application of short range wireless technologies to industrial automation

8/8/2019 Application of Short Range Wireless Technologies to Industrial Automation

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ABSTRACT

Wireless technologies are being more and more used in automation, not only because the

installation costs are much lower, but also the true self-reconfiguration of a system without any

rewiring becomes possible as ever did before. Together with other technologies like service

oriented architectures and the use of agent technology, wireless at the physical level play an

important role towards flexible and self-reconfiguring systems. Bluetooth, ultra-wideband

(UWB), ZigBee, and Wi-Fi are four popular wireless standards for short-range communications.

Specifically, ZigBee network is an emerging technology designed for low cost, low power

consumption and low-rate wireless personal area networks (LR-WPAN) with a focus on the

device-level communication for enabling the wireless sensor networks. In this Report, after a

brief overview of the four short-range wireless standards, the developed ZigBee platforms, ITRI

ZBnode, have been presented for wireless sensor networking applications. Moreover, design

issues for ZigBee industrial applications and the experimental implementation have been

demonstrated via a multi-hop tree network. The ZigBee standard provides network, security,

and application support services operating on top of the IEEE 802.15.4 Medium Access

Control (MAC) and Physical Layer (PHY) wireless standard. It employs a suite of technologies

to enable scalable, self-organizing, self-healing networks that can manage various data traffic

patterns. The network layer supports various topologies such star, clustered tree topology

and self healing mesh topology which is essential in Smartdust Apart from easy installation

and easy implementation ZigBee has a wide application area such as home networking,

industrial networking, Smartdust, many more, having different profiles specified for each field.


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1. INTRODUCTION:

For interconnection purposes, an industrial control system can be combined with various sensors,

controllers, and heterogeneous machines using a common message specification. A typical

control system with wired network is shown in Fig. 1 (a). Many different network types have

been promoted for use on a shop floor, including the control area network (CAN), DeviceNet,

Process fieldbus (Profibus), ControlNet, Modbus, and so on [1]. In the past decades, for

accessing networks and services without cables, wireless communication is a fast-growing

technology to provide the flexibility and mobility [2]. Fig. 1 (b) shows the industrial control

system with wireless technology applied. Obviously, reducing the cable restriction is clearly one

of the benefits of wireless with respect to cabled devices. Other benefits include the dynamic

network formation, easy deployment, and low cost in some cases.

Bluetooth (over IEEE 802.15.1), ultra-wideband (UWB, over IEEE 802.15.3), ZigBee (over

IEEE 802.15.4), and Wi-Fi (over IEEE 802.11) are four protocol standards for short-range

wireless communications with low power consumption. From an application point of view,

Bluetooth is intended for a cordless mouse, keyboard, and hands-free headset, UWB is oriented

to high-bandwidth multimedia links, ZigBee is designed for reliable wirelessly networked

monitoring and control networks, while Wi-Fi is directed at computer-to-computer connections

as an extension or substitution of cabled networks.

In general, the wireless networking has followed a trend of throughput increase due to theincreasing exchange of data in services such as the Internet, e-mail, and data file transfer. The

capabilities needed to deliver such services are characterized by an increasing need for data

throughput. However, in applications to the industrial, vehicular, and residential fields, sensors

[3] may have more relaxed throughput requirements. Moreover, applications to industrial control

and home automation require lower power consumption and low complexity wireless links for a


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low cost (relative to the device cost). Based on our previous work [2], after a study of these

popular wireless standards, the ZigBee wireless technology would be the one that suitable for

industrial control and home automation on the device-level communication. Based on the IEEE

802.15.4 standard, ZigBee is a global specification created by a multi-vendor consortium called

the ZigBee Alliance. Whereas 802.15.4 defines the physical and MAC layers of an application,

ZigBee defines the network and application layers, application framework, application profile,

and the security mechanism. ZigBee provides users in specific applications with a simple, low-

cost global network that supports a large number of nodes with an extremely low power drain on

the battery. In this work, after an evaluation of the short-range wireless communication

standards, the ZigBee-based platforms, named ITRI ZBnode, have been designed and

implemented for practical WSN applications.

1.1 SHORT-RANGE WIRELESS STANDARDS:

Bluetooth, UWB, ZigBee, and Wi-Fi protocols, which corresponds to the IEEE 802.15.1,

802.15.3, 802.15.4, and 802.11a/b/g standards, respectively. The IEEE defines only the PHY and

MAC layers in its standards. For each protocol, separate alliances of companies worked to

develop specifications covering the network, security and application profile layers so that the

commercial potential of the standards could be realized. Table I summarizes the main differences

among the four protocols. Each protocol is based on an IEEE standard. Obviously, UWB and

Wi-Fi provide a higher data rate, while Bluetooth and ZigBee give a lower one. In general, the

Bluetooth, UWB, and ZigBee are intended for WPAN communication (about 10m), while Wi-Fi

is oriented to WLAN (about 100m). However, ZigBee can also reach 100m in some applications.

