WIRELESS EQUIPMENT CONTROLLER USING BLUETOOTH

8/7/2019 WIRELESS EQUIPMENT CONTROLLER USING BLUETOOTH

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AJMER INSTITUTE OF

TECHNOLOGY


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INTRODUCTION:

A Wireless equipment control system was developed inthis project leveraging on the emerging wirelesstechnologies of Bluetooth. As the name indicates it iswithout wire line connection.

We can control the equipment from the far distancewithout using wire. It mainly works on four varieties:Bluetooth, mobile, internet and infrared.

The Bluetooth has to develop a wireless standard forinterconnecting computing and communication devicesand accessories using short range, low power,inexpensive wireless links. So the project was namedWIRELESS EQUIPMENT CONTROL USING

BLUETOOTH.


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BLUETOOTH:

Bluetooth is a wireless personal area network technology(WPAN for short), a low-range wireless network

technology used for linking devices to one another

without a hard-wired connection.

Bluetooth technology eliminates the need for numerous

and inconvenient cable attachments for connecting fixed

computers, mobile phones, mobile computers, handheld

devices, digital cameras and even new breed of digital

appliances.

It will enable users to connect a wide range of computing

and telecommunications devices easily and simply,

without the need to buy, carry, or connect cables


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BLUETOOTH:Briefly, Bluetooth

technology

uses radio waves in 2.4GHz band - therefore, noline of sight is required

supports multipoint, not justpoint to point

works in a small confinedarea - 10 to 15 meters apart

is able to support speeds of1-2 Mbps today but will offerhigher speeds in future


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HOW BLUETOOTH TECHNOLOGY

WORKS:

Bluetooth is a high-speed, low-power microwavewireless link technology, designed to connect phones,laptops, PDAs and other portable equipment togetherwith little or no work by the user.

Unlike infra-red, Bluetooth does not require line-of-sightpositioning of connected units. The technology usesmodifications of existing wireless LAN techniques but ismost notable for its small size and low cost.

When one Bluetooth product comes within range ofanother, (this can be set to between 10cm and 100m)they automatically exchange address and capability

details.


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How Bluetooth Createsa

Connection

Bluetooth takes small-area networking to the next level

by removing the need for user intervention and keeping

transmission power extremely low to save battery power.

There are other ways to get around using wires,

including infrared communication. Infrared (IR) refers tolight waves of a lower frequency than human eyes can

receive and interpret.

Infrared is used in most television remote control

systems. Infrared communications are fairly reliable anddon't cost very much to build into a device, but there are

a couple of drawbacks. First, infrared is a "line of sight"

technology.


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How Bluetooth Createsa

Connection:

For example, you have to point the remote control at the

television orDVD playerto make things happen. The

second drawback is that infrared is almost always a "one

to one" technology. You can send data between your desktop computer and

yourlaptop computer, but not your laptop computer and

yourPDA at the same.

These two qualities of infrared are actually advantageousin some regards. Because infrared transmitters and

receivers have to be lined up with each other, interference

between devices is uncommon.


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How Bluetooth Operates:

Bluetooth networking transmits data via low-power radiowaves.

It communicates on a frequency of2.45 gigahertz

(actually between 2.402 GHz and 2.480 GHz, to be

exact).

This frequency band has been set aside by international

agreement for the use of industrial, scientific and medical

devices (ISM).

A no. of devices that you may already use take

advantage of this same radio-frequency band. Babymonitors, garage-door openers and the newest

generation ofcordless phones all make use of

frequencies in the ISM band. Making sure that Bluetooth

and these other devices don't interfere with one another


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How Bluetooth Operates: Bluetooth uses a technique called spread-spectrum

frequencyhopping that makes it rare for more than onedevice to be transmitting on the same frequency at thesame time.

In this technique, a device will use 79 individual, randomlychosen frequencies within a designated range, changingfrom one to another on a regular basis.

In the case of Bluetooth, the transmitters change

frequencies 1,600 times every second, meaning that moredevices can make full use of a limited slice of the radiospectrum.

Since every Bluetooth transmitter uses spread-spectrumtransmitting automatically, its unlikely that two transmitters

will be on the same frequency at the same time.


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Bluetooth Pico nets

Lets say you have a typical modern living room withtypical modern stuff inside.

Theres an entertainment system with a stereo, a DVD

player, a satellite TV receiver and a television; there's

also a cordless telephone and a personal computer. Each of these systems uses Bluetooth, and each forms

its own Pico net to talk between the main unit and

peripheral. The cordless telephone has one Bluetooth

transmitter in the base and another in the handset.

When the base is first turned on, it sends radio signals

asking for a response from any units with an address in a

particular range. Since the handset has an address in the

range, it responds, and a tiny network is formed.


