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Automatic Irrigation System Based on Wireless Network

Genghuang Yang, Yuliang Liu, Li Zhao, Shigang Cui, Qingguo Meng and Hongda Chen

AbstractConsidering the characteristic of irrigation in the

rural area of China, this paper brings forward new devices

based on wireless network, that are GSM (Global System

Mobile) network and radio communication. Three levels are

included in the system: the PC control platform or common cell

phone for surveillance, the controller and the action unit.

Simple GSM modules are available in the PC control platform

and the controller. Orders can be sent from the PC control

platform or cell phone to the controller and the information

such as temperature, soil moisture and air humidity sampled by

the controller can also be sent to the PC platform or cell phone

by GSM message. Emitter and receiver of short-wave radio are

embedded in the controller and the action unit respectively.

Radio communication works between the controller and theaction units. Database of spot information sampled can be

analyzed and browsed by friendly interface in PC. The devices

have been installed in some farms of Mentougou district in

Beijing, capital of China, and Xinjiang, northwest of China.

I. INTRODUCTIONITH the development of technology in water saving

irrigation and automation, automatic irrigation is more

popular in farms in China. Most of the technology and device

comes from other countries such as Israel or America. They

are too expensive to come into common farmers. Always it is

difficult for the farmers to operate. The foreign technology

and devices are only used in farms for experiment ordemonstration by fund of government. Less cost and simple

operation are principles to develop new devices for common

farmers in China.

There are some characteristics in automatic irrigation.

Firstly, the area to irrigate maybe covers several hundreds of

hectares [1][2]. Secondly, the points to irrigate and sample by

sensors spread around [3]. The parameters to sample include

temperature, soil moisture and air humidity. Thirdly, farming

keeps close to soil and wire is difficult to lay out [4]. Fourthly,

the bad conditions such as high temperature by sunlight and

high moisture by drench form the difficulties for devices to

run for a long time. The last factor is that a majority of the

farmers in China are illiterate and have only little ability for

operation and maintenance.

Manuscript received October 29, 2009. This work is supported by

National High-tech R&D Program (863 Program), 2007AA04Z254,

2006AA03Z0418, Tianjin Binhai New Areas Construction Science and

Technology Action Planning Project Supported by Chinese Academy of

Sciences, TJZX2-YW-06, the key project of Tianjin Science and Technology

Planning, 08ZCKFSF03400 and China Postdoctoral Science Foundation,

20090460501.

Genghuang Yang is with the Tianjin Key Laboratory of InformationSensing & Intelligent Control in Tianjin University of Technology and

Education, Tianjin, 300222 P.R.C (phone and fax: +862288181115; e-mail:

ygenghuang@yahoo.com.cn).

Yuliang Liu is with Tianjin University of Technology and Education,

Tianjin, 300222 P.R.C (tjtute@126.com)

,Li Zhao is with Tianjin University of Technology and Education, Tianjin,

300222 P.R.C(jinshihui@163.com)

Shigang Cui is with Tianjin University of Technology and Education,

Tianjin, 300222 P.R.C(cuisg@163.com)

Qingguo Meng is with Tianjin University of Technology and Education,

Tianjin, 300222 P.R.C(ygenghuang@126.com)

Hongda Chen is with the Semiconductor Institute of CAS, Beijing,

100083, P.R.C(hdchen@semi.ac.cn)

From above description, credible communication is the

most important. Wireless communication avoids laying wires

in the soil and is obviously the best way for data transmission.

There are three levels in the devices: the PC controlplatform [5] or cell phone for surveillance, the controller and

the action unit [6][7]. GSM network is the 2nd generation

mobile communication platform. It is credible to transmit

data by GSM network [8]. Once GSM module is embedded in

device or connected to PC peripheral interface,

communication between the PC control platform or cell

phone and the controller can be easily achieved. Short-wave

radio can reach 1-4 kilometers with low power supply. The

controller with an emitter sends signal to the action units with

receivers by radio.

II.

PROCEDURE FORPAPERSUBMISSIONAs the area to irrigate is different from each other, the

devices should be extensible. Even part of the devices can also

work. For a medium scale of several hundreds of hectares,

three levels are included as figure 1 shows.

