GREENHOUSE ENVIRONMENTAL

MONITORING AND CONTROL USING

WIRELESS TECHNOLOGY

Anirban Shaw

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GREENHOUSE ENVIRONMENTAL MONITORING AND

CONTROL USING WIRELESS TECHNOLOGY

Submitted in partial fulfillment of the requirement for the award of

the degree of Master of Technology in Applied Electronics &

Instrumentation Engineering

HERITAGE INSTITUTE OF TECHNOLOGY

By:

ANIRBAN SHAW

University Roll No: 12610313002

University Reg. No: 131260410019 Of (2013-2014)

Under The Supervision of

Prof. Sreeparna Dasgupta

Department of Applied Electronics & Instrumentation Engineering MAY 2015

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Certificate of Approval

22/05/2015

Certified that the thesis entitled GREENHOUSE ENVIRONMENTAL MONITORING

AND CONTROL USING WIRELESS TECHNOLOGY submitted by ANIRBAN

SHAW to Heritage Institute of Technology, Kolkata, for the award of the degree of M.

Tech. in Applied Electronics and Instrumentation Engineering has been accepted by the

external examiner(s) and board of examiners that the student has successfully defended

the thesis in the viva-voce examination held today.

Signature Signature

Prof. Sreeparna Dasgupta Prof. (Dr.) Madhurima Chattopadhyay

(Supervisor) (H. O. D.)

Signature Signature

(External Examiner) (External Examiner)

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Certificate

22/05/2015

This is to certify that the thesis entitled GREENHOUSE ENVIRONMENTAL

MONITORING AND CONTROL USING WIRELESS TECHNOLOGY, submitted by

ANIRBAN SHAW to Heritage Institute of Technology, Kolkata, is a record of bona fide

thesis work under my supervision and is worthy of consideration for the award of the

degree of Master of Technology in Applied Electronics and Instrumentation Engineering

under West Bengal University of Technology, Kolkata.

Prof. Sreeparna Dasgupta

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ACKNOWLEDGEMENTS

The project entitled ―GREENHOUSE ENVIRONMENTAL MONITORING

AND CONTROL USING WIRELESS TECHNOLOGY‖ has been carried out at

Heritage Institute of Technology, Kolkata.

It gives me immense pleasure to express my deepest respect and gratitude to my

project supervisor Prof. Sreeparna Dasgupta for her kind and valuable guidance

throughout this entire journey from the inception to the successful completion of my

project work. Without her gracious initiation and motivation, the execution of this

endeavor would not have been possible.

I accept this opportunity to also place forward my warm regards and indebtedness

to Prof. (Dr.) Madhurima Chattopadhyay, H.O.D, for her support and encouragement

throughout the period of this work.

I express my genuine reverence to Prof. Reshma Sengupta and all other faculty

members of the A.E.I.E department as well for ushering their priceless support to me.

Last but not the least, I would like to articulate my immense thanks to my parents

for encouraging me, instilling confidence in me, providing moral support and standing by

me through the period of this project work and throughout my life.

______________________________

ANIRBAN SHAW

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CONTENTS

Title Page i

Certificate of Approval ii

Certificate by the Supervisor iii

Acknowledgement iv

Contents v

List of Figures vii

List of Tables ix

Abstract x

Chapter 1 Introduction 1

1.1 Importance of Present Research Work 2

1.2 Wireless Technology 3

1.3 Zigbee and XBee 4

1.4 Applications of the Project 8

1.5 Greenhouse 8

1.6 Previous Research Work 10

1.7 Aim of the Thesis 14

Chapter 2 Theoretical Background 15

2.1 Components of Remote Sensor Node 16

2.2 Components of Base Station 30

Chapter 3 System Design and Methodology 32

3.1 Block Diagram of Complete Circuit 33

3.2 XBee Setup 34

3.3 Interfacing of AT89S52 with ADC 0808 38

3.4 LM 35 and SY-HS-220 Setup 42

3.5 Data Transfer and Further Processing 45

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Chapter 4 Conclusion and Future Scope of Study 50

References 53

Gallery 55

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List of Figures

CHAPTER 2: THEORETICAL BACKGROUND

Figure 2.1 LM 35 18

Figure 2.2 SY-HS-220 19

Figure 2.3 SY-HS-220 Characteristic Curves 20

Figure 2.4 AT89S52 Pin Diagram 22

Figure 2.5 Pin Diagram of ADC 0808 26

Figure 2.6 555 Timer Circuit 28

Figure 2.7 Timer Output Waveforms 29

Figure 2.8 Non Inverting Amplifier 30

Figure 2.9 CP2102 USB to UART module 32

CHAPTER 3: SYSTEM DESIGN AND METHODOLOGY

Figure 3.1 Block Diagram of Setup 34

Figure 3.2 XCTU Main Terminal 35

Figure 3.3 XCTU Add Devices Terminal 36

Figure 3.4 XCTU XBee Configurations Terminal 37

Figure 3.5 XBee Loop Test Interface 38

Figure 3.6 XBee Loop Test Console Log 38

Figure 3.7 Microcontroller Setup 39

Figure 3.8 Interfacing of ADC and 8051 41

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Figure 3.9 Data Line Connections between ADC and 8051 42

Figure 3.10 Interfacing between sensors and ADC 0808 44

Figure 3.11 Final Interfacing Circuit 45

Figure 3.12 Program Flowchart 47

Figure 3.13 Docklight Terminal 48

Figure 3.14 Sensor Reader Window 49

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List of Tables

CHAPTER 2: THEORETICAL BACKGROUND

Table 2.1 SY-HS-220 Standard Characteristics 20

Table 2.2 Port 1 alternate functions 23

Table 2.3 Port 3 alternate functions 24

Table 2.4 Analog Channel Selection 27

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Abstract

The project looks forward to bringing real time monitoring of a greenhouse with

ease. The project incorporates 2 sensors viz. a temperature sensor (LM35) and a

humidity sensor (SY-HS-220) to maintain functionality of a greenhouse. Once the

temperature/humidity exceeds or falls below a certain pre-defined range, an action can

be taken to control the parameters so as to not harm any plants present inside the

greenhouse. The project consists of a sensor node and a base station. The two are

connected wirelessly by two XBee S2 chips. The base station also comprises of a data

logger where the real time data will be stored. The project in future may later add other

sensors along with the temperature and humidity sensors, to observe other parameters

such as levels of gas emission.

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CHAPTER 1

INTRODUCTION

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CHAPTER 1

INTRODUCTION

1.1 Importance of Present Research Work

Monitoring and control is an important aspect of all of the greenhouse‘s present

around the world. To monitor the greenhouse environment parameters effectively, it is

necessary to design a measurement and control system. The present research work is

generally directed to a system for monitoring a variety of environmental and/or other

conditions within a defined remotely located region. Using a variety of sensors we are

able to determine the conditions present at a given time and take action if a

parameter/condition present exceeds or falls below a pre-determined range. Also using

wireless technology we can encompass a wide area of operation which would not have

been available if we used a traditional wire based system.