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Now, even if one of these devices should receive a

signal from another system, it will ignore it since its not

from within the network. The computer and entertainment system go through

similar routines, establishing networks among addresses

in ranges established by manufacturers.

Once the networks are established, the systems begintalking among themselves.

Each Pico net hops randomly through the available

frequencies, so all of the Pico nets are completely

separated from one another.

Now the living room has three separate networks

established, each one made up of devices that know the

address of transmitters it should listen to and the

address of receivers it should talk to.


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Since each network is changing the frequency of itsoperation thousands of times a second, its unlikely thatany two networks will be on the same frequency at thesame time.

If it turns out that they are, then the resulting confusionwill only cover a tiny fraction of a second, and softwaredesigned to correct for such errors weeds out the

confusing information and gets on with the networksbusiness.


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Bluetooth Security

In any wireless networking setup, security is a concern.Devices can easily grab radio waves out of the air, so

people who send sensitive information over a wireless

connection need to take precautions to make sure those

signals aren't intercepted.

Service-levelsecurity and device-levelsecurity worktogether to protect Bluetooth devices from unauthorized

data transmission.

Security methods include authorization and identification

procedures that limit the use of Bluetooth services to theregistered user and require that users make a conscious

decision to open a file or accept a data transfer.

As long as these measures are enabled on the user's

phone or other device, unauthorized access is unlikely.


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However, since most cell phones use a secure Bluetooth

connection that requires authorization and authentication

before accepting data from an unknown device, theinfected file typically doesn't get very far.

When the virus arrives in the user's cell phone, the user

has to agree to open it and then agree to install it. This

has, so far, stopped most cell-phone viruses from doing

much damage.

Other problems like "blue jacking," "blue bugging" and

"Car Whisperer" have turned up as Bluetooth-specific

security issues.

Blue jacking involves Bluetooth users sending abusiness card (just a text message, really) to other

Bluetooth users within a 10-meter (32-foot) radius.


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If the user doesn't realize what the message is, he might

allow the contact to be added to his address book, andthe contact can send him messages that might beautomatically opened because they're coming from aknown contact.

Blue bugging is more of a problem, because it allowshackers to remotely access a user's phone and use itsfeatures, including placing calls and sending textmessages, and the user doesn't realize its happening.

The Car Whispereris a piece of software that allowshackers to send audio to and receive audio from aBluetooth-enabled car stereo. Like a computer securityhole.


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WORKING:

In the wireless equipment controller using Bluetooth thereare two sections such as transmitter and receiver.

TRANSMITTER:

Address and control data placed on the HT-12E encoder

by PC LPT port exits the HT-12E encoder IC on pin #17DOUT. This outgoing data enters the data input pin ofthe RF transmitter the figure given below showsschematic diagram of transmitter using IC HT12E.

The TX433 wireless RF transmitter uses on/off keying totransmit data to the matching receiver, RX433. The datainput keys the saw resonator in the transmitter whenthe input is +3 volts or greater, AM modulating the dataonto the 433 MHz carrier.


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The data is then demodulated by the receiver, whichaccurately reproduces the original data.

The data input is CMOS level Compatible when the unit is

run on +5 volts. When driving with a CMOS input, there must be enough

level to achieve at least 3V on the data input, 5V ispreferable.

This is due to the start-up time of the oscillator needing to

be fast to accurately reproduce your data.

If the voltage is too low, the oscillator will not start fastenough to accurately reproduce your data, especially athigher data rates.

Almost any CMOS output will drive this without anyproblems.

There are some CMOS outputs which have very littledrive capability which may not work, so testing the voltageat the data input may be a wise choice if you are having

problems.


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Connections:

As shown in figure all the address lines A0-A7 areconnected to ground.

You can either connect all the lines to Vcc or to ground

but keep in mind that on the receiver side you have to do

same. This is to set same address both the sides. Resistor

R1(1.1M?) is connected between oscillator pins (Osc1 &

Osc2) to set transmitter frequency = 50Receiver

Frequency.

Data lines D0-D3 are connected with switches S1-S4

through diodes D1-D4 respectively. The other terminal of

all the switches is connected with ground.


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The TE pin (transmission enable) is

also connected to all the switches

through four different diodes D5-D8.

The D out pin of HT12E isconnected to Din pin of 433.92MHz

serial data transmitter. 9V standard

battery supplies power to the circuit.

The SM TX 4 is a AM / ASK

transmitter module which canfacilitate OEM manufactures to

design remote control application in

shortest way. Low power

consumption and wide.

Pin1 : Ground

Pin2 : Data In

Pin3 : Vcc

Pin4 : Antenna


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Operation:

Whenever you press any key TE pin will be groundedthrough that diode, at the same time particular data line is

also grounded.

So we can set the data at the same time we can pull theTE pin low by pressing single key.

