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S.T. Sanamdikar et al. / IJAIR ISSN: 2278-7844

© 2012 IJAIR. ALL RIGHTS RESERVED 131

AUTOMATION IN POLYHOUSE USING

PLC

S.T.Sanamdikar#¹, V.G.Suryawanshi²*S.S.Shete#³

Instrumentation& Control Dept. PDEA’s, COEM, Pune.INDIA

[email protected]

Abstract : Agriculture is the backbone of our country. The available management is not sufficient to that of requirement.

Today the farmer themselves manages all the things which crop requires, but every person do not have the exact knowledge of

the quantity and the time to apply to the crop. So here we have developed the system that will manage the temperature, humidity

and intensity for the crop one year using the Programmable logic controller (PLC). Every seeds manufacturing company as well

as regional agricultural colleges provide the yearly scheduled for the crop. Our system will take this as the input through the

program and then it will maintain temperature, humidity and intensity of polyhouse.

We can achieve desire results with the help of PLC. Using PLC we want to develop an automated continuous process

system for maintaining the house. Though the process seems to be simple but degree of automation is higher for proper operation

of a system. In this paper, we are discussing how we are going to develop this system, what is the basic theme of this project and

how our ideas will be applicable to the theme. We have designed a control system. We are detailing areas which are more

important to instrumentation and control engineer. The purpose of the project is to grow a crop in any climatic conditions at any

time. Proper design, selection, construction and management of the polyhouse and upgrading, construction of polyhouse using

sensors will give effect to house.

I. INTRODUCTION:-

At this point in time, the world’s pollution problem

has led to unpredictable weather conditions all over

the world. With these ever changing weather

conditions, it is expected that the number of

polyhouses will significantly increase in the near

future, thus leading to a great demand for automated

polyhouse monitoring systems .The main goal is to

build a miniature polyhouse which is equipped with

an automatic monitoring system. This monitoring

system will constantly monitor the conditions in the

polyhouse to ensure that it remains at preset

temperature, light humidity conditions.

If these conditions differ from the preset levels, the

monitoring system will automatically turn on certain

devices to return the polyhouse to the required

conditions.

Automatically control the crop growing environment

within the walls so that any type of plants can be

grown all year round. Eliminates the risk of the

polyhouse not being kept at crop specified conditions

due to human error. Minimizes the labor costs crop

involved in maintaining a playhouse. Customer will

be able to define their crop preferred polyhouse

conditions and have the system function as specified.

This will be a “plug-and play” product..

Detect temperatures from -40°C to 125°C. Maintain

a temperature of about 10°C to about 40°C. Detect

humidity between 5% RH and 95% RH. Maintain a

humidity of about 40% to 80% RH. Detect sunlight

and artificial light. Turn on artificial lighting in the

event that there is insufficient light.

1.1 Overall design:-

For our Automated Polyhouse Monitoring System,

we are implement 3 types of sensors. The sensors to

be used are photodiodes, a temperature sensor and a

humidity sensor. We are building a miniature

polyhouse and determine the appropriate positions to

place the sensors. A series of tests will be done to

make sure that all the sensors are working

accordingly. These sensors will be connected to a

PLC which will function as the main control unit.

The sensors will send signals to the plc and the plc

will translate the signals and determine if the input is

within the preset range. For instance, if the preset

temperature range is from 20°C to 25°C, the plc will

make sure that the polyhouse temperature is within

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this range. If the temperature exceeds the maximum

value, the plc will then turn on the fan. If the

temperature drops below the minimum value, the

bulb will turn on. As for the photodiode, if the

polyhouse is exposed to insufficient light, it will send

a signal to the plc. The plc will then process the

signal and turn on the artificial light in the polyhouse.

As for the humidity sensor, it will detect a change in

humidity levels of soil and send a signal to the plc. If

the humidity level is not within the required range,

the water supply will be turned on or off. The plc will

be the central processing unit which will translate the

input signals from the sensors and turn on or off the

necessary devices to maintain the polyhouse at the

preset levels.

“To maintain environmental conditions inside the

house for better production of crop with the help of

PLC which make it suitable for productive uses and

help improve crop quality and quantity.”

II FORMULATION OF PROBLEM:

Agriculture has a vital role in our economy.

About 40 to 50 percent of our population depends on

the agriculture and its related field for their survivor.

The available management is not sufficient to that of

requirement. In manual system there is wastage of

water & fertilizers provided to the crop. In manual

system there is damage to crop because of heavy rain

or high temperature. The manpower required is more.

The process is time consuming. Maintenance is

required.

Thus we have developed the system that will

manage the temperature, humidity and intensity for

the crop with less manpower using Programmable

logic controller.

III SYSTEM IMPLEMENTATION:

The block diagram of “Automation in polyhouse

using PLC ” is shown in figure (III.1). Details of each

block are given below.

a) BLOCK DIAGRAM DESCRIPTION:

1. Programmable Logic Controller:

We will use PLC uses 24V dc power supply.