PC contro l platform

Controller Controller

Action unit Action unit Action unit

Cell phone

Fig.1 Frame of devices in scheme

The first level includes the PC control platform and cell

phone. The controllers are in the second level. The

microprocessor runs in the controller as a core [9]. The

bottom level is made up of the action units. The controller

W

2010 8th IEEE International Conference on

Control and Automation

Xiamen, China, June 9-11, 2010

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decodes the orders from cell phone or the PC control platform

by GSM message and encodes again to send to the action

units by radio communication. One cell phone or PC can

communicate with hundreds of controllers and one controller

can control 1 to 255 action units.

A. Orders for cell phone or PC control platformCell phone and the PC control platform are two ways to edit

order before sending to the controllers. Cell phone is popular

in China and almost everybody can edit and send GSM

message. For PC, the order is stored as a database file. Some

simple clicks of mouse can complete the operation.

A fixed format is applied to make the controller decode the

order easily.

1 2 3 4 5 6 7 8 9 n-1 n

Password Type of order Content of order End

Fig.2 Format of order

As fig.2 shows, checking password avoids disturb from cellphones without authorization. Type of order labels the order

and content of order means the detail operation. At the end of

every order, a symbol denotes the end of this order. Only

Chinese characters, number and punctuations are used in the

order.

The orders can be divided into two types: one is preset

irrigation plan and the other is instant order. The preset plan is

stored in the controller. Once activated, the controller makes

decision of when and where to irrigate by preset plan. For the

different habits of farmers, there are two ways to denote time:

date and weekday. The following shows the detail of the

orders. Two preset plan include:

Preset plan I: preset the interval days to irrigate,

Preset plan II: preset the weekday to irrigate.

The preset plan include:

Valve ID: which valve to open,

Time (hour : minute): when to open,

Minutes: how long to keep valve open.

The instant orders include:

Halt preset plan: closes all the valves opened by preset plan

and inactivates the plan,

Activate preset order: activates or reactivates the preset

plan and the controller runs by the plan,

Run preset plan instantly: opens the valves involved in the

preset plan instantly, always for testing,Delete preset order: closes all the valves involved in the

preset plan, and then sets the plan as blank,

Open valve: opens the valve set in the content of order,

Close valve: closes the valve set in the content of order,

Close all valves: closes all the valves,

Set sensor: sets the thresholds of parameter such as soil

moisture and valve IDs to open or close, so as to form the

feedback to keep the parameter between the thresholds,

Activate feedback: enables the controller to run in feedback,

Inactivate feedback: disables the controller to run in

feedback,

Set prefix: sets the prefix of address, see latter chapter,

Renew password: changes the password,

Set time: sets time in the format of year, month, date,

weekday, hour, minute and second,

Check valve: when this order is received by the controller, thestatus of valves, open or close, will be transmitted to cell

phone or PC,

Check sensor: when this order is received by the controller,

the values of parameters sampled by sensors will be

transmitted to cell phone or PC.

As the GSM message has length limit, 70 unicodes in China,

one order always exceeds the length. One order is divided

into several messages. It is necessary to add the current

section of an order to the last section. An order to combine

GSM messages is available.

B.

Information management on PC control platformAlthough cell phone can browse the data sampled by

controllers, the information is rough and dispersed. If the area

to irrigate is more than one hundred hectares, too much data

results in difficulty to manage the information. Data

processing by PC helps to resolve this problem.

Information management is made up of classification of

data and analysis of data. Data sampled by different sensors at

different time and different points needs to be classified and

stored as history data. Tab I describes the detail. Statistics is

adopted to analyze the history data. When crop data are added

together with sensor data, function between environmental

parameters and crop, especially soil moisture and crop, will be

gained. New layout of sensors and irrigation plan can also be

redesigned. With simple and friendly interface, farmers can

browse the information in CRT after data classification and

analysis.

TABLEI

STATISTICS OF DATA SAMPLED BY CONTROLLER

Point X

Aug.1, 2005 Temperature Soil moisture Air humidity

8:00 31 48 55

10:00 33 49 50

12:00 34 48 50

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C. Controller and sensorsDS1302 GSM module

MSP430F149

Sensor interfaces

24LC26

Radio emitter

module

Fig.3 Structure of the controller

Texas Instruments (TI) MSP430F149 is adopted to be the

microprocessor [10]. The characteristic of this chip is listed as

following: 3.3V power supply and 5 power saving modes,

60Kbyte flash EEPROM, 2Kbyte SRAM, 8 channel 12 bits

AD converters, 2 programmable USARTs and two 16-bit

timers. The structure is as Fig.3 shows.

