Field of Invention
The present invention relates to an automated irrigation system to irrigate agricultural
plots with reference to conditions such as soil moisture levels and or time. The system is
adapted to facilitate monitoring and controlling the irrigation process based on soil
moisture content and /or duration thereby avoiding the ill effects of over & under
irrigation.
Background and Prior art
Computer controlled irrigation systems are known. They supply water to the field on
basis of volume or time or soil moisture status. Some of these irrigation systems are able
to take feedback from the field. The known automated irrigation system can be classified
based on the type of control unit or the scope of control. On the basis of type of control
unit an automated irrigation system is classified into
I. Sequential Type and
II. Non Sequential Type.
The Sequential type is again classified into
1. Hydraulically operated
2. Electrically operated
3. Combination of above two methods.
The Non Sequential type is again classified into
1. Feed back control system
2. Inferential control system
3. Combination of above two methods with time based control.
On the basis of the scope of control an automated irrigation system is classified into
I Spot automation
II Local automation
III Central automation
However such known systems suffer from certain drawbacks. These systems are very
expensive and not suitable for small farm size. The criterion used in the computer
program for scheduling irrigation is not known i.e. the exact circuitry, source code for
operating such systems, mode of operation and basis of scheduling irrigation are not
available. In addition the existing systems are assembled by different components (i.e.
high speed data logger), which are not as per requirements. Also option for soil moisture
and time based irrigation scheduling is not available in some systems.
Objects of invention
It is thus the basic object of the present invention to provide computer controlled cost
effective irrigation system essentially based on soil moisture and duration of irrigation to
thereby provide for effective control over the irrigation process.
Another object of the present invention is directed to provide a computer controlled
irrigation system suitable for automated irrigation of small, medium and large size farms
which employs different lower and upper limits of soil moisture content for starting and
stopping irrigation at different stages of a crop and also for different crops.
Another object of the present invention is to provide for an automated irrigation system
adapted to set the priority incase two or more plots require irrigation at the same time.
Another object of the present invention is to save water as the system starts and stops
irrigation at the right time
Another object of the present invention is to prevent leaching of minerals and nitrogen
vital for healthy growth of plants and eliminate the long-term ill effects of over irrigation
leading to development of salinity.
Yet another object of the present invention is to provide adequate quantity of water and
nutrients supply to crops to result in quality produce and high yield.
A further object of the present invention is to save labour cost involved with manual
operation and eliminate the need to visit farm at odd hours.
Summary of invention
Thus according to the basic aspect of the present invention there is provided an
automated irrigation system comprising:
a frequency generator circuit adapted to generate selective operative frequencies to a
sensor means;
said sensor means adapted to sense the soil moisture level at the said selective frequency
to generate voltage signals corresponding to the sensed soil moisture content;
inteilacing circuitry operatively connected to such sensor means and to a \alve operating
circuit and microprocessor/ computer means adapted it) supply water based on said soil
moisture content sensed by the sensor.
The distinguishing feature of the above system of the invention is its low cost, simple
design and robustness. The system can be adapted to store databases for the commonly
grown crops and operate based on such input data. Further it can adjust irrigation
schedule as per the growth stage of the crop. In addition the system has provision to keep
history files record of starting and stopping of irrigation and volume of water supplied to
each plot. Moreover it would have the option for time and soil moisture based irrigation
scheduling.
Sensor Based Irrigation-With the present invention multiple plots can be irrigated at a
time based on the signals from the sensors in the different plots. The precise level of
moisture content for each plot can be calculated. The irrigation starts and stops taking
into account the upper and lower limits of moisture set for each plot and priorities set for
different crops.
Time Based Irrigation - For time based irrigation scheduling there are options of
operating either at regular time interval or at particular date and time.
Moreover the sensor based irrigation system of the present invention takes into account
effective rainfall as well rain forecast for scheduling irrigation.
