Bluetooth based home appliances control

Introduction

This project is designed to operate electrical loads using any Bluetooth enabled device.  The system operates electrical loads depending on the data transmitted from the Android application device. Operating conventional wall switches is difficult for elderly or physically handicapped people. This proposed system solves the problem by integrating house hold appliances to a control unit that can be operated by a smart-phone/Tablet etc.

Bluetooth communication

Bluetooth is a wireless technology standard for exchanging data over short distances (using short-wavelength UHF radio waves in the ISM band from 2.4 to 2.485 GHz) from fixed and mobile devices, and building personal area networks (PANs). Invented by telecom vendor Ericsson in 1994,  it was originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices, overcoming problems of synchronization. Bluetooth is managed by the Bluetooth Special Interest Group (SIG), which has more than 25,000 member companies in the areas of telecommunication, computing, networking, and consumer electronics. 

Design principle and operation

In this project Bluetooth module is interfaced to 8051 microcontroller through a DTMF decoder. This Bluetooth receives the DTMF commands from the mobile phone using Bluetooth communication device using wireless communication. The program which is written to the 8051 microcontroller communicates with Bluetooth module to receive the commands through a decoder after a successful pairing. The Bluetooth based Wireless Appliance control system accepts input from a mobile console. The mobile sets must have a key pad, few keys from that keypad designated for control of the Appliances connected at the user end. In this project ‘1’,’2’, ‘3’,’4’,’5’ & ’6’ of the keyboard is activated, each key is assigned with one of the appliance through an non potential contact relay. On pressing a Key automatically one DTMF code is generated and transmitted. Microcontroller switches the electrical loads automatically based on the commands received from the Bluetooth. All the loads are connected through a solid state relay and motor driver.

Block diagram

Sections description

Power supply

In this we are using Transformer (0-12) v, 1Amp, IC 7805 & 7812, diodes IN 4007, LED & resistors. Here 230V, 50 Hz ac signal is given as input to the primary of the transformer and the secondary of the transformer is given to the bridge rectification diode. The o/p of the diode is given as i/p to the IC regulator (7805 &7812) through capacitor (1000mf/35v). The o/p of the IC regulator is given to the LED through resistors.

Circuit diagram

LED

LED

1k

- +

IN4007 * 4

GND

9-0-9Vac/1Amp

1000uF/35V

7812

POWER SUPPLY

+5V

+12V230VAC50Hz 2.2k

7805

DTMF decoder

Introduction to DTMF DTMF means: Dual Tone Multi-Frequency, There is no base band multiplexing done on DTMF signals. The signal generated by a DTMF encoder is a direct algebraic summation, in real time, of the amplitudes of two sine (cosine) waves of different frequencies. i.e. pressing '1' will send a tone made by adding 1209 Hz and 697 Hz to the other end of the line.

DTMF decoder

There are many ways to detect and decode these DTMF tones. One idea could be an eight sharp-tuned filter combination with detection circuits. Needless to say, this is very impractical, considering the various ICs (Integrated Circuits or 'chips') made by different manufacturers all over the world. Most of these ICs do not require more than one (inexpensive) 3.58 MHz x-tal or resonator and the power circuitry. Usually the output is 4-bit binary + 1 strobe.

Decoder IC Operation.

The Bluetooth receiver receives the frequency modulated DTMF signals and the output (DTMF tones) are fed to the dedicated IC KT3170 which is a DTMF-to-BCD converter. This IC when fed with the DTMF tones gives corresponding BCD output; for example, when digit 1 is pressed, the output is 0001 and when digit 4 is pressed the output is 0100. This IC also requires a 3.58MHz crystal for its operation.

Circuit diagram

1m

15

DTMF DECODER

L ED1

14

0.1u f0.1u f

18

95

217

11

CM 8870

4

12

330e

8

signal i/p

6

7

163

C RYST A L

V C C

101m

13

330k

Mother board

The motherboard of this project is designed with a MSC –51 core compatible micro controller. The motherboard is designed on a printed circuit board, compatible for the micro controller. This board is consisting of a socket for micro controller, input /output pull-up registers; oscillator section and auto reset circuit. Micro controller core processor:IntroductionDespite it’s relatively old age, the 89C51 is one of the most popular Micro controller in use today. Many derivatives Micro controllers have since been developed that are based on--and compatible with--the 8051. Thus, the ability to program an 89C51 is an important skill for anyone who plans to develop products that will take advantage of Micro controller.

Mother board

The memory types are illustrated in the following graphic. They are: On-Chip Memory, External Code Memory, and External RAM. On-Chip Memory refers to any memory (Code, RAM, or other) that physically exists on the Microcontroller itself. On-chip memory can be of several types, but we'll get into that shortly. External Code Memory is code (or program) memory that resides off-chip. This is often in the form of an external EPROM. External RAM is RAM memory that resides off-chip. This is often in the form of standard static RAM or flash RAM. Code Memory Code memory is the memory that holds the actual 8051 program that is to be run. This memory is limited to 64K and comes in many shapes and sizes: Code memory may be found on-chip, either burned into the Microcontroller as ROM or EPROM. Code may also be stored completely off-chip in an external ROM or, more commonly, an external EPROM.

