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Fish Dryer v2 is an advanced, modular ESP32-based control system designed for automated fish drying applications. The system combines precision temperature control, real-time weight monitoring, and intelligent automation to achieve optimal drying conditions while ensuring safety and energy efficiency.

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Fish Dryer v2 🐟

Version: 2.0.0
Target Platform: ESP32 (38-pin development board)
License: MIT
Status: Development

📋 Table of Contents

🎯 Project Overview

Fish Dryer v2 is an advanced, modular ESP32-based control system designed for automated fish drying applications. The system combines precision temperature control, real-time weight monitoring, and intelligent automation to achieve optimal drying conditions while ensuring safety and energy efficiency.

Key Highlights

  • Modular Architecture: Independent, swappable hardware modules with centralized pin configuration
  • PID Temperature Control: Automatic thermostat with tunable parameters (Kp=4.0, Ki=0.0, Kd=22.0)
  • Weight-Based Automation: Load cell integration for water content calculation and automatic stop
  • Safety-First Design: Sensor failure detection, thermal protection, and fail-safe relay control
  • Extensible Platform: Easy integration with HMI displays, cloud logging, and power management systems
  • Non-Blocking Architecture: Real-time responsiveness with millis()-based timing and event handling

Target Applications

  • Commercial fish drying operations
  • Food preservation and dehydration
  • Agricultural product drying
  • Research and development testbeds

🏗️ System Architecture

The Fish Dryer v2 employs a centralized ESP32 controller managing multiple peripheral systems through digital and analog interfaces. The architecture prioritizes modularity, real-time control, and fault tolerance.

graph TB
    subgraph Power["⚡ Power System"]
        Solar[2x 300W Solar Panels<br/>600W Total]
        MPPT[40A MPPT Controller]
        Battery[LiFePO4 Battery<br/>300Ah 12V]
        Inverter[3000W Inverter]
        Breakers[DC Breakers & LVD]
        Mains[Mains AC<br/>Backup]
        Solar --> MPPT
        MPPT --> Battery
        Battery --> Breakers
        Breakers --> Inverter
        Mains --> Inverter
        Inverter -->|12V DC| Loads[Fish Dryer<br/>650-1300W]
    end
    
    subgraph ESP32["🧠 ESP32 Controller"]
        Core[ESP32 38-Pin<br/>FishDryer.ino]
        PID[PID Controller<br/>Kp=4.0, Ki=0.0, Kd=22.0]
        Logic[Control Logic<br/>Weight Monitor<br/>Auto-Stop]
        Serial[Serial Command<br/>Interface]
    end
    
    subgraph Sensors["📊 Sensor Modules"]
        SHT31[SHT31<br/>Temp & Humidity<br/>I2C 0x44]
        HX711[HX711<br/>Load Cell<br/>Weight Sensor]
    end
    
    subgraph Actuators["🔌 Relay Outputs"]
        SSR1[SSR1: Heating Element<br/>GPIO 16]
        SSR2[SSR2: Convection Fan<br/>GPIO 17]
        SSR3[SSR3: Exhaust Fan<br/>GPIO 18]
    end
    
    subgraph UI["👤 User Interface"]
        BTN1[Button 1<br/>GPIO 32]
        BTN2[Button 2<br/>GPIO 33]
        BTN3[Button 3<br/>GPIO 25]
        BTN4[Button 4<br/>GPIO 26]
        HMI[HMI Display<br/>Serial/ESP-NOW]
    end
    
    PowerMgr -->|5V/3.3V| Core
    
    SHT31 -->|I2C SDA:21, SCL:22| Core
    HX711 -->|DOUT:34, SCK:27| Core
    
    Core --> PID
    PID --> Logic
    Logic -->|PWM Control| SSR1
    Logic -->|ON/OFF| SSR2
    Logic -->|ON/OFF| SSR3
    
    BTN1 --> Core
    BTN2 --> Core
    BTN3 --> Core
    BTN4 --> Core
    
    Core <-->|UART/ESP-NOW| HMI
    Core <-->|115200 baud| Serial
    
    SSR1 -.->|Heat| Chamber[Drying Chamber]
    SSR2 -.->|Airflow| Chamber
    SSR3 -.->|Exhaust| Chamber
    
    style Core fill:#4CAF50,stroke:#2E7D32,color:#fff
    style PID fill:#FF9800,stroke:#E65100,color:#fff
    style Logic fill:#2196F3,stroke:#0D47A1,color:#fff
Loading