This section provides an evaluation of the Bluetooth, UWB, ZigBee, and Wi-Fi on different

aspects. It is important to notice that several slight differences exist in the available sources. For

example, in the IEEE 802.15.4 standard, the action range is about 10m, while it is 70-300m in

the released documents from ZigBee Alliance. Thus, this paper intends to provide information

only, since other factors, such as receiver sensitivity and interference, play a major role in

affecting the performance in realistic implementations.


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COMPARISON OF THE BLUETOOTH, UWB, ZIGBEE, AND WI-FI PROTOCOLS

1.2

CHAPTER - 2

BASIC MODEL OF THE SYSTEM

Block diagram of the ZIGBEE BASED DEVICE FOR INDUSTRIAL CONTROL

SYSTEM

MCU UNIT

OPTO ISOLATORS

AND POWER

AMPLIFIERS

DecoderZIGBEE

POWER SUPPLY


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Figure 2.2 Block diagram of the system

2.2 Parts of the system:

1. Zigbee

2. Microcontroller Unit

3. Max 232

4. Opto Isolator and Power amplifier

5. Relay

6. Power Supply

1. Zigbee:ZigBee is a low-cost, low-power, wireless mesh networking proprietary standard. The

low cost allows the technology to be widely deployed in wireless control and monitoring

applications, the low power-usage allows longer life with smaller batteries, and the mesh

networking provides high reliability and larger range.


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Fig 2.1shows the the zigbee module

3. Microcontroller Unit: The AT89S52 is a low-power, high-performance CMOS 8-bit

microcontroller with 8K bytes of in-system programmable Flash memory. A microcontroller

(sometimes abbreviated C, uC or MCU) is a small computer on a single integrated circuit

containing a processor core, memory, and programmable input/output peripherals. Program

memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a

typically small amount of RAM.


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Fig 2.2shows the microcontroller PCB

4. MAX 232: The MAX232 is an integrated circuit that converts signals from an RS-232 serial

port to signals suitable for use in TTL compatible digital logic circuits. The MAX232 is a dual

driver/receiver and typically converts the RX, TX, CTS and RTS signals.

Fig2.3 shows MAX 232 using at baud rate 9600

5. Opto isolator and Power amplifier: In electronics, an opto-isolator, also called an

optocoupler, photocoupler, or optical isolator, is "an electronic device designed to transfer

electrical signals by utilizing light waves to provide coupling with electrical isolation between its

input and output". The main purpose of an opto-isolator is "to prevent high voltages or rapidly

changing voltages on one side of the circuit from damaging components or distorting

transmissions on the other side. Commercially available opto-isolators withstand input-to-output

voltages up to 10 kV and voltage transients with speeds up to 10 kV/s. Power Amplifier is

used to boost the signal.

6. Relay: A relay is an electrically operated switch. Many relays use an electromagnet to operate

a switching mechanism mechanically, but other operating principles are also used. Relays are

used where it is necessary to control a circuit by a low-power signal (with complete electrical

isolation between control and controlled circuits), or where several circuits must be controlled by

one signal.


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Fig 2.4 shows the isolation circuit

7. Power Supply:Power supply is rthe heart of the system ,without power supply system can not

do anything .All circuit components work only when there is power. This project circuit based on

+5v power supply.

Fig 2.5 power supply circuit:

TOOLS/SOFTWARES /COMPONENTS REQUIRED

1. KEIL Vision2 Software for programming of Microcontroller.

2. I.C Programmer and Software for the burning of the Microcontroller


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3. ZigBee Tools., PC , MATLAB software

4. Components for designing of the embedded part.

5. Soldering kit.

6. Measuring Instruments (Multi-meter), etc.

CHAPTER3

LITERATURE REVIEW

ZIGBEE

ZigBee is a wireless networking standard that is aimed at remote control and sensor applications

which is suitable for operation in harsh radio environments and in isolated locations, It builds on

IEEE standard 802.15.4 which defines the physical and MAC layers. Above this ZigBee defines

the application and security layer specifications enabling interoperability between products from

different manufacturers. In this way ZigBee is a superset of the 802.15.4 specification. With the

applications for remote wireless sensing and control growing rapidly it is estimated that the

market size could reach hundreds of millions of dollars as early as 2007. This makes ZigBee a

very attractive proposition, and one, which warrants the introduction of a focused standard.

1.2.1Introduction to ZigBee

The past few years have witnessed a rapid growth of wireless networking. However, up to now

wireless networking has been mainly focused on high speed communications, and relatively


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longrange applications such as IEEE 802.11 wireless local area network standards. The first well

known standard focusing on low rate wireless personal area networks was BLUETOOTH.

However it has limited capacity for networking of many nodes. There are many wireless

monitoring and control applications in industrial and home environments which require longer

battery life, lower data rates and less complexity than those from existing standards. For such

wireless applications, a new standard called IEEE 802.15.4 has been developed by IEEE. The

new standard is also called ZigBee.

