ABSTRACT

Appropriate environmental conditions are necessary for optimum plant growth,

improved crop yields, and efficient use of water and other resources. Automating the data

acquisition process of the soil conditions and various climatic parameters that govern plant

growth allows information to be collected at high frequency with less labor requirements. The

existing systems employ PC or SMS-based systems for keeping the user continuously informed

of the conditions inside the greenhouse; but are unaffordable, bulky, difficult to maintain and

less accepted by the technologically unskilled workers.

The objective of this project is to design a simple, easy to install, microcontroller-based

circuit to monitor and record the values of temperature, humidity, soil moisture and sunlight

of the natural environment that are continuously modified and controlled in order optimize

them to achieve maximum plant growth and yield. The controller used is a low power, cost

efficient chip manufactured by ATMEL having 8K bytes of on-chip flash memory. It

communicates with the various sensor modules in real-time in order to control the light,

aeration and drainage process efficiently inside a greenhouse by actuating a cooler, fogger,

dripper and lights respectively according to the necessary condition of the crops. An integrated

Liquid crystal display (LCD) is also used for real time display of data acquired from the

various sensors and the status of the various devices. Also, the use of easily available

components reduces the manufacturing and maintenance costs. The design is quite flexible as

the software can be changed 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, especially in rural areas and for small scale agriculturists.

CONTENTS

NAME OF THE C H APTER PAGE NO.

1. INTRODUCTION

1.1 CURRENT SCENARIO……………………………………………………………..2

1.1.1 MANUAL SETUP……………………………………………………………..2

1.1.2 PARTIALLY AUTOMATED SETUP…………………………………….…..2

1.1.3 FULLY AUTOMATED SETUP……………………………………….……...3

1.2 PROBLEM DEFINITION…………………………………………………………...3

1.3 PROPOSED MODEL FOR AUTOMATION OF GREENHOUSE………………...4

2. SYSTEM MODEL

2.2 BASIC MODEL OF THE SYSTEM……………………………………………......6

2.3 PARTS OF THE SYSTEM………………………………………………………….7

2.4 STEPS FOLLOWED IN DESIGNING THE SYSTEM…………………………….8

3. BASIC THEORY

3.1 LIFE PROCESSES INSIDE A GREENHOUSE

3.1.1 PHOTOSYNTHETIC PROCESS…………………………………………….12

3.1.2 TRANSPIRATION…………………………………………………………...13

4. HARDWARE DESCRIPTION

4.1 TRANSDUCERS

4.1.1 SOIL MOISTURE SENSOR………………………………………………...164.1.1.1 FEATURES 16

4.1.1.2 FUNCTIONAL DESCRIPTION 17

4.1.2 LIGHT SENSOR

4.1.2.1 FEATURES 18

4.1.2.2 FUNCTIONAL DESCRIPTION 19

4.1.3 HUMIDITY SENSOR

4.1.3.1 FEATURES-------------------------------------------------------------

20

4.1.3.2 FUNCTIONAL DESCRIPTION--------------------------------

21

4.1.4 TEMPERATURE SENSOR

4.1.4.1 FEATURES-----------------------------------------------------------

22

4.1.4.2 FUNCTIONAL DESCRIPTION------------------------------------

23

4.2 ANALOG TO DIGITAL CONVERTER (ADC 0809)

4.2.1 DESCRIPTION----------------------------------------------------------------

24

4.2.2 FEATURES---------------------------------------------------------------------

24

4.2.3 CONVERSION METHOD USED-------------------------------------------

25

4.2.4 PIN DIAGRAM OF ADC 0809----------------------------------------------

26

4.2.5 SELECTING AN ANALOG CHANNEL-----------------------------------------

27

4.3 CLOCK CIRCUITRY FOR THE ADC

4.3.1 FUNCTIONAL 29

4.4 MICROCONTROLLER

4.4.1 CRITERIA FOR CHOOSING A MICROCONTROLLER--------------------------

31

4.4.2 DESCRIPTION-----------------------------------------------------------------

31

4.4.2 FEATURES---------------------------------------------------------------------

32

4.4.4 PIN CONFIGURATION---------------------------------------------------

33

4.4.5 BLOCK DIAGRAM--------------------------------------------------------

34

4.4.6 PIN DESCRIPTION---------------------------------------------------------

35

4.4.6.1 POWER-ON RESET CIRCUIT-----------------------------------

36

4.4.6.2 OSCILLATOR CLOCK CIRCUIT----------------------------------

37

4.4.7 SPECIAL FUNCTION REGISTERS-------------------------------------

38

4.4.8 MEMORY ORGANIZATION----------------------------------------------

39

4.4.9 WATCHDOG TIMER------------------------------------------------------

40

4.4.10 TIMERS AND COUNTERS………………………………………………..41

4.4.11 INTERRUPTS………………………………………………….…………...42

4.4.12 MICROCONTROLLER CONFIGURATION USED IN THE SET-UP…..42

4.5 LIQUID CRYSTAL DISPLAY……………………………………………..…….44

4.5.1 SIGNALS TO THE LCD………………………………………………..........44

4.5.1.1 LOGIC STATUS ON THE CONTROL LINES………………………45

4.5.1.2 WRITING AND READING DATA FROM THE LCD………………45

4.5.2 PIN DESCRIPTION………..……………………………………………........45

4.6 ALARM CIRCUITRY……………………………………………………...……..46

4.7 RELAYS…………………………………………………………………...….........47

4.8 POWER SUPPLY CONNECTION……………………………………….……...50

5. SYSTEMS USED IN WORK MODE

5.1 DRIP IRRIGATION SYSTEM FOR CONTROLLING SOIL MOISTURE……….54

5.2 ARTIFICIAL GROWING LIGHTS FOR CONTROLLING ILLUMINATION......55

5.3 HEATERS AND FANS FOR CONTROLLING TEMPERATURE

5.3.1 COOLING EQUIPMENT……………………………………………….…….56

5.3.2 HEATING EQUIPMENT…………………………………………….……….56

5.4 HUMIDIFICATION SYSTEMS……………………………………………………56

6. SOFTWARE

6.1 INTRODUCTION TO KEIL SOFTWARE

6.1.1 WHAT IS µVision3?..........................................................................................59

6.1.2 STEPS FOLLOWED IN CREATING AN APPLICATION IN µVision3……59

6.1.3 DEVICE DATABASE………………………………………………………...64

6.1.4 PERIPHERAL SIMULATION………………………………………………..64

6.2 PROGRAMMER……………………………………………………………………64

6.3 ProLoad PROGRAMMING SOFTWARE………………………………………..65

7. FLOWCHART

7.1 FLOWCHART REPRESENTING THE WORKING OF THE SYSTEM…………...68

7.2 FLOWCHART FOR LCD INITIALIZATION………………………..………….......69

7.3 FLOWCHART FOR ADC INITIALIZATION……………………………………….71

8. RESULT ANALYSIS

8.1 SENSOR READINGS

8.1.1 SOIL MOISTURE SENSOR……………………………….………..…….……..74

8.1.2 LIGHT SENSOR……………………………………………………………........75

8.1.3 HUMIDITY SENSOR………………………………………………………........76

8.1.4 TEMPERATURE SENSOR………………………………………………………77

9. ADVANTAGES AND DISADVANTAGES

9.1 ADVANTAGES………………………………………………………………………..80

9.2 DISADVANTAGES……………………………………………………………………80

10. FUTURE SCOPE …………………………………………………………………….82

11. CONCLUSION……………………………………………………………………….84

I. REFERENCES…………………………………………………………………….85

II. ANNEXURE-I…………………………………………………………………….. 87

III. ANNEXURE-II ……………………………………………………………………91

IV. ANNEXURE-III…………………………………………………………………...95

V. ANNEXURE-IV…………………………………………………………………...97

LIST OF FIGURES

I. Figure 2.1 Block diagram of the system……………………………………..6

II. Figure 3.2 Block diagram of photosynthesis………………………………..12

III. Figure 3.2 Transpiration…………………………………………………….14

IV. Figure 4.1 Soil moisture sensor circuit……………………………………..17

V. Figure 4.2 Light Dependent Resistor……………………………………….18

VI. Figure 4.2.1 Structure of a Light Dependent Resistor……………………...18

VII. Figure 4.3 Light sensor circuit……………………………………………...19

VIII. Figure 4.4 HIH-4000-001 Humidity sensor………………………………...20

IX. Figure 4.5 Humidity sensor circuit………………………………………….21

X. Figure 4.6 LM35 temperature sensor……………………………………….22

XI. Figure 4.7 Temperature sensor circuit……………………………………...23

XII. Figure 4.8 Getting data from the analog world……………………………..24

XIII. Figure 4.9 Block diagram of ADC 0809……………………………………25

XIV. Figure 4.10 Flowchart explaining the Successive Approximation method...26

XV. Figure 4.11 Pin diagram of ADC 0809……………………………………..26

XVI. Figure 4.12 ADC 0809 pin details for the system…………………………..28

XVII. Figure 4.13 Timing diagram of ADC 0809…………………………………29

XVIII. Figure 4.14 Clock circuitry for the ADC…………………………………...30

XIX. Figure 4.15 The effect of using a Schmitt trigger instead of a comparator…30

XX. Figure 4.16 Pin diagram of AT89S52………………………………………33

XXI. Figure 4.17 Block diagram of the microcontroller………………………….34

XXII. Figure 4.18 Power-on reset circuit………………………………………….36

XXIII. Figure 4.19 Oscillator clock circuit…………………………………………38

XXIV. Figure 4.20 Internal memory block…………………………………………40

XXV. Figure 4.21 Microcontroller Pin Details…………………………………….43

XXVI. Figure 4.22 Address locations for a 2x16 line LCD………………………..44

XXVII. Figure 4.23 Pin diagram of 2x16 line LCD…………………………………46

XXVIII. Figure 4.24 Electrical symbol of a buzzer…………………………………..46

XXIX. Figure 4.25 Buzzer circuitry………………………………………………..47

XXX. Figure 4.26 Sugar Cube Relay……………………………………………...48

XXXI. Figure 4.27 Circuit symbols of relays………………………………………49

XXXII. Figure 4.28 Relay circuitry…………………………………………………50

XXXIII. Figure 4.29 +5V Power supply circuit……………………………………...51

XXXIV. Figure 4.30 +12V Power supply circuit…………………………………….51

XXXV. Figure 5.1 Drip irrigation system…………………………………………...54

XXXVI. Figure 6.1 Window for choosing the target device…………………………60

XXXVII. Figure 6.2 Project workspace pane………………………………………….61

XXXVIII. Figure 6.3 Project options dialog…………………………………………...61

XXXIX. Figure 6.4 “Save All” and “Build All Target Files” buttons………………..61

XL. Figure 6.5 µVision3 Debugger window…………………………………….62

XLI. Figure 6.6 ‘Reset’, ‘Run’ and ‘Step into’ options…………………………..63

XLII. Figure 6.7 Programming window…………………………………………..66

XLIII. Annexure-I: Snapshots of the System…………………………………..88-90

LIST OF TABLES

I. Table 2.1 Importance of the various parameters…………………………….8

II. Table 4.1 Selection of the input channels…………………………………..27

III. Table 4.2 Alternate functions of Port 3……………………………………..36

IV. Table 4.3 Pin description of the LCD………………………………………46

V. Table 8.1 Soil moisture sensor readings……………………………………74

VI. Table 8.2 Light sensor readings…………………………………………….75

VII. Table 8.3 Humidity sensor readings………………………………………..76

VIII. Table 8.4 Temperature sensor readings…………………………………….77

CHAPTER 1

INTRODUCTION

INTRODUCTION

We live in a world where everything can be controlled and operated

automatically, but there are still a few important sectors in our country where

automation has not been adopted or not been put to a full-fledged use, perhaps because of

several reasons one such reason is cost. One such field is that of agriculture. Agriculture

has been one of the primary occupations of man since early civilizations and even today

manual interventions in farming are inevitable. Greenhouses form an important part of

the agriculture and horticulture sectors in our country as they can be used to grow plants

under controlled climatic conditions for optimum produce. Automating a greenhouse

envisages monitoring and controlling of the climatic parameters which directly or

indirectly govern the plant growth and hence their produce. Automation is process control

of industrial machinery and processes, thereby replacing human operators.

1.1 C UR R E N T S C E N ARIO

Greenhouses in India are being deployed in the high-altitude regions where the sub-

zero temperature up to -40° C makes any kind of plantation almost impossible and in arid

regions where conditions for plant growth are hostile. The existing set-ups primarily are:

1.1.1 MANU AL SET -U P:

This set-up involves visual inspection of the plant growth, manual irrigation of

plants, turning ON and OFF the temperature controllers, manual spraying of the

fertilizers and pesticides. It is time consuming, vulnerable to human error and hence

less accurate and unreliable.

