Programmable Logic Controller (PLC) is a form of controller which can be programmed for various needs. The basic mechanism of how PLC works is by connecting or disconnecting electric current of an instrument. The objective of this research is to design and evaluate the performance of PLC in handling Multi Input and Multi Output (MIMO) in floriculture for chrysanthemum. The PLC is given task to activate pump for supplying nutrient solution periodically and to control plant environment according to specified set point. The environmental parameters are acidity and temperature of nutrient solution, air temperature and humidity inside the greenhouse. If one of these environmental parameters is above or below the set point, then an appropriate action will be taken according to the programmed algorithm in the PLC. Special attention has been paid for controlling the acidity of nutrient solution. If the acidity of nutrient solution is 5.257, then it will be corrected by opening the bases solenoid valve for 75 times until the acidity increase to 6.017, according to the specified set point (6.0 – 6.5). If the acidity is 6.755, then it will be corrected by opening the acids solenoid valve for 23 times until its acidity decrease to 6.505. Results showed that PLC performed well in controlling the environment parameters of chrysanthemum grown in ebb and flow system.
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