DALLAS DS1302 [11] is the real-time clock. It

communicates with MSP430F149 with a three-wire serial

interface and supplied from board or by backup battery.

Q24plus GSM module is used in this application which is

produced by Wavecom Co. ltd.. MP-406 produced by

ZhongTian sensor Co. ltd is adopted to be the soil moisture

sensor. Temperature sensor and air humidity sensor are

produced in China Agricultural University. GSM module is

connected to MSP430F149 by RS-232 interface in TTL. The

soil moisture sensors output signal is voltage between 0 to1.12V or current between 0 to 20mA. The temperature

sensors output signal is voltage between 0 to 5V and the air

humidity sensors output is voltage between 0 to 1V.

Connected to the 8 channel 10 bits AD converters, 8 analog

input modules with different scope for different signals are

formed to be the interfaces for sensors. MICROCHIP 24LC64

acts as the accessional EEPROM to store data. MSP430f149

reads or writes 24LC64 by I2C interface. Radio emitter

module is connected to MSP430F149 by only 2 I/O wires, one

for chip selection and the other for pulse control. Solar battery

supplies the power for the controller. When MSP430F149 is

free, it will get into sleep mode to save power.

As only the typical data is available in the converting data

table for sensors. Tab II shows the typical data of mineral soil

moisture sensor MP-406 in this application.

TABLEII

CONVERTING DATA TABLE FORMP-406

VSW%Voltage

(mV)

Current

(mA)VSW%

Voltage

(mV)

Current

(mA)

-5.00 0.0 4.00 55.00 1015 18.50

0.00 120 5.71 60.00 1025 18.64

5.00 210 6.99 65.00 1035 14.785

10.00 310 8.43 70.00 1045 18.93

15.00 415 9.93 75.00 1055 19.07

20.00 510 11.285 80.00 1065 19.21

25.00 610 12.71 85.00 1070 19.28

30.00 720 14.285 90.00 1080 19.43

35.00 825 15.785 95.00 1095 19.64

40.00 895 16.785 100.00 1120 20.00

45.00 955 17.64 105.00 2090

50.00 1005 18.35

When the wire connected to sensor is longer than 50m,

voltage to current converter should be added and current

column is used to compute the VSW%, otherwise the

converter is unnecessary and voltage column is used directly.

The result of AD conversion can be computed to VSW%.

As the types of soil are different from each other, adding of +2,

-2, +3, -3 can amend the difference. The voltage or current are

frequently not exactly the typical data, linear interpolation is

used to compute the VSW%.

Example: if the voltage measured is 782mV, then the

VSW% is:

30.00+(782-720)*(35.00-30.00)/(825-720)=32.95.

The computing for temperature sensor, air humidity sensor

is the same as the above.

D. Action unit

The action unit is used to open or close valve of nozzle and

switch of pump. Corresponding to the radio emitter in the

controller, radio receiver is embedded in the action unit to

form the communication between the controller and the action

unit.

There are two kinds of action unit in use. One is without

microprocessor and the other has a simple microprocessor. Fig.

4 (a) shows the structure of the action unit without

microprocessor. Fig. 4 (b) shows the structure of the action

unit with microprocessor.

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Power saving

module

Relay IRadio receiver

module

Solar battery

Relay II

Relay III

Relay IV

(a)

MSP430F149

Relay IRadio receiver

module

Solar battery

Relay II

Relay III

Relay IV

(b)

Fig.4 Structure of the action unit

As the action units are much more than the controllers, solar

battery costs the most. Power saving by intermittent power

supply can reduce the capability of battery so as to reduce the

cost. When the pulse generated by 555 is low, the solar battery

supplies power to radio receiver module, otherwise power

supply interrupts. In one cycle, the time for low pulse is 1s and

the time for high pulse is 5s.

The improvement of the action unit includes the

microprocessor. As fig. 4 (b) shows, another MSP430F149 is

used to control the valves reliably. The microprocessor costs

little power which has the same function as power saving

module shown in fig. 4 (a).

