<![CDATA[PH and TDS were critical parameters in hydroponic systems that directly influenced nutrient absorption and plant growth. This study developed an automatic nutrient solution control system for NFT hydroponics using a Proportional-Integral-Derivative (PID) controller with coupled and decoupled approaches. The system employed a DFRobot Gravity: Analog TDS sensor to measure TDS, an Electrode Probe pH-4502C to monitor pH, and an Arduino Uno microcontroller to regulate peristaltic pumps in real time. Lettuce was used as the test crop, requiring 550 ppm TDS and pH 6.5. System performance was evaluated through MATLAB Simulink simulations and hardware implementation based on rise time, settling time, overshoot, and steady-state error. The simulation results showed that the coupled method had slightly faster rise time and settling time compared to the decoupled method, whereas the decoupled method had less overshoot than the coupled. The hardware test showed that the decoupled method performed better, with a pH rise time of 8.34 s, a settling time of 11 s, an overshoot of 10%, and a steady-state error of 0.90%, as well as a TDS rise time of 30.7 s, a settling time of 36 s, an overshoot of 4.36%, and a steady-state error of 0.60%. In contrast, the coupled method exhibited slower responses, longer settling times, and higher steady-state errors. Overall, the decoupled method proved more effective and reliable in maintaining pH and TDS stability, showing strong potential to enhance the efficiency and robustness of NFT hydroponic control systems.]]>
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