`1.2.2 The Zigbee Alliance

The ZigBee standard is organized under the auspices of the ZigBee Alliance. The ZigBee

alliance is an organization of companies working together to define an open global standard for

making low power wireless networks. The intended outcome of ZigBee alliance is to create a

specification defining how to build different network topologies with data security features and

interoperable application profiles. This organization has over 150 members, of which seven have

taken on the status of what they term promoter. These seven companies are Ember,

Honeywell, Invensys, Mitsubishi, Motorola, Philips and Samsung. A big challenge for the

alliance is to make the interoperability to work among different products. To solve this problem,

the ZigBee Alliance has defines profiles, depending on what type of category the product

belongs to. For example there is a profile called home lightning that exactly defines how

different brands of home lightning-products should communicate with each other. Under the

umbrella of the ZigBee Alliance, the new standard will be pushed forward, taking on board the

requirements of the users, manufacturers and the system developers. The Alliance has specified

three profiles:

Private Profile: In this profile interoperability is not at all important. However producers cannot

use the official ZigBee stamp, but can claim that based on ZigBee platform.

Published Profile: A private profile is shared among other users. Still one cannot use official

ZigBee stamp, but can claim based on ZigBee platform.

Public profile: It is the official ZigBee profile.


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1.2.3 The Name ZigBee

The name ZigBee is said to come from the domestic honeybee which uses a zig-zag type of

dance to communicate important information to other hive members. This communication dance

(The ZigBee Principle) is what engineers are trying to emulate with this protocol a bunch of

separate and simple organisms that join together to tackle complex tasks.

1.2.4 Why ZigBee?

There are a multitude of standards like Bluetooth and Wi-Fi that address mid to heigh data rates

for voice, PC LANs, video etc. However, up till now there hasnt been a wireless network

standard that meets the unique needs of sensors and control devices. Sensors and controls dont

need high bandwidth but they do need low latency and very low energy consumption for long

battery lives and for large device arrays. There are a multitude of proprietary wireless systems

manufactured today to solve a multitude of problems that dont require high data rates but do

require low cost and very low current drain. These proprietary systems were designed because

there were no standards that met their application requirements. These legacy systems are

creating significant interoperability problems with each other and with newer technologies. The

ZigBee Alliance is not pushing a technology; rather it is providing a standardized base set of

solutions for sensor and control systems. Here are the following points that justify the use of

ZigBee over the existing standards.

1.1.5 ZigBee/IEEE 802.15.4 General Characteristics

1. Data rates of 250 kbps (@2.4 GHz), 40 Kbps (@ 915 MHz) and 20 kbps (@868 MHz)

2. Optimized for low duty-cycle applications (


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6. Addressing space of 64 bits 18,450,000,000,000,000,000 devices (64 bit IEEE address)

65,535 networks.

7. Optional guaranteed time slot for applications requiring low latency.

8. Fully hand-shaked protocol for transfer reliability

9. Range: 50m typical (5-500m based on environment).

1.1.6 ZigBee Protocol Stack

The ZigBee protofol stack is 1/4th of that of Wi-Fi and Bluetooth. It may be helpful to think of

IEEE 802.15.4 as the physical radio and ZigBee as the logical network and application software.

Following the standard Open Systems Intenconnection (OSI) reference model, ZigBees protocol

stack is structured in layers. The first two layers, physical (PHY) and media access (MAC) are

defined by the IEEE 802.15.4 standard as shown in the figure fig 5.1. The layers above them

are defined by the ZigBee Alliance. The IEEE working group passed the first draft of PHY and

MAC in 2003.

Fig Zigbee protocol stack

Automation is the need of today. The ultimate aim of technology is to reduce the load of

mankind. To reduce the amount of human effort required to perform a task is the objective. One

of such means can be through Zig Bee Technology, that can be used to automate the devices of

the home along with the doors.


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The 802 Wireless Space:

`

Once on a specific channel, the 802.15.4 radio relies on a number of mechanisms to ensure

reliable data transmission. First, the PHY layer uses binary phase shift keying (BPSK) in the

868/915 MHz bands and offset quadrature phase shift keying (O-QPSK) at 2.4 GHz. Both are

robust and simple forms of modulation that work well in low SNR environments.


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After receiving a data packet, the receiver performs a 16-bit cyclic redundancy check (CRC) to

verify that the packet was not corrupted in transmission. With a good CRC, the receiver can

automatically transmit an acknowledgement packet (depending on application and network

needs), allowing the transmitting station to know that the data were received in an acceptable

form. If the CRC indicates the packet was corrupt, the packet is dropped and no

acknowledgement is transmitted. When a developer configures the network to expect

acknowledgement, the transmitting station will retransmit the original packet a specified number

of times to ensure successful packet delivery. If the path between the transmitter and receiver has

become less reliable or a network failure has occurred, ZigBee provides the network with self-

healing capabilities when alternate paths (if physically available) can be established autono-

mously.

Battery Life

In many applications, you cant afford to make regular trips back to a sensor to change the

battery. Ideally, the sensor is good for the life of the battery.

The basic 802.15.4 node is fundamentally efficient in terms of battery performance. You can

expect battery lifetimes from a few months to many years as a result of a host of system power-

saving modes and battery-optimized network parameters, such as a selection of beacon intervals,guaranteed time slots, and enablement/disablement options.