1.1.2 P AR T I AL L Y AU T O M A TE D S E T - U P :

This set-up is a combination of manual supervision and partial automation and

is similar to manual set-up in most respects but it reduces the labor involved in

terms of irrigating the set-up.

1.1.3 F ULLY- A UT OMA TED :

This is a sophisticated set-up which is well equipped to react to most of the

climatic changes occurring inside the greenhouse. It works on a feedback system which

helps it to respond to the external stimuli efficiently. Although this set-up overcomes

the problems caused due to human errors it is not completely automated and expensive.

1.2 PROBLEM D EFINITI O N

A number of problems associated with the above mentioned systems are

enumerated as below:

1. Complexity involved in monitoring climatic parameters like humidity, soil moisture,

illumination, soil pH, temperature, etc which directly or indirectly govern the

plant growth.

2. Investment in the automation process are high, as today’s greenhouse control systems

are designed for only one parameter monitoring (as per GKVK research center); to

control more than one parameter simultaneously there will be a need to buy

more than one system.

3. High maintenance and need for skilled technical labor. The modern proposed systems

use the mobile technology as the communication schemes and wireless data acquisition

systems, providing global access to the information about one’s farms. But it suffers

from various limitations like design complexity, inconvenient repairing and high

price. Also the reliability of the system is relatively low, and when there are

malfunctions in local devices, all local and tele data will be lost and hence the whole

system collapses. More over farmers in India do not work under such sophisticated

environment and find no necessity of such an advanced system, and cannot afford the

same.

Keeping these issues in view, a microcontroller based monitoring and control

system is designed to find implementation in the near future that will help Indian farmers.

1.3 PROPOSED MO DEL FO R AUTOMATION OF GREENHOUSE

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

control the microclimatic 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 and to eliminate the difficulties involved in

the system by reducing human intervention to the best possible extent. The system

comprises of sensors, Analog to Digital Converter, microcontroller and actuators.

When any of the above mentioned climatic parameters 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. The microcontroller then performs the needed actions by

employing relays until the strayed-out parameter has been brought back to its optimum

level. Since a microcontroller is used as the heart of the system, it makes the set-up low-

cost and effective nevertheless. As the system also employs an LCD display for

continuously alerting the user about the condition inside the greenhouse, the entire set-up

becomes user friendly.

Thus, this system eliminates the drawbacks of the existing set-ups mentioned in the

previous section and is designed as an easy to maintain, flexible and low cost solution.

CHAPTER 2

SYSTEM MODEL

BASIC MODEL OF THE SYSTEM

F ig . 2 .1 B lo ck d iag ram of the system

2.1 PA RTS OF THE SY STEM:

• Sensors (Data acquisition system)ƒ Temperature sensor (LM35)ƒ Humidity sensor / Soil Moisture sensorƒ Light sensor (LDR)ƒ Wind Sensor

• Analog to Digital Converter ( ADC 0808/0809)

• Microcontroller (AT89S52)

• Liquid Crystal Display (Hitachi's HD44780)

• Actuators – Relays

• Devices controlledƒ Water Pump (simulated as a bulb)ƒ Sprayer (simulated as a bulb)ƒ Cooler (simulated as a fan)ƒ Artificial Lights (simulated as a bulb)

T R AN S D U CERS ( D a t a acqui s i t ion s y s tem):

This part of the system consists of various sensors, namely soil moisture, humidity,

temperature and light. These sensors sense various parameters- temperature, humidity, soil

moisture and light intensity and are then sent to the Analog to Digital Converter.

A NA LOG TO DIG ITAL CON VE RD ER (AD C):

The analog parameters measured by the sensors are then converted to

corresponding digital values by the ADC.

MICR O C ONTROLLER:

The microcontroller is the heart of the proposed embedded system. It

constantly monitors the digitized parameters of the various sensors and verifies

them with the

predefined threshold values and checks if any corrective action is to be taken for the

condition at that instant of time. In case such a situation arises, it activates the

actuators to perform a controlled operation.

A CTUAT OR S:

An array of actuators can be used in the system such as relays, contactors, and

change over switches etc. They are used to turn on AC devices such as motors,

coolers, pumps, fogging machines, sprayers. For the purpose of demonstration relays have

been used to drive AC bulbs to simulate actuators and AC devices. A complete working

system can be realized by simply replacing these simulation devices by the actual devices.

DIS P LAY UN I T:

A Liquid crystal display is used to indicate the present status of parameters and the

respective AC devises (simulated using bulbs). The information is displayed in two modes

which can be selected using a push button switch which toggles between the modes. Any

display can be interfaced to the system with respective changes in driver circuitry and

code.

2.2 STEPS FOLLOWED IN DESIGNING TH E SYSTEM:

Three general steps can be followed to appropriately select the control system:

Step # 1: I d enti f y mea s urable variabl e s im p o r t a n t to pro d uct i o n .

• It is very important to correctly identify the parameters that are going to be

measured by the controller’s data acquisition interface, and how they are to be

measured. The

set of variables typically used in greenhouse control is shown below:

Sl. No. Variable to be monitored Its Importance

1 Temperature Affects all plant metabolic functions.

2 Humidity Affects transpiration rate and the plant's thermal

control mechanisms.3 Soil moisture Affects salinity, and pH of irrigation water

4 Solar Radiation Affects photosynthetic rate, responsible for most

thermal load during warm 5 Speed of the Wind Affects the plants polination and growth

Ta ble 2 .1 Impo rta nce o f t he var io us pa ra me ters

An electronic sensor for measuring a variable must readily available, accurate, reliable

and low in cost. If a sensor is not available, the variable cannot be incorporated into

the control system, even if it is very important. Many times variables that cannot be

directly or continuously measured can be controlled in a limited way by the system.

For example, fertility levels in nutrient solutions for greenhouse production are difficult to

measure continuously.

Ste p#2 :Inve stig ate t he co nt ro l strateg ies.

• An important element in considering a control system is the control strategy that

is to be followed. The simplest strategy is to use threshold sensors that

directly affect actuation of devices. For example, the temperature inside a

greenhouse can be affected by controlling heaters, fans, or window openings

once it exceeds the maximum allowable limit. The light intensity can be

controlled using four threshold levels. As the light intensity decreases one light

may be turned on. With a further decrease in its intensity a second light would be

powered, and so on; thus ensuring that the plants are not deprived of adequate

sunlight even during the winter season or a cloudy day.

• More complex control strategies are those based not only on the current values of

the controlled variables, but also on the previous history of the system, including

the rates at which the system variables are changing.

Step #3: Id e n t i f y the software and t he hardwa r e to be use d .

• It is very important that control system functions are specified before deciding

what software and hardware system to purchase. The model chosen must have

the ability

to:

1. Expand the number of measured variables (input subsystem) and

controlled devices (output subsystem) so that growth and changing

needs of the production operation can be satisfied in the future.

2. Provide a flexible and easy to use interface.

3. It must ensure high precision measurement and must have the ability

resist noise.

Hardware must always follow the selection of software, with the hardware required

being supported by the software selected. In addition to functional capabilities, the

selection of the control hardware should include factors such as reliability,

support, previous

experiences with the equipment (successes and failures), and cost.

CHAPTER 3

BASIC THEORY

BASIC THEORY

3.1 L I FE PROCESSES I NS I D E GREENHOUSE:

3.1.1 P HOTO SY NT HETIC PR OCE SS

The two major life-processes occurring in plants are photosynthesis and

transpiration. Photosynthesis is the conversion of light energy into chemical energy by

living organisms. The raw materials are carbon dioxide and water; the energy source is

sunlight; and the end- products are oxygen and (energy rich) carbohydrates, for

example sucrose, glucose and starch. This process is arguably the most important

biochemical pathway, since nearly all

life on Earth either directly or indirectly depends on it.

Fi g 3 .1 B lock diag ram o f p hot osynthe sis

A commonly used but slightly simplified equation for photosynthesis is:

6 CO2(g) + 12 H2O(l) + photons → C6H12O6(aq.) + 6 O2(g) + 6 H2O(l) …(3.1)

Carbon dioxide + water + light energy → glucose + oxygen + water

Light energy obtained from the sun is very essential for photosynthesis. The

photons present in light are responsible for triggering the light-reaction in plants.

Plants need an optimum amount of exposure to light in a day. This optimum period

is called its photo- period. The plant sensitivity curve for photosynthesis has its peak

at the red side of the spectrum. This indicates that providing plants with the wavelengths

best suited to photosynthesis is most efficient with the use of artificial light. Tests show a

mean deviation from the average sensitivity curve of less than 5% for a wide variety

of plants. The curve shows that the maximum sensitivity for photosynthesis lies in the

far red at approximately

675 nm. The plant sensitivity curve disputes two common misconceptions. The first is that

an "ideal" plant growing lamp duplicates the spectral energy distribution of the sun.

Sunlight has a continual spectrum, radiating energy in wavelengths that contribute less to

photosynthesis, and are therefore "wasted" on the plant. For this reason, many lamps are

more efficient than sunlight for plants.

Plants need dark periods. Periods of light (called photo-periods) and dark periods

and their relative lengths have an effect on plant maturity. The dark period of each day

affects flowering and seeding of most plants. Although many plants can grow under

continuous light, nearly all plants prefer a dark period each day for normal growth. All

plants need some darkness to grow well or to trigger flowering. The ideal photoperiods of

plants vary, some preferring long days and short nights; others the reverse; and some do

best when the length of

the night and day periods are equal.

3.1.2 TRANSP I RAT I ON

Transpiration is the evaporation of water from the aerial parts of plants,

especially leaves but also stems, flowers and roots Transpiration also cools plants and

enables mass flow of mineral nutrients and water from roots to shoots. Mass flow is

caused by the decrease in hydrostatic (water) pressure in the upper parts of the plants

due to the diffusion of water out of stomata into the atmosphere. Water is absorbed at

the roots by osmosis, and any dissolved mineral nutrients travel with it through the

xylem.

The rate of transpiration is directly related to the degree of stomatal opening,

and to the evaporative demand of the atmosphere surrounding the leaf. The amount of

water lost by a plant depends on its size, along with the surrounding light intensity,

temperature, humidity, and wind speed (all of which influence evaporative demand).

Soil water supply and soil

temperature can influence stomatal opening, and thus the transpiration rate.

F i g 3 . 2 T r ans p i r at i o n

The moisture content in the soil is a very crucial factor in the process of

transpiration as the absorption of mineral salts from the soil through the process of

osmosis is directly dependent on the moisture content in the soil.

The greenhouse works best when the temperature is not too hot and not too cold.

Though it sounds simple in the spring and autumn we can easily have a wide range of

temperatures from the cold in the middle of the night to the excessive heat of the day

when the sun is shining. During the day the rays from the sun penetrate the greenhouse

and warm up and light up the surroundings. Light escapes through the glass walls but

the heat in form of infra-red radiations gets trapped inside the green house leading to an

incubating effect and the temperature inside gradually increases. This increased

temperature leads to an increase in

the rate of transpiration which is harmful to the plants.

CHAPTER 4HARDWARE

DESCRIPTION

H ARDWARE DESCRIPTION

4.1 TRANS D U C ERS:

A transducer is a device which measures a physical quantity and converts it

into a signal which can be read by an observer or by an instrument. Monitoring and

controlling of a greenhouse environment involves sensing the changes occurring

inside it which can influence the rate of growth in plants. The parameters which

are of importance are the temperature inside the greenhouse which affect the

photosynthetic and transpiration processes are humidity, moisture content in the soil, the

illumination etc. Since all these parameters are interlinked, a closed loop (feedback)

control system is employed in monitoring it. The sensors used in this system are:

1. Humidity Sensor / Soil moisture Sensor

2. Light Sensor ( LDR (Light Dependent Resistor) )

3. Wind Sensor

4. Temperature Sensor (LM35)

4.1.1 SOIL MOISTURE SENSOR

4.1.1.1 Fea t ures of the So i l m o ist u re sen s or:

1. The circuit designed uses a 5V supply, fixed resistance of 100Ω, variable

resistance of 10ΚΩ, two copper leads as the sensor probes, 2N222N transistor.

2. It gives a voltage output corresponding to the conductivity of the soil.

3. The conductivity of soil depends upon the amount of moisture present in

it. It increases with increase in the water content of the soil.

4. The voltage output is taken at the transmitter which is connected to a variable

resistance. This variable resistance is used to adjust the sensitivity of the sensor.

