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Wireless greenhouse environment monitoring through sensors
Raj Kumar Goel Institute Of Technology
“Wireless Greenhouse Environment Monitoring through
Wireless Greenhouse Environment
Monitoring through Sensors
Devices controlled :
Water Pump (simulated as a bulb)
Sprayer (simulated as a bulb)
Cooler (simulated as a fan)
Artificial Lights (simulated as 2 bulbs)
This part of the system consists of various sensors, namely soil moisture, humidity,
temperature and light. These sensors sense various parameters- temperature, humidity,
soil moisture and light intensity and are then sent to the Analog to Digital Converter.
The microcontroller is the heart of the proposed embedded system. It constantly
monitors the digitized parameters of the various sensors and verifies them with the
predefined threshold values and checks if any corrective action is to be taken for the
condition at that instant of time. In case such a situation arises, it activates the actuators
to perform a controlled operation.
A Liquid crystal display is used to indicate the present status of parameters and the
respective AC devises (simulated using bulbs). The information is displayed in two
modes which can be selected using a push button switch which toggles between the
modes. Any display can be interfaced to the system with respective changes in
driver circuitry and code
Power supply: The power supply section consists of step down transformers of
230V primary to 12V secondary voltages for the +5V power supplies respectively.
The stepped down voltage is then rectified by 4 1N4007 diodes. The high value of
capacitor 1000 µF charges at a slow rate as the time constant is low, and once the
capacitor charges there is no resistor for capacitor to discharge. This gives a constant
value of DC. IC 7805 is used for regulated supply of +5 volts in order to prevent the
circuit ahead from any fluctuations. The filter capacitors connected after this IC
filters the high frequency spikes.
If internal power dissipation becomes too high for the heat sinking provided, the
thermal shutdown circuit takes over preventing the IC from overheating.
A temperature sensor (LM35DZ) can measure from 0°C to 100°C. However, the
output is 0V at 2°C. Hence the measurable temperature is above 2°C. The output of a
sensor goes up by 10mV for every 0°C. The output voltage in 32°C is 300mV.
The output voltage of a sensor is amplified by an operational amplifier, and is inputted
into the base of transistor .The temperature sensitivity adjusting the gain of an
operational amplifier by VR.
So in the normal mode when temperature is below 60C the output or LM358 is not
sufficient to drive transistor BC 548. When temperature raises above 60C the output
of LM358 is about 3V which is sufficient to drive transistor thus microcontroller get
Soil moisture sensor:
This sensor is based on the fact that water is not pure water which is non
conductor, but it is impure which is slightly conductor.
Water sensor is nothing but a series of very close PCB tracks. In normal mode
these tracks are not conducting, but when some water fall on these tracks these
line slightly start conducting and some positive voltage is available at the base of
transistor So NPN transistor is on and NPN transistor provide a negative voltage
as a pulse to the microcontroller.
The humidity sensor SYS-1used for sensing the humidity. It delivers instrumentation
quality RH (Relative Humidity) sensing performance in a low cost, solderable SIP
(Single In-line Package). Relative humidity is a measure, in percentage, of the
vapour in the air compared to the total amount of vapor that could be held in the air
at a given temperature.
• Linear voltage output vs. %RH
• Laser trimmed interchangeability
• Low power design
• High accuracy
• Fast response time
• Stable, low drift performance
• Chemically resistant
• The RH sensor is a laser trimmed, thermoset polymer capacitive sensing element
with on-chip integrated signal conditioning.
Light intensity sensor:
The light intensity in the green house is sensed by a photo sensor and a signal in the
form of voltage is sent to the microcontroller. This signal is scaled in such a way that
5V is generated in the day lit environment. The lamp is dimmed based on this signal.
A photo sensor is a complete assembly that includes the optical arrangement and
electronic circuitry that is coupled to an electronic component called a photocell. A
photocell is a light responding silicon chip that converts incident radiant energy into an
electrical signal. Photo sensor includes a diffuser or lens that collects light and an
optical filter that rejects the UV and IR spectra. The electronic circuitry amplifies the
dc voltage generated by the photocell, and after comparing it with a reference voltage,
sends an appropriate signal to the control device.
The PIC family of microcontrollers is based on an architecture which is highly
optimized for embedded control systems. It is used in a wide variety of applications
from military equipment to automobiles to the keyboard. The manufacturers have
added numerous features and peripherals to the PIC such as I2C interfaces, analog to
digital converters, watchdog timers, and pulse width modulated outputs. Variations of
the PIC with clock speeds up to 40MHz and voltage requirements down to 1.5 volts are
available. This wide range of parts based on one core makes the 8051 family an
excellent choice as the base architecture for a company's entire line of products since it
can perform many functions and developers will only have to learn this one platform.
The 16f877a is a low-power, high-performance CMOS 8-bit microcontroller with
8K bytes of in-system programmable Flash memory. The device is manufactured
using Microchip high-density nonvolatile memory technology and is compatible
with the industry standard
PIC 16f877a provides a highly-flexible and cost effective solution to embedded
control applications. In addition, the 16f877a is designed with static logic for
operation down to zero frequency and supports two software selectable power
saving modes. The Idle Mode stops the CPU while allowing the RAM,
timer/counters, serial port, and interrupt system to continue functioning. The
Power-down mode saves the RAM con-tents but freezes the oscillator, disabling
all other chip functions until the next interrupt or hardware reset.
The display section consists of 16*2 LCD, which used to display Summary of IC
being Inserted and result of test being conducted.
LCDs can add a lot to your application in terms of providing an useful interface for
the user, debugging an application or just giving it a "professional" look. The most
common type of LCD controller is the Hitachi 44780 which provides a relatively
simple interface between a processor and an LCD.