The proposed system is an embedded system which will closely monitor and

control the climatic parameters of a greenhouse on a regular basis round the clock for

cultivation of crops or specific plant species which could maximize their production over

the whole crop growth season.

The controller used is a low power, cost efficient chip manufactured by ATMEL,

the AT89s52 chip. It communicates with the two sensor modules in real-time in order to

control the temperature and humidity respectively according to the necessary condition of

the crops. Using wireless technology the maintenance of the greenhouse can be carried on

from outside in the supervisory station where all the data will be directed to. The use of

easily available components reduces the manufacturing and maintenance costs. The

design is quite flexible as extra sensors can be added any time. It can thus be tailor-made

to the specific requirements of the user. This makes the proposed system to be an

economical, portable and a low maintenance solution for greenhouse applications.

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1.2 Wireless Technology

Wireless communication involves transfer of information between two or more points

which are not connected by any electrical conductors. This makes hassle free transfer of

data/ communication possible.

A wireless communication network has numerous advantages, not least the mobility

of the devices within the network. It is a simple matter to relocate a communicating

device, and no additional cost of rewiring and excessive downtime is associated with

such a move. It is also a simple matter to add in a communication device to the network

or remove one from the network without any disruption to the remainder of the system.

Other than the initial outlay on setting up a wireless network, the cost of running and

maintaining it is minimal.

Using wireless technology in our given project we enable the wide geographical

area of the greenhouse to send in values/parameters from different locations to a central

supervisory system without the need for wires taking up space in the green house. Also as

the communication between the sensors and the supervisory system is wireless in nature,

the supervisory station can be set outside of the greenhouse as long as it is within range

of the wireless communicators.

The specific wireless technology that we are using in our project is the Zigbee

communication protocol which is based on the IEEE 802.15.4 standard. The range varies

between 10 – 100 meters depending on power output and environmental characteristics.

Zigbee devices can transmit data over long distances by passing data through a mesh

network of intermediate devices to reach more distant ones.

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1.3 Zigbee And XBee

1.3.1 What is Zigbee?

ZigBee is a wireless technology developed as an open global standard to address

the unique needs of low-cost, low-power wireless M2M networks. The ZigBee standard

operates on the IEEE 802.15.4 physical radio specification and operates in unlicensed

bands including 2.4 GHz, 900 MHz and 868 MHz.

The 802.15.4 specification upon which the ZigBee stack operates gained

ratification by the Institute of Electrical and Electronics Engineers (IEEE) in 2003. The

specification is a packet-based radio protocol intended for low-cost, battery-operated

devices. The protocol allows devices to communicate in a variety of network topologies

and can have battery life lasting several years.

1.3.2 Zigbee Protocol

The Zigbee protocol includes:-

Support for multiple network topologies such as point-to-point, point-to-

multipoint and mesh networks.

Low duty cycle – provides long battery life.

Low latency.

Direct Sequence Spread Spectrum (DSSS).

Up to 65,000 nodes per network.

128-bit AES encryption for secure data connections.

Collision avoidance, retries and acknowledgements

1.3.3 Zigbee Networks

Zigbee devices can form networks with Mesh, Star and Generic Mesh topologies

among themselves. The network can be expanded as a cluster of smaller networks. A

Zigbee network can have three types of nodes: Zigbee Coordinator (ZBC), Zigbee router

(ZBR) and Zigbee End Device (ZBE) each having some unique property.

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There can be only one ZBC in a network, the one that initiates the network in the

first place and stores the information about the network. All the devices in the network

communicate with this ZBC. It has routing capabilities and acts as a bridge to other

networks on other floors. A ZBR is an optional component used to extend the coverage.

The router itself may host an application or handle local address allocation or de-

allocation. A ZBE is optimized for low power consumption and is the cheapest among

the three node types. It communicates only with the coordinator and is the point where

sensors are deployed. Unicast Device Discovery is done if Network ID is available; else

Broadcast Device Discovery is done. A ZBR or ZBC‘s response to Device Discovery

query is a payload containing IEEE address, the Network Address and all known network

addresses.

1.3.4 What is XBee and Types of XBee

XBee is the brand name from Digi International for a family of form

factor compatible radio modules that are Zigbee compliant . The first XBee radios were

introduced under the MaxStream brand in 2005 and were based on the 802.15.4-2003

standard designed for point-to-point and star communications at over-the-air baud rates

of 250 kbit/s.

Two models were initially introduced—a lower cost 1 mW XBee and the higher

power 100 mW XBee-PRO. Since the initial introduction, a number of new XBee radios

have been introduced and all XBees are now marketed and sold under the Digi brand.

The XBee radios can all be used with the minimum number of connections –

power (3.3 V), ground, data in and data out (UART), with other recommended lines

being Reset and Sleep. Additionally, most XBee families have some other flow

control, I/O, A/D and indicator lines built in. A version of the XBees called the

programmable XBee has an additional onboard processor for user‘s code.

XBee Modules are available in two form-factors; through-hole and surface

mount (SMT). All XBees (with the exception of the XBee 868LP) are available in the

popular 20-pin Through-Hole form-factor. Certain XBee modules are also available in a

37-pad Surface Mount design, which is popular for higher volume applications due to the

reduced manufacturing costs of SMT.

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XBee Modules typically come with several antenna options, including U.FL, PCB

Embedded, Wire, and RPSMA.

The XBees can operate either in a transparent data mode or in a packet-

based application programming interface (API) mode.[8]

In the transparent mode, data

coming into the Data IN (DIN) pin is directly transmitted over-the-air to the intended

receiving radios without any modification. Incoming packets can either be directly

addressed to one target (point-to-point) or broadcast to multiple targets (star). This mode

is primarily used in instances where an existing protocol cannot tolerate changes to the

data format. AT commands are used to control the radio‘s settings. In API mode the data

is wrapped in a packet structure that allows for addressing, parameter setting and packet

delivery feedback, including remote sensing and control of digital I/O and analog input

pins.

XBee 802.15.4 – The initial point-to-point topology or star topology module

running the IEEE 802.15.4 protocol.

XBee-PRO 802.15.4 – A higher power, longer range version of the XBee

802.15.4

XBee DigiMesh 2.4 – A 2.4 GHz XBee module which uses DigiMesh, a

sleeping mesh networking protocol developed by Digi International.

XBee-PRO DigiMesh 2.4 – A higher power, longer range version of the XBee

DigiMesh 2.4.

XBee ZB – An XBee module that incorporates the ZigBee PRO mesh

networking protocol.

XBee-PRO ZB – A higher power, longer range version of the XBee ZB.

XBee ZB SMT – A surface mount XBee running the ZigBee protocol.

XBee-PRO ZB SMT – A higher power, longer range version of the XBee ZB

SMT.

XBee SE – An XBee ZB module that incorporates the security cluster for the

Zigbee Smart Energy public profile.