VCC SENSOR LEADS

100 Ω2N222N

ADC IN 5

10 k Ω

F i g. 4 . 1 S o il moistu r e s ensor

4.1.1.2 Funct i o n al d e s c ript i o n of S o il m oistu r e s e nso r :

The two copper leads act as the sensor probes. They are immersed into the specimen

soil whose moisture content is under test. The soil is examined under three conditions:

Case#1: D r y condit i on- The probes are placed in the soil under dry conditions and

are inserted up to a fair depth of the soil. As there is no conduction path between the two

copper leads the sensor circuit remains open. The voltage output of the emitter in this

case ranges from 0 to 0.5V.

Case#2: Optimum c o ndition- When water is added to the soil, it percolates through the

successive layers of it and spreads across the layers of soil due to capillary force. This

water increases the moisture content of the soil. This leads to an increase in its

conductivity which forms a conductive path between the two sensor probes leading to a

close path for the current flowing from the supply to the transistor through the sensor

probes. The voltage output of the circuit taken at the emitter of the transistor in the

optimum case ranges from 1.9 to 3.4V approximately.

Case#3: E x cess water cond i t i on- With the increase in water content beyond the optimum

level, the conductivity of the soil increases drastically and a steady conduction path is

established between the two sensor leads and the voltage output from the sensor increases

no

further beyond a certain limit. The maximum possible value for it is not more than 4.2V.

CadmiumSulphide

4.1.2 LI GH T SEN SOR

Light Dependent Resistor (LDR) also known as photoconductor or photocell, is a

device which has a resistance which varies according to the amount of light falling on its

surface. Since LDR is extremely sensitive in visible light range, it is well suited for the

proposed application.

F i g . 4 . 2 Light Depen d ent Re s i s t or

4.1.2.1 Features of the lig ht sensor:

• The Light Dependent Resistor (LDR) is made using the semiconductor Cadmium

Sulphide (CdS).

• The light falling on the brown zigzag lines on the sensor causes the resistance

of the device to fall. This is known as a negative co-efficient. There are some

LDRs that work in the opposite way i.e. their resistance increases with light (called

positive co- efficient).

• The resistance of the LDR decreases as the intensity of the light falling on it increases.

Incident photons drive electrons from the valence band into the conduction band.

conduction band

Cadmium Sulphide track

Band gap

valence band

F i g. 4 . 2.1 Structure of a Light Dependent Resistor, s h owing C a d m ium Su l phide track a nd a n atom to il l ust r a t e ele c tr o n s i n t he va l e nce and c o nd uction b a nd s

4.1.2.2 Fun ct io nal de script io n

• An LDR and a normal resistor are wired in series across a voltage, as shown in

the circuit below. Depending on which is tied to the 5V and which to 0V, the

voltage at the point between them, call it the sensor node, will either rise or fall

with increasing light. If the LDR is the component tied directly to the 5V, the

sensor node will increase in voltage with increasing light

• The LDR's resistance can reach 10 k ohms in dark conditions and about 100 ohms

in full brightness.

• The circuit used for sensing light in our system uses a 10 kΩ fixed resistor

which is tied to +5V. Hence the voltage value in this case decreases with increase

in light intensity.

VCC

10K ΩADC_IN4

LDR

GND

F i g. 4 . 3 Light sen s or cir c uit

• The sensor node voltage is compared with the threshold voltages for different

levels of light intensity corresponding to the four conditions- Optimum, dim, dark

and night.

• The relationship between the resistance RL and light intensity Lux

for a typical LDR is:

RL = 500 / Lux kΩ …(4.1)

• With the LDR connected to 5V through a 10K resistor, the output voltage of the LDR

is :

Vo = 5*RL / (RL+10) …(4.2)

• In order to increase the sensitivity of the sensor we must reduce the value of the

fixed resistor in series with the sensor. This may be done by putting other

resistors in parallel with it.

4.1.3 HUMIDITY SENSOR

The humidity sensor HIH4000, manufactured by Honeywell is used for sensing the

humidity. It delivers instrumentation quality RH (Relative Humidity) sensing

performance in a low cost, solder able SIP (Single In-line Package). Relative humidity is

a measure, in percentage, of the vapour in the air compared to the total amount of vapour

that could be held

in the air at a given temperature.

Fig. 4 . 4 H I H - 4 00 0 - 0 01 Humidi t y S e nsor

4.1.3.1 F e a t u r es:

• Linear voltage output vs. %RH

• Laser trimmed interchangeability

• Low power design

• High accuracy

• Fast response time

1

2

• Stable, low drift performance

• Chemically resistant

• The RH sensor is a laser trimmed, thermoset polymer capacitive sensing element

with on-chip integrated signal conditioning. The sensing element's multilayer

construction provides excellent resistance to most application hazards such as

wetting, dust, dirt,

oils and common environmental chemicals.

VCC

12.5 k Ω

Vin HIH4000

GND

Vout3

To ADC IN6

Fig 4 . 5 H u midi t y s e n s or c i r c u it

4.1.3.2 Fun ct io nal de script io n

• The sensor develops a linear voltage vs. RH output that is ratiometric to the

supply voltage. That is, when the supply voltage varies, the sensor output voltage

follows in the same proportion. It can operate over a 4-5.8 supply voltage range. At

5V supply voltage, and room temperature, the output voltage ranges from 0.8 to

3.9V as the humidity varies from 0% to 100% (noncondensing).

• The humidity sensor functions with a resolution of up to 0.5% of relative humidity

(RH).

• With a typical current draw of only 200 µA, the HIH-4000 Series is ideally suited

for low drain, battery operated systems.

• The change in the RH of the surroundings causes an equivalent change in the voltage

output. The output is an analog voltage proportional to the supply voltage.

Consequently, converting it to relative humidity (RH) requires that both the

supply and sensor output voltages be taken into account according to the formula:

RH = ((Vout / Vsupply) – 0.16) /0.0062, typical at 25°C ….(4.3)

• This voltage is converted to the digital form by the ADC and then sent as input to

the microcontroller which reads the data.

4.1.4 TE MPE RA TU RE SENS OR

National Semiconductor’s LM35 IC has been used for sensing the temperature. It

is an integrated circuit sensor that can be used to measure temperature with an electrical

output proportional to the temperature (in oC). The temperature can be measured more

accurately

with it than using a thermistor. The sensor circuitry is sealed and not subject to oxidation, etc.

F i g. 4 . 6 L M 35 temperature sen s or

4.1.4.1 F e a t u r es:

• Calibrated directly in ° Celsius (Centigrade)

• Linear + 10.0 mV/°C scale factor

• 0.5°C accuracy guaranteed (at +25°C)

• Rated for full −55° to +150°C range

• Suitable for remote applications

• Low cost due to wafer-level trimming

• Operates from 4 to 30 volts

• Less than 60 µA current drain

• Low self-heating, 0.08°C in still air

• Nonlinearity only ±1⁄4°C typical

Fig. 4 .7 T em pe ratu re s ensor ci rcuit

4.1.4.2 Fun c t i o n al d e s cr i p t i on:

• The sensor has a sensitivity of 10mV / oC.

• The output of LM35 is amplified using a LM324 single power supply (+5V) op-amp.

• The op-amp is designed to have a gain of 5.

• The circuitry measures temperatures with a resolution of up to 0.5 degree Celsius.

• The output voltage is converted to temperature by a simple conversion factor.

The general equation used to convert output voltage to temperature is:

Temperature ( oC) = (Vout * 100 ) / 5 oC …(4.4)

So if Vout is 5V, then, Temperature = 100 oC

• The output voltage varies linearly with temperature.

4.2 ANA L OG TO DIG I TAL C O N V E R TER ( A D C 0 8 0 9)

In physical world parameters such as temperature, pressure, humidity, and

velocity are analog signals. A physical quantity is converted into electrical signals. We

need an analog to digital converter (ADC), which is an electronic circuit that converts

continuous signals into discrete form so that the microcontroller can read the data.

Analog to digital converters

are the most widely used devices for data acquisition.

Analog world (temperature, pressure, etc.)

TransducerSignal

ConditioningAnalog to

Digital Converter Microcontroller

F ig. 4 . 8 G e t ti n g d a t a f r om the a n a l og wo r l d

4.2.1 DE SC RI P T I ON

The ADC0809 data acquisition component is a monolithic CMOS device with an

8- bit analog-to-digital converter, 8-channel multiplexer and 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 design of the ADC0809 has been optimized by incorporating the most

desirable aspects of several A/D conversion techniques. The device offers high speed, high

accuracy, minimal temperature dependence, excellent long-term accuracy and

repeatability, and consumes minimal power. These features make it ideally suited for

applications from process and machine control to consumer and automotive applications.

4.2.2 F EA T U R ES

1. Easy interface to all microcontrollers.

2. Operates ratiometrically or with 5 VDC or analog span adjusted voltage reference.

3. No zero or full-scale adjust required.

4. 8-channel multiplexer with address logic.

5. 0V to 5V input range with single 5V power supply.

6. Outputs meet TTL voltage level specifications.

7. 28-pin molded chip carrier package.

Fig . 4 .9 B lock diag ram o f ADC 080 9

4.2.3 C O N VERS I ON ME T H OD USED

Following are the most used conversion methods:ƒ Digital-Ramp ADCƒ Successive Approximation ADCƒ Flash ADC

Successive approximation ADC is suitable for the proposed application. It is

much faster than the digital ramp ADC because it uses digital logic to converge on the

value closest to the input voltage. A comparator and a DAC (Digital to Analog

Converter) are used in the

process. A flowchart explaining the working is shown below.

Fig . 4.10 Flow chart explaining the Successive approximation method

4.2.4 P I N DI AGR A M OF A D C 0808/0809

Fig . 4 .1 1 Pin diag ram o f ADC 0809

We use A, B, C addresses to select IN0-IN7 and activate Address latch enable

(ALE) to latch in the address. SC is for Start Conversion. EOC is for End of Conversion

and OE is for Output Enable. The output pins D0-D7 provides the digital output from

the chip. Vref (-) and Vref (+) are the reference voltages.

4.2.5 S E LEC T ING AN A N AL O G C HA N NEL

How to select the channel using three address pins A, B, C is shown in Table below:

Select Analog Channel C B A

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

Ta bl e 4.1 Sel ection o f the input cha nnel s

The ADC 0804 is most widely used chip, but since it has only one analog input, ADC

0809 is chosen as this chip allows the monitoring of up to 8 different transducers using only

a single chip. The 8 analog input channels are multiplexed and selected according to

the requirement. But for the proposed application only the last 4 channels i.e., IN4, IN5, IN6

and IN7 are used to monitor the four parameters- temperature, humidity, soil moisture and

light intensity. Hence the address line ADD_C is given to Vcc (+ 5V) as it is always high

in this case. Vref (+) and Vref (-) set the reference voltages. If Vref (-) =Gnd and Vref (+)

=5V, the step size is 5V/256=19.53.

Since there is no self clocking in this chip, the clock must be provided from an

external source to the Clock (CLK) pin. The 8-bit output from the ADC is given to Port 0 of

D0

D1

D2

the microcontroller and the control signals ADD_A, ADD_B, ADD_C, ALE, START, OE,

EOC are given to Port 1 as shown in the figure below.+5V

26

27

28

1

2

TEMPERATURE SENSOR

3MOISTURE SENSOR

4

HUMIDITY SENSOR

5

LIGHT SENSOR

IN0

IN1

IN2

IN3

IN4

IN5

IN6

IN7

11

VCC

ADC0809

17

14

15

8D3

18D4

19D5

20D6

21D7

PIN 1.0 OF MC

PIN 1.1 OF MC

PIN 1.2 OF MC

PIN 1.3 OF MC

PIN 1.4 OF MC

PIN 1.5 OF MC

PIN 1.6 OF MC

PIN 1.7 OF MC

12+5v

16

Vref+ ADD_A25

PIN 3.4 OF MC

24

10

9

PIN 3.0 OF MC

7

PIN 3.3 OF MC

Vref-

CLOCK

OE

EOC GND

ADD_B

23

ADD_C

6

START

22ALE

PIN 3.5 OF MC

VCC

PIN 3.1 OF MC

PIN 3.7 OF MC

13

Fi g. 4.12 ADC 0809 pin details as used for this application

At a certain point of time, even though there is no conversion in progress

the ADC0809 is still internally cycling through 8 clock periods. A start pulse can occur

any time during this cycle but the conversion will not actually begin until the

converter internally cycles to the beginning of the next 8 clock period sequence. As

long as the start pin is held

high no conversion begins, but when the start pin is taken low the conversion will start within

8 clock periods. The EOC output is triggered on the rising edge of the start pulse. It, too, is

controlled by the 8 clock period cycle, so it will go low within 8 clock periods of the

rising edge of the start pulse. One can see that it is entirely possible for EOC to go low

before the conversion starts internally, but this is not important, since the positive

transition of EOC, which occurs at the end of a conversion, is what the control logic is

looking for. Once EOC does go high this signals the interface logic that the data

resulting from the conversion is

ready to be read. The output enable (OE) is then raised high.