Now we know when TE pin is low the address and data

are transmitted serially through D out pin.

So 8-bit address and 4-bit of data are together

transmitted over 433.92 MHz carrier frequency.


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RECEIVER:

The receiver shown in Figure also contains just one

transistor. It is biased to act as a regenerative oscillator, in which

the received antenna signal causes the transistor toswitch to high amplification, thereby automaticallyarranging the signal detection.

Next, the raw demodulated signal is amplified andshaped-up by op-amps.

The result is a fairly clean digital signal at the output ofthe receiver. The logic high level is at about 2/3 of thesupply voltage, i.e., between 3 V and 4.5 V.

The range of the simple system shown in Figures ismuch smaller than that of more expensive units, mainlybecause of the low transmit power (approx. 1 mW) andthe relative insensitivity and wide-band nature of thereceiver.

Moreover, amplitude-modulated noise is not suppressed

in any way.


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Receivercircuitusing IC HT12D isasshown

below.


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These modules are now widely and cheaply availablewith the operating frequency of 433 MHz The transmittermodule accepts serial data.

The encoder IC takes in parallel data at the TX sidepackages it into serial format and then transmits it withthe help of a RF transmitter module.

At the RX end, the decoder IC receives the signal via theRF receiver module, decodes the serial data and

reproduces the original data in the parallel format. To receive information simply hook up the HT-12D output

pins to the microcontroller.

The VT or valid transmission pin of the HT-12D couldsignal the microcontroller to grab the 4-bits of data from

the data output pins. The receiver uses the ULN2803 Darlington transistor

array to drive four mechanical relays.

Each of the four outputs has a status LED for a visualindication of each output ON or OFF status.


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Pin1 : Ground

Pin2 : Digital Out

Pin3 : Linear Out

Pin4 : Vcc 5V

Pin5 : Vcc 5V

Pin6 : Ground

Pin7 : Ground

Pin8 : Antenna


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Connections

All the address lines are connected to ground to setsame address.

Resistor R2 (51K?) is connected between Oscillator pins.

All the data line D0-D3 are connected to different LEDs

L1-L4 respectively.

LED L5 is connected to VT (valid transmission) pin

through transistor Q1 to indicate valid transmission.

The D out pin of 433.92 MHz serial data receiver is

connected with Din pin of IC HT12D.


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Operation

When 5V supply is given to circuit all the data lines are

low so LEDs will not glow. Whenever you press any switch from Tx address & data

are transmitted together

The 433.92MHz serial data receiver will demodulate thecarrier and gives this address & data to IC HT12D

IC HT12D first compares the address three times and if itmatches it gives high pulse on VT pin (so LED L5 willblink) and latch the data.

Suppose you pressed S4. So the data transmitted willbe 1110 and address will be of course 00000000.

HT12D receives the signals compares address thrice,gives high pulse on pin VT and then latch the data.Because data is 1110 LED L1 will not glow and rest allthe LEDs will glow.


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Same way if you press S2 data will be 1011. So nowLED L3 will be off and rests are on.

Simply you can see which ever switch is pressed on Txside that particular data line is low on Rx side.

To receive information simply hook up the HT-12Doutput pins to the microcontroller.

The VT, or valid transmission pin of the HT-12D couldsignal the microcontroller to grab the 4-bits of data from

the data output pins.

The HT-12D data output pins will LATCH and remain inthis state until another valid transmission is received.


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ADVANTAGES

Bluetooth has a number of benefits within an more

and more difficult market place. Bluetooth helps tobring with it the prediction of freedom from the cables

and simplicity in networking that has yet to be

reached by LAN.

Infrared holds many key features, although the line of

sight it provides doesn't go through walls or through

objects like that of the Bluetooth technology.

Unlike infrared, Bluetooth isn't a line of sight and it

comes with ranges of up to 100 meters. Bluetooth is

even low power and low processing with an overheadprotocol.

Thus it's optimal for implementation into small battery

powered devices. Shortly said, the possibilities with

Bluetooth are nearly endless.


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APPLICATIONS:

Bluetooth has a tremendous potential in moving and

synchronizing information in a localized setting. Each Bluetooth device could be connected to 200 other

devices making the connection of every device withevery other possible.

The Bluetooth technology connects all your officeperipherals wirelessly.

Bluetooth allows us to have three way phones. At home,your phone functions as a portable phone .

IBM researchers are working on a number of personaldevices like a Watch Pad that could be connected withother devices through Bluetooth.

The Watch Pad is very thin and contains 8MB of RAM.They are also working on a version of Cyber Phonecalled Cyber Phone - that can project data onto a smallmirror. The Cyber Phone can show as much informationas a small PDA because of high resolution VGA screen.


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WIRELESS EQUIPMENT CONTROLLER USING BLUETOOTH

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