Proceedings of the 24 th Conference on Automation Technology 台灣 台中 國立中興大學 National Chung Hsing University, Taichung, 4~5 November, 2016 Raspberry Pi based pH Control for Nutrient Film Hydroponic System Ryan Laksmana Singgeta* a , Hung-Wei Lin b , and Yeong-Hwa Chang a Department of Electrical Engineering, Chang Gung University, Kwei-Shan, Tao-Yuan 333, Taiwan a *a E-mail:ryansinggeta@gmail.com a E-mail:yhchang@mail.cgu.edu.tw Department of Electrical Engineering, Lee-Ming Institute of Technology, New Taipei City 243, Taiwan b b E-mail:hwlin@mail.lit.edu.tw Abstract — This paper presents an automated hydroponic system, where a Raspberry Pi is used to maintain the pH level in the presence of time-delay. The Ziegler-Nichols method is used for tuning the parameters of the PID controller. Moreover, a Web user interface is developed to control, monitor, and record the pH level, temperature, and water level. Experimental results illustrate that the required pH level can be attained by the proposed control scheme. Keyword: Hydroponic, PID controller, Time-delay, Ziegler-Nichols, Web interface. 1. INTRODUCTION Hydroponic is a plant growing method through water culture without the use of any solid substrates [1]. Recently, hydroponic has popularly spiked because the crop quality and productivity has significantly increased [2]. Many methods are provided to build and develop hydroponic systems. According to [3], the conventional method needs more time and manpower to control and monitor hydroponic systems where everything should have manually. The pH water solution takes a time to read pH value which is needed to periodically monitor and balance a required value of maintaining a quality of the nutrients solution. Researchers have interested to develop the hydroponic system to be automatically in terms of monitoring and controlling. The automated pH controller system for hydroponic cultivation has been proposed in [3]-[6]. In [7], the authors provided a smart fuzzy logic control to manage an agriculture production system. In addition, this system control was enhanced with wireless data monitoring platform for data routing and logging, which provides real time data access. Initially scientists used hydroponics mainly as a research tool to study particular aspects of plant nutrition and root function [1]. In [8], the authors developed a hydroponic system to monitor parameters for the nutrition such as pH and EC (electrical conductivity). This study focuses on developing the hydroponic system especially for the plant nutrition which is using mineral nutrient solutions in water. The water quality is essential for hydroponics. The pH level in water affects the absorption of certain nutrients by the roots. Therefore, pH level is considered to be one of the most important determining factors of crop yield and quality [2]. The pH value is a parameter that measures the acidity or alkalinity of a solution. This value indicates the relationship between the concentration of free ions H + and OH - solution with ranges 0 to 14 [2]. In general, a range of irrigation solution pH levels between 5.6 and 6.8 is required [1]. Accordingly, this paper aims to maintain the pH level in hydroponic system. In this study, the mixing process between pure water and pH decreasing is distributed by a DC motor in the box with a delay time. The variations of the pH value in the box are not directly measured by the pH sensor. Therefore, the action of the DC motor as a output and pH sensor as a input in control system will lead to delays and error actions. The paper [9] proposed a fuzzy- PID control method to adjust the pH value which has time delay in acid and alkali neutral reaction process. The other technique, in [10], the paper proposed reset control of an industrial in-line pH process with significant time delay and gain uncertainties. Basically, a time delay will tend to destabilize a closed-loop system and hence makes it much more difficult to control [11]. It is a challenge how to control the pH value with consider the delay/dead time in hydroponic system. In recent years, the PID controller is one of main control tools being used to solve the industrial problem, particularly those of the process industries. The PID control module is a building block which provides the regulation and disturbance rejection for single loop, cascade, multi-loop, multi-input, and multi-output scheme. For tuning the PID coefficients, the Ziegler-Nichols open loop method is used in this study. The Ziegler-Nichols method is heuristic rule for experimental design. Furthermore, an embedded system is developed to integrate the temperature sensor LM35, pH sensor, SRF08 range sensor, the DC motor and AC motors as actuators, Raspberry Pi as a master control, and PIC18F4525 microcontroller as a slave for control of the hydroponic system. Also, to enhance the hydroponic system, a web interface for monitoring the data access is provided, which includes pH value, temperature, and water level through wireless communication. As a whole, this paper aims to maintain the quality of the water in hydroponic system with controlling the pH level by using a PID controller for time-delay system and design a web interface and database to monitor the data access in directly.