Consider a typical security application, such as a magnetic reed switch door sensor. The sensor

itself consumes almost no electricity; its the radio that uses the bulk of the power. The sensor is

configured to have a heartbeat at 1 min. intervals and to immediately send a message when an

event occurs. Assuming dozens of events per day, analysis shows that the sensor can still outlast

an alkaline AAA battery. The configuration allows the network to update the sensor parameters

remotely, change its reporting interval, or perform other remote functions and still have

(theoretical) battery longevity well beyond the shelf life.

The network configuration plays an important part in the equation; most networks are expected

to be stars or cluster trees rather than true meshes (see Figure 4), allowing the individual client

devices to conserve battery energy.


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Figure:

Star networks are the most common, basic structure with broad utility. For larger physical

environments, the cluster tree is a good way to aggregate multiple basic star networks into one

larger network. Some applications will make best use of the mesh structure, which provides

alternate route flexibility and the capability for the network to heal itself when intermediate

nodes are removed or RF paths

.

Nodes that form the hubs or coordinator routes in the cluster tree can take advantage of beacon-

based operation for synchronization across a widely dispersed network with only moderate

impact on their own battery life.

Cost

System, individual node, service, and battery costs are all important. ZigBee and 802.15.4

maximize utility over this multidimensional space. There is sufficient flexibility in both

standards to provide the sensor system developer with an assortment of tradeoffs to optimize cost

with respect to system performance. For example, battery life can be optimized at the expense of

service interval, and node cost and complexity can be traded for network complexity.

First-generation silicon is only now getting to the early adopters, and the system simplicity and

the underlying flexibility of 802.15.4 promise that system developers will find ZigBee-based

platforms more cost effective (at the same unit volumes) than Bluetooth or proprietary


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bidirectional wireless solutions. While platform hardware cost is always a critical part of the

overall system cost, you must also consider the less tangible costs of system maintenance,

flexibility, and battery life.

Transmission Range

ZigBee relies on the basic 802.15.4 standard to establish radio performance. As a short-range

wireless standard, 802.15.4 doesnt try to compete with high-powered transmitters but instead

excels in the ultra-long battery life and low transmitter power. The standard specifies transmitter

output power at a nominal 3 dBm (0.5 mW), with the upper limit controlled by the regulatory

agencies of the region in which the sensor is used. At 3 dBm output, single-hop ranges of 10 to

more than 100 m are reasonable, depending on the environment, antenna, and operating

frequency band.

Instead of pure power, ZigBee augments the basic 802.15.4 simple transmitter and protocol with

an extensible, sophisticated network function that allows multi-hop and flexible routing,

providing communication ranges that can exceed the basic single-hop. Indeed, depending on the

data latency re-quirements, you can practically create networks that use dozens of hops, with

cumulative ranges inthe hundreds to thousands of meters. Networks can have star, cluster tree, or

mesh structures; each comes with its own strengths.

Data Rate

It may not be obvious why a simple temperature or intrusion sensor needs to transmit data at 250

Kbps (at 2.4 GHz) or even 20 Kbps (at 868 MHz), but the reason becomes clear when you

consider the need to prolong battery life. Even when the sensor is transmitting only a few bits or

bytes, the system can be more efficient if it transmits and receives the data quickly. For instance,

a 0.5 mW transmitter consumes many milliwatts whether its transmitting 100 or 100,000 bps.

For any given quantity of data, transmitting at a higher data rate allows the system to shut down

the transmitter and receiver more quickly, saving significant power.


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Higher data rates at a given power level mean theres less energy per transmitted bit, which

generally implies reduced range. But both 802.15.4 and ZigBee value battery life more than raw

range and provide mechanisms to improve range while always concentrating on battery life.

Data Latency

Sensor systems have a broad range of data-latency requirements. If sensor data are needed within

tens of milliseconds, as op-posed to dozens of seconds, the requirement places different demands

on the type and extent of the intervening network. For many sensor applications, data latency is

less critical than battery life or data reliability.

For simple star networks (many clients, one network coordinator), ZigBee can provide latencies

as low as ~16 ms in a beacon-centric network, using guaranteed time slots to prevent interference

from other sensors. You can further reduce latencies to several milliseconds if you forego the

beacon environment and are willing to risk potential interference from accidental data collision

with other sensors on the network.

Data latency can also affect battery life. Generally, if you relax data-latency requirements, you

can assume that the battery life of the client nodes will increase. This is even truer of network

hubs, which are required to coordinate and supervise the network.

Consider a simple network that has de-manding latency requirements (e.g., a wireless computer

keyboard and mouse). The user expects that a keyboard stroke or mouse movement will be

reflected on screen in one or two screen-refresh intervals, generally between 16 and 32 ms. For

this kind of star network, you can achieve data latency that beats this requirement.

Size

As silicon processes and radio technology progress, transceiver systems shrink in physical size.

Forty years ago, a simple radio transceiver was the size of a shoebox and weighed 10 kg. Today,

a similar transceiver might easily fit inside a thimble. In the case of ZigBee systems, the radio

transceiver has become a single piece of silicon, with a few passive components and a relatively

noncritical board design.


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Microcontrollers that have native ability to interface with sensors (e.g., built-in digital I/O and

A/D converters) have eclipsed even the radios rapid reduction in size. Today, the 8-bit MCU

that hosts the application may already include dozens of kilobytes of flash memory, RAM, and

various hardware-based timer functions, along with the ability to interface directly to the radio

transceiver IC. The MCU requires only a few external passive components to be fully functional.