Data Flow

  1. Input Layer: Sensors continuously measure temperature, humidity, and weight
  2. Processing Layer: ESP32 executes PID calculations and control logic every 2 seconds
  3. Output Layer: SSR relays modulate heating and ventilation based on control signals
  4. Feedback Loop: Temperature readings feed back into PID controller for closed-loop regulation

🔧 Hardware Components

Bill of Materials

Component Model/Spec Purpose Interface GPIO Pin(s)
Microcontroller ESP32 38-Pin DevKit Central controller - -
SSR1 Solid State Relay (rated for load) Heating element control Digital Output 16
SSR2 Solid State Relay Convection fan control Digital Output 17
SSR3 Solid State Relay Exhaust fan control Digital Output 18
SHT31 Sensirion SHT31-D Temperature & humidity sensor I2C (0x44) SDA:21, SCL:22
HX711 24-bit ADC + Load Cell Weight measurement 2-Wire Serial DOUT:34, SCK:27
Button 1-4 Tactile push button (NO) User input (short/long press) Digital Input (Pullup) 32, 33, 25, 26
Power Supply 5V/3A (minimum) ESP32 and peripherals - -
LiFePO4 Battery 300Ah 12V Energy storage for off-grid operation - -
Solar Panels 2x 300W (600W total) Solar energy harvesting - -
Charge Controller 40A MPPT Solar battery charging - -
Inverter 3000W DC to AC conversion - -
Solar Cables 10AWG+ (rated for current) Power transmission - -
Breakers DC rated (40A+ main, 10A branches) Overcurrent protection - -
LVD (Low Voltage Disconnect) 12V system compatible Battery protection - -

Pin Assignment Table

Digital Outputs (SSR Control)

Signal GPIO Function Active State Notes
SSR1_PIN 16 Heating Element HIGH = ON High-power relay
SSR2_PIN 17 Convection Fan HIGH = ON Airflow circulation
SSR3_PIN 18 Exhaust Fan HIGH = ON Moisture exhaust

Digital Inputs (Buttons)

Signal GPIO Function Active State Detection
BUTTON1_PIN 32 User Button 1 LOW (Pullup) Short/Long press
BUTTON2_PIN 33 User Button 2 LOW (Pullup) Short/Long press
BUTTON3_PIN 25 User Button 3 LOW (Pullup) Short/Long press
BUTTON4_PIN 26 User Button 4 LOW (Pullup) Short/Long press

I2C Bus (SHT31 Sensor)

Signal GPIO Function Protocol
I2C_SDA_PIN 21 I2C Data I2C (400kHz)
I2C_SCL_PIN 22 I2C Clock I2C (400kHz)

Load Cell Interface (HX711)

Signal GPIO Direction Notes
LOADCELL_DOUT_PIN 34 Input Input-only GPIO acceptable
LOADCELL_SCK_PIN 27 Output Clock signal to HX711

Hardware Design Considerations

  • ESP32 Pin Safety: Avoids flash pins (GPIO 6-11) and boot-critical pins
  • SSR Ratings: Ensure SSRs are rated for heating element and fan loads (typically 10-40A for heating)
  • Load Cell Capacity: Select load cell based on maximum product weight (e.g., 5kg, 10kg, 20kg)
  • Enclosure: Use NEMA-rated enclosure if operating in humid environments
  • Thermal Management: Provide adequate ventilation for ESP32 and SSRs during operation

Wiring Diagram

Wiring Diagram

For the interactive wiring diagram, visit: Cirkit Designer

💻 Software Features & Logic

Core Features

1. PID Temperature Control

The system implements a PID (Proportional-Integral-Derivative) controller for precise temperature regulation within the drying chamber.

PID Configuration:

  • Kp (Proportional Gain): 4.0 — Immediate response to temperature error
  • Ki (Integral Gain): 0.0 — No integral action (disabled to prevent windup)
  • Kd (Derivative Gain): 22.0 — Strong damping to prevent overshoot
  • Output Range: 0 to 5000 (arbitrary units for relay control logic)
  • Update Interval: 2000ms (2 seconds)

Control Strategy:

  • When PID output > 0: Heating + Convection ON, Exhaust OFF
  • When PID output ≤ 0: Heating + Convection OFF, Exhaust ON
  • Default setpoint: 60°C (adjustable via serial command)
flowchart TD
    Start([PID Loop Start]) --> CheckEnabled{PID Enabled?}
    CheckEnabled -->|No| End([End])
    CheckEnabled -->|Yes| CheckInterval{2 sec elapsed?}
    CheckInterval -->|No| End
    CheckInterval -->|Yes| ReadTemp[Read SHT31<br/>Update CURRENT_TEMPERATURE]
    ReadTemp --> Compute[PID Compute<br/>Error = Setpoint - Current<br/>Output = Kp*E + Kd*dE/dt]
    Compute --> CheckOutput{Output > 0?}
    CheckOutput -->|Yes| HeatMode[SSR1: ON Heating<br/>SSR2: ON Convection<br/>SSR3: OFF Exhaust]
    CheckOutput -->|No| CoolMode[SSR1: OFF Heating<br/>SSR2: OFF Convection<br/>SSR3: ON Exhaust]
    HeatMode --> UpdateTime[Update lastPIDUpdate]
    CoolMode --> UpdateTime
    UpdateTime --> End
Loading

2. Weight Monitoring & Automatic Stop

The HX711 load cell continuously monitors product weight to calculate water content loss and trigger automatic shutdown when target dryness is achieved.

Weight-Based Control Logic:

  • Initial weight captured at start
  • Continuous weight tracking during operation
  • Water content percentage = (Initial - Current) / Initial × 100
  • Auto-stop threshold configurable (e.g., 70% water loss)
flowchart TD
    Start([Weight Monitor Loop]) --> ReadWeight[Read HX711<br/>Get Current Weight]
    ReadWeight --> CheckInit{Initial Weight<br/>Set?}
    CheckInit -->|No| SetInit[Store as Initial Weight]
    SetInit --> End([End])
    CheckInit -->|Yes| CalcLoss[Calculate Water Loss<br/>Loss% = Initial - Current / Initial × 100]
    CalcLoss --> CheckThreshold{Loss ≥<br/>Target%?}
    CheckThreshold -->|No| Log[Log Weight Data<br/>Update HMI Display]
    CheckThreshold -->|Yes| AutoStop[Trigger Auto-Stop<br/>Disable PID<br/>Turn Off All SSRs<br/>Alert User]
    Log --> End
    AutoStop --> End
Loading

3. Button Interaction System

Four tactile buttons provide local user control with debouncing and press-duration detection.

Button Features:

  • Debounce Time: 50ms — Eliminates mechanical noise
  • Short Press: < 1000ms — Quick actions (start/stop, mode change)
  • Long Press: ≥ 1000ms — Advanced functions (calibration, settings)
  • Non-Blocking: millis()-based timing for real-time responsiveness

Button Functions (Customizable):

Button Short Press Long Press
BTN1 (GPIO 32) Start/Stop Drying Cycle Enter Calibration Mode
BTN2 (GPIO 33) Increase Setpoint (+5°C) Reset to Default Setpoint
BTN3 (GPIO 25) Decrease Setpoint (-5°C) Tare Load Cell
BTN4 (GPIO 26) Toggle Display Mode System Diagnostics 
flowchart TD
    Start([Button Update Loop]) --> ReadAll[Read All 4 Button States]
    ReadAll --> Loop{For Each<br/>Button}
    Loop --> ReadPin[Read GPIO Pin State]
    ReadPin --> CheckChange{State Changed?}
    CheckChange -->|Yes| ResetDebounce[Reset Debounce Timer]
    CheckChange -->|No| CheckDebounce{Debounce Time<br/>Elapsed?}
    ResetDebounce --> Next([Next Button])
    CheckDebounce -->|No| Next
    CheckDebounce -->|Yes| UpdateState[Update Current State]
    UpdateState --> CheckPress{Pressed?<br/>LOW}
    CheckPress -->|Yes| StartTimer[Start Press Timer<br/>isPressed = true]
    CheckPress -->|No| CheckRelease{Was Pressed?}
    StartTimer --> CheckLongPress{Press Time<br/>≥ 1000ms?}
    CheckLongPress -->|Yes| TriggerLong[Trigger Long Press<br/>longPressTriggered = true]
    CheckLongPress -->|No| Next
    TriggerLong --> Next
    CheckRelease -->|Yes| CheckLong{Long Press<br/>Triggered?}
    CheckRelease -->|No| Next
    CheckLong -->|No| TriggerShort[Trigger Short Press<br/>Execute Action]
    CheckLong -->|Yes| ResetFlags[Reset Press Flags]
    TriggerShort --> ResetFlags
    ResetFlags --> Next
    Next --> Loop
Loading

4. Non-Blocking Architecture

The entire system operates on a non-blocking event loop using millis() for timing, ensuring:

  • Real-time button responsiveness
  • Smooth PID updates without delays
  • Concurrent sensor reading and relay control
  • No delay() calls that would freeze execution

Physical Button Control

Local control via 4 tactile buttons mounted on the enclosure:

  • Button 1: Primary control (Start/Stop)
  • Button 2: Temperature adjustment (Up)
  • Button 3: Temperature adjustment (Down)
  • Button 4: Mode/View toggle

All button actions are logged to serial for diagnostics.