Detailed Description
The system developed has different strategies to operate the irrigation system. It converts
1 the voltage read from the sensor into soil moisture content and accordingly assesses the
need to irrigate or not to irrigate the fields and gi\es directions.
The system of the present invention basically comprises a frequency generator circuit
which is provided with means to generate certain frequency wave using integrated
circuits, resistances and capacitors; a sensor circuit with means to generate frequency that
are passed through soil moisture sensors in the various plots and to amplify the weak
signals from the sensors using amplifiers to be fed into integrated circuit; an interfacing
circuit comprising an eight -bit Analogue to Digital converter with multiplexing
capability for input channels coming from the sensor circuit which is interfaced to
parallel port of computer which access the input channel as well as the integrated circuit
with demultiplexing capability for output channels to the valve operating circuit; and a
valve ^operating circuit carrying output from the interfacing circuit through integrated
circuits , amplifying them using amplifiers and then connecting to DC relay coils for
operating solenoid valves which in turn are activated or deactivated in order to irrigate
the plots as per pre set operations of the device driver..
The automated irrigation system of the present invention comprises of the following:
Sensor circuit: The signals generated in the frequency generator circuit are made to 12
volts using amplifiers and passed through soil moisture sensors. The sensor used in the
present invention is of Granular Matrix type Soil Moisture sensor. The said granular
matrix type sensor comprises of a perforated wire mesh cover, pipes supporting the
gypsum wafer, a nylon cloth between the wafer and the outer mesh cover and electrodes
spaced from each other with the granular matrix in between. This sensor can be used only
for sensing soil moisture, which provides output in voltage for corresponding soil
moisture status and the calibration curve, plotted between voltage and soil moisture is
independent of time and salt content of soil and water. Another amplifier is used to
amplify the weak signals coming from the soil moisture sensor and pass into an
integrated circuit for sample and hold purpose and transmit them to the interfacing circuit
as input signal from each plot. The sensors are thus connected through proper interfacing
circuit to a personal computer with a program tojake irrigation scheduling decisions.
Frequency generator circuit: The frequency generator circuit employs integrated circuits
and various resistors and capacitors to generate 12 volt square wave at a certain
frequency. This circuit provides the sensor circuit with the optimum frequency to operate.
Interfacing circuit: The standard bi-directional parallel port has been used for interfacing
.The main part of the interfacing circuit is the eight-bit Analogue to Digital Conversion
chip (ADC) with multiplexing capability for eight input channels. Analogue signals from
0 to 5 volts can be converted to eight bit digital signals, which can be suitably interfaced
to parallel port of the computer. Any one of the input channels can be accessed by three
bits and addressed by pin numbers of the parallel port. The same pins are used for
addressing integrated circuit (3- 8 line Decoders / Multiplexer) with a demultiplexing
capability for eight channels to operate the irrigation valve via a 12 volt DC relay.
Valve operating circuit: The output from the integrated circuit of the interfacing circuit is
inverted using another integrated circuit and then made 12volts by an amplifier and
connected to the 12 volt DC relay coil for operating solenoid valves at 220 volts AC.
The invention is now described in greater detail in relation to non-limiting exemplary
illustration of the irrigation system of invention in relation to the accompanying figures
wherein:
Fig 1: Circuit diagram showing different components of the automated irrigation system
Fig 2: Flow chart describing the preferred manner of irrigation scheduling
Fig 3: Different components of the automated irrigation system and their layout
Reference is now invited to figures 1 & 2 regarding the description of the circuits and the
functioning of the automated irrigation system as per the present invention.
The frequency generator circuit is shown in Fig. 1, which makes use of IC 555 and
various resistors and capacitors to generate 12-volt square wave at certain frequency
(Fig. 1 Shows circuit for 100 Hz).