F i g 4 . 13 Ti m ing dia g r a m of ADC 0809

4 .3 C LO CK C IR CU IT RY F OR A DC:

4.3.1 Fun c t i o n a l D e s cri pt i o n :

The clock for the ADC is generated using the IC CD4093, which is a 2-input

Schmitt triggered NAND gate. A Schmitt trigger is a comparator circuit that incorporates

positive feedback.

The Control pin is pulled high and the capacitor charges and discharges producing

alternate patterns of 0’s and 1, generating a square waveform. When the input is higher

than a certain chosen threshold, the output is high; when the input is below another

(lower) chosen threshold, the output is low; when the input is between the two, the

output retains its value.

The trigger is so named because the output retains its value until the input changes

sufficiently to trigger a change. This dual threshold action is called hysteresis, and implies

that the Schmitt trigger has some memory.

Fig. 4 .14 C lo ck ci rcu it ry for AD C

The benefit of a Schmitt trigger over a circuit with only a single input threshold is

greater stability (noise immunity). With only one input threshold, a noisy input signal

near that threshold could cause the output to switch rapidly back and forth from noise

alone. A noisy Schmitt Trigger input signal near one threshold can cause only one switch

in output value, after which it would have to move to the other threshold in order to

cause another

switch.

Fig . 4.15 The effe ct of using a Schmitt t rigger (B) i nst ea d of a co mpa rato r (A)

4.4 MICROCO NTROLLER (AT89S52)

4.4.1CR I TER I A F OR CHOOSI N G A MICR OCO N T R O L L E R

The basic criteria for choosing a microcontroller suitable for the application are:

1) The first and foremost criterion is that it must meet the task at hand efficiently and cost

effectively. In analyzing the needs of a microcontroller-based project, it is seen whether an

8- bit, 16-bit or 32-bit microcontroller can best handle the computing needs of the task

most effectively. Among the other considerations in this category are:

(a) Speed: The highest speed that the microcontroller supports.

(b) P a c ka g i n g : It may be a 40-pin DIP (dual inline package) or a QFP (quad

flat package), or some other packaging format. This is important in terms of space,

assembling, and prototyping the end product.

(c) Power c o nsumptio n : This is especially critical for battery-powered

products. (d) The number of I/O pins and the timer on the chip.

(f) How easy it is to upgrade to higher –performance or lower consumption

versions. (g) C o s t per uni t : This is important in terms of the final cost of the

product in which a microcontroller is used.

2) The second criterion in choosing a microcontroller is how easy it is to develop products

around it. Key considerations include the availability of an assembler, debugger, compiler,

technical support.

3) The third criterion in choosing a microcontroller is its ready availability in

needed quantities both now and in the future. Currently of the leading 8-bit

microcontrollers, the

8051 family has the largest number of diversified suppliers. By supplier is meant a

producer besides the originator of the microcontroller. In the case of the 8051, this has

originated by Intel several companies also currently producing the 8051.

Thus the microcontroller AT89S52, satisfying the criterion necessary for the proposed application is chosen for the task.

4.4.2 E SC RI P T I O N :

The 8051 family of microcontrollers is based on an architecture which is

highly optimized for embedded control systems. It is used in a wide variety of

applications from

military equipment to automobiles to the keyboard. Second only to the Motorola 68HC11

in eight bit processors sales, the 8051 family of microcontrollers is available in a wide

array of variations from manufacturers such as Intel, Philips, and Siemens. These

manufacturers have added numerous features and peripherals to the 8051 such as I2C

interfaces, analog to digital converters, watchdog timers, and pulse width modulated

outputs. Variations of the 8051 with clock speeds up to 40MHz and voltage

requirements down to 1.5 volts are available. This wide range of parts based on one core

makes the 8051 family an excellent choice as the base architecture for a company's entire

line of products since it can perform many functions and developers will only have to

learn this one platform.

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 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 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. 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 con-tents but freezes the oscillator,

disabling all other chip functions until the next interrupt or hardware reset.

4.4.3 EA T U R ES:

The basic architecture of AT89C51 consists of the following features:

• Compatible with MCS-51 Products

• 8K Bytes of In-System Programmable (ISP) Flash Memory

• 4.0V to 5.5V Operating Range

• Fully Static Operation: 0 Hz to 33 MHz

• 256 x 8-bit Internal RAM

• 32 Programmable I/O Lines

• Three 16-bit Timer/Counters

• Eight Interrupt Sources

• Full Duplex UART Serial Channel

• Low-power Idle and Power-down Modes

• Interrupt Recovery from Power-down Mode

• Watchdog Timer

• Fast Programming Time

• Flexible ISP Programming (Byte and Page Mode)

4.4.4 P IN CONFI GURAT ION

Fig. 4 .16 Pin di ag ram of AT89S52

4.4.5 B LO CK D IA GR AM

Fig. 4 .17 B lo ck di ag ram of the mic ro co ntro ller

4.4.6 P I N D E S C RI P T I ON

• 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 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

low-order address/data bus during accesses to external program and data memory.

In this mode, P0 has internal pull-ups.

• 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),

respectively, as shown in the following table.

• 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

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

uses 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2

Special Function register.

•

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 also serves the functions of various special features of the AT89S52, as

shown in the following table.

Alt er nate funct io ns of Port 3:

T a ble 4 . 2 Alt e rn a t e fun c ti o ns of Port 3

• 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.

4.4.6.1 Po we r- On R es et ci rcuit

Fig. 4 .18 Po wer -on re set ci rcu it

In order for the RESET input to be effective, it must have a minimum duration of

two machine cycles.

• 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, 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: 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.

4.4.6.2 The A T89 S52 o sci lla tor clo ck c ir cuit

• It uses a quartz crystal oscillator.

• We can observe the frequency on the XTAL2 pin.

C2

30pF

C1

30pF

XTAL2

XTAL1

GN D

Fig 4 .19 T he AT89 S52 oscillator clock circuit

• The crystal frequency is the basic internal frequency of the microcontroller.

• The internal counters must divide the basic clock rate to yield

standard communication bit per second (baud) rates.

• An 11.0592 megahertz crystal, although seemingly an odd value, yields a

crystal frequency of 921.6 kilohertz, which can be divided evenly by the standard

communication baud rates of 19200, 9600, 4800, 2400, 1200, and 300 hertz.

4.4.7 SP EC IAL F U NC T I ON RE G I ST E R S

The Special Function Registers (SFRs) contain memory locations that are used

for special tasks. Each SFR occupies internal RAM from 0x80 to 0xFF.They are 8-bits

wide.

• The A (accumulator) register or accumulator is used for most ALU operations and

Boolean Bit manipulations.

• Register B is used for multiplication & division and can also be used for

general purpose storage.

• PSW (Program Status Word) is a bit addressable register

• PC or program counter is a special 16-bit register. It is not part of SFR.

Program instruction bytes are fetched from locations in memory that are

addressed by the

PC.

• Stack Pointer (SP) register is eight bits wide. It is incremented before data

is stored during PUSH and CALL executions. While the stack may reside

anywhere in on-chip RAM, the Stack Pointer is initialized to 07H after a

reset. This causes the stack to begin at location 08H.

• DPTR or data pointer is a special 16-bit register that is accessible as two 8-

bit registers: DPL and DPH, which are used to used to furnish memory

addresses for internal and external code access and external data access.

• Control Registers: Special Function Registers IP, IE, TMOD, TCON, SCON,

and PCON contain control and status bits for the

interrupt system, the Timer/Counters, and the serial port.

• Timer Registers: Register pairs (TH0, TL0) and (TH1, TL1) are the 16-bit

Counter registers for Timer/Counters 0 and 1, respectively.

4.4.8 ME MO RY OR GANI ZATI ON

MCS-51 devices have a separate address space for Program and Data Memory. Up to

64K bytes each of external Program and Data Memory can be addressed.

• P r og r am M e m o r y : If the EA pin is connected to GND, all program fetches

are directed to external memory. On the AT89S52, if EA is connected to

VCC, program fetches to addresses 0000H through 1FFFH are directed to

internal memory and fetches to addresses 2000H through FFFFH are to external

memory.

• D a ta M e mo r y: The AT89S52 implements 256 bytes of on-chip RAM. The upper

128 bytes occupy a parallel address space to the Special Function Registers.

This means that the upper 128 bytes have the same addresses as the SFR space

but are physically separate from SFR space. When an instruction accesses an

internal location above address 7FH, the address mode used in the instruction

specifies whether the CPU accesses the upper 128 bytes of RAM or the SFR

space. Instructions which use direct addressing access the SFR space. The

lower 128bytes of RAM can be divided into three segments:

1. R e g i st e r B a n k s 0 -3: locations 00H through 1FH (32 bytes). The device after

reset defaults to register bank 0. To use the other register banks, the user must

select them in software. Each register bank contains eight 1-byte registers R0-R7.

Reset initializes the stack point to location 07H, and is incremented once to start

from 08H, which is the first register of the second register bank.

2. B i t Address a b l e Ar e a : 16 bytes have been assigned for this segment 20H-

2FH. Each one of the 128 bits of this segment can be directly addressed (0-7FH).

Each of the 16 bytes in this segment can also be addressed as a byte.

3. Sc r a tch P a d Area: 30H-7FH are available to the user as data RAM.

However, if the data pointer has been initialized to this area, enough bytes should

be left aside to prevent SP data destruction.

Fig. 4 . 20 I n ter n a l m e m o ry b l o c k

4.4.9 WATCHDOG TIMER (One-time Enabled wit h Reset-out)

The WDT is intended as a recovery method in situations where the CPU may be

subjected to software upsets. The WDT consists of a 14-bit counter and the Watchdog Timer

Reset (WDTRST) SFR. The WDT is defaulted to disable from exiting reset. To enable the

WDT, a user must write 01EH and 0E1H in sequence to the WDTRST register (SFR location

0A6H). When the WDT is enabled, it will increment every machine cycle while the

oscillator is running. The WDT timeout period is dependent on the external clock

frequency. There is no way to disable the WDT except through reset (either hardware

reset or WDT overflow reset). When WDT over-flows, it will drive an output RESET

HIGH pulse at the RST pin.

4.4.10TI M E RS A N D COU N TE R S

Many microcontroller applications require the counting of external events such as

the frequency of a pulse train, or the generation of precise internal time delays between

computer actions. Both of these tasks can be accomplished using software techniques,

but software loops for counting or timing keep the processor occupied so that, other

perhaps more important, functions are not done. Hence the better option is to use

interrupts & the two 16- bit count- up timers. The microcontroller can programmed for

either of the following:

1. Count internal - acting as timer

2. Count external - acting as counter

All counter action is controlled by the TMOD (Timer Mode) and the TCON

(Timer/Counter Control) registers. TCON Timer control SFR contains timer 1& 2

overflow flags, external interrupt flags, timer control bits, falling edge/low level

selector bit etc. TMOD timer mode SFR comprises two four-bit registers (timer #1, timer

#0) used to specify the timer/counter mode and operation.

The timer may operate in any one of four modes that are determined by modes bits

M1 and M0 in the TMOD register:

TIMER M O D E - 0 : Setting timer mode bits to 00b in the TMOD register results in using

the TH register as an 8-bit counter and TL as a 5-bit counter. Therefore mode0 is a

13-bit counter.

TIMER MOD E - 1 : Mode-1 is similar to mode-0 except TL is configured as a full

8-bit counter when the mode bits are set to 01b in TMOD.

TIMER M O DE- 2 : Setting the mode bits to 10b in TMOD configures the timer to use

only the TL counter as an 8-bit counter. TH is used to hold a value that is loaded into

TL every

time TL overflows from FFh to 00h. The timer flag is also set when TL overflows.

TIMER MOD E - 3 : In mode-3, timer-1 simply hold its count, where as timer 0 registers

TL0 and TH0 are used as two separate 8-bit counters. TL0 uses the Timer-0 control

bits. TH0 counts machine cycles and takes over the use of TR1 and TF1 from Timer-1.

4.4.11I N T E R RU P TS

A computer has only two ways to determine the conditions that exist in internal

and external circuits. One method uses software instructions that jump to subroutines

on the states of flags and port pins. The second method responds to hardware

signals, called interrupts that force the program to call a subroutine.

The AT89S52 has a total of six interrupt vectors: two external interrupts (INT0 and

INT1), three timer interrupts (Timers 0, 1, and 2), and the serial port interrupt. Each of

these interrupt sources can be individually enabled or disabled by setting or clearing

a bit in Special Function Register IE. IE also contains a global disable bit, EA, which

disables all interrupts at once.