Mother board

Auto reset circuit

The auto reset circuit is a RC network as shown in the mother board circuit diagram. A capacitor of 1-10mfd is connected in series with a 8k2 resister the R-C junction is connected to the micro controller pin –9 which is reset pin. The reset pin is one when ever kept high( logic 1) the program counter (PC) content resets to 0000h so the processor starts executing the program. from that location. When ever the system is switched ON the mother board gets power and the capacitor acts as short circuit and the entire voltage appears across the resistor, so the reset pin get a logic 1 and the system get reset, whenever it is being switched ON.

Circuit diagram

RST10uF

22pF

22pF

8.2k

4 - 12Mhz

VCC=+5vdcAT89C51

9

1819

2930

31

12345678

2122232425262728

1011121314151617

3938373635343332

RST

XTAL2XTAL1

PSENALE/PROG

EA/VPP

P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7

P2.0/A8P2.1/A9P2.2/A10P2.3/A11P2.4/A12P2.5/A13P2.6/A14P2.7/A15

P3.0/RXDP3.1/TXDP3.2/INT0P3.3/INT1P3.4/T0P3.5/T1

P3.6/WRP3.7/RD

P0.0/AD0P0.1/AD1P0.2/AD2P0.3/AD3P0.4/AD4P0.5/AD5P0.6/AD6P0.7/AD7

MICROCONTROLLER

Mother board

Crystal OscillatorThe 8051 family microcontroller contains an inbuilt crystal oscillator, but the crystal has to be connected externally.

This family of microcontroller can support 0 to 24MHz crystal and two numbers of decoupling capacitors are connected as shown in the figure. follows, . These capacitors are decouples the charges developed on the crystal surface due to piezoelectric effect. These decoupling capacitors are normally between 20pf to 30pf. The clock generator section is designed as

Motor driver

The D.C. Motor used in this project operates at 12 volt and carries approximately 400mA of current. The motor driver is designed to inter face the motor with micro controller. The micro controller out put is +5volt and can maximum give a current of 5mA. The driver stage changes the current and voltage level suitably to drive the motor. The driver stage not only drives the motor but also helps to control the direction of rotation. As the output current (Ic) is large the driver section requires a Darlington pair to switch the load. The Darlington pair I.C. TIP 122 is used here for designing.

FROM PWM FILTER

1.5kTIP 122

M

V cc = +12V

DC MOTOR DRIVER

Solid state relay

Here in this section, to activate/deactivate the load a solid state device is used to drive the load but the load is an AC load for that we have to isolate that for that we have used an opto-isolator (MOC3201) as a driver. It is an electronics device which isolates between input to output, that device is consisting of a LED and a DIAC which is fabricated on a single chip. Whenever a high voltage is given as input to the LED the LED gets forward biased which in turn ON the LED, the light falls on the DIAC which in turn the DIAC thus gets a sufficient current to drive the gate of the TRIAC to make turn ON the LOAD.

Circuit diagram

Buzzer driver

This section interfaces one audible piezo electric buzzer with the controller. The controller activates the buzzer whenever there is any valid data receives.PIEZO ELECRTIC BUZZER:It is a device that converts electrical signal to an audible signal (sound signal).The Microcontroller cannot drive directly to the buzzer, because the Microcontroller cannot give sufficient current to drive the buzzer for that we need a driver transistor (BC547), which will give sufficient current to the buzzer.Whenever a signal received to the base of the transistor through a base resistance (1.5k) is high, the transistor comes to saturation condition i.e. ON condition thus the buzzer comes to on condition with a audible sound. Similarly, whenever the signal is not received to the base of the transistor, thus the transistor is in cut-off state i.e. is in OFF state thus the buzzer does not gets activated.

Circuit diagram

BUZZER DRIVER

1.5K

BC 547DATAINPUT

BUZZER

V CC

Conclusion

The system is designed in the laboratory and tested in the laboratory condition. It is observed that the system is operating satisfactorily with a very minimum error which is quit less than the experimental tolerance level. The design is quite stable and economical.

Future expansion

This project has a vast field for expansion. The controller is designed with latest technology of communication and control. This project is designed with constraint of time and cost. This project can be modified and expanded in the following fields,-The controller can be interfaced to with sensor to send back the information to the user regarding its initial position.-The music generator can be replaced with multiple voice stack. So a status message can be send back to the user.-Multiple devices can be controlled by single command.-A timer base control unit can be developed so that ON TIMER and OFF TIMER can be implemented -A SMS base protection system or security system can be combined with this Design.

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