International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 10 - Mar 2014
Monitoring and Control of Relative Humidity in Soil
using LabVIEW
Arutselvi.S#1, Sarah Maria Louis#2, Srinithi.S#3
#1
Guide, Instrumentation & Control Engineering, Saranathan College OF Engineering,Trichy-620012,India
Student, Instrumentation & Control Engineering, Saranathan College of Engineering,Trichy-620012, India
#3
Student, Instrumentation & Control Engineering, Saranathan College of Engineering,Trichy-620012, India
#2
Abstract— The key objective of our paper is to monitor
the soil’s moisture content during it’s dry and wet
conditions with the aid of a moisture sensor circuit,
calculate the corresponding Relative Humidity and irrigate
it based on its nature , using a PC based LabVIEW system,
NI ELVIS and an automatic water inlet setup. The moisture
sensor circuit which is built on the NI ELVIS consists of
two copper strips as probes, to sense the soil’s condition.
The sensed signal from the NI ELVIS is interfaced to a PC
with LabVIEW using a PCI 6221 cable. A LabVIEW block
diagram is constructed which acquires this signal as a
voltage and displays the numerical value, the equivalent
relative humidity and a filtered waveform graph in the
front panel.
The acquired voltage is then generated in
LabVIEW, the mechanism by which with a help of a relay
circuitry, a submissive pump turns on automatically to
irrigate at the soil’s dry condition, and turns off when wet
as sensed by the probes. A record of the relative humidity
is also stored in an EXCEL file format for backup.
Corresponding to the surface’s atmospheric conditions,
transmission of the sensed voltage signal from the hardware
circuitry on the NI ELVIS interfaced to a PC with LabVIEW,
uses a graphical development environment that is powerful
and intuitive which could rapidly develop a user interface for
data visualization and automatic irrigation of the soil.
II.
THE FUNCTIONAL SCHEME
This section elaborates the assessing and
controlling of the relative humidity using LabVIEW.
The hardware and software implementation are
discussed here below. The block diagram shows the
flow of how the complete process is carried out.
Keyword- LabVIEW, NI ELVIS, Relative Humidity, Soil, Moisture
I. INTRODUCTION
This paper emphasizes on the fact that the technique which
is incorporated here to monitor the soil’s moisture content,
enables agriculturalists feasibility of humidity of humidity
measurement and a conventional automatic irrigation with
the potential for eliminating excessive irrigation cycles
thereby saving water to a significant extent. Besides the
normal modes of measurement and analysis, LabVIEW
stands unique as a grooming software in the field of
Instrumentation and control Engineering, which facilitates
engineers to work in one platform with infinite possibilities
along with a sophisticated control system.
Effective crop treatment and water management is the
major requisite in most of the cultivating estates in semi-arid
regions. Monitoring the soil’s nature, estimating it’s relative
humidity and controlling it concurring to the necessity,
proposes a potential solution to endorse landsite irrigation
management and thus, to treat desiccated fields and provide
prominent yield to producers.
ISSN: 2231-5381
Figure 1: Block Diagram
A. HARDWARE IMPLEMENTATION:
The Hardware primarily consists of an integrated
circuitry which is constructed on the NI ELVIS.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 10 - Mar 2014
The overall circuit diagram is as shown below. during the wet condition and in the range of (2.9 V
– 3.9 V) for the soil’s dry condition.
The output signal from transistor Q1 on the NI
ELVIS as per the soil’s condition is given to the
relay circuit which is responsible for the
determination of the switching of the ON or OFF of
the pump which is also controlled by a transistor Q2.
Power supply of 12V is fed to the relay by means of
an RPS. When the signal from the NI ELVIS is
high, the emitter and collector terminals of
transistor Q1 get shorted. Therefore the entire
supply gets grounded. When the signal from the NI
ELVIS is low, the 12V supply is fed to the
transistor Q2. Hence the Common and Normally
Open (NO) terminals are shorted and the load
(pump) gets the supply which irrigates the dry soil.
Figure 1: Circuit Diagram
The BC 548 Q1 transistor acts as a switch.
When the base switch is closed, a small amount of
current flows through 470K Ω resistor to the base
junction of the transistor, which turns the transistor
fully ON and makes it saturated. A 47KΩ resistor is
connected in parallel to the 470KΩ resistor which is
coupled to Probe A. The 470KΩ resistor is
connected across the collector and emitter junctions.
The emitter terminal is grounded.
The cathode of the LED which also acts as a
diode is connected to the collector terminal of the
transistor. The anode is connected in series with the
330Ω resistor to which the VCC (5V) is supplied.
Probe B is also coupled to it. The two probes A and
B, which are copper strips, are made to be in
contact with the soil.
During the soil’s damp conditions, the two
probes behave as electrodes and therefore current
flows in a closed circuit due to the presence of
water (which is a good conductor of electricity)
content, between the two electrodes. This turns the
transistor Q1 to an ON state. The circuit’s working
or conducting condition is indicated by the glowing
of the LED due to the passage of current.