XBee-PRO SE – A higher power, longer range version of the XBee SE.

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XBee-PRO 900HP - A 900 MHz XBee-PRO module with up to 28 mile range

with high-gain antenna, which supports DigiMesh networking protocol.

XBee-PRO 900 (Legacy) – A 900 MHz proprietary point-to-point and star

topology module, not recommended for new design.

XBee-PRO XSC (S3B) – A 900 MHz module compatible over the air with the

Digi 9XStream radios.

XBee-PRO DigiMesh 900 (Legacy) – A 900 MHz module which uses

DigiMesh, not recommended for new design (see XBee-PRO 900HP for new

designs).

XBee-PRO 868 – An 868 MHz 500 mW long-range module which supports

proprietary point-to-point and star, for use in Europe.

XBee 865/868LP - An 868 MHz XBee module which uses DigiMesh,

available in Surface Mount form-factor (also configurable to 865 MHz for use

in India).

1.3.5 XBee Data Transfer Modes

The two main modes of data transfer in XBee are AT mode and API mode.

AT mode is synonymous with "Transparent" mode. In AT mode, any data sent to the

XBee module is immediately sent to the remote module identified by the Destination

Address in memory. When the module is in AT mode, it can be configured by the user or

a host microcontroller by first placing the module in Command mode and then sending

predefined AT commands through the UART port. This mode is useful when you don't

need to change destination addresses very often, or you have a very simple network, or

simple point to point communication. For larger networks that involve nodes talking to

multiple targets, API mode is more useful. In API mode, rather than sending AT

commands serially, data packets are assembled that include the Destination Address. API

mode allows you to change destination address much more quickly because Command

Mode doesn't need to be entered. API mode is also useful if the user needs to change the

configuration of a remote module.

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1.4 Applications of the project

Even though the project focuses on control and monitoring of the greenhouse,

monitoring and controlling devices have a vast field of applications. There are a variety

of systems for monitoring and controlling manufacturing processes, inventory systems,

emergency control systems, and the like. Most automatic systems use remote sensors and

controllers to monitor and automatically respond to system parameters to reach desired

results. A number of control systems utilize computers to process system inputs, model

system responses, and control actuators to implement process corrections within the

system. Both the electric power generation and metallurgical processing industries have

had success controlling production processes by implementing computer controlled

control systems in individual plants. A number of environmental and safety systems also

require constant or real-time monitoring. Heating, ventilation, and air-conditioning

systems, fire reporting and damage control systems, alarm systems, and access control

systems are representative systems that utilize real-time monitoring and often require

immediate feedback and control. These real-time systems have been the target of control

systems theory and application thereof for some time.

1.5 Greenhouse

A greenhouse (also called a glasshouse or a hothouse) is a building or complex in

which plants are grown. These structures range in size from small sheds to industrial-

sized buildings. A miniature greenhouse is known as a cold frame. Commercial glass

greenhouses are often high tech production facilities for vegetables or flowers. The glass

greenhouses are filled with equipment like screening installations, heating, cooling and

lighting and also may be automatically controlled by a computer to maximize potential

growth.

A greenhouse is a structural building with different types of covering materials,

such as a glass or plastic roof and frequently glass or plastic walls; it heats up because

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incoming visible sunshine is absorbed inside the structure. Air warmed by the heat from

warmed interior surfaces is retained in the building by the roof and wall; the air that is

warmed near the ground is prevented from rising indefinitely and flowing away.

Greenhouses allow for greater control over the growing environment of plants.

Depending upon the technical specification of a greenhouse, key factors which may be

controlled include temperature, levels of light and shade, irrigation, fertilizer application,

and atmospheric humidity. Greenhouses may be used to overcome shortcomings in the

growing qualities of a piece of land, such as a short growing season or poor light levels,

and they can thereby improve food production in marginal environments.

As they may enable certain crops to be grown throughout the year, greenhouses

are increasingly important in the food supply of high-latitude countries. One of the largest

complexes in the world is in Almeria, Andalucía, Spain, where greenhouses cover almost

200 km2 (49,000 acres).

Greenhouses are often used for growing flowers, vegetables, fruits, and

transplants. Special greenhouse varieties of certain crops, such as tomatoes, are generally

used for commercial production. Many vegetables and flowers can be grown in

greenhouses in late winter and early spring, and then transplanted outside as the weather

warms. Bumblebees are the pollinators of choice for most pollination, although other

types of bees have been used, as well as artificial pollination. Hydroponics can be used to

make the most use of the interior space.

The relatively closed environment of a greenhouse has its own unique

management requirements, compared with outdoor production. Pests and diseases, and

extremes of heat and humidity, have to be controlled, and irrigation is necessary to

provide water. Most greenhouses use sprinklers or drip lines. Significant inputs of heat

and light may be required, particularly with winter production of warm-weather

vegetables.

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1.6 Previous Research Work

A wireless sensor network (WSN) is a system consisting of a collection of nodes

and a base station. A node is composed by a processor, local memory, sensors, radio and

battery and a base station is responsible for receiving and processing data collected by the

nodes.[1] The technological development in Wireless Sensor Networks made it possible

to use in monitoring and control of greenhouse parameter in precision agriculture. In last

decades there have been tremendous advancements in technology for agriculture and

growth of final yield.[2] The use of computational systems and technology in agricultural

applications has become viable, since the associated costs are decreasing.[3] In

agricultural applications, monitoring and control are essential to support consumer

requirements and to get productivity improvements. Two important branches of

agriculture are precision agriculture and vegetable cultivation in greenhouses, in which

the production management has to be more controlled, so that the values of a set of

parameters have to be approximated to a value considered ideal.[2][4][19]

. Temperature, humidity and water, radiation and CO2 concentration are the major

features that are monitored in greenhouses. WSNs should be applied in greenhouse

control systems, providing a distributed and real time sensing, obtaining parameters

values differences inside the greenhouse.[6] A distributed greenhouse control system

based on LonWorks technology is presented in (Pereira and Cugnasca, 2005)[19], where

the processing and communication connections are distributed among the components of

the system, called nodes.

Many researchers observed that, the greenhouse technology is well accepted in

agriculture engineering. The integration of wireless sensor network in green house is the

recent concept which leads to precision agriculture. Blackmore et al. in 1994 [4],

explained that, the system can be designed to increase the quality agricultural yield by,

properly monitoring soil and environment. They also observed that, in early stage of

WSN, farmers were reluctant to deploy it, because of high cost. Technological

development has reduced the cost. In addition to MEMS technology for hardware, some

other technologies like, satellite sensing, Remote Sensing, Global Positioning System and

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Geographical Information System are also contributing in overall progress [5]. Beckwith

et al. had worked on WSN in large scale vineyard on very large scale design and

deployment [6]. They work on 65 motes, which have only eight hops, to collect the data

of pH values. Predesigned crop management in precision agriculture is studied in the

Lofar Agro project, in Europe. In this project, Proper application of pesticides and

fertiliser as per real time environmental changes is explored. For effective control of crop

diseases like phytophthora, the information collected from a weather station and the

wireless network is very much useful [7].