The above two kinds of action unit are both used in

irrigation.

III. COMMUNICATION MODULES AND OPERATIONA. GSM module

Cell phone or the PC control platform communicates with

the controllers by GSM network. Before the GSM module

transmits a message, it encodes the Chinese characters,

number and punctuations to unicodes. After the GSM module

receives a message, it decodes the unicodes. As number and

punctuation have two types of Unicode, Chinese and English,

the design in software should include two types.

Once the GSM module checks the change of voltage on the

RS-232 interface, it will send a message to cell phone or

another GSM module. When the GSM module receives a

message, it will send the data stream to RS-232 interface and

then desert the message. As the module doesnt have backup

of the received message, the controller should receive data

immediately by interrupt handling. The GSM module can

remember the latest phone number of cell phone or module.

In the next communication, the module will automatically

send the message to the very cell phone or module.

B. Radio communication and operation of action unitThe controller communicates with the action units by radio.

A radio emitter is embedded in the controller and a receiver is

embedded in the action unit. The radio emitter and receiver

work at 433MHz. With the 6V power supply, the receivers at a

distance of 2Km from the emitter can touch the radio without

barrier between them. When the emitter works, the maximal

peak value of current is 1A. The emitter can work 7 seconds

continuously because of high-power and high-heat.

Some device guards against theft also run by radio

communication. Special coding prevents the action unit fromdisturb. Fig.5 describes the format of coding.

128 pulses 20 bits 4 bits

Synchronization Addressing Operation

Fig.5 Format of coding in radio communication

Each bit is made up of 16 pulses. 12 high pulses plus 4 low

pulses denotes bit 1 and 4 high pulses plus 12 low pulses

denotes bit 0 as Fig.6 shows.

12 pulses 4 pulses Bit 1

4 pulses 12 pulses Bit 0

Fig.6 Denotation of bit

The width of a pulse is 90us and a bit is 1.44ms. Coding of

synchronization is made up of 128 pulses: 4 high pulses plus

124 low pulses.

Coding of address includes:

Prefix of address: 12 bits, to avoid disturb,

Address of the receiver: 8 bits, to denote the ID.

The farmers can set the prefix of address by order, see

former chapter. The address of the receiver has 8 bits with 256

IDs. No. 1 to 200 is used to address valves of nozzle and No.

201 to 255 is used to address switches of pump.

The receiver has self-study ability. Push the button on thereceiver and it goes into the status of self-study for 30s. If the

receiver gets pulse synchronization with the emitter in the 30s,

it will store the address as the ID. When the self-study is

completed, the LED on the receiver will flash. The receiver

can store 20 addresses. Pushing the button for 10s, the

addresses stored in the receiver will be erased.

Coding of operation decides the status of relays and then

controls the valves.

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TABLEIII

RELATION AMONG BITS,RELAYS AND VALVES

1st

bit

2nd

bit

3rd

bit

4th

bitRelay

Status

of

relay

Valve

Status

of

valve

I open1 0 x x

II close1 on

I close0 1 x x II open 1 off

III openx x 1 0

IV close2 on

III closex x 0 1

IV open2 off

As Tab III shows, the 1st and the 2nd bit decide to open or

close the relays. The status of the two relays decides to turn

on or off the valve 1. The 3rd bit works in the same way as the

4th bit. One action unit can only control two valves. The

action unit can also be used to start up or shut the pump with

only 1st and 2nd bit or 3rd bit and 4th bit.

IV. SOFTWARE DESIGNThere are two parts in software design, one for the PC

control platform and the other for the controller. For the

application on the PC control platform, database is established

by Microsoft Access 2000. Microsoft Visual Basic 6.0 is used

to operate the database and form the browser of information.

GSM module is connected to PC by RS-232 serial interface.

Microsoft Comm. Control 6.0 (MSComm) simplifies the

communication between application on the PC platform and

the GSM module. Clicks on popup menu by mouse establish

an order with a backup stored in the database. Another click on

button activates the order and sent it to the controller by GSM

message.

For the controller, foreground application and backgroundapplication are included. The following is the flow chart of

the foreground application.