Each interrupt forces the processor to jump at the interrupt location in the

memory. The interrupted program must resume operation at the instruction where the

interrupt took place. Program resumption is done by storing the interrupted PC address on

to stack.

RETI instruction at the end of ISR will restore the PC address.

4.4.12 MICROCON TRO LL ER CONFIG URAT ION U SED IN THE SET-UP

The microcontroller is interfaced with the ADC in polling mode. INT0 is used for the

LCD mode selection switch in order to switch between two modes of display:

1) Sensor output display

2) Actuator status display

Port details:

• Port 0: Interfaced with the LCD data lines.

• Port 1: Interfaced with the ADC data lines

• Port 2: Interfaced with the LCD Control lines and AC Interface control

• Port 3: Interfaced with the ADC control lines

4.5 LIQU I D CRY S TAL DIS P LAY

A liquid crystal display (LCD) is a thin, flat display device made up of any number

of color or monochrome pixels arrayed in front of a light source or reflector. Each pixel

consists of a column of liquid crystal molecules suspended between two transparent

electrodes, and two polarizing filters, the axes of polarity of which are perpendicular to

each other. Without the liquid crystals between them, light passing through one would

be blocked by the other. The liquid crystal twists the polarization of light entering one

filter to allow it to pass through the other.

Many microcontroller devices use 'smart LCD' displays to output visual

information. LCD displays designed around Hitachi's LCD HD44780 module, are

inexpensive, easy to use, and it is even possible to produce a readout using the 8x80

pixels of the display. They have a standard ASCII set of characters and mathematical

symbols.

For an 8-bit data bus, the display requires a +5V supply plus 11 I/O lines. For a 4-

bit data bus it only requires the supply lines plus seven extra lines. When the LCD display

is not enabled, data lines are tri-state and they do not interfere with the operation of the

microcontroller.

Data can be placed at any location on the LCD. For 16×2 LCD, the address locations

are:

First line 80 81 82 83 84 85 86 through 8F

Second line C0 C1 C2 C3 C4 C5 C6 through CF

Fig 4 .22 A ddr ess lo cations for a 2 x16 li ne LCD

4.5.1 SIGNALS TO THE LCD

The LCD also requires 3 control lines from the microcontroller:

1) E n a b le (E)

This line allows access to the display through R/W and RS lines. When this

line is low, the LCD is disabled and ignores signals from R/W and RS. When (E)

line is high, the LCD checks the state of the two control lines and responds

accordingly.

2) Read/Write (R / W )

This line determines the direction of data between the LCD and microcontroller.

When it is low, data is written to the LCD. When it is high, data is read from the

LCD.

3) R e gi ster s e l e ct ( R S)

With the help of this line, the LCD interprets the type of data on data lines. When it

is low, an instruction is being written to the LCD. When it is high, a character is being

written to the LCD.

4.5.1.1 Logic s t atus on c o n t r o l lines:

• E - 0 Access to LCD disabled

- 1 Access to LCD enabled

• R/W - 0 Writing data to LCD

- 1 Reading data from LCD

• RS - 0 Instruction

- 1 Character

4.5.1.2 W r i t i n g a n d r e ad ing the d a t a f r om the L C D:

Writing data to the LCD is done in several steps:

1) Set R/W bit to low

2) Set RS bit to logic 0 or 1 (instruction or character)

3) Set data to data lines (if it is writing)

4) Set E line to high

5) Set E line to low

Read data from data lines (if it is reading):

1) Set R/W bit to high

2) Set RS bit to logic 0 or 1 (instruction or character)

3) Set data to data lines (if it is writing)

4) Set E line to high

5) Set E line to low

4.5.2 P I N D E S C RI P T I ON

Most LCDs with 1 controller has 14 Pins and LCDs with 2 controller has 16 Pins

(two pins are extra in both for back-light LED connections).

Fig 4 . 23 Pin d i a g ram o f 2 x 16 l i ne LCD

Table 4 . 23 P i n descri p tion o f t he LCD

4.6 A LA RM C IR CU ITRY

BUZ Z ER:

A buzzer or beeper is a signaling device, usually electronic, typically used

in automobiles, household appliances such as a microwave oven.

Fig . 4.24 Elec trical symbol of a bu zzer

It is connected to the control unit through the transistor that acts as an

electronic switch for it. When the switch forms a closed path to the buzzer, it sounds a

warning in the form of a continuous or intermittent buzzing or beeping sound.

The transistor acts as a normal controlled by the base connection. It switches

ON when a positive voltage from the control unit is applied to the base. If the positive

voltage is less than 0.6V, the transistor switches OFF. No current flows through the buzzer

in this case and it will not buzz. As can be seen in the buzzer circuitry given below, a

protection resistor of 10k ohm is used in order to protect the transistor from being

damaged in case of excessive current flow. In our system, the buzzer is designed to give a

small beep whenever one of the devices such as a cooler or a bulb turns on in order to

alert the user.

Fi g. 4 .25 Buzzer circuitry

4.7 R E L A YS

A relay is an electrical switch that opens and closes under the control of another

electrical circuit. In the original form, the switch is operated by an electromagnet to open

or close one or many sets of contacts. It was invented by Joseph Henry in 1835. Because

a relay is able to control an output circuit of higher power than the input circuit, it can be

considered

to be, in a broad sense, a form of an electrical amplifier.

Fig . 4 .26 Suga r cube relay

Despite the speed of technological developments, some products prove so

popular that their key parameters and design features remain virtually unchanged for

years. One such product is the ‘sugar cube’ relay, shown in the figure above, which

has proved useful to many designers who needed to switch up to 10A, whilst using

relatively little PCB area

Since relays are switches, the terminology applied to switches is also applied

to relays. A relay will switch one or more poles, each of whose contacts can be thrown by

energizing the coil in one of three ways:

1.N o rmally - open (N O ) contacts connect the circuit when the relay is activate d; the

circuit is disconnected when the relay is inactive. It is also called a FORM A contact or

“make” contact.

2.N o rmally - c l o s ed (N C) contacts disconnect the circuit when the relay is activated ; the

circuit is connected when relay is inactive. It is also called FORM B contact or”

break” contact

3.Cha n g e - o ver or dou b l e -th r ow contacts control two circuits ; one normally open

contact and one normally –closed contact with a common terminal. It is also called a

Form C “transfer “contact.

The following types of relays are commonly encountered:

"C" denotes the common terminal in SPDT and DPDT types

Fi g . 4 . 27 Di f ferent t y p e s of R e la y s

• SPST - S in g le P ole S in g le T hr o w : These have two terminals which can be

connected or disconnected. Including two for the coil, such a relay has four

terminals in total. It is ambiguous whether the pole is normally open or normally

closed. The terminology "SPNO" and "SPNC" is sometimes used to resolve the

ambiguity.

• SPDT - S in g l e P ole D ou b le T hr o w : A common terminal connects to either of

two others. Including two for the coil, such a relay has five terminals in total.

• DPST - D ou b le P ole S in g l e T hr o w : These have two pairs of terminals. Equivalent

to two SPST switches or relays actuated by a single coil. Including two for the coil,

such a relay has six terminals in total. It is ambiguous whether the poles are

normally open, normally closed, or one of each.

• DP D T - D ou b le P ole D ou b le T hrow: These have two rows of change-over terminals.

Equivalent to two SPDT switches or relays actuated by a single coil. Such a relay

has eight terminals, including the coil.

• QPDT - Q uadr up le P o l e D o uble T h r ow : Often referred to as Quad Pole Double

Throw, or 4PDT. These have four rows of change-over terminals. Equivalent to

four SPDT switches or relays actuated by a single coil, or two DPDT relays. In

total, fourteen terminals including the coil.

The Relay interfacing circuitry used in the application is:

1N4148

Fig. 4 .28 R el ay ci rcuit ry

4.8 PO W ER S UP P LY CON N E C T I O N

The power supply section consists of step down transformers of 230V primary to

9V and 12V secondary voltages for the +5V and +12V power supplies respectively. The

stepped down voltage is then rectified by 4 1N4007 diodes. The high value of capacitor

1000 µF charges at a slow rate as the time constant is low, and once the capacitor charges

there is no resistor for capacitor to discharge. This gives a constant value of DC. IC 7805

is used for regulated supply of +5 volts and IC 7812 is used to provide a regulated supply

of +12 volts in order to prevent the circuit ahead from any fluctuations. The filter

capacitors connected after this IC filters the high frequency spikes. These capacitors

are connected in parallel with supply and common so that spikes filter to the common.

These give stability to the power supply circuit.

As can be seen from the above circuit diagrams, the rectified voltage from

the 4 diodes is given to pin 1 of the respective regulators. Pin 2 of the regulators is

connected to ground and pin 3 to Vcc. With adequate heat sinking the regulator can

deliver 1A output current. If internal power dissipation becomes too high for the heat

sinking provided, the

thermal shutdown circuit takes over preventing the IC from overheating.

1Vin 7805 Vout

GND2

230V, 50Hz

1000uf 10

uf1uf

Fi g . 4.29 +5V Power supply circuit

Fig . 4 .30 +12V Power suppl y Circui t

CIRCUIT SCHEMATIC OF THE SYSTEM

CHAPTER 5

SYSTEMS USED IN

WORK MODEL

5.1 DRIP IR RIGATION SY STEM FO R CONTROLLIN G SOIL MOISTURE

Drip, or micro-irrigation, technology uses a network of plastic pipes to carry a

low flow of water under low pressure to plants.

Polyethylene tubing is run from the source of water to the plant, where the emitter

is attached for dripping water. Emitter line (poly tubing with pre-installed emitters) is

used where a continuous band of water is needed. Fittings are available to make sharp

turns (elbows), branch lines (tees), and to make the transition between different sizes of

tubing. When plants are removed or die, drip lines should be plugged.

Fig. 5 . 1 D r ip irrigation s y s t em

Drip irrigation (sometimes called trickle irrigation) works by applying water

slowly, directly to the soil. The high efficiency of drip irrigation results from two

primary factors. The first is that the water soaks into the soil before it can evaporate or run

off. The second is that the water is only applied where it is needed, (at the plant's roots)

rather than sprayed everywhere.

A drip irrigation system slowly provides water to the plant's root system. Regular

watering prevents plant dehydration, but roots don't get overly soaked and in turn,

plant growth can increase up to 50%. Drip systems irrigate all types of landscape:

shrubs, trees,

perennial beds, ground covers, annuals and lawns. Drip is the best choice to water roof gar-

dens, containers on decks and patios, row crops and kitchen gardens, orchards,

and vineyards.

5.2 A RTI FICI AL GROW IN G LI GHTS F OR CON TRO LLI NG ILLUM IN AT ION

Growing lights enable cultivators to extend daylight hours - useful for winter

and spring growing when levels of natural lights can be low, and one can therefore

improve plant growth. Three basic types of lamps used in greenhouse lighting are:

• Flu o r e scent lamps - These have the advantage of higher light efficiency with

low heat. This type of lamp is the most widely used for supplemental light. It is

available in a variety of colors but cool-white lamps are the most common.

High intensity (1500 ma) fluorescent tubes that require higher wattage are also

commonly used to reach 2000 foot candles.

• Incandesc e nt l a mps - These vary in size from 60 watts to 500 watts. The grower

can vary foot-candle levels by adjusting the spacing and mounting height

above the plants.

• High-i n tensity d i s c harge (HID) lamps - These have a long life (5000 hours

or more). With improvements made possible by the addition of sodium and

metal- halides, the lamp has a high emission of light in the regions utilized by

plants.

The following generally accepted cultural divisions describe light levels:

• Ve r y h i g h : Over 5000 footcandles--nearly full sun except at midday, when

full summer sun in most latitudes may reach 10,000 fc.

• High: 4000-5000 footcandles--bright light, just under 50% of the full midday sun.

• Int e r m edi a t e : 1800-4000 footcandles--dappled sunlight.

• Low: 1000-1800 footcandles--reduced sunlight, so that if a hand is passed over

the leaves it does not produce a shadow.

One footcandle is equal to 10.76 lux, although in the lighting industry, typically

this is approximated as 1 footcandle being equal to 10 lux.

5.3 TEM PERATUR E CONTR OL LER S

5.3.1 CO OL I N G EQ UI PME N T

There are three primary cooling devices in most greenhouses. These are the vent

system, exhaust fan, and swamp cooler. Some greenhouses may make use of air

conditioners and/or misting systems as well.

• Vents are hinged or track connected panels in the roof or sides of greenhouses.

They open up the greenhouse to outside natural air. Hot air that builds up in the

greenhouse can escape, and fresh air can enter the house. The microcontroller can

be used to automate the opening and closing of these vents depending upon

requirement. But during hot summer days, venting alone will not get the job done.