Actual programming is stored in the PLC.

2. Humidity:

We will use humidity sensor for sensing the

humidity of soil. After that this signal is

send to plc. In that plc a particular set point

is given and if it is below or above it take

action likewise.

3. Temperature:

We will use thermocouple as temperature

sensor. Temperature is sense an after that

this signal is send to plc. In that plc a

particular set point is given and if it is below

or above it take action likewise.

4. Intensity:

Intensity will be sense by photodiode. If

intensity of sun increases then green net is

used for reducing the intensity using plc.

5. Cooling Pad

The cross fluted cellulose pad is

preferred. These are available mostly in

100mm thickness. One meter of pad height

is given for every 20m of pad to fan

distance. However, the fan to pad distance

should not exceed 60m.The air flow rate

should be of 75 cubic meter/minute/sq.m of

pad. The water flow rate should be of 9 liters

per minute/linear meter pad. The uniform

distribution of water on pad is to be

maintained.

6. Exhaust Fan:

The fans should deliver the required air

at 15mm static pressure. The maximum

center to center spacing between the two

fans should be of 7.5m. The height of the

fans is to be determined based on the plant

height which is proposed to be grown in the

greenhouse. The fan blades and frame are to

be made of non-corrosive materials like

aluminum/stainless steel.

7. Relative humidity control:

The humidistat coupled to water

circulating pump to control the relative

humidity of soil. Here we maintain the

relative humidity of soil. This is one type of

watering system in this soil sensor is use to

find out humidity in soil and if it is less then

motor pump start and water is giving to the

soil.

8. Light intensity control:

In certain areas where natural

illumination is absent or very low,

illumination for plants may be provided by

artificial sources. Incandescent bulbs

generate excessive heat and are

unsatisfactory in most instances. Fluorescent

tubes are useful as the sole source of light



for African violets, gloxinias and many

foliage plants which grow satisfactorily at

low light intensities. Excessive light

intensity destroys chlorophyll even though

the synthesis of this green pigment in many

plants is dependent upon light.

Chrysanthemum is a classic example for a

short-day plant. However, flower buds will

not form unless the night temperature is high

enough. Chrysanthemum is flowered on a

year-round basis as a cut flower or potted

plant simply by controlling the length of day

and temperature.

IV: SOFTWARE DESIGN:

This chapter is basically gives the details of

software. The main software is PLC and in this

chapter it gives the details of which PLC is use and

the ladder diagram

a) Flow chart: flow chart of above system as shown

in figure IV-1.

b) Programming Logic Controller :

Control engineering has evolved over

time. In the past humans were the main methods for

controlling a system. More recently electricity has

been used for control and early electrical control was

based on relays. These relays allow power to be

switched on and off without a mechanical switch. It

is common to use relays to make simple logical

control decisions. The development of low cost

computer has brought the most recent revolution, the

Programmable Logic Controller (PLC). The advent

of the PLC began in the 1970s, and has become the

most common choice for manufacturing controls.

PLCs have been gaining popularity on the factory

floor and will probably remain predominant for some

time to come. Most of this is because of the

advantages they offer.

Now why only PLC? We use PLC

because it is capable of handling large no of inputs

without need of human interfacing. Once it is

correctly programmed the operator doesn’t have to

bother about the process.

• Cost effective for controlling complex systems.

• Flexible and can be reapplied to control other

systems quickly and easily.

• Computational abilities allow more sophisticated

control.

• Trouble shooting aids make programming easier

and reduce downtime.

c) Manufacturers of PLC:-Allen

radley.Siemens.Mitsubishi.Honeywell.Fanuc.Toshi

ba.Anshuman. In our system the PLC program is

going to control the valve i.e. is amount of acid or

base is to be adding into treated water. It also controls

the positions of all the levels of the different tanks in

the process. This will help to control the system

smoothly.

IV.2 Basic Elements of PLC:

PLC mainly consists of a CPU, memory areas and

appropriate circuits to receive input/output data. We

actually consider the PLC to be a box full hundreds

and thousands of relays, counters, timers and data

storage locations. They don’t physically exist but

rather they are simulated and can be considered as

software counters, timers, etc. Each components of

PLC has specific function.

Input relays (contacts):- These are connected to

outside world. They physically exist and receive

signals from switches, sensors, etc. Typically

they are not relays but rather they are transistor.

Internal Utility Relay:- These do not receive

signals from outside world nor do they

physically exist. They are simulated relays and

enables PLC to eliminate external relays. There

are also some special relays that are dedicated to

perform only one task. Some are always on

while some are always off. Some are on only

once during power-on and typically used for

initializing data that was stored.

Counters:- These are simulated counters and

they can be programmed to count pulses.

Typically these counters can count up, down or

both. Since they are simulated they are limited to

their speed. Some manufactures also includes

high speed counters that are hardware based. We

can think it as a physical existence.

Timers:-These come in many varieties and

increments. Most common type is on-delay type.