The generated signals from the frequency generator circuit are then transmitted to the
sensory circuit. Here they are amplified to 12 volt using the first amplifier Op Amp and
passed through soil moisture sensor. In order to assess the soil moisture status from eight
different plots, soil moisture sensors are read at certain frequency ranging from 50 Hz to
1MHz Moreover the frequency of current for reading the sensor can be changed without
change in the interfacing circuits. The second amplifier OpAmp is used to amplify the
weak signals coming from the soil moisture sensor and fed them to IC 398 for sample and
hold purpose as shown in the Fig. 1
The interfacing circuit has the eight-bit jAnalojgue to Digital Conversion (ADC) 0808/
0809 means with multiplexing capability for eight input channels. 0 to 5 volts analogue
signals can be converted into eight bit digital signals, which can be suitably interfaced to
parallel port of the computer. In Fig 1, IN 0 to 7 indicates the connection point of the
eight input analogue channels, coming from the eight sensory circuits of the eight plots as
mentioned earlier, which is converted to digital format. Any one of the channel numbered
0 to 7 can be accessed by three bits (A, B, C in Fig. 1) addressed by pin no 1, 14 and 16 of
the parallel port. The same pins are used for addressing integrated circuit (IC) 74LS138
(3-8 line Decoders/Multiplexer) with a demultiplexing capability for eight output
channels. The IC 74LS138 is put to action when pin 17 of the parallel port (connected as
shown in the Fig. 1) is made high and ADC 0808/0809 is put to action when pin 17 is
made low.
The out put of the IC 74LS138 from the interfacing circuit is transmitted to the valve
operating circuit for each plot where it is inverted using IC 74LS04 and then made 12
volts with the help of OpAmp 741 and connected to the 12 volt DC relay coil for
operating solenoid valves at 220 volts AC and thus irrigate the fields as per need.
A device driver program is adapted to perform the following functions:
(i) Addressing 0808 Multiplexer for reading sensors.
The ADC contains an 8-channel single-ended analog signal multiplexer. A particular
input channel is selected by using the address decoder. Table 1 shows the input states
for the address lines to select any one of eight channel. The address is latched into the
decoder on the low-to-high transition of the address latch enable signal Fig. 1. In order
to operate the addressing the device driver first send positive pulse to Address Enable
Latch (AEL) pin of ADC through pin number 17 of parallel port and then send three
bit addressing code to pins number 1,14 and 16 of parallel port which are connected
to the pin A, B and C of ADC.
(ii) Reading the eight bit signal
After enabling the a channel to be read its analog input is converted in to eight bit
digital format by ADC, which is read by device driver through pin number 2-9 of the
parallel port. This value is written in to a file, which can be accessed by main
program.
(iii) Addressing the demultiplexer 74LS138 for operating the solenoid valves
After processing the information
about the soil moisture content of
different plots the main program will
send instructions to the device driver
about the opening and closing of the
irrigation valves. Based on this, the
device driver after enabling the
demultiplexer 74LS138(3-8 pin
decoder/demultiplexer), sends a
three bit address of the channels to
be put On or Off through the pin no
1, 14 and 16 of the parallel port that
are connected to the addressing pins
of the multiplexed.
Irrigation Decisions
The system developed in the present invention can be adapted to be integrated with
compatible software. It has certain distinguishing features and its operation for irrigation
decisions is shown through the flow chart in fig2
The system developed will have different strategies to operate the irrigation system and h
uses the calibration curve for the sensor to convert the voltage in to soil moisture content
.The irrigation decision will be taken based on set upper and lower limits of soil moisture
which may vary depending on the crop as well as the stages of the crop. The system has
provision to keep the history files of starting and stopping the irrigation and variation of
soil moisture with the time for different plots.
The user will have option to set the upper and lower limits of soil moisture for each plot
manually or it will be set automatically from the database of water requirement of crops
provided with the software .He can set the priorities for different crops based on which
the program will decide which plot to irrigate in case of two or more plots demand
irrigation at the same time. Moreover the time period for reading the sensor will be set by
the user.