Wireless sensors and smart transducers are equipped with some micro-controllers

for providing processing and network management capability. Standard like IEEE 1451.5

is also suitable to integrate the wireless sensors with the special transducer to build

intelligent wireless sensors with sensing, computing and communication capabilities.

Intelligent sensors and actuators can be used to carry out various automatic functions.

Wireless communication protocols, such as 802.11, 802.15.4 and 802.15.5 [8][20] can

also combine. A requirement for design of wireless sensor communications, including

issues related to wireless sensor model, user requirements, data integrity, security and

bandwidth all are well defined in this Standards.[2]

The total number of sensor nodes and actuators are depends on the size of

greenhouse. About 200 nodes are sufficient if the size of green house is 35m x 200 m.

This is the physical size of the targeted area. It is under the range of sensing capacity of

the hardware. The sensor nodes can be classified as ‗A‘, ‗B‘ and ‗C‘. Where type ‗A‘ is

climate sensor for outside, and type ‗B‘ is climate sensor for the inside of the greenhouse.

Maximum two nodes are more than enough for outside. Type ‗B‘ sensors can be placed at

a distance of 10 to 15 meters of diameter, to capture precise environmental condition. The

type ‗C‘ sensors are soil sensors, which are recommended to use, as per the layout plan of

the crop plantation. They can also control water flow of irrigation system used in

Greenhouse. They are typically used after every two meters. The different controlling

parameter ranges in various modes for some typical crop is as shown in Table 1. This

information collected from the data sheet about the crop [2][12].

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As the climate and fertilization are independent issues, they have different control

problems. The exact need of nutrients and amount water for different crop species can be

very well controlled, by automated machine which works on collected data. The amount

of water and fertilizers require to the plant is a function of climate environmental

conditions on which growth of the crop is depended. So that greenhouse crop production

is a complex issue [13]. The Climatic Control Variables are the dynamic behavior of the

greenhouse. Microclimate is a combination of physical processes involving energy

transfer (which includes radiation and heat) and mass balance (which includes water

vapour fluxes and CO2 concentration). This system depends on the outlet environmental

conditions, architecture of the greenhouse, performance of the control actuators and

variety of crop. Proper ventilation and heating are the main way controlling greenhouse

climate. For controlling inside temperature, humidity and shading the artificial light is

used. CO2 injection is a control to influence photosynthesis and fogging [14].

Growth of Plants depends on the photosynthesis process which is a

measure of photosynthetically active radiation. It is observed that proper temperature

level influences the speed of sugar production by photosynthesis radiation. Temperature

has to be control properly since higher radiation level may give a higher temperature.

Hence, in the diurnal state, it is necessary to adjust the temperature at an optimal level for

the photosynthesis process. In nocturnal conditions, plants are not active therefore; it is

not necessary to maintain such a high temperature. For this reason, two temperature set-

points are usually considered are diurnal and nocturnal [15].

Water vapour inside the greenhouse is one of the most significant variables

affecting the crop growth. High humidity may increase the probability of diseases and

decrease transpiration. Low humidity may cause hydria stress, closing the stomata and

thus it may lower down the process of photosynthesis which depends on the CO2

assimilation. The humidity control is complex because if temperature changes then

relative humidity changes inversely. Temperature and humidity are controlled by the

same actuators. The main priority is for temperature control because it is the primary

factor in the crop growth. Based on the inside relative humidity value the temperature set-

point can be adjusted to control the humidity within a determined range. Hence to control

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the required humidity is very complex task. For proper control of humidity internal air

can be exchange with outside air by properly controlling ventilations of the green house

[16].

Soil water also affects the crop growth. Therefore, the monitor & control of soil

condition has a specific interest, because good condition of a soil may produce the proper

yield. The proper irrigations and fertilizations of the crops are varies as per the type, age,

phase and climate. The pH value, moisture contains, electric conductivity and the temp of

a soil are some key parameters. The pH valves and other parameters will help to monitor

the soil condition. The temperature and the moisture can be controlled by the irrigation

techniques like drift and sprinkles system in a greenhouse. The temperature of the soil

and the inside temperature of the green house are interrelated parameters, which can be,

control by proper setting of ventilation. Since the temperature control is depends on direct

sun radiation and the screen material used, the proper set point can adjust to control soil

temperature. The temperature set-point value depends on actual temperature of the inside

and outside of the greenhouse [17].

In green house technology, more number of the parameters is to be control

because, the varieties of the crop are large. They are increasing day by day because of the

development in agriculture technology. In this situation, the wireless sensor network with

additional hardware and software is an efficient solution for green house control.

Experimentally it is proved that the hardware develop by Cypress Inc. is the best solution

which works on low power with less complexity and high reliability for greenhouse

control. In the future, if parameter still increase, then for WSN technology with currently

available bandwidth, may not be sufficient. Then WSN with cognitive radio technology

may be the solution. This advancement in precision agriculture through Wireless Sensor

Network in green house control is extremely useful. This has scope in developing

countries in globe, where agriculture is the main business.[2]

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1.7 Aim of the thesis

The project aims at bringing low cost and hassle free maintenance of a

greenhouse with relative ease. All the components required are easily available and are

easily replaceable.

A system is provided having one or more sensors to be read and/or actuators to be

controlled, ultimately through a computer via Xbee. The sensors and/or actuators are

interfaced with wireless transceivers (XBee chips) that transmit and/or receive data to and

from the sensor node. It should be appreciated that, a portion of the information

communicated includes data that uniquely identifies the sensors and/or actuators.

When any of the climatic parameters (temperature and humidity in this particular

thesis) cross a safety threshold which has to be maintained to protect the crops, the

sensors sense the change and the microcontroller reads this from the data at its input ports

after being converted to a digital form by the ADC. Since a microcontroller is used as the

heart of the system, it makes the set-up low-cost and effective nevertheless. This data is

then sent to the XBee end device which transfers the data to the coordinator. The data is

then stored in the supervisory station PC and is evaluated to see whether the temperature

and the humidity are in the specified range. If the range falls below or goes above a

threshold a control action is taken manually or remotely to prevent any damage to the

crops.

Being a wireless design the system does not take up too much space inside the

greenhouse and has the flexibility of having the supervisory station at a distance. Thus,

this system eliminates the drawbacks of the wired set-ups and is designed as an easy to

maintain, flexible and low cost solution.

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CHAPTER 2

THEORETICAL BACKGROUND

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CHAPTER 2

THEORETICAL BACKGROUND

2.1 Components of remote sensor node

The remote sensor node consists of the following:-

LM-35 Temperature sensor.

SY-HS-220 Humidity Sensor.

AT89S52 microcontroller.

ADC 0808.

1 x 555 timer for the design of the clock circuit.

2 x 741 op amps for the design of 2 instrumentation amplifiers.

