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The requirement of the system is to regulate the temperature to a user defined value and control the amount of light intensity around a defined value in the program and control the soil moisture around the predefined value in the program while displaying the current temperature value, user set temperature value, soil moisture value and the light intensity value.
The system consists of three subsystems in it and they are,
The system’s temperature monitor and control system works according to the temperature value set by the user. First it gets the value from the user and maintains the temperature around that value. It also displays the target temperature (temperature set by the user) and the current temperature in the LCD screen for user reference. The temperature inside is reduced accordingly by the aid of two fans that are placed at the two ends of the greenhouse where one sucks in air from outside and the other sucks out air from the greenhouse thus providing a passage of air through the greenhouse and hence cooling the air inside the greenhouse and therefore the temperature reduces. The temperature of the greenhouse is increased accordingly by using a heater which is placed at the floor of the greenhouse (ideal position needs to be identified by testing). By placing the heater at the bottom it is ensured that the whole greenhouse is warmed by convectional currents where less dense warm air rises up and dense cold air comes down.
The light control system controls the amount of light falling on to the greenhouse. When there is not enough light the LDR detects this and the microprocessor (PIC16F877A) processes this information send by the LDR and switch on the light bulbs and when there is more light the bulbs are turned off. But at night the system will automatically switch on the lights and this has harmful effects on the plants therefore a switch is placed to off the lights at times when he feels the lights are unnecessary.
The soil moisture level monitoring system monitors and the current soil moisture level and maintain it around a predefined value. When the system detects a drop in soil moisture level it opens a solenoid valve allowing water to flow on to the network of pipelines installed inside the greenhouse floor. The pipes contain small drilled holes and hence allow water to drip out as a fine jet out into the soil as the water pressure inside the pipe is high. The pipes are placed at the ground level allowing water to reach the soil quickly. When soil moisture level reaches the correct value the systems shuts the solenoid valve and the flow of water stops.