With the minimal overhead added by a ZigBee transceiver, the MCU can often continue to host

the application along with the ZigBee protocol. Therefore, the silicon system size of a ZigBee

solution (excluding sensors or batteries) is generally smaller than the batteries themselves. This

compact form factor lends itself well to innovative uses of radio technology in sensor

applications. Cer-tainly, with the advances in silicon-based sensors that have been coming to

market over the past five years, its practical to design entire systems that take up


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approved applications, security will already be a seamless part of the overall system.The current

list of application profiles either published or in the works are:

y Industrial Automation.

y ZigBee Smart Energy

y Commercial Building Automation

y Telecommunication Applications

y Personal, Home, and Hospital Care

y Toys

The relationship between IEEE 802.15.4 and ZigBee is similar to that between IEEE 802.11 and

the Wi-Fi Alliance. The ZigBee 1.0 specification was ratified on 14 December 2004 and is

available to members of the ZigBee Alliance. Most recently, the ZigBee 2007 specification was

posted on 30 October 2007. The first ZigBee Application Profile, Home Automation, was

announced 2 November 2007.

ZigBee operates in the industrial, scientific and medical (ISM) radio bands; 868 MHz in Europe,

915 MHz in the USA and Australia, and 2.4 GHz in most jurisdictions worldwide. The

technology is intended to be simpler and less expensive than other WPANs such as Bluetooth.

ZigBee chip vendors typically sell integrated radios and microcontrollers with between 60K and

128K flash memory, such as the Jennic JN5148, the Freescale MC13213, the Ember EM250 and

the Texas Instruments CC2430. Radios are also available stand-alone to be used with any

processor or microcontroller. Generally, the chip vendors also offer the ZigBee software stack,

although independent ones are also available.

Because Zigbee can activate (go from sleep to active mode) in 15 msec or less, the latency can

be very low and devices can be very responsive particularly compared to Bluetooth wake-up

delays, which are typically around three seconds. Because Zigbees can sleep most of the time,

average power consumption can be very low, resulting in long battery life.

The first stack release is now called Zigbee 2004. The second stack release is called Zigbee

2006, and mainly replaces the MSG/KVP structure used in 2004 with a "cluster library". The

2004 stack is now more or less obsolete


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MICROCONTROLLER: Micro controller-AT89S52

Features

Compatible with MCS-51 Products

8K Bytes of In-System Reprogrammable Flash Memory

Endurance: 1,000 Write/Erase Cycles

Fully Static Operation: 0 Hz to 24 MHz

Three-level Program Memory Lock

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Three 16-bit Timer/Counters

Eight Interrupt Sources

Programmable Serial Channel

Low-power Idle and Power-down Modes

Description

The AT89C52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K bytes of

Flash programmable and erasable read only memory (PEROM). The device is manufactured

using Atmels high-density nonvolatile memory technology and is compatible with the industry-

standard 80C51 and 80C52 instruction set and pinout. The on-chip Flash allows the program

memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer.

By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C52 is a

powerful microcomputer which provides a highly flexible and cost-effective solution to many

embedded control applications. To use the AT89C52 to develop a microcontroller-based system

requires a ROM burner that supports flash memory: However, a ROM eraser is not needed.

Notice that in flash memory you must erase the entire contents of ROM in order to program itagain. The PROM burner does this erasing of flash itself and this is why a separate burner is not

needed. To eliminate the need for a PROM burner Atmel is working on a version of the

AT89C51 that can be programmed by the serial COM port of the PC.


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The AT89C52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM,

32 I/O lines, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full-

duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89C52 is designed

with static logic nfor operation down to zero frequency and supports two software selectable

power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters,

serial port, and interrupt system to continue functioning.

The Power-down mode saves the RAM contents but freezes the oscillator, disabling all other

chip functions until the next hardware reset.

Pin Description

VCCSupply voltage.

GND

Ground.

Port 0

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can sink eight

TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs.

Port 0 can also be configured to be the multiplexed loworder address/data bus during accesses to

external program and data memory. In this mode, P0 has internal pullups. Port 0 also receives the

code bytes during Flash programming and outputs the code bytes during program verification.

External pullups are required during program verification.

Port 1

Port 1 is an 8-bit bi-directional I/O port with internal pullups. The Port 1 output buffers can

sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the

internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled

low will source current (IIL) because of the internal pullups. In addition, P1.0 and P1.1 can be

configured to be the timer/counter 2 external count input (P1.0/T2) and the timer/counter 2


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trigger input (P1.1/T2EX), respectively, as shown in the following table. Port 1 also receives the

low-order address bytes during Flash programming and verification.

Port 2




low will source current (IIL) because of the internal pullups. Port 2 emits the high-order address

byte during fetches from external program memory and during accesses to external data memory

that use 16-bit addresses (MOVX @ DPTR). In this application, Port 2 uses strong internal pull-

ups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX

@ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the

high-order address bits and some control signals during Flash programming and verification.