Description of the preferred manner of working of the irrigation system as per the
flowchart (fig 2)
Initially the system displays four options:
1. Setting
This button is for setting the various options regarding irrigation at the eight
different plots (The number of plots can be increased if required). First window
under the setting option asks the user to choose from
i. Time based Irrigation
If time based irrigation is chosen for a particular plot it prompts the user to
enter time base irrigation schedule i.e.
a) the starting date, starting time and
b) stopping time of irrigation.
The user can enter as many irrigation schedules as desired.
The software makes the following checks at the time of entering an
irrigation schedule.
a) Check for expired date i.e. It prompts user, if he has entered an
already expired date.
b) Check for expired time i.e. it prompts user, if he has entered an
already expired time for a particular date.
c) Check and prompts for clash/overlapping with previously
entered schedule
ii. Sensor based Irrigation
Selecting soil moisture based irrigation scheduling, the software asks for
a) Lower limit of the soil moisture content at which to start irrigation.
b) Upper limit of the soil moisture content at which to stop irrigation.
c) Date of sowing and
d) Rain forecast
After completing the setting the 'Done' button is pressed which take the user back
to first window.
2. Run
Pressing this button passes the control to the part of software, which takes care of
running the above set irrigation scheduling as described in the flow chart Fig.
No.2. Program starts execution from box labeled nol. Box no 2 shows that
program has previously stored data base for crop water requirement of some
commonly grown crops as well as the calibration curve of soil moisture vs. sensor
that is used for scheduling irrigation in case of sensor based scheduling. In box no
3 Rain forecast is used to stop irrigation if there is probability of rain on particular
day. Upper and lower limit of irrigation, starting and stopping time of irrigation,
date of sowing are used as explained above in the setting. For timer based
irrigation starting and stopping time of irrigation are used. Box no. 4 sets the
current irrigation demand for all the plots to "No" (Id[n] = 0). Box no. 5 reads the
voltage output of the soil moisture sensor for all the plots. Box no. 6 converts the
voltage read from the sensor to their equivalent soil moisture with the help of
previously fed calibration curve. Box no 7 & 8 if the soil moisture content values
read by sensor is less than the set lower soil moisture value or the set start time for
irrigation is equal to the current time the irrigation for that plot is made from 0
(No) to l(Yes) as shown in the box 9. Box no. 10 denotes a command to call an
; executable program, which interacts with the interfacing circuit to operate
solenoid valves and sense soil moisture. Box no. 11 represents the executable
program. When all the scheduling data for all the plots are read the device driver
function is called which opens the solenoid valves (Box. No 13) for the given
plots with the irrigation demand as l(Yes), and priority higher than the other plots
(as checked in the box. No. 12) which have irrigation demand as 1 (Yes). Box No
15. for stopping the irrigation, in case of soil moisture based irrigation the soil
moisture status from the soil moisture sensors and in case of time based irrigation
the stopping time from the file is read and the irrigation is stopped in case the
current soil moisture is more than or equal to the upper soil moisture limit and
current time is equal to the stopping time.
3. View History
It shows the Time Vs soil moisture content of plots and starting and stopping time
of irrigation.
4. Exit
A typical diagram of the complete system with four sub-units is shown in fig. 3
Here it is seen that each sensor in each of the four sub-units of the farm is connected via
communication line to the interfacing unit The interfacing unit, through parallel or series
port, communicates with the computer or the microprocessor. The information is
processed here and accordingly the instructions are send out. Accordingly the parallel or
series port carries them to the interfacing unit. From here another set of communication
lines carry the instructions to the solenoid valves that are fitted to the water lines coming
from the irrigation pump. Accordingly the valves are opened or closed to start and stop
the irrigation respectively as the need may be.
We Claim:
1. An automated irrigation system comprising:
a frequency generator circuit adapted to generate selective operative frequencies
to a sensor means;
said sensor means adapted to sense the soil moisture level at the said selective
frequency to generate voltage signals corresponding to the sensed soil moisture
content;
interfacing circuitry operatively connected to such sensor means and to a valve
operating circuit and microprocessor/ computer means adapted to supply water
based on said soil moisture content sensed by the sensor.