• E xhaust fans can move a large volume of the hot greenhouse air out and pull

fresh air in through the rear vent. They're powerful for a reason, as full sun

on a hot summer day can cause temperatures inside the greenhouse to superheat.

An exhaust fan must be able to pull this air out, or the temperatures will continue

to rise.

• Swamp coo l ers: come in different widths and lengths. They can be configured to

the appropriate size, as this varies depending on the length and width of the

greenhouse, location where you live, and type of plants you wish to grow.

5.3.2 H E ATING E Q U I P M E N T

• H ot-w a ter o r steam h e at e r : A hot-water system with circulator or a steam

system linked with automatic ventilation will give adequate temperature

control. In some areas, coal or natural gas is readily available at low cost. This

fuel is ideal for hot- water or a central steam system. Steam has an advantage in

that it can be used to sterilize growing beds and potting soils.

• E lectric h e a t e r s : Overhead infrared heating equipment combined with soil cable

heat provides a localized plant environment, which allows plants to thrive even

though the surrounding air is at a lower than normal temperature. Electric

resistance-type heaters

are used as space heaters or in a forced air system.

5.4 HU MIDIFCATION SYSTEMS

Many evaporative cooling and humidifying systems are available: Foggers,

Mist systems, Roof Sprinklers, and Pan & Fan Systems. They add water vapour to the

air, and may subsequently reduce the amount of water that the plants need to transpire.

• Ro o f spr i nk l ers add water vapour and cool the incoming air. On large ranges, it

is possible to decrease the temperature by 3 - 5 C and increase the humidity by 5-

10%.

• Pad and fan syste m s consist of porous wet pads at the inlet end of a fan ventilated

greenhouse. As the exhaust fans draw air through the wet pads, water evaporates,

cooling and humidifying the air. Temperatures tend to be coolest nearer the fans and

hottest at the exhaust when using these systems.

• M i st a nd fog s y s t e m s produce tiny water droplets that evaporate, thereby cooling

and humidifying the greenhouse air. A misting system can provide needed

moisture to maintain a healthy humidity level of 50 to 70%.

CHAPTER 6SOFTWARE

USED

6.1 INTRODUCTIO N TO KEIL SOFTWARE

Keil MicroVision is an integrated development environment used to create

software to be run on embedded systems (like a microcontroller). It allows for such

software to be written either in assembly or C programming languages and for that

software to be simulated on a computer before being loaded onto the microcontroller.

6.1.1 W H A T IS µ V is i o n 3?

µVision3 is an IDE (Integrated Development Environment) that helps write,

compile, and debug embedded programs. It encapsulates the following components:

¾ A project manager.¾ A make facility.¾ Tool configuration.¾ Editor.

¾ A powerful debugger.

6.1.2 STEPS FOLLOWED IN CREA TI NG AN APPLIC AT ION IN uVisio n3 :

To create a new project in uVision3:

1. Select Project - New Project.

2. Select a directory and enter the name of the project file.

3. Select Project –Select Device and select a device from Device Database.

4. Create source files to add to the project

5. Select Project - Targets, Groups, and Files. Add/Files, select Source Group1, and

add the source files to the project.

6. Select Project - Options and set the tool options. Note that when the target device

is selected from the Device Database™ all-special options are set automatically.

Default memory model settings are optimal for most applications.

7. Select Project - Rebuild all target files or Build target

To create a new project, simply start MicroVision and select “Project”=>”New

Project” from the pull–down menus. In the file dialog that appears, choose a name and base

directory for the project. It is recommended that a new directory be created for each

project, as several files will be generated. Once the project has been named, the dialog

shown in the figure below will appear, prompting the user to select a target device. In

this lab, the chip

being used is the “AT89S52,” which is listed under the heading “Atmel”.

Fig. 6 . 1 Wi n dow f o r c h o o s ing the t a rget d e vice

Next, MicroVision must be instructed to generate a HEX file upon program

compilation. A HEX file is a standard file format for storing executable code that is to be

loaded onto the microcontroller.

In the “Project Workspace” pane at the left, right–click on “Target 1” and select

“Options for ‘Target 1’ ”.Under the “Output” tab of the resulting options dialog, ensure

that both the “Create Executable” and “Create HEX File” options are checked. Then

click “OK”

as shown in the two figures below.

Fi g. 6 .2 Projec t Workspace Pa ne Fig. 6.3 Project Options Dia log

Next, a file must be added to the project that will contain the project code. To do

this, expand the “Target 1” heading, right–click on the “Source Group 1” folder, and select

“Add files…” Create a new blank file (the file name should end in “.asm”), select it,

and click “Add.” The new file should now appear in the “Project Workspace” pane under

the “Source Group 1” folder. Double-click on the newly created file to open it in the

editor. All code for this lab will go in this file. To compile the program, first save all

source files by clicking on the “Save All” button, and then click on the “Rebuild All

Target Files” to compile the program as shown in the figure below. If any errors or

warnings occur during compilation, they will be displayed in the output window at

the bottom of the screen. All errors and warnings will reference the line and column

number in which they occur along with a description of the problem so that they can

be easily located. Note that only errors indicate that the compilation failed, warnings do

not (though it is generally a good idea to look into them anyway).

Fig. 6.4 “Save All” and “ Build All Ta rget Fi les” Buttons

When the program has been successfully compiled, it can be simulated using the

integrated debugger in Keil MicroVision. To start the debugger, select

“Debug”=>”Start/Stop Debug Session” from the pull–down menus.

At the left side of the debugger window, a table is displayed containing several key

parameters about the simulated microcontroller, most notably the elapsed time (circled in

the figure below). Just above that, there are several buttons that control code

execution. The “Run” button will cause the program to run continuously until a

breakpoint is reached, whereas the “Step Into” button will execute the next line of code

and then pause (the current

position in the program is indicated by a yellow arrow to the left of the code).

Fig. 6.5 µVision3 Debugg er window

Breakpoints can be set by double–clicking on the grey bar on the left edge of

the window containing the program code. A breakpoint is indicated by a red box next to

the line

of code.

Fig . 6.6 ‘R eset’, ‘Run’ and ‘Step into ’ options

The current state of the pins on each I/O port on the simulated microcontroller

can also be displayed. To view the state of a port, select “Peripherals”=>”I/O

Ports”=>”Port n” from the pull–down menus, where n is the port number. A checked box

in the port window indicates a high (1) pin, and an empty box indicates a low (0) pin. Both

the I/O port data and the data at the left side of the screen are updated whenever the

program is paused.

The debugger will help eliminate many programming errors, however the

simulation is not perfect and code that executes properly in simulation may not

always work on the

actual microcontroller.

6.1.3 DEV ICE D ATABA SE

A unique feature of the Keil µVision3 IDE is the Device Database, which contains

information about more than 400 supported microcontrollers. When you create a

new

µVision3 project and select the target chip from the database, µVision3 sets all assembler,

compiler, linker, and debugger options for you. The only option you must configure is the

memory map.

6.1.4 P E R I PHE RA L SIM U L A T I ON

The µVision3 Debugger provides complete simulation for the CPU and on-chip

peripherals of most embedded devices. To discover which peripherals of a device are

supported, in µVision3 select the Simulated Peripherals item from the Help menu. You

may also use the web-based Device Database. We are constantly adding new

devices and simulation support for on-chip peripherals so be sure to check Device

Database often.

6.2 GRAM MER

The programmer used is a powerful programmer for the Atmel 89 series of

microcontrollers that includes 89C51/52/55, 89S51/52/55 and many more.

It is simple to use & low cost, yet powerful flash microcontroller programmer for

the Atmel 89 series. It will Program, Read and Verify Code Data, Write Lock Bits, Erase

and Blank Check. All fuse and lock bits are programmable. This programmer has

intelligent onboard firmware and connects to the serial port. It can be used with any

type of computer and requires no special hardware. All that is needed is a serial

communication port which all computers have.

All devices also have a number of lock bits to provide various levels of software

and programming protection. These lock bits are fully programmable using this

programmer. Lock bits are useful to protect the program to be read back from

microcontroller only allowing erase to reprogram the microcontroller.

Major parts of this programmer are Serial Port, Power Supply and Firmware

microcontroller. Serial data is sent and received from 9 pin connector and converted

to/from

TTL logic/RS232 signal levels by MAX232 chip. A Male to Female serial port

cable, connects to the 9 pin connector of hardware and another side connects to back of

computer.

All the programming ‘intelligence’ is built into the programmer so you do not

need any special hardware to run it. Programmer comes with window based software for

easy programming of the devices.

6.3 ProLo ad PRO GRA MM IN G SOF TW ARE

‘ProLoad’ is a software working as a user friendly interface for programmer boards

from Sunrom Technologies. Proload gets its name from “Program Loader” term,

because that is what it is supposed to do. It takes in compiled HEX file and loads it to

the hardware. Any compiler can be used with it, Assembly or C, as all of them

generate compiled HEX files. ProLoad accepts the Intel HEX format file generated from

compiler to be sent to target microcontroller. It auto detects the hardware connected to

the serial port. It also auto detects the chip inserted and bytes used. The software is

developed in Delphi and requires no overhead of any external DLL.

The programmer connects to the computer’s serial port (Comm 1, 2, 3 or 4) with a

standard DB9 Male to DB9 Female cable. Baud Rate - 57600, COMx Automatically

selected by window software. No PC Card Required.

After making the necessary selections, the ‘Auto Program’ button is clicked as

shown in the figure below which burns the selected hex file onto the microcontroller.

Fig. 6 .7 Prog rammi ng win dow

CHAPTER 7

FLOWCHART

7.1 FLOWCHART REPRESENTING THE WORKING OF THE SYSTEM:

START

INITIALISE THE LCD

DISPLAY INITIALISATION MESSAGE

B

INITIALISE THE ADC

OBTAIN THE SENSOR DATA

OBTAIN DIGITIZED DATA FROM ADC

STORE DIGITAL OUTPUT IN THE BUFFER MEMORY OF THE MICROCONTROLLER

CLEAR THE LCD

IS MODE

BUTTON

PRESSED

YES

NO

DISPLAY THE DEVICE STATUS

DISPLAY THE SENSOR DATA

A

A

YES SENSOR NO

THRESHOLD CROSSED?

TURN ON ACTUATOR

TURN OFF ACTUATOR

B

7.2 FLOWCHART FOR LCD IN ITI ALIZ ATI ON

START

INTILIAZE THE LCD WITH 2LINES, 5X7 MATRIX

CLEAR REGISTER SELECT, READ/WRITE AND SET THE ENABLE PIN OF THE LCD

CALL SOME DELAY

CLEAR THE ENABLE PIN OF THE LCD

CALL SOME DELAY

C

C

SET THE DISPLAY ON AND THE CURSOR ON

CLEAR REGISTER SELECT, READ/WRITE AND SET THE ENABLE PIN OF THE LCD

CALL SOME DELAY

CLEAR THE ENABLE PIN OF THE LCD

CALL SOME DELAY

CLEAR THE LCD AND SHIFT THE CURSOR TO RIGHT

CLEAR REGISTER SELECT, READ/WRITE AND SET THE ENABLE PIN OF THE LCD

CALL SOME DELAY

CLEAR THE ENABLE PIN OF THE LCD

CALL SOME DELAY

SHIFT THE CURSOR AT LINE 1, POSITION 0

CLEAR REGISTER SELECT, READ/WRITE AND SET THE ENABLE PIN OF THE LCD

D

D

CALL SOME DELAY

CLEAR THE ENABLE PIN OF THE LCD

CALL SOME DELAY

STOP

7.3 FLOWCHART FOR ADC INITIALIZATION

START

SELECT AN ANALOG CHANNEL BY SETTING THE ADDRESS LINES A, B AND C

CLEAR THE OUTPUT ENABLE PIN

ACTIVATE THE ALE PIN WITH A LOW TO HIGH PULSE

ACTIVATE THE START PIN BY A HIGH TO LOW PULSE TO INITIATE CONVERSION

NOIS

EOC =0?YES

A

A

SET THE OUTPUT ENABLE PIN

CALL SOME DELAY

READ DATA OUT OF THE ADC CHIP

CLEAR THE OUTPUT ENABLE PIN

STOP

CHAPTER 8

RESULT ANALYSIS

R ESULT ANALY SIS

Readings taken at room temperature of 270C

8.1 TRANSDUC E R READ I NGS

8.1.1 SOIL MOISTURE SENSOR

Tolerance= ± 0.2 V

Ta bl e 8 .1 So il moi st ure se nso r readi ng s

Soil Condition Transducer

Optimum Range

Soil is dry 0V

Optimum level of

soil moisture

1.9- 3.5V

Slurry soil >3.5V

8.1.2 LIGHT SENSOR

Tolerance = ±0.1V

Table 8 .2 Lig ht sen sor r ea din gs

Illumination Status Transducer Optimum

Range

OPTIMUM

ILLUMINATION

0V-0.69V

DIM LIGHT 0.7V-2.5V

DARK 2.5V- 3V

NIGHT 3V-3.47V

8.1.3 HUMIDITY SENSOR

8.1.3.1 FOR M U L A:

RH = ((Vout / Vcc) – 0.16 )/0.0062, typical at 25°C (Ref. Eq.4.3)

where, Vsupply =

4.98V Tolerance=

±0.1V

Table 8 .3 Humidity sensor r eadi ngs

Percentage RH

(RELATIVE

HUMIDITY)

