14-08-2012, 10:17 AM
IMPLEMENTATION OF WIRELESS SENSORS NETWORK TO MONITOR HUMIDITY OF POLYHOUSE ENVIRONMENT
[attachment=31377]
Introduction to polyhouse
Polyhouse is a protective shade made up of polythene used for growing high value agricultural products.
Temperature, humidity, ventilation of air are controlled by the equipments fixed in the polyhouse.
Crops grown in the polyhouse are protected from intense heat, bright sunlight, strong winds, hailstones and cold waves
A prime example would be the ability to grow vegetables/fruits when its usually off season.
Wireless sensor network
(WSN) is the ubiquitous field showing wide spectrum of applications in various sectors
It combines sensing, computation and communication
Majority of the applications of the WSN lies in information sensing, real time tracking, monitoring of the various physical parameters of industrial, environmental, health, automobile
Two types of technologies used for the nodes of Wireless Sensor Network Zigbee and Bluetooth
Zigbee technology is mostly reliable and suitable for indoor as well as outdoor sensor network
Wireless Sensor Node
The heart of Wireless Sensor Network (WSN) is the Sensor Node.
wireless sensor node is designed with advanced microcontroller AVR Atmega8L.
It comprises smart sensor, signal conditioner, data acquisition system, the microcontroller, display unit and power supply section
to ensure the wireless communication the RF module Zigbee is employed.
Wireless sensor node consist:
The Humidity sensor module [SY-HS-220]
Signal Conditioner
Offset Voltage Compensator
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity
humid air is not "moist air" but a mixture of water vapor and other constituents of air,
it commonly refers to relative humidity
RH is defined as the ratio of the partial pressure of water vapor in the air-water mixture to the saturated vapor pressure of water at those conditions.
The relative humidity of air depends not only on temperature but also on pressure of the system of interest
Principle of humidity sensor
Humidity sensors determine relative air humidity using capacitive measurement technology.
For this principle, the sensor element is built out of a film capacitor on different substrates (glass, ceramic, etc.).
The dielectric is a polymer which absorbs or releases water proportional to the relative environmental humidity,
thus changes the capacitance of the capacitor, which is measured by an onboard electronic circuit.
The Humidity sensor module
To measure humidity, amount of water molecules dissolved in the air of polyhouse environments, a smart humidity sensor module SY-HS-220 is opted
The humidity sensor is of capacitive type, comprising on chip signal conditioner
This work with +5 Volt power supply and the typical current consumption is less than 3 mA.
Signal Conditioner
A smart humidity sensor SY-HS-220 provides the D.C. output voltage (mV) linearly proportional to the humidity in RH%
To pick up this signal and to amplify the same, an instrumentation amplifier AD 620 is employed
AD 620 is programmable instrumentation amplifier exhibiting very high input impedance, which could really help to isolate the sensor from remaining analog part of the hardware.
[attachment=31377]
Introduction to polyhouse
Polyhouse is a protective shade made up of polythene used for growing high value agricultural products.
Temperature, humidity, ventilation of air are controlled by the equipments fixed in the polyhouse.
Crops grown in the polyhouse are protected from intense heat, bright sunlight, strong winds, hailstones and cold waves
A prime example would be the ability to grow vegetables/fruits when its usually off season.
Wireless sensor network
(WSN) is the ubiquitous field showing wide spectrum of applications in various sectors
It combines sensing, computation and communication
Majority of the applications of the WSN lies in information sensing, real time tracking, monitoring of the various physical parameters of industrial, environmental, health, automobile
Two types of technologies used for the nodes of Wireless Sensor Network Zigbee and Bluetooth
Zigbee technology is mostly reliable and suitable for indoor as well as outdoor sensor network
Wireless Sensor Node
The heart of Wireless Sensor Network (WSN) is the Sensor Node.
wireless sensor node is designed with advanced microcontroller AVR Atmega8L.
It comprises smart sensor, signal conditioner, data acquisition system, the microcontroller, display unit and power supply section
to ensure the wireless communication the RF module Zigbee is employed.
Wireless sensor node consist:
The Humidity sensor module [SY-HS-220]
Signal Conditioner
Offset Voltage Compensator
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity
humid air is not "moist air" but a mixture of water vapor and other constituents of air,
it commonly refers to relative humidity
RH is defined as the ratio of the partial pressure of water vapor in the air-water mixture to the saturated vapor pressure of water at those conditions.
The relative humidity of air depends not only on temperature but also on pressure of the system of interest
Principle of humidity sensor
Humidity sensors determine relative air humidity using capacitive measurement technology.
For this principle, the sensor element is built out of a film capacitor on different substrates (glass, ceramic, etc.).
The dielectric is a polymer which absorbs or releases water proportional to the relative environmental humidity,
thus changes the capacitance of the capacitor, which is measured by an onboard electronic circuit.
The Humidity sensor module
To measure humidity, amount of water molecules dissolved in the air of polyhouse environments, a smart humidity sensor module SY-HS-220 is opted
The humidity sensor is of capacitive type, comprising on chip signal conditioner
This work with +5 Volt power supply and the typical current consumption is less than 3 mA.
Signal Conditioner
A smart humidity sensor SY-HS-220 provides the D.C. output voltage (mV) linearly proportional to the humidity in RH%
To pick up this signal and to amplify the same, an instrumentation amplifier AD 620 is employed
AD 620 is programmable instrumentation amplifier exhibiting very high input impedance, which could really help to isolate the sensor from remaining analog part of the hardware.