2. The automated irrigation system as claimed in claim 1 comprising:
said frequency generator circuit provided with means to generate certain
freauencv wave length;
said sensor means comprising a sensor circuit adapted to operate based on the
generated frequency and soil moisture sensors to sense soil moisture from various
plots and generate output voltage corresponding to sensed soil moisture status ;
said interfacing circuit comprising multiplexing means for input of soil moisture
voltage signals and demultiplexing means for generating corresponding outputs
to said valve operating circuit; and
said valve operating circuitry operatively connecting the output from the
interfacing circuit to solenoid valves, which in turn are activated or deactivated
for supply of desired irrigation water.
3. The automated irrigation system as claimed in claim 2 wherein:
said frequency generator circuit comprises of integrated circuits, resistances and
capacitors to generate the said frequency ;
said sensor means comprising sensory circuit having means to amplify the
generated frequency from the frequency generator circuit, sensors adapted to
sense the soil moisture and convert to corresponding voltage and second amplifier
to amplify the signals and an integrating means for sample and hold purpose;
said interfacing circuit comprising an eight -bit Analogue to Digital converter, for
the said multiplexing activity, which is interfaced to parallel port of a computer
adapted to access the input channels as well as the integrated circuit with the said
demultiplexing activity; and
said valve operating circuit comprising integrated circuit to receive the said
output, amplifiers to amplify them and DC relay coils for operating the said
solenoid valves.
4. The automated irrigation system as claimed in any one of the above claims for
irrigating multiple plots comprising :
a frequency generator circuit adapted to generate selective operative frequencies
to sensor means for each said plot;
each said sensor means adapted to sense the soil moisture level at the said
selective frequency to generate voltage signals corresponding to the sensed soil
moisture content for each plot;
interfacing circuitry operatively connected to such sensor means and to a valve
operating circuit adapted to supply water based on said soil moisture content
sensed by the sensors for each ploL_
5. The automated irrigation system as claimed in any one of the above claims for
irrigating multiple plots comprising :
a frequency generator circuit adapted to generate selective operative frequencies
to sensor means located at each said plot;
each said sensor means adapted to sense the soil moisture level at the said
selective frequency to generate voltage signals corresponding to the sensed soil
moisture content in the respective plots;
interfacing circuitry operatively connected to such sensor means and to a valve
operating circuit adapted to supply water based on said soil moisture content
sensed by the sensors in each plot.
6. The automated irrigation system as claimed in any one of the preceding claims
wherein the frequency generator circuit is adjusted to generate 12 Volt square
wave at selected frequency levels to be transmitted to the sensor circuit.
7. The automated irrigation system as claimed in claim 4 wherein the said frequency
generator circuit is adapted to generate frequency in the range of 50 Hz to 1 MHz.
8. The automated irrigation system as claimed in any one of the preceding claims
wherein the first amplifier of the sensor means amplifies the frequency generated
by the frequency generator circuit to 12 Volts which is passed through soil
moisture sensor.
9. The automated irrigation system as claimed in any one of the preceding claims
wherein the said sensor of the sensor means senses the soil moisture status from
each of the plots.
10. The automated irrigation system as claimed in claim 8 wherein the said sensor is
granular matrix type.
11. The automated irrigation system as claimed in claim 9 wherein the said granular
matrix type sensor comprises of a perforated wire mesh cover, pipes supporting
the gypsum wafer, a nylon cloth between the wafer and the outer mesh cover and
electrodes spaced from each other with the granular matrix in between.
12. The automated irrigation system as claimed in claim 10 wherein a stable
calibration curve is plotted between voltage and soil moisture, which is
independent of time and salt content of soil and water.