InitialSystem( );

Start:

If (EnablePresetPlan)

{

ReadTime( );/*Get time from DS1302*/

FlagCheckPlan=CheckPlan ( );

/*Check if meet the condition to operate by plan*/

If (FlagCheckPlan)

{

OperationPlan( );/*Open or close the preset valves or pumps*/

}

}

If (EnableFeedback)

{

ADConversion( );/*Start up AD conversion*/

FlagCheckSensor=CheckSensor( );

/*Check if get across the preset thresholds*/

If (FlagCheckSensor)

{

OperationSensor( );

/*Open or close the preset valves or pumps*/

}

}

Goto Start;

From the above description, two parts are included: one forirrigating by preset plan and the other for automatic irrigating

to form feedback.

The background application is interrupt handling: GSM

communication and radio communication. The following is

the flow chart of the background application.

GSMInterrupt( )

{

ReceiveOrder( );

FlagPassword=CheckPassword();/*Check

password*/

If (FlagPassword)/*Password is right*/

{FlagAnalyzeOrder= AnalyzeOrder( );

/* Check and classify the order*/

If (FlagAnalyzeOrder)/*Format of order is right*/

{

ExecuteOrder( );/*Operate by the order*/

}

Else/*Format is error*/

{

OrderErrorHandle( );

/*Send back message to report the error*/

}

}Else

{

PasswordErrorHandle( );

/*Send back message to report the error*/

}

}

RadioInterrupt( )

{

OrderToBit( ); /*Decode order to bits*/

BitToPulse( );/*Decode bit to Pulses*/

90usPulseOut( );

/*Establish pulses to radio emitter module*/

}The radio interrupt handling is enabled in the GSM

interrupt handling when the order requires the controller to

communicate with the action unit, otherwise the radio

interrupt handling is disabled.

The application of the controller and the action unit with

microprocessor are developed by IAR C compiler for

MSP430.

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V. CONCLUSION New devices is brought forwards to used in automatic

irrigation. The application of the devices in some farms for

more than one year proves its feasibility. Also some problems

appear such as misact of relay. The probability going wrong

is 0.3%. As part of the devices can also function well, it is

unnecessary to lay out all the devices especial the PC controlplatform. The solar batters supply power to the controllers

and the action units, so additional power sources and wires

are taken off. Any cell phone can send order to the controllers

or browse the information from the controllers. GSM network

and radio provides credible communication for the devices.

REFERENCES

[1] Ji Xiaohua and Tang Fangpin, The study and development of systemfor automatic irrigation, Irrigation and Drainage, Vol 21, no.4, pp.25-27, Dec. 2002.

[2] Cui Yi, Technology and Application of Water Saving Irrigation,Beijing, China: Chemical Industry Press, 2005, pp. 345-349.

[3] Liu Guihong and Sun Jian, The development and application ofautomatic system for irrigation management, Irrigation and Drainage,Vol. 20, no. 1, pp. 65-68, Mar. 2001.

[4] Li Kai, Mao Hanping and Li Baijun, The development of automaticsystem for irrigation and fertilization, Journal of Jiangsu University ofScience and Technology (Natural Science), Vol. 22, no. 1, pp. 12-15,Jan. 2001.

[5] Wang Weimin, Ran Gangjun and Guo Qinhai, Thecomputer-controlled management system of water-save irrigation,Water Conservancy & Electric Power Machine, Vol.23, no.1, pp.51-52,Feb. 2001.

[6] Yang Genghuang, Guo Kairong and Li Yawei, Development ofcontroller for automatic irrigation based on GSM network, Journal ofShenyang Agricultural University, Vol. 36, no. 6, pp. 753-755, Dec.2005.

[7] Gao Qiang, Wang Hehui and Hang Shuming, Research of greenhouseenvironment intellectual control system, Water Saving Irrigation, Vol.30, no. 4, pp. 35-37. Aug. 2005

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[9] Li Rui, Yang Jun and Gu Haiying, The Application of Microprocessorin Automatic Irrigation and fertilization, Journal for Application ofComputer, Vol. 21, no.8, pp. 219-221, Aug. 2001.

[10] TI Inc (2005, Mar): Data Sheet of MSP430X14X [Online]. Available:http://www.TI.com

[11] Maxim Inc. (2005, Mar): Data Sheet of DS1302, [Online]. Available:http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2685.

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