NFN Sensor Unit (SEN v1 & v2)

End-to-End Industrial IoT Solution for Precision Fish Farming

1. Project Overview

Client: Nexus Fish Network (NFN)

Device Type: Floating Water Quality Profiler

Role: Senior IoT Engineer (Firmware & Hardware Architect )

Core Tech: ESP32, Modbus RS485, ADS1115, Solar, BMS

The NFN SEN Unit is the data acquisition node of the Nexus Fish Network ecosystem. Designed as a standalone, energy-autonomous device, it floats on the water surface to continuously monitor critical aquaculture parameters.

The device features a unique "Ring Buoy" Mechanical Architecture:

Structure: A custom metal chassis mounted on a standard life-saving ring buoy for stability in turbulent water.
Enclosure: IP65-rated waterproof boxing housing the MCU, battery management system (BMS), and signal processing circuits.
Power System: 100% off-grid operation using a 12V Solar Panel, a 4S LiFePO4 Battery Pack, and a solar charge controller.

2. SEN v1.0: The "Active Sampling" Approach

The initial version addressed the limitations of hobby-grade sensors through mechanical ingenuity.

The Challenge:

The initial prototype utilized DFRobot Gravity Analog Sensors (DO SKU: SEN0237, pH V2 SKU: SEN0161-V2, and Analog ORP Pro). Field testing revealed that these sensors degraded rapidly when submerged continuously due to bio-fouling and electrolysis.

The Engineering Solution (The Sampling Box):

To extend sensor life, I engineered an Active Sampling System:

Mechanism: A secondary plastic reservoir (Sampling Box) was installed on the buoy.
Logic: A 12V DC Pump would activate periodically to fill the box with pond water.
Sensing: The DO, pH, ORP, and Turbidity sensors were housed inside this box, taking readings only when fresh water was pumped in.
Direct Sensors: Robust sensors like TDS, Temperature (DS18B20), and Ultrasonic Water Level (mounted on a guide pipe) remained continuously deployed in the pond.
ADC Interfacing: Utilized Dual ADS1115 (16-bit ADC) modules to handle the high resolution required for the analog sensor array.

3. SEN v2.0: The Industrial Evolution

The current iteration focuses on durability, precision, and minimising mechanical failure points.

The Upgrade:

v2.0 eliminates the mechanical pump system entirely by migrating to Industrial-Grade Probes capable of 24/7 submersion.

Key Technical Improvements:

Communication Protocol Shift (RS485):
- Migrated Dissolved Oxygen (DO) and pH monitoring to Industrial RS485 Modbus sensors. This eliminated analog signal noise and removed the need for frequent re-calibration.
Hardware Reverse Engineering (ORP):
- To integrate a high-quality Analog ORP probe cost-effectively, I reverse-engineered a commercial ORP analyzer.
- Implementation: I extracted the internal signal conditioning module from the analyzer and successfully interfaced it with the ADS1115 on my custom PCB.
Custom Sensor Modification:
- Modified the Gravity Analog Turbidity Sensor by custom-waterproofing the electronics, allowing it to be submerged directly into the pond without a sampling chamber.
Result: A solid-state system with zero moving parts (no pumps), significantly reducing maintenance requirements.

4. System Intelligence & Telemetry

Both versions feature advanced telemetry for remote troubleshooting:

Internal Climate Monitoring: A DHT22 sensor is embedded directly onto the PCB inside the main enclosure.
- Purpose: It monitors the internal temperature and humidity of the waterproof box. A rise in humidity alerts the engineering team to potential seal failures (water ingress) before the electronics are damaged.
Data Transmission:
- The ESP32 aggregates data from Modbus (RS485), I2C (ADS1115), and OneWire (Temp) protocols.
- Payloads are optimized and sent via MQTT to the cloud for real-time visualization.

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NFN Sensor Unit (SEN v1 & v2)

End-to-End Industrial IoT Solution for Precision Fish Farming

1. Project Overview

Get in touch at "ramim.cse.uctc@gmail.com"

https://www.facebook.com/IoTWithRamim/
linkedin.com/in/ramim256
+8801836655062

NFN Sensor Unit (SEN v1 & v2)

End-to-End Industrial IoT Solution for Precision Fish Farming

1. Project Overview

Get in touch at "ramim.cse.uctc@gmail.com"

https://www.facebook.com/IoTWithRamim/linkedin.com/in/ramim256+8801836655062

https://www.facebook.com/IoTWithRamim/
linkedin.com/in/ramim256
+8801836655062