Industrial RO Plant Controller – Complete PCB & Electronics Design

PCB Design & Engineering for HydroNest RO Plant Controller 1. Project Objective We are developing a professional controller PCB for commercial/light-commercial RO water treatment plants under HydroNest India. The objective is to take our existing functional requirements, selected components/modules and control logic, and have an experienced electronics engineer design, optimize and finalize the complete electronic controller. We are not looking only for PCB layout work. The engineer should be capable of taking the requirements at a system level and developing the complete electrical design, schematic, component selection/optimization and production-ready PCB. ⸻ 2. What We Will Provide We will provide: * RO plant operating requirements and sequence * List of pumps, solenoid valves, sensors, switches and other field devices * Required inputs and outputs * Existing/ preferred components and modules * ESP32-based controller/HMI requirements * Communication requirements * Existing firmware/control logic where applicable * Electrical voltage/current requirements wherever known * Physical/enclosure constraints wherever applicable The engineer should review the provided components and recommend better alternatives wherever required for reliability, availability, cost or manufacturability. ⸻ 3. Controller Requirements The PCB will act as the main electronic controller for the RO plant and should be designed around an ESP32-based control system. The controller should support, as applicable: Digital Inputs * Float/level switches * Tank level inputs * Pressure switches * Plant fault inputs * Other ON/OFF field sensors Sensor Inputs * Flow sensors * TDS/EC or water-quality sensors where required * Other analog/digital sensors required by the final system Outputs The controller should be capable of controlling: * High-pressure pump * Raw-water/feed pump * Solenoid valves * Flush valves * Dosing systems where applicable * Other RO plant actuators The exact output architecture should be determined by the engineer based on the loads. Where pumps or high-power equipment cannot be driven directly, the PCB should provide the appropriate relay/contactor/driver interface. ⸻ 4. Power Supply The controller is intended to operate in an industrial RO plant environment with a 24V DC control supply / field environment. The engineer should design the required power architecture, including appropriate: * 24V input protection * Fuse/protection * Reverse-polarity protection * Surge/transient protection * DC-DC regulation * 5V and/or 3.3V rails * ESP32 power supply * Protection for sensitive electronics The design should account for the electrically noisy environment created by pumps, solenoid valves, contactors and other inductive loads. ⸻ 5. Relay / Output Protection All inductive outputs should be designed appropriately. The engineer should determine and implement the required: * Flyback protection * TVS/surge suppression * MOSFET/driver stages where appropriate * Relay driver circuits * Isolation where appropriate * Protection between field wiring and the ESP32 The ESP32 GPIOs must not be exposed directly to unsuitable field voltages or loads. ⸻ 6. HMI & Communication The system will communicate with an ESP32-S3 based HMI/display controller. The current system uses an ESP32-S3 7-inch touchscreen HMI and wireless communication is being explored/implemented using ESP-NOW/Wi-Fi. The PCB engineer should design the controller architecture so that communication with the HMI is reliable and practical. The engineer should also recommend the most appropriate physical communication/interface architecture if changes are required. ⸻ 7. Cellular / Connectivity A cellular communication module such as the A7672S 4G module is being considered for remote connectivity. The engineer should evaluate the best way to integrate this into the overall controller architecture, including: * UART communication * Power requirements * SIM/network requirements * Antenna connection * Power supply/current requirements * GPIO requirements * Electrical protection If integrating the cellular modem directly onto the main PCB is not advisable, the engineer may recommend a modular approach. ⸻ 8. Industrial Reliability This is intended to be a real commercial RO plant controller, not a hobby/Arduino development board. The PCB should therefore be designed with consideration for: * Electrical noise * Inductive loads * Voltage transients * Field wiring * Proper grounding * Signal integrity * Separation of noisy and sensitive circuits * Appropriate creepage/clearance * Connector reliability * Serviceability * Long-term operation * Manufacturability The engineer should identify potential reliability issues in our initial component selections and propose improvements. ⸻ 9. PCB Design The engineer will be responsible for the complete PCB design, including: 1. System architecture 2. Circuit design 3. Schematic 4. Component selection/review 5. PCB layout 6. Routing 7. Power and ground design 8. Input/output protection 9. Connector placement 10. Design for manufacturing 11. Design for assembly 12. Final design review The PCB should be designed for practical production rather than only prototype operation. ⸻ 10. Modular / Future Expansion Where practical, the design should allow future expansion of the controller. Potential future requirements include: * Additional sensors * Additional outputs * Different RO plant capacities * Additional communication interfaces * Remote monitoring * Additional automation functions The engineer should recommend a sensible architecture that allows expansion without unnecessarily increasing PCB cost and complexity. ⸻ 11. Required Deliverables The final project should include: * Complete electrical schematic * PCB design/layout * Complete BOM * Component part numbers * Gerber files * Drill files * Pick-and-place/CPL files if applicable * Assembly drawings * PCB fabrication files * PCB 3D model/render * Source design files * Design docu