Multi-Arduino Industrial Control System Development (Isolated Communication + Analog + Digital I/O)

Multi-Arduino Industrial Control System Development (Isolated Communication + Analog + Digital I/O) Project Overview We are developing a modular measurement instrument based on multiple interconnected Arduino boards. Each Arduino handles a dedicated subsystem (UI, motor control, pH control, temperature control) coordinated by a Master Arduino. We require an experienced embedded systems freelancer to: • Design robust firmware architecture • Implement reliable inter-Arduino communication • Ensure electrical isolation to prevent analog noise/crosstalk • Optimize motor control, sensor acquisition, and closed-loop control • Deliver clean, documented, production-ready code • All components should be easily sourced in India This is not a beginner Arduino project — we are building a lab-grade instrument requiring stable analog performance. System Architecture 1. UI Subsystem Arduino • Keypad interface • Graphic LCD • Touchscreen display (also modular) • Menu navigation • Parameter entry • Sends user commands to Master • Communicate with a PC 2. Motor Control Arduino • PMDC motor control • Hall-effect RPM sensing • PWM via MOSFET driver (circuit is already designed for an old PIC microcontroller) • Closed-loop speed regulation • Target range: ~50–1200 RPM • Stable low-speed control required 3. pH Control Arduino • High-impedance pH probe input (JFET/op-amp front end) (circuit is already designed for an old PIC microcontroller) • Analog signal conditioning (circuit is already designed for an old PIC microcontroller) • pH measurement (circuit is already designed for an old PIC microcontroller) • Acid/base pump control (MOSFET driven) (circuit is already designed for an old PIC microcontroller) • Closed-loop pH regulation (control scheme is already designed for an old PIC microcontroller) • Noise immunity critical 6. Temperature Control Arduino • Temperature sensor reading (e.g., PT100) (circuit is already designed for an old PIC microcontroller) • PWM output to SSR (circuit is already designed for an old PIC microcontroller) • Stable temperature control loop (control scheme is already designed for an old PIC microcontroller) • Avoid PWM noise affecting analog subsystems 5. Master Arduino • Coordinates all sub-systems • Central command routing • Status aggregation • Fault monitoring • Communication management • Safety logic • PC connectivity (PC interface software is already designed and working) IMPORTANT: Electrical Isolation Analog readings (especially pH) must not be corrupted by: • Motor PWM noise • SSR switching noise • Ground loops • Crosstalk between subsystems Freelancer must propose and implement: • Opto-isolated communication (RS-485 preferred) • Proper grounding strategy • Digital isolators where required • ADC noise mitigation strategies • Shielding recommendations Isolation architecture design is part of this job. Communication Requirements Preferred options: • (Modbus RTU or custom protocol) OR • I2C with digital isolators OR • CAN Bus (if justified) Freelancer must: • Recommend best communication protocol • Implement reliable packet structure • Implement CRC/error detection • Provide timeout and fault recovery logic System must be robust in noisy environments. Deliverables 1. Firmware for: o UI Arduino o Motor Arduino o pH Arduino o Temperature Arduino o Master Arduino 2. Communication protocol documentation 3. Commented, modular Arduino code 4. PCBs in KiCAD (all Arduino boards should be like shields) Required Skills • Advanced Arduino development • Embedded C/C++ • RS-485 / Modbus / CAN • Analog signal conditioning • PID control systems • Motor control with hall sensors • EMI/EMC mitigation • Industrial control systems experience • Experience with laboratory or scientific instruments (preferred) Nice to Have • Experience with high-impedance sensor design (pH, ion-selective electrodes) • Knowledge of op-amp/JFET front-end design • Experience designing noise-resistant analog systems • Prior multi-microcontroller architecture experience Milestones 1: Master Arduino with UI interface to one of the sub-systems 2,3…: Subsequent sub-systems Expected Freelancer Profile We are not looking for a hobbyist Arduino coder.

Project ID: 40222429