13. The automated irrigation system as claimed in any one of the preceding claims
where in the second amplifier of the sensory means amplifies the signals from the
said sensor and pass them to the integrated circuit.
14. The automated irrigation system as claimed in any one of the preceding claims
wherein the said integrated circuit of the sensor means receives the amplified
signals from the said sensor for sample and hold purpose and transmit them to the
interfacing circuit as input signal from each plot.
15. The automated irrigation system as claimed in any one of the preceding claims
wherein the Analogue to Digital Conversion means with multiplexing capability
is adapted to receive analogue input signals from each plot and convert them to
digital signal and interface them to the parallel port of the computer.
16. The automated irrigation system as claimed in claim 14 wherein the Analogue to
Digital Conversion means converts analogue signals that are in the range of 0-5
volts.
17. The automated irrigation system as claimed in any one of the preceding claims
wherein the said parallel port of the interfacing circuit is adapted to access any
one of input channels as well as the integrating circuit.
18. The automated irrigation system as claimed in any one of the preceding claims
wherein the integrating circuit of the interfacing circuit is provided with
demultiplexing capability for the output channel for each plot
19. The automated irrigation system as claimed in any one of the preceding claims
wherein the integrated circuit of the valve operating circuit inverts the output from
the interfacing circuit.
20. The automated irrigation system as claimed in any one of the preceding claims
wherein the amplifier of the valve operating circuit amplifies the said signals to
12 volts which is conveyed to the 12 volt DC relay coil for operating the solenoid
valves.
21. The automated irrigation system as claimed in claim 19 wherein the said solenoid
valves are operated at 220 volts.
22. The automated irrigation system as claimed in any one of the above claims with
means to irrigate multiple plots at a time based on the signals from the sensors in
the different plots.
23. The automated irrigation system as claimed in any one of the above claims with
means to calculate the precise level of moisture content for each plot.
24. The automated irrigation system as claimed in any one of the above claims
comprising storage means to store data of the pre set upper and lower limits of
soil moisture content, records of starting and stopping irrigation and variation of
soil moisture level, date of sowing.
25. The automated irrigation system as claimed in any one of the above claims
comprising comparator means to compare the sensed signals with the pre set
stored data and adapted to generate corresponding output signals to activate said
valve operating means.
26. The automated irrigation system as claimed in claim 24 wherein said comparator
means is adapted to compare and assess the need for soil irrigation based on
stored data of other related parameters of irrigation.
27. The automated irrigation system as claimed in any one of the above claims
wherein said comparator means is adapted to start and stop irrigation taking into
account the upper and lower limits of moisture set for each plot.
28. The automated irrigation system as claimed in any one of the above claims
comprising means to start and stop irrigation taking into account the_priqrities set
for different crops. ,
29. The automated irrigation system as claimed in any one of the above claims
comprising means for time based irrigation scheduling with options for operating
either at regular time interval or at particular date and time.
30. The automated irrigation system as claimed in any one of the above claims
comprising means to taking into account effective rainfall as well rain forecast for
scheduling irrigation.
31. An automated irrigation system substantially as herein described and illustrated
i with reference to the exemplary illustrations.

An automated irrigation system to irrigate agricultural plots with reference to conditions such as soil moisture levels and /or time. The system is directed to provide a computer controlled irrigation suitable for automated irrigation of small, medium and large size farms. The system employs different lower and upper limits of soil moisture content for starting and stopping irrigation depending upon the crop, stage of a crop as well as set the priority incase two or more plots require irrigation at the same time. The system essentially involves the use of sensor based information from the respective plots to be irrigated. The sensor means are adapted to sense the soil moisture level from the plots and transmit the signals to an interfacing circuitry operatively connected to such sensor means and to a valve operating circuit and microprocessor/ computer means adapted to thereby automatically supply water based on said soil moisture content sensed by the sensor. The system can be adapted to store databases for the commonly grown crops and operate based on such input data. Moreover it would have the option for time and soil moisture based irrigation scheduling.