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Introduction
We live in a world where everything can be controlled and operated automatically, but there are still a few important sectors in our country where automation has not been adopted or not been put to a full-fledged use, perhaps because of several reasons one such reason is cost. One such field is that of agriculture. Introduction
Agriculture has been one of the primary occupations of man since early civilizations and even today manual interventions in farming are inevitable. Greenhouses form an important part of the agriculture and horticulture sectors in our country as they can be used to grow plants under controlled climatic conditions for optimum produce. Automating a greenhouse envisages monitoring and controlling of the climatic parameters which directly or indirectly govern the plant growth and hence their produce. Automation is process control of industrial machinery and processes, thereby replacing human operators.
Objectives:
System Model
- Sensors (Data acquisition system)
¨ Temperature sensor (LM35)
¨ Humidity sensor (HS1101)
¨ Light sensor (LDR)
- Analog to Digital Converter ( built in microntroller)
- Microcontroller (16F877A)
- Liquid Crystal Display
- Actuators – Relays-Transistors
- Devices controlled
§ Sprayer (simulated as a bulb)
§ 12 v Fan
§ Heater (3 LEDs).
§ Lamp(220-v)
TRANSDUCERS (Data acquisition system)
This part of the system consists of
various sensors, namely humidity, temperature and light. These sensors sense various parameters- temperature, humidity and light intensity and are then sent to the Analog to Digital Converter.
ANALOG TO DIGITAL CONVERDER (ADC)
The analog parameters measured by the sensors are then converted to corresponding
digital values by the ADC, this
ADC is buit in microcontroller.
MICROCONTROLLER
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 instant of time. In case such a situation arises, it activates the actuators to perform a controlled operation.
ACTUATORS
An array of actuators can be used in the system such as relays, contactors, and change
over switches etc.
They are used to turn on AC devices such as motors, coolers, pumps, fogging machines, sprayers.
For the purpose of demonstration relays have been used to drive AC bulbs to simulate actuators and AC devices.
A complete working system can be realized by simply replacing these simulation devices by the actual devices.
They are used to turn on AC devices such as motors, coolers, pumps, fogging machines, sprayers.
For the purpose of demonstration relays have been used to drive AC bulbs to simulate actuators and AC devices.
A complete working system can be realized by simply replacing these simulation devices by the actual devices.
DISPLAY
UNIT
A Liquid crystal display is used to indicate the present status of parameters and the respective AC devises (simulated using bulbs). Any display can be interfaced to the system with respective changes in driver circuitry and code.
STEPS FOLLOWED
IN DESIGNING THE SYSTEM
Three general steps can be followed to appropriately select the control system:
Step # 1: Identify measurable variables important to production.
• It is very important to correctly identify the parameters that are going to be measured
by the controller’s data acquisition interface, and how they are to be measured.
Step # 2: Investigate the control strategies
- An important element in considering a control system is the control strategy that is to be followed. The simplest strategy is to use threshold sensors that directly affect actuation of devices.
Step #3: Identify the software and the hardware to be used.
• It is very important that control system functions are specified before deciding what software and hardware
system to purchase. The model chosen must have
the ability
to:
1. Expand the number of measured variables (input subsystem) and controlled devices
(output subsystem)
so
that
growth
and
changing needs of the production
operation can be satisfied in the future.
2. Provide a flexible and easy to use interface.
3. It must ensure high precision measurement and must have the ability resist noise.
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