05-03-2013, 04:21 PM
BLUETOOTH BASED HOME AUTOMATION SYSTEM
USING CELL PHONE
BLUETOOTH BASED HOME AUTOMATION.pdf (Size: 236.42 KB / Downloads: 216)
ABSTRACT
Technology is a never ending process. To be able to
design a product using the current technology that will be
beneficial to the lives of others is a huge contribution to
the community. This paper presents the design and
implementation of a low cost but yet flexible and secure
cell phone based home automation system. The design is
based on a stand alone Arduino BT board and the home
appliances are connected to the input/ output ports of this
board via relays. The communication between the cell
phone and the Arduino BT board is wireless. This system
is designed to be low cost and scalable allowing variety of
devices to be controlled with minimum changes to its core.
Password protection is being used to only allow authorised
users from accessing the appliances at home.
INTRODUCTION
Wireless technologies are becoming more popular around
the world and the consumers appreciate this wireless
lifestyle which gives them relive of the well known “cable
chaos” that tends to grow under their desk. Now with the
embedded Bluetooth technology, digital devices form a
network in which the appliances and devices can
communicate with each other. Today, home automation is
one of the major applications of Bluetooth technology.
Operating over unlicensed, globally available frequency of
2.4GHz, it can link digital devices within a range of 10m
to 100m at the speed of up to 3Mbps depending on the
Bluetooth device class. With this capability of Bluetooth;
we propose a home automation system based on Bluetooth
technology [1].
There are few issues involved when designing a home
automation system. The system should be scalable so that
new devices can easily be integrated into it. It should
provide a user- friendly interface on the host side, so that
the devices can be easily setup, monitored and controlled.
This interface should also provide some diagnostic
services so that if there is any problem with the system, it
can be tracked down. Moreover the overall system should
be fast enough to realize the true power of wireless
technology. Finally the system should be cost effective in
order to justify its application in home automation.
HARDWARE ARCHITECTURE AND
IMPLEMENTATION
This home automation system consists of two main
hardware components: the cell phone and the Arduino BT
board. The cell phone hosts the Python script which
enables the user to access the home appliances and also
the control commands for the appliances. This Python
script communicates with the Arduino BT board and sets
up an ad-hoc communication protocol between the two
devices, which allows controlling the behaviour of the
Arduino BT board.
An off-the-shelf ready made Arduino BT is an 8-bit
microcontroller board based on the ATmega168 and the
Bluegiga WT11 Bluetooth module [11] is used. It supports
wireless serial communication over Bluetooth. This board
has 23 digital input and output ports, 16kB of flash
memory, 10-bit analog to digital converter, pulse width
modulator and extra hardware resources which makes it
suitable for the required task. The Arduino BT board can
be programmed wirelessly over the Bluetooth connection
using the microcontroller’s high-level interactive C
language [11].
The Bluetooth antenna in our module picks up the packets
sent from the cell phone. Subsequently, these packets
containing the appliance status commands are pipelined
through ATmega168 microcontroller and the designed
analogue circuitry according to the definition of each
output. Different home appliances are connected to the
digital output ports of the Arduino BT board via relays to
provide sufficiently high currents and voltage
compatibility. For test purposes, 25W, 240V lamps have
been used. Figure 2 shows the relay configuration for each
device and Figure 3 depicts the Arduino BT board’s
communication with the home appliances.
Stack Initialization Module
Bluetooth stack is a piece of software or firmware that
manages and controls a Bluetooth device. The stack
initialization process will involve a number of steps to get
the Bluetooth device ready for wireless communication.
This means setting several parameters such as serial port
name, baud rate, connectable mode and discoverable
mode. In this project, the open source software provided
with the Arduino BT (Arduino Alpha) was used for the
initialization. The code is shown below.