⚡ Power & Energy Management

Multi-Source Power Architecture

The Fish Dryer v2 is designed to operate with flexible power sources for off-grid or hybrid applications:

Supported Power Sources

  1. Solar Power

    • Panels: 2x 300W monocrystalline panels (600W total)
    • Charge Controller: 40A MPPT controller for efficient charging
    • Voltage: 12V nominal system
    • Expected Daily Energy: ~3-4 kWh (depending on location and weather)
    • Cabling: 10AWG+ solar cables with proper MC4 connectors

  2. Battery Bank

    • Type: LiFePO4 (Lithium Iron Phosphate)
    • Capacity: 300Ah at 12V (3600Wh total energy)
    • Runtime: ~3-5 hours continuous drying (at 650-1300W load)
    • Cycle Life: 2000+ cycles (10+ years with proper usage)
    • Protection: Built-in BMS (Battery Management System)
    • Low Voltage Disconnect: Automatic cutoff at ~10.5V to prevent damage

  3. Mains AC Power

    • Primary power source for continuous operation
    • Inverter: 3000W pure sine wave for AC loads
    • 110V/220V AC to 12V DC conversion
    • Automatic failover to battery backup during outages
    • Breakers: DC-rated circuit protection (40A main, 10A branches)

Power Consumption Profile

Component Power Draw Duty Cycle Avg. Consumption
ESP32 Controller 500mW 100% 500mW
SHT31 Sensor 1.5mW 100% 1.5mW
HX711 + Load Cell 10mW 100% 10mW
Heating Element 1000-2000W 40-60% (PID) 600-1200W
Convection Fan 20-50W 60-80% 16-40W
Exhaust Fan 20-50W 20-40% 4-20W
Total System ~1100-2100W Variable ~650-1300W

System Runtime Calculations (300Ah LiFePO4 Battery)

Load Scenario Power Draw Runtime Notes
Low Power Mode 650W ~5.5 hours Fans only, minimal heating
Medium Load 1000W ~3.6 hours Balanced heating/fans
High Load 1300W ~2.8 hours Maximum heating output
Solar Replenish - 2-4 hours Full charge from 600W panels

Daily Operation Example:

  • 4 hours drying (1000W avg) = 4 kWh consumed
  • 6 hours solar charging (600W panels) = 3.6 kWh generated
  • Net: 0.4 kWh deficit (minimal battery draw)

Solar System Installation Guidelines

Panel Mounting:

  • South-facing orientation (northern hemisphere)
  • 30-45° tilt angle for optimal year-round performance
  • Secure mounting to withstand wind loads
  • Shade-free installation for maximum efficiency

Cable Routing:

  • Use 10AWG or larger solar cable
  • Minimize cable length to reduce voltage drop
  • Proper MC4 connectors for weatherproofing
  • Separate DC and AC cable runs

Safety Considerations:

  • All DC connections behind breakers
  • Ground-mounted system with proper earthing
  • Lightning protection for exposed installations
  • Regular maintenance and cleaning of panels ├── Fish Dryer (650-1300W) ├── Other Loads └── LVD Protection

**Key Components:**
- **Solar Panels:** 2x 300W panels in series/parallel configuration
- **MPPT Controller:** 40A unit optimizes charging efficiency (95%+)
- **LiFePO4 Battery:** Deep cycle battery with built-in protection
- **Inverter:** 3000W pure sine wave for clean AC power
- **Breakers:** DC-rated for system protection
- **LVD:** Automatic disconnect prevents battery damage

#### Battery Management & Safety

**LiFePO4 Advantages:**
- **Long Cycle Life:** 2000+ charge cycles vs. 500 for lead-acid
- **High Efficiency:** 95%+ charge/discharge efficiency
- **Safe Chemistry:** Stable lithium iron phosphate technology
- **Wide Temperature Range:** -20°C to 60°C operating range
- **Lightweight:** ~40% lighter than equivalent lead-acid