Port 3




low will source current (IIL) because of the pullups. Port 3 also serves the functions of various

special features of the AT89C51, as shown in the following table. Port 3 also receives some

control signals for Flash programming and verification


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RST

Reset input.A high on this pin for two machine cycles while the oscillator is running resets the

device.

ALE/PROG

Address Latch Enable is an output pulse for latching the low byte of the address during accesses

to external memory. This pin is also the program pulse input (PROG) during Flash

programming. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator

frequency and may be used for external timing or clocking purposes. Note, however, that one

ALE pulse is skipped during each access to external data memory. If desired, ALE operation can

be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a

MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable

bit has no effect if the microcontroller is in external execution mode.

PSEN

Program Store Enable is the read strobe to external program memory. When the AT89C52 is

executing code from external program memory, PSEN is activated twice each machine cycle,

except that two PSEN activations are skipped during each access to external data memory.

LIQUID CRYSTAL DISPLAY

Liquid crystal displays (LCD) are widely used in recent years as compares to LEDs. This is due

to the declining prices of LCD, the ability to display numbers, characters and graphics,

incorporation of a refreshing controller into the LCD, their by relieving the CPU of the task of

refreshing the LCD and also the ease of programming for characters and graphics. HD 44780

based LCDs are most commonly used.


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LCD Pin descriptions

The LCD discussed in this section has 16 pins. The function of each pin is given in Table.

Pin Symbol I/O Description1 Vss - Ground2 Vcc - +5V Power supply3 VEE - Power supply to control Contrast4 RS I RS = 0 to select command register RS = 1 to select data register5 R/W I R/W = 0 for write, R/W = 1 for read6 E I/O Enable7 DB0 I/O The 8-bit data bus8 DB1 I/O The 8-bit data bus9 DB2 I/O The 8-bit data bus10 DB3 I/O The 8-bit data bus

11 DB4 I/O The 8-bit data bus12 DB5 I/O The 8-bit data bus13 DB6 I/O The 8-bit data bus14 DB7 I/O The 8-bit data bus15 LED- I Ground for LED backlight16 LED+ I +5v for LED backlightVCC, VSS, VEE

The voltage VCC and VSS provided by +5V and ground respectively while VEE is used for

controlling LCD contrast. Variable voltage between Ground and Vcc is used to specify the

contrast (or "darkness") of the characters on the LCD screen.

RS (register select)

There are two important registers inside the LCD. The RS pin is used for their selection as

follows. If RS=0, the instruction command code register is selected, then allowing to user to

send a command such as clear display, cursor at home etc.. If RS=1, the data register is selected,

allowing the user to send data to be displayed on the LCD.

R/W (read/write)

The R/W (read/write) input allowing the user to write information from it. R/W=1, when it read

and R/W=0, when it writing.


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EN (enable)

The enable pin is used by the LCD to latch information presented to its data pins. When data is

supplied to data pins, a high power, a high-to-low pulse must be applied to this pin in order to for

the LCD to latch in the data presented at the data pins.

D0-D7 (data lines)

The 8-bit data pins, D0-D7, are used to send information to the LCD or read the contents of the

LCDs internal registers. To displays the letters and numbers, we send ASCII codes for the

letters A-Z, a-z, and numbers 0-9 to these pins while making RS =1. There are also command

codes that can be sent to clear the display or force the cursor to the home position or blink the

cursor.

We also use RS =0 to check the busy flag bit to see if the LCD is ready to receive the

information. The busy flag is D7 and can be read when R/W =1 and RS =0, as follows: if R/W

=1 and RS =0, when D7 =1(busy flag =1), the LCD is busy taking care of internal operations and

will not accept any information. When D7 =0, the LCD is ready to receive new information

Interfacing Diagram ofLCD with 89C52


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RS 232 CONVERTER (MAX 232N) Serial Port:

This is the device, which is used to convert TTL/RS232 vice versa. RS-232 pin-outs for

IBM compatible computers are shown below. There are two configurations that are typically

used: one for a 9-pin connector and the other for a 25-pin connector.


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The standard voltage range on RS-232 pins is _15V to +15V. This voltage range applies to all

RS-232 signal pins. The total voltage swing during signal transmission can be as large as 30V. In

many cases, RS-232 ports will operate with voltages as low as _5V to +5V. This wide range

of voltages allows for better compatibility between different types of equipment and allows

greater noise margin to avoid interference. Because the voltage swing on RS-232 lines is so

large, the RS-232 signal lines generate a significant amount of electrical noise. It is important

that this signal does not run close to high impedance microphone lines or audio lines in a system.

In cases where you must run these types of signals nearby one another, it is important to make

sure that all audio wires are properly shielded. The main role of the RS232 chip is to convert the

data coming for the 12-volt logic to 5 volt logic and from 5 volt logic to 12 volt logic.

Opto-isolators, or opto-couplers, are made up of a light emitting device, and a light sensitive

device, all wrapped up in one package, but with no electrical connection between the two, just a

beam of light. The light emitter is nearly always an LED. The light sensitive device may be a

photodiode, phototransistor, or more esoteric devices such as thyristors, triacs etc.