XBee end device.

5V power supply.

2.1.1 LM-35 Sensor

LM35 is a precision IC temperature sensor with its output proportional to the

temperature (in oC). The sensor circuitry is sealed and therefore it is not subjected to

oxidation and other processes. With LM35, temperature can be measured more accurately

than with a thermistor. It also possess low self-heating and does not cause more than

0.1 o

C temperature rise in still air.

The operating temperature range is from -55°C to 150°C. The output voltage

varies by 10mV in response to every oC rise/fall in ambient temperature, i.e., its scale

factor is 0.01V/ o

C .

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Fig. 2.1: LM-35

The LM 35 sensor has an advantage over linear temperature sensors calibrated in

Kelvin, as the user is not required to subtract a large constant voltage from the output to

obtain convenient Centigrade scaling. The LM35 device does not require any external

calibration or trimming to provide typical accuracies of ±¼°C at room temperature and

±¾°C over a full −55°C to 150°C temperature range. Lower cost is assured by trimming

and calibration at the al wafer level. The low-output impedance, linear output and precise

inherent calibration of the LM35 device makes interfacing to readout or control circuitry

especially easy. The device is used with single power supplies, or with plus and minus

supplies. As the LM35 device draws only 60 μA from the supply, it has very low self-

heating of less than 0.1°C in still air. The LM35 device is rated to operate over a −55°C

to 150°C temperature range.

~ 18 ~

2.1.2 SY-HS-220 Sensor

Fig. 2.2: SY-HS-220 Humidity Sensor

Specifications:

• Operating voltage: 5V.

• Operating humidity range: 30 - 90% RH.

• Operating temperature range: 0 - 60°C.

• Storable temperature range: 30°C - 85°C

• Storable humidity range: within 95% RH.

• Accuracy: 5% RH (at 25°C, 60% RH).

~ 19 ~

Fig. 2.3: SY-HS-220 Characteristic Curve

The SY-HS-220 humidity sensor has an operating temperature range of 0°C to 60°C and

an operating humidity range of 30% - 90% relative humidity. The following table

illustrates the approximate voltage output at a specific RH percentage.

%RH O/P(mV)

30 990

40 1300

50 1650

60 1980

70 2310

80 2640

90 2970

Table 2.1: SY-HS-220 Standard Characteristics

The PCB unit in the sensor contains a thermistor or diode for temperature compensation.

~ 20 ~

2.1.3 AT89S52 Microcontroller

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller

with 8K bytes of in-system programmable Flash memory. The device is manufactured

using Atmel‘s high-density nonvolatile memory technology and is compatible with the

industry-standard 80C51 instruction set and pin out. 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 in-system programmable

Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which

provides a highly-flexible and cost-effective solution to many embedded control

applications.

The AT89S52 provides the following standard features: 8K bytes of Flash, 256

bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, 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 AT89S52 is designed with static logic

for 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

interrupt or hardware reset.

~ 21 ~

Fig. 2.4: AT89S52 Pin Diagram

Pin Descriptions:-

VCC - Supply voltage.

GND - Ground.

Port 0 - Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each

pin can sink eight TTL inputs. When 1‘s are written to port 0 pins, the pins can be

used as high-impedance inputs.

~ 22 ~

Port 0 can also be configured to be the multiplexed low-order address/data bus

during accesses to external program and data memory. In this mode, P0 has

internal pull-ups.

Port 0 also receives the code bytes during Flash programming and outputs the

code bytes during program verification. External pull-ups are required during

program verification.

Port 1 - Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. 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 pull-ups 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 pull-ups.

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 trigger input (P1.1/T2EX).Port 1

also receives the low-order address bytes during Flash programming and

verification.

Port 1 also has some alternate functions.

Table 2.2: Port 1 alternate functions

Port 2 - Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2

output buffers can sink/source four TTL inputs. When 1s are written to Port 2

pins, they are pulled high by the internal pull-ups and can be used as inputs. As

inputs, Port 2 pins that are externally being pulled low will source current (IIL)

because of the internal pull-ups.

Port 2 emits the high-order address byte during fetches from external program

memory and during accesses to external data memory that uses 16-bit addresses

(MOVX @ DPTR). In this application, Port 2 uses strong internal pull-ups when

~ 23 ~

emitting 1s. During accesses to external data memory that uses 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 - Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3

output buffers can sink/source four TTL inputs. When 1s are written to Port 3

pins, they are pulled high by the internal pull-ups and can be used as inputs. As

inputs, Port 3 pins that are externally being pulled low will source current (IIL)

because of the pull-ups.

Port 3 receives some control signals for Flash programming and verification.

Port 3 also has some alternate functions.

Table 2.3: Port 3 alternate functions

RST - Reset input. A high on this pin for two machine cycles while the oscillator

is running resets the device. This pin drives high for 98 oscillator periods after the

Watchdog times out. The DISRTO bit in SFR AUXR (address 8EH) can be used

to disable this feature. In the default state of bit DISRTO, the RESET HIGH out

feature is enabled.

ALE/PROG - Address Latch Enable (ALE) 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,

~ 24 ~

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 (PSEN) is the read strobe to external program

memory.

When the AT89S52 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.

EA/VPP - External Access Enable. EA must be strapped to GND in order to

enable the device to fetch code from external program memory locations starting

at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will

be internally latched on reset.

EA should be strapped to VCC for internal program executions. This pin also

receives the 12-volt programming enable voltage (VPP) during Flash

programming.

XTAL1 - Input to the inverting oscillator amplifier and input to the internal clock

operating circuit.

XTAL2 - Output from the inverting oscillator amplifier.

~ 25 ~

2.1.4 ADC 0808

Fig. 2.5: Pin diagram of ADC 0808

~ 26 ~

The ADC0808 data acquisition component is a monolithic CMOS device with an

8-bit analog-to- microprocessor compatible control logic. The 8-bit A/D converter uses

successive approximation as the conversion technique. The converter features a high

impedance chopper stabilized comparator, a 256R voltage divider with analog switch tree

and a successive approximation register. The 8-channel multiplexer can directly access

any of 8-single-ended analog signals. The device eliminates the need for external zero

and full-scale adjustments. Easy interfacing to microprocessors is provided by the latched

and decoded multiplexer address inputs and latched TTL outputs. The design of the

ADC0808 has been optimized by incorporating the most desirable aspects of several A/D

conversion techniques. The ADC0808 offers high speed, high accuracy, minimal

temperature dependence, excellent long-term accuracy and repeatability, and consumes

minimal power. These features make this device ideally suited to applications from

process and machine control to consumer and automotive applications.

The device contains an 8-channel single-ended analog signal multiplexer. A

particular input channel is selected by using the address decoder. Table 4 shows the input

states for the address lines to select any channel. The address is latched into the decoder

on the low-to-high transition of the address latch enable signal.