When dry, it becomes an open circuit because
there is no medium for the electricity to flow, the
transistor is in the OFF state therefore the LED
turns OFF.
The output voltage is obtained from the leads
that are connected across the collector and ground
terminals. The voltage completely drops to zero
ISSN: 2231-5381
B. SOFTWARE IMPLEMENTATION:
The software module that is incorporated in
developing the graphical program structure is
LabVIEW (version 2010). It consists of a block
diagram which the sequence of icons connected
with wires in the manner of flow of operation. The
front panel is wherein the acquired and generated
parameters are displayed in numerical, graphical
waveform or as a control.
LabVIEW BLOCK DIAGRAM:
Description:
The block diagram depicts the acquisition and
generation of the input and output signals. The
signal that is sensed from the soil on the NI ELVIS
is interfaced to the PC with LabVIEW through PCI
6221 cable. This signal is acquired in LabVIEW
with a DAQ Assistant which renders the signal as a
voltage value according to the soil’s condition. The
soil’s relative humidity is also calculated using the
respective formula concording to the status of the
soil. The voltage signal is filtered to eliminate noise
and any other distortions and is displayed in the
form of a waveform graph.
Based on the voltage obtained in the range of viz,
3V for dry condition and 0V for wet condition,
comparators compare the corresponding values and
indicate with the glowing of the LED on the front
panel.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 10 - Mar 2014
The voltage is then generated by building another
DAQ Assistant for the generation of the output
signals. 3V that is obtained during the soils dry
condition is generated as input to the NI ELVIS for
the relay mechanism which drives the pump to
water the parched soil.
The front panel presents the icons and
graphical displays of each parameter utilized in the
block diagram. The toggle switch is employed and
has to be manually operated to set in dry and wet
modes for displaying the values of the calculated
relative humidity according to the soil’s condition
corresponding to the indication in the LED. The
graph shows the filtered waveform of the output
incurred corresponding to the time vs voltage and
the LED indication as sensed by the sensors. The
program could be terminated by clicking on to the
STOP button which completely ceases the
functioning. The values could be imported to an
Excel file for reuse and backup.
CONCLUSIONS
Figure 2: LabVIEW Block Diagram
This project involves the didactics of establishing a
contemporary design technique of monitoring and controlling
the relative humidity of soil using LabVIEW. Providing
comprehensive tools that need to build any measurement or
control application in dramatically less time, LabVIEW is the
ideal development environment for innovation, discovery, and
accelerated results. Combine the power of LabVIEW software
with modular, reconfigurable hardware to overcome the everincreasing complexity involved in delivering measurement
and control systems on time and under budget.
ACKNOWLEDGMENT
Figure 3: LabVIEW Front Panel (Wet Condition)
Figure 4: LabVIEW Front Panel (Dry Condition)
ISSN: 2231-5381
We would sincerely like to express our
heartfelt gratitude to the Management and the Staffs
who were solely responsible in rendering us the
necessitated ambience and guidance for the
progress and completion of our paper with success.
We are obliged in conveying our profound
gratitude to our college Secretary, Mr. S.
Ravindran, our beloved Principal, R. Revathy,
and thes Directors of our esteemed Institution, for
providing us splendid workplace to accomplish our
paper work.
We are indebted to the Head of the
Department, Dr. Giriraj Kumar who inculcated the
spirit of innovation and constant encouragement in
our team, which enabled us finish our paper.
We would also like to convey our gratitude
to our project guides Ms. Arutselvi. S, Assistant
Professor, ICE and Mr. Saju. S, Assistant Professor,
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 10 - Mar 2014
ICE for their continuous support and valuable
guidance during the course of this paper. We also
thank the lab assistants for aiding us with their
guidance and endorsement.
REFERENCES
[1]. Moumita Sahoo, ACEEE Int. J. on Control System and
Instrumentation, Vol. 03, No. 02, March 2012. “An Approach to
LabVIEW Based Temperature &Relative Humidity Monitoring System”
[2]. T.Bheema lingaiah, D.Hanumesh Kumar, C.Nagaraja, Solomon
Woldetsadik International Journal of Advanced Research in Electrical,
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Electronics and Instrumentation Engineering(An ISO 3297: 2007
Certified Organization) Vol. 2, Issue 10, December 2013 “Development
of Humidity and Temperature Measurement Instrumentation System
using LabVIEW”
[3]. Online. “Data sheet of BC 548”
[4].A.K. Sawhney “A Course in Electrical and Electronics
Measurements and Instrumentation”
[5]. Online, “Diode- IN4001 datasheet and specification”
[6]. Hosni Abu-Mulaweh, Indiana University-Purdue University-Fort
Wayne American Society for Engineering Education, 2007. “The Use of
LabVIEW and Data acquisition unit to Monitor & Control AirConditioning Processes”
[7]. Online. “Relay datasheet”
[8]. www.ni.com.. National Instruments
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