Low-cost Hydroponic Cell with Microcontroller Reintegration to Programmable Logic Controller

Introduction. High start-up costs and excessive automation when implementing vertical farms and hydroponic systems increase the risk of project failure in the early stages. The aim of this study is to formalize and validate a stepwise methodology for transferring control of a hydroponic cell from a microcontroller to an industrial controller without loss of controllability or data, thereby maintaining low startup costs. Materials and Methods. The prototype is a hydroponic cell operating a 2-hour/15-minute flood–drain cycle. The hardware includes an Iskra Mega microcontroller, peristaltic and air pumps, pH and electrical conductivity (EC) sensors, dimmable horticultural luminaires, and Modbus RTU over RS-485. Methods comprised laboratory experimentation, sensor calibration, event logging and auditing, stress testing of the communication bus, and modeling of online-takeover and offline-migration algorithms. pH/EC control loops were implemented with proportional-integral (PI) controllers using integrator anti-windup protection. Results. The scheduling was deterministic, with phase-switching errors < 0.1 %. pH and EC settled within ≤12–15 minutes with low overshoot. The fraction of frames rejected by the CRC integrity check was low. The online takeover was executed within milliseconds without frame loss, while the offline migration correctly restored all monitoring trend plots. Discussion and Conclusion. The feasibility of multi-stage transition from a microcontroller to industrial implementation is confirmed. The synchronization bus and address-based subroutine activation provide a seamless handover and preserve data integrity. Economically, the microcontroller is justified for 1–3 cells, whereas industrial controllers are preferable for ≥ 6–12 cells. The results are useful for industrial automation and control system (IACS) integrators and vertical-farm developers, offering step-by-step procedures for online/offline reintegration, requirements for bus/addressing, and criteria for transitioning to industrial implementation when scaling the system.