen shots of the app are given below.

droid_remote2droid_remote1

 

droid_remote3

Part List:

Resistors

1. R1 –  68K, 1/4 Watt – 1 nos
2. R2 – 115K, 1/4 Watt – 1 nos
3. R3 – 4.7K, 1/4 Watt – 1 nos 

Capacitors

1. C1 –  0.1uF – 1 nos
2. C2 – 470uF – 1 nos
3. C3 – 47pF – 1 nos
4. C4 – 1uF – 1 nos 

Integrated Circuits (ICs)

1. U1 – Microcontroller – ATMEGA8 – 1 nos
2. U2 – 78E05 – 1 nos
3. U3 –  ULN2803 or ULN2003 – 1 nos
4. U4 – TC1185 or any 3.3 V regulator – 1 nos 

Diodes

1. D1 1N4001 – 1 nos 

Misc

1. BT MODULE – ESD200 – 1nos
2. DC1- DC SOCKET – 1 nos
3. ISP HEADER – 10 Pin Connector – 1 nos
4. RL1-RL4 – 12 V Relay – 4 nos ( can be increased or decreased as per your requirement)

Schematic:

sch_dr

Source Code:

 

Droid Remote App at Google Play

Droid Remote.apk (Android Application)

C Source Code for ATmega8

HEX code to directly burn on to the Microcontroller


 

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