Transducer Optimum Range

0% 0-0.8V

0% to 9.81% 0.8-1.1V

12.9% to 20.1% 1.2-1.45V

22.7% to 30.06% 1.5-1.725V

30.8% to 40.5% 1.75-2.05V

41.3%to50.3% 2.075-2.35V

51%to 60.02% 2.375-2.65

61.6%to70.5% 2.7-2.975V

71%to80.2% 3-3.275V

81.1%to 90% 3.3-3.6V

91%to 100% 3.6-3.9V

8.1.4 TE MPE RA TU RE SENS OR

8 . 1 . 4 . 1 F O R MU L A:

Temperature ( oC ) = (Vout/5) *100( oC/V) (Ref. Eq.4.4)

Ta bl e 8 .4 Te mpera ture se nso r readi ng s

Temperature range

in degree Celsius

Temperature

sensor

output(Vout)100 C 0.5V

150 to 200 C 0.75-1.0V

20 0to 250 C 1.0-1.25V

250 to 30 0C 1.25-1.5V

30 0to 35 0C 1.5-1.75V

350 to 400 C 1.75-2.0V

400 to 45 0C 2.0-2.25V

450 to 500 C 2.25-2.5V

500 to 55 0C 2.5-2.75V

550 to 600C 2.75-3.0V

600 to 650 C 3.0-3.25V

650 to 70 0C 3.25-3.5V

70 0to 750 C 3.5-3.75V

75 0to 80 0C 3.75-4.0V

80 0to 850 C 4.0-4.25V

85 0to 900 C 4.25-4.5V

900 to 95 0C 4.5-4.75V

950 to 1000 C 4.75-5V

CHAPTER 9

ADVANTAGES AND DISADVANTAGES

ADVANTAG ES A ND DISADVANTAGES

9.1 ADVANTAG E S

1. Sensors used have high sensitivity and are easy to handle.

2. Low cost system, providing maximum automation.

3. Closed loop design prevents any chances of disturbing the greenhouse environment.

4. User is indicated for changes in actuator state thereby giving an option for

manual override.

5. Low maintenance and low power consumption.

6. The system is more compact compared to the existing ones, hence is easily portable.

7. Can be used for different plant species by making minor changes in the

ambient environmental parameters.

8. Can be easily modified for improving the setup and adding new features.

9. Labour saving.

10. Provides a user-friendly interface hence will have a greater acceptance by

the technologically unskilled workers.

11. In response to the sensors, the system will adjust the heating, fans, lighting,

irrigation immediately, hence protect greenhouse from damage.

12. Malfunctioning of single sensor will not affect the whole system.

13. Natural resource like water saved to a great extent.

9.2 DISADVANTAGES

1. Complete automation in terms of pest and insect detection and eradication

cannot be achieved.

2. No self-test system to detect malfunction of sensors.

3. Requires uninterrupted power supply.

4. Facility to remotely monitor the greenhouse is not possible.

CHAPTER 10

FUTURE SCOPE

SCOPE FO R FURT HER DE VELOPMENT

1) The performance of the system can be further improved in terms of the operating

speed, memory capacity, instruction cycle period of the microcontroller by using other

controllers such as AVRs and PICs. The number of channels can be increased to

interface more number of sensors which is possible by using advanced versions of

microcontrollers.

2) The system can be modified with the use of a datalogger and a graphical LCD

panel showing the measured sensor data over a period of time.

3) A speaking voice alarm could be used instead of the normal buzzer.

4) This system can be connected to communication devices such as modems, cellular

phones or satellite terminal to enable the remote collection of recorded data or

alarming of certain parameters.

5) The device can be made to perform better by providing the power supply with the help

of battery source which can be rechargeable or non-rechargeable, to reduce the

requirement of main AC power.

6) Time bound administration of fertilizers, insecticides and pesticides can be introduced.

7) A multi-controller system can be developed that will enable a master controller along

with its slave controllers to automate multiple greenhouses simultaneously.

CHAPTER 11

CONCLUSION

CO NCLUSION

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

for measurement and control of the four essential parameters for plant growth, i.e.

temperature, humidity, soil moisture, and light intensity, has been followed. The results

obtained from the measurement have shown that the system performance is quite reliable

and accurate.

The system has successfully overcome quite a few shortcomings of the

existing systems by reducing the power consumption, maintenance and complexity, at the

same time providing a flexible and precise form of maintaining the environment.

The continuously decreasing costs of hardware and software, the wider acceptance

of electronic systems in agriculture, and 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. Further

improvements will be made as less expensive and more reliable sensors are developed for

use in agricultural production.

Although the enhancements mentioned in the previous chapter may seem far in the

future, the required technology and components are available, many such systems have

been independently developed, or are at least tested at a prototype level. Also,

integration of all

these technologies is not a daunting task and can be successfully carried out.

RE FERE NCE S

[1] Dr. R. Jayanthi, Prof. of Horticulture, UAS, GKVK, Bangalore.

I EEE Pa p ers

[2] Stipanicev D., Marasovic J., Networked embedded greenhouse monitoring and control,Proceedings of 2003 IEEE Conference on Control Applications, June 2003.

[3] Turnell, D.J. de Fatima, Q.V., Turnell, M., Deep, G.S., Freire, R.C.S., FarmWeb-an integrated, modular farm automation system, Proceedings of IEEE International Conference on Systems, Man, and Cybernetics, Vol. 2, Oct. 1998.

Books

[3] Rebecca Tyson Northen, Orchids As House Plants, Dover Publications, New York, 2nd

Edition, 1985.

[4] Muhammad Ali Mazidi, Janice Gillispie Mazidi, Rolin D. Mc Kinlay , The 8051Microcontroller & Embedded Systems, Pearson Education Inc. 2nd Edition, 2008.

[5] Myke Predko, Programming and Customising the 8051 Microcontroller, TMH, 1999.

[6] Kenneth J Ayala, The 8051 Microcontroller Architecture, Programming & Applications,

Penram International, 2nd Edition, 1996.

[7] Ramakant Gayakwad, Operational Amplifiers Linear Integrated Circuits, Prentice Hall of

India, 3rd Edition.

[8] National Semiconductors, CMOS Logic Databook

[9] SENSORS- The Journal of Applied Sensing Technology, Advanstar Communications Inc

We b R e sour ces

[10] h t t p : / /f r eew e b s.c o m/ma h eshwan k ede

[11] h t t p : / / w w w .f a l u d i. c o m

[12] h tt p : / /www.e l ec t r o - t ech-o n li n e.c o m

[12] h t tp : / / w w w . 80 52. c o m

[13] h t t p : / /www.80 5 1 p roje c ts.net / f o r u m

[14] h t t p : / /www.ro b oticsindia.c o m

[15] h t tp : / / w w w . d at a s h e e t d ir e c t. c om

[16] h ttp :/ /w ww .k eil .co m/a ppno tes

[17] http://www.google.com

1. Final Prototype:

19 20 21 22

18

17

1 6 16

8 102 15

143

13

4

9145

712

1. Power Supply +5V 15. AC- switch2. Temperature Sensor 16. AC fan3. Humidity Sensor 17. Power Supply +12V4. Light sensor 18. 230V- 9V transformer5. Moisture Sensor 19. AC- bulb simulating light16. Power supply junction 20. AC- bulb simulating light27. ADC and Clock circuit board 21. AC- bulb simulating sprayer8. Relay board. 22. AC-bulb simulating pump9. Buzzer circuit board10. Microcontroller board11. Buzzer12. Mode selection switch13. DC -switch14. LCD Display

Light Sensor Soil Moisture Sensor

Humidity Sensor Temperature Sensor

ADC and Clock Circuit

Microcontroller Board and Buzzer Circuitry

The Two Display Modes of LCD

AC Interface – Relay Board

Bill Of Materials:

Sl. No. List of electrical componentsQuantity

in

1. 230V, 50Hz,9V transformer 1

2. 12-0-12V, 500mA, 1

3. Bridge rectifier

3

4. 1000uF Electrolytic capacitor 3

5. 10uF Electrolytic capacitor 3

6. 1uF Electrolytic capacitor 4

7. 30pF Ceramic capacitor 2

8. 1nF Ceramic capacitor 5

9. 10k Ω resistance 20

10. 8.2k Ω resistance 1

11. 1.2k Ω resistance 1

12. 1k Ω resistance

1

13. 1.8k Ω resistance 1

14. 330 Ω resistance 8

15. 100 Ω resistance 1

16. 12.5k Ω resistance 1

17. LM7805 2

18. LM7812 1

19. 2x16 Matrix LCD 1

41. 16 Pin Connector 2

42. 10 Ω Preset 5

43. 10k Ω Bourns Pot 3

44. 2.2K Ω Resistor

5

45. 10k Ω Strip Resistor 1

46. 0.1uF Tantalum Capacitor 1

47. Heat Sink

3

48. LED 10

49. Copper Wire 32AWG 0.5 m

50. AC Power Cord 2 m

51. Wire Cap 1 m

52. Varo Board(Shoted, Non Shoted ) 4 pc, 5pc

53. HOT GLUE GUN 1

54. Fevi QuickAs per

requirement

55. Connecting Wires 2 m

20. ADC0809 1

21. AT89S52 Microcontroller 1

22. Push to ON button 2

23. Toggle switches

2

24. BC107 1

25. Buzzer 1

26. 8-pin connectors 5

27. 3-pin connectors 2

28. 2-pin connectors 15

Single connectors 35

29. CD4093 Schmitt trigger IC 1

30. BC547 Transistor 10

31. Sugar cube relays 5

32. 11.0592 MHz Crystal 1

33. LDR 12mm 1

34. LM324 1

35. LM35 1

36. 2N222N Transistor 1

37. HIH4000-001

1

38. 12.5 k Ω Resistor 1

39. AC 5W bulbs

4

40. AC 230V Cooling Fan 1

S YS TEM INS TAL LA T ION AND FAULT REDUCTION:

The system has to be provided with uninterrupted power supply and should

be installed with care, in a place where the changes in microclimatic parameters are well

pronounced.

For best results with the moisture sensor, the probes must be inserted into

the specimen soil when the soil is dry.

For best results with the humidity sensor HIH4000

• Do not expose sensor to condensing environments. Exposure to

condensing environments will cause sensor output to indicate 0 %RH.

• Sensor is light sensitive. For best performance, shield sensor from bright light.

• Sensor is static sensitive. Sensor connection protected to 15 kV maximum.

For best results with the temperature sensor, the LM35 and accompanying wiring

and circuits must be kept insulated and dry, to avoid leakage and corrosion.

Printed-circuit coatings and varnishes such as Humiseal and epoxy paints or dips can be

used to insure that moisture does not corrode the LM35 or its connections.

1. TROUBLE SHOOTING:

In case of a system hang-up condition, the reset button in the vicinity of the

Microcontroller can be used to revive the system.

In case of anomalies in the readings of the humidity sensor, it is recommended

that the sensor be kept in an air -tight container with silica-gel inside.

In case of anomalies with the moisture sensor, the probes can be stripped off the

soil or mud particles deposited on its surface and in case of sensor-leads-

oxidation, it is

recommended that the leads be replaced.

Source Code

; Microcontroller connections to LCD.

RS BIT P2.5 ; P2.5 is connected to RS pin of LCDRW BIT P2.6 ; P2.6 is connected to R/W pin of LCDE BIT P2.7 ; P2.5 is connected to E pin of LCD

LCDDATA equ P0 ; P0.0-P0.7 are connected to LCD data pins D0-D7

SWITCH equ P3.2 ; P3.2 (INT0) is connected to SWITCH for LCD

; Microcontroller connections to ADC0808/9 lines.

OE EQU P3.0 ; Pin 9 Output EnableSTART EQU P3.1 ; Pin 6 StartEOC EQU P3.3 ; Pin 7 EOCADD_A EQU P3.4 ; Pin 25 ADD AADD_B EQU P3.5 ; Pin 24 ADD BALE EQU P3.7 ; Pin 22 ALE

ADCDATA EQU P1 ; Data Lines

; Microcontroller connections to Actuators

COOLER EQU P2.4PUMP EQU P2.3SPRAYER EQU P2.2LIGHT1 EQU P2.1LIGHT2 EQU P2.0BUZZER EQU P3.6;---------------------------------------------------------

; Register definitions.