Analog Channel Address A Address B Address

C

IN0 0 0 0

IN1 0 0 1

IN2 0 1 0

IN3 0 1 1

IN4 1 0 0

IN5 1 0 1

IN6 1 1 0

IN7 1 1 1

Table 2.4: Analog Channel Selection

The step size is decided based on set reference value. Step size is the change in analog

input to cause a unit change in the output of ADC. The default step size is 19.53mV

corresponding to 5V reference voltage. In the ADC0808, Vref(+) and Vref(-) set the

~ 27 ~

reference voltage. If Vref(-) = Gnd and Vref(+) = 5V, the step size is 5V/256 = 19.53mV.

Therefore, to get a 10mV step size we need to set Vref(+) = 2.56V and Vref(-) =

Gnd. ADC0808 needs an external clock to operate unlike ADC0804 which has an

internal clock.

2.1.5 555 Timer Circuit

Fig. 2.6: 555 Timer Circuit (Astable Multivibrator)

An Astable Multivibrator is an oscillator circuit that continuously produces

rectangular wave without the aid of external triggering. So an Astable Multivibrator is

also known as Free Running Multivibrator. Astable Multivibrators using 555 Timers are

very simple, easy to design, very stable and low cost. It can be used for timing from

microseconds to hours.

In the 555 Oscillator circuit in Fig. 2.6, pin 2 and pin 6 are connected together allowing

the circuit to re-trigger itself on each and every cycle allowing it to operate as a free

running oscillator. During each cycle capacitor, C charges up through both timing

resistors, R1 and R2 but discharges itself only through resistor, R2 as the other side

of R2 is connected to the discharge terminal, pin 7.

~ 28 ~

Then the capacitor charges up to 2/3Vcc (the upper comparator limit) which is

determined by the 0.693(R1+R2)C combination and discharges itself down to 1/3Vcc

(the lower comparator limit) determined by the 0.693(R2.C) combination. This results in

an output waveform whose voltage level is approximately equal to Vcc – 1.5V and whose

output ―ON‖ and ―OFF‖ time periods are determined by the capacitor and resistors

combinations.

Fig. 2.7: Timer Output Waveforms

In the thesis project, a clock frequency of a 100 KHz is needed to run the ADC 0808.

This frequency is obtained by giving the following values:-

R1 = 100 ohm

R2 = 500 ohm

C1 = 0.01 µF

By giving the above values in the clock circuit we get an output frequency of 100 KHz

according the equation:

[( ) ]

~ 29 ~

2.1.6 Non Inverting Amplifier using 741 Op-Amp

Fig. 2.8: Non Inverting Amplifier

A non-inverting amplifier is a special case of the differential amplifier in which

the circuit's inverting input V1 is grounded and non-inverting input V2 is identified with

Vin above.

The LM 35 sensor gives output in the range of millivolts which is not enough to

identify the change of temperature via binary output. To remedy this we are using a non-

inverting amplifier with a gain of 10 insuring that we get a differentiable voltage output.

To get the required gain we use the formula:

Where we give Rf = 900 ohms and R2 = 100 ohms, to get a gain of 10.

~ 30 ~

2.2 Components of base station

The base station consists of:

XBee Coordinator.

CP2102 XBee to PC connecter chip and cable.

PC/Laptop for data logging and further processing.

2.2.1 XBee Coordinator

The base station consists of the XBee coordinator where all the sensor data will flow

through into the PC. The coordinator device has to be in sync with the XBee end device

for data to flow from one to the other. The XBee coordinator is set in API mode unlike

the XBee end device.

To achieve this we have to program the XBee devices using the CP2102 module and

the XCTU software present in the PC.

2.2.2 CP2102 USB to UART module

The CP2102 module by SI Labs is the device that helps the XBee module to

connect to the PC via a RS 232 to USB cable without the additional need for devices such

as a MAX 232. It is an easy to use plug and play device that makes communication with

the XBee hassle free.

This board can be used to connect raw module of XBee to make communication

between PC to PC, PC to Mechanical Assembly, PC to embedded and microcontroller

based Circuits possible. This board can also be used to configure XBee according to

application. As XBee communicates through Serial Communication so the other end of

the USB which is connected to PC, is treated as a COM port for Serial Communication. It

is provided with indication LEDs for ease.

~ 31 ~

Fig. 2.9: CP2102 USB to UART module

2.2.3 PC for data logging and further processing.

The PC is used to read the data that is coming from the microcontroller through

the XBee devices. The XBees themselves have been configured using the PC. XCTU a

software from Digi International is used to configure the XBee chips. XCTU is a free

multi-platform application designed to enable interaction with Digi RF modules through

a simple-to-use graphical interface.

For Data logging, Docklight software is being used. The docklight software uses

com port, baud rate and serial bits to choose the receiving connection data. Once the data

starts flowing after the serial communication has been established, the data maybe logged

in a text or html format for future reference and study.

Finally, for further processing C++/Java is being used to sort through the data and

find any data that exceeds the pre-determined range set according to greenhouse

protocols.

~ 32 ~

CHAPTER 3

SYSTEM DESIGN

AND

METHODOLOGY

~ 33 ~

CHAPTER 3

SYSTEM DESIGN AND

METHODOLOGY

The following steps were performed in setting up the complete experiment:

1. Setting up the two XBees to communicate with each other.

2. Interfacing of AT89S52 with ADC 0808 (with external clock).

3. Setting up the LM 35 and SY-HS-220.

4. Connecting the XBee end device with the serial output port of the AT89S52.

5. Connecting the XBee coordinator device with the PC for further data processing.

3.1 Block Diagram Of Complete Setup

TXD

Fig. 3.1: Block Diagram of Setup

SY-HS-220

Humidity Sensor

Analog to Digital

Converter

ADC 0808

MICRO-

CONTROLLER

AT89S52

END DEVICE

LM 35

Temp.

Sensor

Non

Inverting

Amplifier

COORDINATOR

USER

INTERFACE

CP2102

USB TO UART

~ 34 ~

3.2 XBee Setup.

To setup the two XBees to communicate with each other and test whether they are

communicating, a loopback test must be performed.

Step 1 : Connect the XBees using an RS232-USB cable to the PC.

Step 2 : Open the XCTU software

Fig. 3.2

Step 3 : Click on Add devices to find the XBees connected to the PC

Step 4: Click on the appropriate com port that is shown.

The com ports that are shown vary on the module used to make the XBee

communicate with the PC.

~ 35 ~

Fig. 3.3

Step 4 : Choose the parameters of the XBee to add. Baud rate can be changed

later.

Step 5 : Once this is done, the window for writing the parameters to the XBee

chip opens. The firmware of the XBee as well the mode of data transfer of the

particular XBee can be edited and written in this window.

~ 36 ~

Fig. 3.4

Choose XBee coordinator AT for the coordinator device.

Choose XBee end device AT for the end device.

Set similar PAN ID‘s for both the XBees.

The destination address defines which XBee the source XBee is talking to.

There are actually two values used to set the destination: destination high

(DH) and destination low (DL). Set DH to the Serial Number High (SH) and

DL to the Serial Number Low (SL) of the destination XBee.