The cheapest kind have phototransistors. Below is a basic circuit diagram using one of these

types (4N25):


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The output of this circuit simply follows the input:

Note the slight curving of the square wave input. All opto-isolators will only work up to a certain

frequency. Some are much faster than others. Make sure that the opto-isolator you use is fast

enough for the signals you are putting through it - more details in section 4. The reason the rise

time is slower than the fall time of the output waveform is that the rising edge is due to the 4k7

pull-up resistor, which has to discharge the capacitance in the opto transistor. If this needs to be


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speeded up, the 4k7 resistor value can be reduced, at the expense of using more current when the

output is low.

When the LED is driven with a current of 10mA or so, it shines onto the phototransistor, which

then starts to conduct (turn on). This takes the output voltage low. However much electrical

noise is on one side, it can never be transmitted over to the other side. We may use an opto-

isolator to send PWM signals from the low-power electronics side to the MOSFET drivers on the

high-power side, and we may use them to transmit information from the high- power side back to

the low-power side.

To complete the isolation of the low and high power sides, each must be powered by a

completely separate battery. The high power side will be powered by the main 12v or 24v

battery. The low-power side can be powered by a much smaller battery, maybe 6v.

2. Opto-isolator parameters

If you open a datasheet for an opto-isolator in a separate browser window, we can go through

some of the parameters and describe what they mean. Click here to open a datasheet for the

Sharp PC123 in another window, because we will be referring to it.

Collector-emitter voltage

This is the maximum voltage that can be present from the collector to the emitter of the receiving

phototransistor (when it is turned off - no light) before it may break-down.


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Creepage distance

This is physically how far a spark would have to travel around the outside of the package to get

from one side to the other. If the package has contaminants on it, solder flux, or dampness, then a

lower-resistance path can be created for noise signals to travel along.

Forward current

This is the current passing through the sending LED. Typically, an opto-isolator will require

about 5mA to turn the output transistor on.

Forward voltage

This is the voltage that is dropped across the LED when it is turned on. Most normal diodes drop

about 0.7v, but with LEDs it is typically 1 - 2 volts.

Collector dark current

This is the current that can flow through the output phototransistor when it is turned off.

Collector-emitter saturation voltage

When the output transistor is fully turned on (saturated), this is the voltage there will be between

the collector and emitter.

Isolation resistance

This is the resistance from a pin in the input side to a pin on the output side. It should be very

high.

Response time

Thee rise and fall times are the times that the output voltage takes to get from zero to maximum.

The rise time is very much dependant on the load resistor, since it is this that is pulling the output

up. Therefore this value is always quoted with a fixed load resistance. Note however that the

value, 100 Ohms, is much less than you are likely to use in practice. This is another of the

manufacturer's attempts to make the product look better than it is!

Cutoff frequency

This is effectively the highest frequency of square wave that can be sent through the opto-

isolator. It is actually the frequency at which the output voltage is only swinging half the

amplitude than at DC levels (-3dB = half). It is therefore linked with the rise and fall times.


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Current Transfer Ratio (CTR)

This is the ratio of how much collector current in the output transistor that you get given a certain

amount of forward current in the input side LED. It is affected by how close the LED and

phototransistor are inside the device, how efficient they both are, and many other factors.


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CHAPTER -4

OPERATION OF THE SYSTEM

4.1Working of the system :

In this project, Application of short range wireless technology to industrial automation using

zigbee it is basically working on the principle of zigbee technology which is wireless technique

used in industrial automation to control the devices of industry. In this project two ZigBee

modules are used , one for transmitting the data and other for receiving the data. which involves

the control of the devices connected to the microcontroller.

The Zigbee receiver will receive the output transmitted at a particular frequency by anotherZigBee device. In accordance to the frequency received the operations on the PC will be

performed. Like, various application programs can be started and shut down depending on a the

frequency being received.

In case of device control, the particular frequency will be converted to a corresponding code by

the decoder section and will be transmitted to the microcontroller. In accordance to the output of

the decoder, the microcontroller will switch on or off a particular device.

Along with the devices connected to the microcontroller, the door motor can also be controlled.

i.e the door will be opened or closed. For that task to be performed, the Zigbee receiver will

receive the output transmitted at a particular frequency by another ZigBee device.The driver

circuit has been used to interface the high load motors to the microcontroller. Using this project

we can control, both the switching on and switching off the devices connected to the

microcontroller.

4.2 Circuit Diagram of INDUSTRIAL AUTOMATION ZIGBEE

Circuit diagram of system is given as under . This particular circuit is used to display the control

of the system on the LCD .circuit works on +5v power supply ,which is generated with the help

of regulator circuit.:


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Fig 4.1(a) shows the Circuit Diagram Fig (b) LCD when power supply on