LCD_INTR BIT 00h ;LCD Interrupt flag bit

T_BUFFER EQU 30h ;Temperature buffer (ADC o/p)M_BUFFER EQU 31h ;Soil Moisture buffer (ADC o/p)RH_BUFFER EQU 32h ;RH buffer (ADC o/p)L_BUFFER EQU 33h ;Light buffer (ADC o/p)LIGHT_LEVEL EQU 34h ;Buffer to store light levelMOIST_LEVEL EQU 35h ;Buffer to store moisture level

;----------------------------------------------------------

org 00h

LJMP mainorg 03h

LJMP int_isr ; Interrupt for the LCD switchorg 07h

;Main Code;-----------------------------------------------------------------------

MOV TMOD, #01h ;Timer 0 Mode 1, 16 bit timer (for generating 5 second delay for LCD)

SETB TCON.0 ;Make INT0 edge triggeredMOV IE, #81h ;Enable INT0CLR LCD_INTR ;Make LCD interrupt flag =0ACALL lcd_init ;LCD initialisation

back:ACALL adcread ;Read sensor data from ADCACALL data_display ;call routine to display to LCDACALL threshold_check ;call routine to check thresholdSJMP back ;repeat ADC process

lcd_init: ;LCD initialisationMOV A, #38H ;init. LCD 2 lines,5x7 matrix

ACALL comnwrt ;call command subroutine ACALL lcddelay ;give LCD some time MOV A, #0EH ;display on, cursor on ACALL comnwrt ;call command subroutine ACALL lcddelay ;give LCD some time MOV A, #01 ;clear LCD ACALL comnwrt ;call command subroutine ACALL lcddelay ;give LCD some time MOV A, #06H ;shift cursor right ACALL comnwrt ;call command subroutine ACALL lcddelay ;give LCD some time

RET

adcread: ;Initializing ADC;SENSOR 1MOV ADCDATA, #0FFH ; Data lines for inputSETB EOC ; Make EOC i/pACALL delayCLR ALE ; clearing ALECLR START ; Make start highCLR OE ; Disable o/pCLR ADD_A ;A=0CLR ADD_B ;B=0 ;Select IN4ACALL delaySETB ALE ;latching the addressACALL delaySETB START ;start conversion pulseACALL delayCLR ALE ;ALE H-L transitionCLR START ;START H-L transition

JB EOC,$JNB EOC,$ ACALL delaySETB OE ;enable o/pACALL delayMOV T_BUFFER, ADCDATA ;store adc data to bufferCLR OE ;disable o/p

;SENSOR 2MOV ADCDATA, #0FFH ; Data lines for inputSETB EOC ; Make EOC i/pACALL delayCLR ALE ; clearing ALECLR START ; Make start highCLR OE ; Disable o/pSETB ADD_A ;A=1CLR ADD_B ;B=0 Select IN5ACALL delaySETB ALE ;latching the addressACALL delaySETB START ;start conversion pulseACALL delayCLR ALE ;ALE H-L transitionCLR START ;START H-L transition

JB EOC,$JNB EOC,$ ACALL delaySETB OE ;enable o/pACALL delayMOV M_BUFFER, ADCDATA ;store adc data to bufferCLR OE ;disable o/p

;SENSOR 3MOV ADCDATA, #0FFH ; Data lines for inputSETB EOC ; Make EOC i/pACALL delayCLR ALE ; clearing ALECLR START ; Make start highCLR OE ; Disable o/pCLR ADD_A ;A=0SETB ADD_B ;B=1 Select IN6ACALL delaySETB ALE ;latching the addressACALL delaySETB START ;start conversion pulseACALL delayCLR ALE ;ALE H-L transitionCLR START ;START H-L transition

JB EOC,$JNB EOC,$ACALL delay

SETB OE ;enable o/pACALL delayMOV RH_BUFFER, ADCDATA ;store adc data to bufferCLR OE ;disable o/p

;SENSOR 4MOV ADCDATA, #0FFH ; Data lines for inputSETB EOC ; Make EOC i/pACALL delayCLR ALE ; clearing ALECLR START ; Make start highCLR OE ; Disable o/pSETB ADD_A ;A=1SETB ADD_B ;B=1 Select IN7ACALL delaySETB ALE ;latching the addressACALL delaySETB START ;start conversion pulseACALL delayCLR ALE ;ALE H-L transitionCLR START ;START H-L transition

JB EOC,$JNB EOC,$ACALL delaySETB OE ;enable o/pACALL delayMOV L_BUFFER, ADCDATA ;store adc data to bufferCLR OE ;disable o/p

RETdelay: ;Delay subroutine

MOV R3, #250here1:

MOV R4, #255here:

DJNZ R4, hereDJNZ R3, here1RET

data_display: ;LCD routine to display sensor and actuator data

JNB LCD_INTR, sensor_display ;if ACT=0, jump to display sensor data labelMOV A, #01h ;clear LCDACALL comnwrtACALL lcddelay ;give LCD some timeMOV A,#80H ;cursor at line 1, position 0

ACALL comnwrt ;call command subroutineACALL lcddelay ;give LCD some timeMOV R0, #60h ;address of display message line 1

line1:CLR AMOV A, @R0 ;moving the data to accumulatorJZ nxt_line ;exit loop on completion of display and start

;display of LCD next lineLCALL datawrt ;call data display routineLCALL lcddelay ;give LCD some timeINC R0 ;increment addressSJMP line1 ;repeat display till end of message

nxt_line: ;Displaying on line 2 of LCD

MOV A, #0C0h ;cursor at line 2, position 0

LCALL comnwrt ;call command subroutineLCALL lcddelay ;give LCD some timeMOV R0, #70h ;address of display message line 2 line2:CLR AMOV A, @R 0 ;moving the data to accumulatorJZ delay_5s ;exit loop on completion of display & call routine

;to wait 5 secLCALL datawrt ;call data display routineLCALL lcddelay ;give LCD some timeINC R0 ;increment addressSJMP line2 ;repeat display till end of message

delay_5s: ;5 second delay routineMOV R7, #100 ;REPEAT 100 TIMES (50ms*100= 5sec)sec_5:MOV TL0, #0FDh ;load 4BFDh for 5ms delayMOV TH0, #4BhSETB TR0 ;Start timer 0JNB TF0, $ ;Check for end of countCLR TR0 ;Stop timerCLR TF0 ;Clear timer 0 flagDJNZ R7, sec_5 ;Repeat till R7=0

MOV A, #01h ;clear LCD LCALL comnwrt

LCALL lcddelay ;give LCD some time

sensor_display: ;displaying sensor dataMOV A,#80H ;cursor at line 1, position 0LCALL comnwrt ;call command subroutineLCALL lcddelay ;give LCD some time

MOV A, #'T' ;display letter TLCALL datawrt ;call display subroutineLCALL lcddelay ;give LCD some timeMOV A, #':' ;display : symbolLCALL datawrt ;call display subroutineLCALL lcddelay ;give LCD some time

MOV A, T_BUFFER ;move sensor data from buffer to accumulatorMOV DPTR, #temp_tens ;address of ASCII code look up table (tens place) MOVC A, @A + DPT R ;store corresponding ASCII code to Accumulator LCALL

datawrt ;call display subroutineLCALL lcddelay ;give LCD some time

MOV A, T_BUFFER ;move sensor data from buffer to accumulator

MOV DPTR, #temp_ones ;address of ASCII code look up table (ones place) MOVC A, @A + DPT R ;store corresponding ASCII code to Accumulator LCALL datawrt ;call display subroutineLCALL lcddelay ;give LCD some time

MOV A, #'.' ;display . symbolLCALL datawrt ;call display subroutineLCALL lcddelay ;give LCD some time

MOV A, T_BUFFER ;move sensor data from buffer to accumulatorMOV DPTR, #temp_dec ;address of ASCII code look up table (dec. place)

MOVC A, @A + DPT R ;store corresponding ASCII code to AccumulatorLCALL datawrt ;call display subroutineLCALL lcddelay ;give LCD some time

MOV A, #0DFh ;display degree symbol LCALL datawrt ;call display subroutine LCALL lcddelay ;give LCD some timeMOV A, #'C' ;display letter CLCALL datawrt ;call display subroutineLCALL lcddelay ;give LCD some time

MOV A, #' ' ;display spaceLCALL datawrt ;call display subroutineLCALL lcddelay ;give LCD some time

threshold_check:

temp_check: ;CHECKING TEMPERATURE THRESHOLD MOV A, T_BUFFER ;read sensor data from bufferCJNE A, #83, t_not_equal ;check for ambient temp (32deg C) SJMP t_within_thresh ;end of threshold checking routine t_not_equal:JC t_within_thresh ;jump to within threshold routine

t_outside_thresh:SETB COOLER ;turn on heaterJB BUZZ, no_buzzSETB BUZZER ;turn on buzzerACALL delayCLR BUZZER ;turn off buzzerSETB BUZZ ;set the buzzer flag high no_buzz:MOV 63h, #' ' MOV 64h, #'O' MOV 65h, #'N'SJMP light_check

t_within_thresh: MOV A,

T_BUFFERCJNE A, #73, ht_off ht_off:JNC light_checkCLR COOLER ;turn off heaterCLR BUZZMOV 63h, #'O' MOV 64h, #'F' MOV 65h, #'F'

light_check: ;CHECKING LIGHT

THRESHOLDS MOV A, LIGHT_LEVELCJNE A, #1, lev2CLR LIGHT1 ;turn off light 1CLR LIGHT2 ;turn off light 2CLR BUZZ1MOV 7Bh, #'O' MOV 7Ch, #'F' MOV 7Dh, #'F'SJMP humid_check lev2:MOV A, LIGHT_LEVEL CJNE A, #2, lev3SETB LIGHT1 ;turn on light1CLR LIGHT2 ;turn off light2ACALL delaybuzzerSETB BUZZ1 no_buzz1:

MOV 7Bh, #' ' MOV 7Ch, #'O' MOV 7Dh, #'N'SJMP humid_check lev3:MOV A, LIGHT_LEVEL CJNE A, #3, lev4SETB LIGHT1 ;turn on light1SETB LIGHT2 ;turn on light2MOV 7Bh, #' ' MOV 7Ch, #'O' MOV 7Dh, #'N'SJMP

humid_check ev4:CLR LIGHT1 ;turn off light1CLR LIGHT2 ;turn off light2CLR BUZZ1MOV 7Bh, #'O' MOV 7Ch, #'F' MOV 7Dh, #'F' humid_check:MOV A, RH_BUFFER ;read sensor data from bufferCJNE A, #40, h_not_equal ;check for ambient RHSJMP h_within_thresh ;end of threshold checking routine h_not_equal:JNC h_within_thresh ;jump to within threshold routine

h_outside_thresh:SETB SPRAYER ;turn on sprayerMOV 73h, #' ' MOV 74h, #'O' MOV 75h, #'N'SJMP moist_check

h_within_thresh: CJNE A,#70, sp_offsp_off: JC moist_check

CLR SPRAYER ;turn off sprayerCLR BUZZ2MOV 73h, #'O' MOV 74h, #'F' MOV 75h, #'F'

moist_check:

CHECKING MOISTURE THRESHOLDS

MOV A, MOIST_LEVEL CJNE A, #1, level2SETB PUMP ;turn on pump

MOV 6Bh, #' 'MOV 6Ch, #'O' MOV 6Dh, #'N'SJMP th_end_check

level2:MOV A, MOIST_LEVEL CJNE A, #2, level3CLR PUMP CLR BUZZ3MOV 6Bh, #'O'MOV 6Ch, #'F' MOV 6Dh, #'F'SJMP th_end_check level3:CLR PUMP ;turn off pumpCLR BUZZ3MOV 6Bh, #'O' MOV 6Ch, #'F' MOV 6Dh, #'F'

th_end_check:end_check: RET

int_isr: ;interrupt routine for LCD buttonMOV IE, #00h ;Disable interrupts PUSH 0E0h ;Push A to stack PUSH 00h ;Push R0PUSH 03h ;Push R3PUSH 04h ;Push R4PUSH 07h ;Push R7PUSH 82h ;Push DPL PUSH 83h ;Push DPHSETB LCD_INTR ;Set flag to check interruptPOP 83h ;Pop DPH POP 82h ;Pop DPLPOP 07h ;Pop R7 from stackPOP 04h ;Pop R4POP 03h ;Pop R3POP 00h ;Pop reg R0POP 0E0h ;Pop AccumulatorMOV IE, #81h ;Enable INT0RET