Now the XBees are set to communicate with each other. The coordinator stays

connected to the PC and the end device is set up on a breadboard, where the

Vcc and Gnd are connected to the breadboard, and the Din and Dout of the

XBee are shorted. Thus any value coming out of the XBee would be sent back

through the XBee performing the loopback test. (Note: This test can only be

done in AT mode.)

~ 37 ~

Fig. 3.5

Click on the terminal window and start writing in the console.

The data should echo back and look like this.

Fig. 3.6

Once the data has echoed, the loopback test is complete thus signifying that the

XBee chips are communicating with each other.

~ 38 ~

3.3 Interfacing of AT89S52 with ADC 0808

Before interfacing the AT89S52 microcontroller with the ADC, we must ensure

that the microcontroller setup is perfect and that the microcontroller itself is working

properly. To do this we perform a blinking LED test.

Step 1: Connect the microcontroller‘s 40th

and 31st pin, which are the Vcc and Ea

respectively with the power supply rail.

Step 2: Connect the 20th

pin to the ground rail of the breadboard.

Step 3: Setup the LED in Port 1 of the microcontroller. A resistor is used with the

LED to prevent damage to the LED.

Step 4: Connect an 11.0592 MHz crystal to the 18th

and 19th

pin of the

microcontroller. The crystal serves as the clock for the microcontroller. A

capacitance of 33 pF is grounded with each leg of the crystal.

Step 5: Connect 8.2k ohm and 10µF capacitance to the 9th

pin of the

microcontroller. The 9th

pin is the reset (RST) pin.

Step 6: The complete microcontroller setup should look like Fig. 3.7.

Fig. 3.7: Microcontroller Setup

~ 39 ~

Step 7: Now the microcontroller must be programmed. The program is written in

notepad and converted to hex. A program with the following algorithm is used.

i. Start.

ii. Turn ON LED.

iii. Wait for some time (delay).

iv. Turn OFF LED.

v. Wait for some time (delay).

vi. Go to ii.

Step 8: For delay we use the following algorithm:

i. Start.

ii. Load R7.

iii. Load R6.

iv. Decrement R6.

v. Is R6=0 if NO go to 4.

vi. Decrement R7

vii. Is R7=0 if NO go to 3.

viii. Stop.

Step 9: Burn the program onto the microcontroller chip using a flash burner.

Step 10: Power on the microcontroller.

The LED connected to Port 1 of the microcontroller will start blinking thus

confirming that the setup and the microcontroller chip are working.

Now since the microcontroller setup is complete we start connecting the ADC

0808 with the microcontroller.

The following interfacing takes place:

The address pins of the ADC, Pins 23,24 and 25 representing Address C,

Address B and Address A respectively are connected to ports 2.0,2.1 and

2.2 of the microcontroller.

The ALE (Address Latch Enable) pin of the ADC which is pin 22 is

connected to pin 25(port 2.4) of the microcontroller.

~ 40 ~

The OE (Output Enable) pin of the ADC i.e. pin 9 is connected to pin 26

or port 2.5 of the microcontroller.

The EOC (End of Conversion) pin of the ADC i.e. pin 7 is connected to

pin 28 or port 2.7 of the microcontroller.

The SC (Start of Conversion) pin of the ADC i.e. pin 6 is connected to pin

27 or port 2.6 of the microcontroller.

For the ADC 0808 pin 11 and pin 12 are supplied with 5V power supply.

Pin 13 and pin 16 of the ADC are grounded.

Pin 10 of the ADC receives input from the 555 clock timer circuit.

The complete interfacing between the ADC and AT89S52 is as follows:

Fig. 3.8: Interfacing of ADC and 8051

~ 41 ~

In addition to the above interfacing Port 1 of the microcontroller will be

connected to D0-D7 of the ADC.

Fig. 3.9: Data Line Connections between ADC and 8051

To complete the interfacing between the microcontroller and the ADC, a program

has to be burned into the microcontroller to enable the ADC to handshake with the

microcontroller and transfer the digital data.

To accomplish this, a program is written and converted to hex based on the following

algorithm:

Step 1: Start

Step 2: Select an analog channel by providing bits to addresses A,B and C based

on Table 4

Step 3: Activate the ALE (address latch enable) pin. It needs a low-to-high pulse

to latch on the address.

Step 4: Activate SC (start of conversion) by providing a low-to-high pulse to

initiate conversion.

~ 42 ~

Step 5: Monitor EOC (end of conversion) to see whether conversion is finished.

High-to-low output indicates that the data has been converted and is ready to be

picked up. If we do not use EOC, we can read the converted digital data after a

small time delay whose size depends on the speed of the external clock we attach

to the CLK pin.

Step 6: Activate OE (output enable) to read data out of the ADC chip. A low-to-

high pulse on the OE pin will bring the digital data out of the chip.

Step 7: Once the data is received transfer it to the serial buffer of the

microcontroller from the accumulator.

Step 8: Clear OE for next conversion.

Step 9: Return to step 2.

Once this program has been burnt on to the microcontroller, the ADC will be sending

parallel data to the microcontroller which will be sending serial data out of the

microcontroller‘s TxD pin into the XBee for further transfer. The data sent to the XBee

will be in hex format.

3.4 LM 35 and SY-HS-220 Setup

The LM 35 and SY-HS-220 are the temperature and humidity sensors

respectively. The LM 35 has a very low output in terms of mV. In order to let the

microcontroller differentiate between the changes in temperature the LM 35 is sent

through a non -inverting amplifier with a gain of 10. Thus the output will be in volts and

the change in output will be large enough for the microcontroller to differentiate.

The interfacing between the sensors and the ADC 0808 will look like Fig. 3.10.

~ 43 ~

Fig. 3.10: Interfacing between sensors and ADC 0808

Once the interfacing is done, the sensors will be sending output to the inputs of

the ADC (IN0 and IN1). These inputs will be transferred to the microcontroller via the

data lines D0-D7 of the ADC. The microcontroller will then proceed to send out the

received data in its port1 serially through its RxD pin into the XBee device, which will

then communicate with the XBee coordinator which is attached to the PC.

The complete interfacing of the circuit will be like Fig. 3.11.

~ 44 ~

Fig. 3.11: Final Interfacing Circuit

~ 45 ~

3.5 Data Transfer and Further Processing

The 2 XBee chips that are being used to transfer data wirelessly are series 2 chips.

The end device which is connected to the sensor node is in AT mode. The coordinator

which is connected to the supervisory station is in API mode. As the base station chip is

in API mode, the data received by the station is in form of packets.

The packets of data that are received are in the following form:

7E YY YY 90 XX XX XX XX XX XX XX XX FF FE RR D1D2 CC

The data received is therefore 17 bytes in size. This type of data is known as a

receive packet.

7E – The start delimiter. The packet starts with this value.

YYYY – Length. It is the number of bytes between length and checksum

fields.

