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The system contains three subsystems temperature monitoring and control system, light intensity monitoring and control system, and soil moisture level monitoring and control system. These are some of the basic control systems that can be made for a cheap price when compared with others in the market. Humidity inside the greenhouse could also be controlled but it is not used since controlling the temperature controls humidity up to a certain extent.
In the temperature monitor and control system an option is given to the user, to set the temperature of the greenhouse to his/her desired temperature. By this means the user will be able to germinate seeds that require temperatures below the normal atmospheric temperature and grow plants that grow in an ideal temperature as given in the seed packet. But there is a drawback since every time the system is switched on the user needs to got user mode and set the desired temperature value once again but this won’t have a big affect since once the system is on the system stays on except till the user offs it or in a power cut. The value of the current temperature and the user defined temperature is displayed on the LCD screen always as a reference for the user and this can be used to check whether the temperature is regulated properly.
Just one LDR is used for the system since light is falling onto the greenhouse evenly. If the light intensity is high the bulbs are switched off if they are once switched on when the light intensity is low to save power and no attempt is made to decrease the light intensity since more light intensity provokes plant growth. A switch is place to cut off the power supply to the bulbs manually this is because having lights on at night (which happens automatically) will make plants grow weak and consumes more power.
The only way the soil inside the moistened significantly is by the watering pipes and not by any other natural means like rain therefore the system is such that it stops the water flow to the pipes when the soil moisture level reaches the adequate value as defined in the program.
The reason for using PIC16F877A instead of PIC16F88 since there are more pins in PIC16F877A (40 pins) therefore it is much easier to use it in the debug mode when testing the code and it allows the user to upgrade the system by connecting more sensors and actuating components as the size of the greenhouse increase. LM35 temperature sensor can be directly connected to the PIC16F877A without using any amplifiers and it is easy to calibrate since it is linear and 1℃ represent 10mV output as given in the datasheet