Development of a Low-Cost TDS Sensor Using an Electric Plug with The Curve Fitting Method Approaches

This paper introduces the development of a low-cost total dissolved solids (TDS) sensor system using an electric plug type C (Indonesian standard electric plug) as the probe. The TDS value is normally identified based on the drop voltage between the plug’s pins, representing the water resistance value. In our developed system design, the TDS data were collected and processed by a low-cost microcontroller using a 10-bit analog-to-digital converter (ADC). Several samples of TDS solutions were made, ranging from approximately 300 to 1500 ppm for the experiment. Then, the ADC values from those solutions, which represent the drop voltage and the water resistance values, were measured and collected. Once the data were collected, three curve fitting techniques (exponential, polynomial, and power) were used to construct graph equation formulas. Finally, the acquired equations were compared using a reversed comparison technique to determine the best equation to apply. The experimental results showed that an electric plug type C as an electrical conductivity (EC) probe had a high capacity to be used as a TDS sensor in our system. The polynomial model matched the TDS graph with a lower root mean squared error (RMSE) value. Moreover, the accurate measurement was followed by an error tolerance of less than 8.2%. From this result, we are fully confident that our TDS sensor system is still suitable for hydroponic and aquaponic monitoring systems.