90 – Signifies the transfer is in API mode and is a receive packet.

XXXXXXXXXXXXXXXX – This is the sender 64-bit (MAC/EUI64)

address.

FFFE – The sender 16 bit network address. It is set to 0xFFFE if

unknown.

RR – This is the receive option of the packet. The various values are:

0x01 - Packet Acknowledged

0x02 - Packet was a broadcast packet

0x20 - Packet encrypted with APS encryption

0x40 - Packet was sent from an end device (if known)

Also values can be combined. For example, a 0x40 and a 0x01 will show

as a 0x41.

Other possible values: 0x21, 0x22, 0x41, 0x42, 0x60, 0x61, 0x62.

D1D2 – This is the received data value and is in hex format.

CC – This is the checksum, 0xFF minus 8-bit sum of bytes between the

length and checksum fields.

~ 46 ~

No

YES

YES YES

No No

Fig. 3.12 Program Flowchart

Start

Initialize

Data

Received

Sort through Data

Is Temp

High

Is

Humidity

High

Show message &

Send Data Packet

to make temp

control pin high

Show message &

Send data packet

to make humidity

control pin high

Log Final Data Using

Appropriate conversion

formula

Send data packet to

make control pins low

END

~ 47 ~

The data packet that is sent, is recorded and logged in the PC using a software

called docklight. In docklight the received serial data can be saved in both text and html

format. For faster and larger logging, text format is preferred. The data logging that takes

place is in real time.

Fig. 3.13: Docklight Terminal

In the terminal Fig. 3.13, we can select the serial port requirements like the

baud rate, stop bits, data bits and parity. Once the parameters are set, the data will be

received and recorded once communication logging is enabled. The data can be logged in

ASCII, HEX, decimal and binary.

Once the data is being logged in text file, a program has been written in eclipse

IDE for java developers. The particular program reads data from the text file and sends

out a warning once the humidity or temperature has gone above or below its

predetermined range.

~ 48 ~

Fig. 3.14: Sensor Reader Window

The temperature and humidity values that are sent are read in hex packets. The

data value which is the 16th

byte and is in hex format is first converted into decimal

format. Once the decimal value is found, the value has to be converted into the

appropriate o/p analog volt. To do this we use the formula:

Once the volt output is achieved, we change it into real time data by multiplying with the

appropriate value. For temperature the value is multiplied by 10, and for humidity

approximately 32. The output is also at the same time recorded in an output log text file

signifying the time and date at which the temperature and humidity were recorded.

Once the temperature and humidity reach a certain point, a single warning

message will not help in fixing the problem. To remedy the situation a control signal

needs to be sent to the device that will help maintain the temperature and humidity. In

this project to demonstrate the control signal a LED will be lit, signifying that a control

signal has been sent. For this to be accomplished a data packet needs to be sent through

the serial port to the XBee. This type of data packet is known as a remote AT command.

~ 49 ~

The data packet is as follows:

7E 00 10 17 01 XX XX XX XX XX XX XX XX FF FE 02 YY YY DD CC

The remote AT command packet unlike the receive packet is 20 bytes in size.

7E – Like the receive packet, the 7E byte is the start delimiter.

00 10 – Length. Number of bytes between length and checksum fields.

17 – Signifies that the packet is a remote AT command.

01 – Frame ID. Identifies the UART data frame for the host to match with

a subsequent response. If zero, no response is requested.

XXXXXXXXXXXXXXXX - This is the sender 64-bit (MAC/EUI64)

address.

FFFE - The sender 16 bit network address. It is set to 0xFFFE if unknown.

02 – The command option. 02 indicates that a change is to be made on the

remote device.

YYYY – The AT command. The input is to be done as two ASCII

characters,

DD – The AT command data.

CC – Checksum.

By sending the appropriate byte through the serial port, any of the data i/o ports of

the XBee can be made high or low. By doing so, a control action can be taken at that

particular port of the XBee. Thus in application if the temperature or humidity exceeds or

falls below its pre-determined range, a control action will be initiated which will help in

maintaining ideal conditions inside of the greenhouse.

~ 50 ~

CHAPTER 4

CONCLUSION

&

FUTURE SCOPE OF STUDY

~ 51 ~

CHAPTER 4

CONCLUSION & FUTURE SCOPE OF STUDY

In traditional method of farming, periodic visits to different areas of the

greenhouse were required to at specific time intervals to check the humidity level and

temperature level manually. This conventional method was time consuming and needed a

lot of work and effort. In recent years various types of sensors have been used to measure

and monitor environmental parameters which affect crop production, and the information

from these sensors have paved the way to what is termed as precision agriculture. One

such area of precision agriculture is greenhouse farming. This work focuses on

developing a system that can remotely monitor changes of temperature and humidity

level in greenhouses, especially those that are spread over vast areas. To get the best plant

growing conditions temperature and humidity (moisture in the air) have to be controlled.

In this situation, the wireless sensor network with additional hardware and software is an

efficient solution for green house environment control. The proposed work has a

measurement system which is capable of detecting the level of ambient temperature and

level of atmospheric humidity. This system also has a mechanism to alert farmers

regarding the temperature changes in the greenhouse so that precautionary steps can be

taken manually also, if so desired.

A step-by-step approach in designing the microcontroller based system for

measurement and control of two of the most important parameters (temperature and

humidity), has been followed. The system has overcome quite a few shortcomings of the

existing systems by reducing the maintenance and complexity, at the same time providing

a flexible and precise form of maintaining the greenhouse conditions. The software

program enables us to easily change the parameters based on any sort of climate. The

system being wireless in nature gives us numerous advantages. In a greenhouse spread

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over a huge area if wired sensors are used then it would not only take up un-necessary

space, have complex wiring and low anti-interference capacity, but also the cost per

measuring node becomes very high. Thus by using wireless technology, we can easily

place as many sensors as is needed for precise controlling of the greenhouse environment

without increasing the complexity of the system. The data acquired at each measurement

node, consisting of information of multiple sensors can be communicated and stored in

one base station thus making the user interfacing with the device trouble free. The project

can easily be improved with the addition of sensors such as CO2 emission and soil

moisture for more precise control over the greenhouse.

With the decreasing costs of hardware and people becoming more software

friendly, precision agriculture is a growing field. An emerging agricultural control system

industry in several areas of agricultural production will result in reliable control systems

that will address several aspects of quality and quantity of production. In green house

technology, more numbers of parameters need to be controlled because the varieties of

the crop are large. They are increasing day by day because of the development in

agriculture technology. Further improvements will be made as less expensive and more

reliable sensors are developed for use in agricultural production.

Thus implementation in future may result in not only higher yield but lower crop

prices. It will also enable production of crops easily in artificial conditions allowing

growth of seasonal crops without using too much of chemicals and fertilizers. Precision

agriculture and Greenhouse cultivation has immense potential offering a wide field of

study and research enabling improved crop production facilities especially in developing

and undeveloped countries.

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GALLERY

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