Others includes off delay and both retentive and

non retentive type. Increment varies from

1milliseconds to 1 second.

Output relays:-These are connected to outside

world. They physically exist and send on or off

signals to solenoids, lights, etc. They can be

transistors or relays depending upon their model.

Data storage:- Typically there are resisters

assigned simply to store data. They are usually

used for temporary storage for math or data

manipulation. They can also be used to store data

when power is removed from the PLC

Languages in PLC:

1. Ladder DiagramFunctional Block

Diagram.Structural text .Instruction List

2. Sequential functional chart



Ladder Diagram:

The ladder diagram has and continues

to be the traditional way of representing electrical

sequences of operations. These diagrams represent

the interconnection of field devices in such a way that

the activation or turning ON, of one device will turn

ON another device according to a predetermined

sequence of events. Figure IV-2 illustrates a simple

electrical ladder diagram. The original ladder

diagrams were established to represent hardwired

logic circuits used to control machines or equipment.

V Testing and Result analysis:

a. Testing of solenoid valve:-

All solenoid valves were tested and verified

by giving them a supply of 24V and a pressure of

1.2Kg/cm2. It was verified that all of them open

when a supply of 24V was given to them. Specific

problem encountered during valve testing was that

diaphragm one of the solenoid valve was damage

which needed replacement.

b. Testing of switches:-

All switches were tested by giving them 24V supply.

All of them have been working fine

c. Testing of Transmitter:-

Transmitter was tested by giving 24V supply. It has

been working fine

d. Testing of Agitator and conveyor motor:-

A motor 24V DC supply is given to

agitator and conveyor motor in order to test it. The

agitator available in the lab has been working nicely

without any error.

e. Testing of pump and automating it:-

The pump had to be tested for its working

and efficiency. We also needed to automate the

pump. The pump is automated by connecting a relay

of 24V to 230V so that once you connect the pump

wiring to the relay, the pump starts as soon as a 24V

signal is given to it by the PLC.

f. Testing of process wiring and troubleshooting it:-

The crux of all troubleshooting was testing

of through process wiring. The entire system had to

be connected to the PLC. In numerable problems

were encountered in this process specially like. Wire

not been connected to the proper port. Wires all

connected at wrong points either on the junction box

and terminal strips. Few instruments were not

connected to the PLC.

V.2 Results:

In this way we maintain the environment of

polyhouse using PLC and sensors.

In this way after taking lots of efforts we are

successful to make automated Polyhouse. PLC

have some Digital as well as some Analog input

after sensing them it will take the decision as per

ladder logic and handle number of digital outputs

for polyhouse.

Due to automation there is no necessity of

number of worker to handle farm. Only one trend

person will easily handle the polyhouse.

VI: Conclusion:

In this paper we can say that automation in

polyhouse is not easy as it seems. It has great

importance in farm as well as in society. During this

project we realize that environment control processes

are very precise and well controlled. Using PLC

techniques we can automate the whole polyhouse. As

we see crop is one of the important parts of all of us

and to increase the crop polyhouse is best option. In

this way we will make automated polyhouse using

plc. And we provide farmers a new world of

technology. Because of this project farmer will

become rich and everyone who think that farming is

from village people or illiterate people they will also

do farming and improving this system.

REFERENCES

1. Clarence A. Phipps, “Fundamentals of electrical control”,

Publisher The Fairmont Press, Inc., 1999, Edition2, illustrated,

213, Page no.162,164,165. 2. Ramakant A. Gayakwad, “Op-Amps and Linear Integrated

Circuits”, Publisher PHI prentice hall India, Fourth Edition, 543,

Page no.438,439 3. Gary Dunning, “Introduction to Programmable Logic”

Controllers, Edition third, 628 .

4.Agricultural Statistics at a Glance (2008), Department of Agriculture and Cooperation, Ministry of Agriculture, Government

of India.

5. A. Rokade, “Assistance and Control System for Polyhouse Plantation”, M. Des. Thesis, IDC IIT Bombay (2004).

6. T. Ahonen, R. Virrankoski, M. Elmusrati, “Greenhouse

Monitoring with Wireless Sensor Network”, IEEE / ASME International Conference on Mechatronic and Embedded Systems

and Applications, pp. 403-408, 2008

7A. Joshi, N. Madame, “System for Polyhouse Farmers and Consultants”, 3rd India International HCI Conference, USID

Foundation, 2009, Hyderabad, India.



INPUT SIDE OUTPUT SIDE

Figure III.1 Block diagram of the system

Figure IV.3: Basic elements of PLC

Temperature

sensor

PROGRAMMABLE

LOGIC CONTROLLER

Humidity sensor

(soil)

Intensity

Sensor

Exhaust fan

Motor pump for feeding water

Bulb for increase temperature

Dc motor for opening and closing of

green net

POWER SUPPLY



Figure IV.1 FLOW CHART



Figure: IV-2Ladder Diagram

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