U1

8051

31

19

18

9

12

13

14

15

1

2

3

4

5

6

7

8

39

38

37

36

35

34

33

32

21

22

23

24

25

26

2728

1716

29

3011

10

40

20

EA/VP

X1

X2

RESET

INT0

INT1

T0

T1

P1.0

P1.1

P1.2

P1.3

P1.4

P1.5

P1.6

P1.7

P0.0

P0.1

P0.2

P0.3

P0.4

P0.5

P0.6

P0.7

P2.0

P2.1

P2.2

P2.3

P2.4

P2.5

P2.6

P2.7

RD

WR

PSEN

ALE/PTXD

RXD

VCC

VSS

IN4007

VCC

AC

LS1

BUZZER

1

2

R1

PC

C3

R3R2

U1

1

6

2

5 4

U2

4N35

1

6

2

5 4

SW1

1

2

Q3

3

2

1

LM7805/TO1

3

2VIN

GND

VOUT

Y1

K4

5

2

1

4

3

C3

IN4007

C1

C2

VCC

R4

K1

5

2

1

4

3

LED

470K

R1

VCC

VCC

IN4007

22OV AC

C1

IN4007

VCC

C2

12V DC

C1

SOCKET

C4

K2

5

2

1

4

3

T1

220V AC

1 5

4 8

1000UF

U3

4N35

1

6

2

5 4

MIC

Q2

3

2

1

U4

4N35

1

6

2

5 4

U1

13

8

11

10

1

3

4

5

2

6

12

9

14

7

16

15

R1IN

R2IN

T1IN

T2IN

C+

C1-

C2+

C2-

V+

V-

R1OUT

R2OUT

T1OUT

T2OUT

VCC

GND

Q1

3

2

1

J8

LCD

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

K3

5

2

1

4

3

Q4

3

2

1


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The Difference between Industrial automation wired and Industrial automation zigbeeCollection of controllers, sensors and actuators working in concert to implement, monitor and

control a discrete or continuous process

Controllers: Central and/or Distributed PLCs

Sensors: Temperature, Acoustic, Pressure, Strain, Vibration

Actuators: Valves, Motors, Solenoids, Relays

PLCs running ladder logic programs implement state machines that change outputs based on

the state of sensor input

Sensor inputs and PLC outputs are made available to monitoring programs

Alarms are generated when process variables exceed preset levels

Fig shows 4.1 industrial automation wired

More that just ZigBee modules are needed to implement ZigBee networks into existing

industrial automation networks

Gateways are key components to get ZigBee data off the ZigBee network

Gateways making use of existing protocols and interfaces, i.e. Modbus, Profibus, OPC, etc.,

allow existing applications to support ZigBee networks without modification.


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Fig shows 4.2 industrial automation Zigbee


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outdoor line of sight range while keeping power consumption at a remarkably low level. WSN

technology continues to find more applications in the industrial automation area, cutting costs

and improving efficiency.

5.2 Scope for Future Development:

Future work would apply the developed ITRI ZigBee platforms to large-scale networking

applications, and move the platform to a commercial product802.15.4 and ZigBee standards are

gaining wide acceptance. In 2008, overall sales revenues for chipsets and modules increased by

nearly 50% over the previous year. Some industry analysts are forecasting 2010 sales to nearly

double the 2009 numbers. The 802.15.4 market continues to show strong growth, even during

these trying. economic times.New and unique applications are demanding chipsetsthat deliver

more processing power, more output power,more memory, faster data rates and unique features

like the ability to transmit voice and video (Fig 5.1). At the same time, other applications are

beginning to demand stripped-down, purpose-built ultra-low power devices designed to run on

energy harvested from sources like ambient light, vibrations and thermal gradients. Futurists

have been trumpeting the arrival of theInternet of Things, a world in which sensors, computers

and controllers are all merged seamlessly across the environment. 6LoWPAN is an internet

protocol standard that defines the compression of internet data packets for transmission over

802.15.4. Developed by the IETF (Internet Engineering Task Force), this standard will

encourage the development of new and imaginative uses for wireless mesh networks. In spite of

the current state of the economy, the state of IEEE 802.15.4 and the products that support it looks

healthy. While it may \not be as appreciated as the sexier technologies driving consumer

handsets, 802.15.4 has thepotential to be ubiquitous, replacing wired networks in both homes

and industry as well as enabling future applications of which we can only dream.

5.3 Adavantages :

1. Reliable and self healing, easy to fabricate.

2. Supports large number of nodes and System is flexible.

3. Easy to deploy Mesh networking overcomes line-of-sight fears


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4. Very long life

5. Secure and system is easily accessible.

6. Low cost of Components. Costs less than sensors and signal conditioners

7. Can be used globally

Disadvantages:

y Required uninterrupted power supply.

y Destination computer should always be on.

y For proper operation of system there will be some delay in the operation.

Application:

Control vs Monitoring

1.ZigBee will provide control functionality in systems where some latency can be tolerated

(250Kbps datarate, < 10msec per hop)

2 ZigBee will be used for monitoring where control can tolerate only extremely low latencies

References:

Books

Muhammad Ali Mazidi ,Janice Gillispie Mazidi ,Rolin D.McKinlay,The 8051

Microcontroller and Embedded system ,Pearson Education Inc. 2nd Addition 2008

Myke predo, programming and customizing the 8051 microcontroller , TMH 1999

Kenneth JAyala, The 8051 Microcontroller architecture ,Programming &application

Ramankant Gayakwad , OPAMP Prentice Hall of india 3rd addition.

Web Resources:

http://www.8051projects.info/datasheets.asp

http://www.electro-tech-online.com

www.mcu.com


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