**Charging Parameters:**
- **Bulk Voltage:** 14.2-14.6V (MPPT controller managed)
- **Float Voltage:** 13.6V (maintenance charging)
- **Max Charge Current:** 40A (limited by MPPT controller)
- **Temperature Compensation:** Automatic adjustment for optimal charging


## 📊 Data Logging & Monitoring

### Logging Capabilities

The system supports multiple logging backends for data persistence and analysis:

#### 1. Serial Logging (Default)

- **Baud Rate:** 115200
- **Format:** Human-readable text with timestamps
- **Data Points:** All sensor readings, relay states, PID output, button events
- **Use Case:** Real-time debugging and development

#### 2. HMI Display Logging

- **Protocol:** UART or ESP-NOW
- **Format:** Tagged data packets for display parsing
- **Retention:** Display-side storage (SD card on HMI)
- **Use Case:** Operator monitoring and historical review

#### 3. SD Card Logging (Future Enhancement)

- **Module:** SPI SD card reader
- **Format:** CSV with Unix timestamps
- **Fields:** `timestamp, temp, humidity, weight, water_loss_pct, pid_output, heater, fan, exhaust`
- **Rotation:** Daily files with automatic rollover

### Logged Parameters

| Parameter | Unit | Precision | Sample Rate | Description |
|-----------|------|-----------|-------------|-------------|
| Temperature | °C | 0.1 | 2s | Chamber air temperature |
| Humidity | % | 0.1 | 5s | Relative humidity |
| Weight | kg | 0.01 | 5s | Current product weight |
| Water Loss | % | 1 | 5s | Calculated drying progress |
| PID Output | units | 1 | 2s | Controller output signal |
| Heater State | bool | - | Event | ON/OFF state change |
| Fan State | bool | - | Event | ON/OFF state change |
| Exhaust State | bool | - | Event | ON/OFF state change |
| Runtime | seconds | 1 | 1s | Total operation time |
| Power Source | enum | - | Event | SOLAR/BATTERY/MAINS |


## 🛡️ Safety & Fail-Safes

### Sensor Failure Handling

The system implements robust error detection and fail-safe responses:

#### SHT31 Temperature Sensor Failure

```mermaid
flowchart TD
    Start([Read SHT31]) --> ReadTemp[Attempt Temperature Read]
    ReadTemp --> CheckNaN{isNaN temp?}
    CheckNaN -->|No| UpdateGlobal[Update CURRENT_TEMPERATURE<br/>Continue Normal Operation]
    CheckNaN -->|Yes| IncrementFail[Increment Failure Counter]
    UpdateGlobal --> ResetCounter[Reset Failure Counter]
    ResetCounter --> End([End])
    IncrementFail --> CheckCount{Failures ≥ 3<br/>Consecutive?}
    CheckCount -->|No| End
    CheckCount -->|Yes| TriggerSafety[SAFETY SHUTDOWN:<br/>Disable PID<br/>Turn OFF Heater SSR1<br/>Turn ON Exhaust SSR3<br/>Alert User]
    TriggerSafety --> Log[Log Error to Serial/HMI<br/>Error: SHT31 Sensor Fault]
    Log --> End

Fail-Safe Actions:

  • Immediate heater cutoff to prevent overheating
  • Exhaust fan activation for rapid cooling
  • PID control disabled
  • Visual and serial alert

Fail-Safe Actions:

  • Immediate heater cutoff to prevent overheating
  • Exhaust fan activation for rapid cooling
  • PID control disabled
  • Visual and serial alert
  • System enters safe mode until sensor recovery or manual reset

HX711 Load Cell Failure

Detection Method:

  • scale.is_ready() check before each reading
  • Consecutive read failures trigger alert

Response:

  • Continue temperature control (drying can proceed without weight monitoring)
  • Disable automatic stop feature
  • Log warning to serial/HMI
  • Operator must manually monitor drying progress

Electrical Safety

  • SSR Isolation: Optocoupler-based SSRs provide galvanic isolation between ESP32 logic and high-voltage loads
  • Overcurrent Protection: Circuit breakers on mains input

Operational Safety Features

Feature Implementation Purpose
Sensor Watchdog 3 consecutive read failures → shutdown Prevent blind operation
Overheat Cutoff Software limit at 85°C (configurable) Thermal protection
Manual Emergency Stop Button 1 long-press → immediate shutdown Operator safety
Power-On Self-Test Sensor checks at boot Early fault detection
Graceful Shutdown Turn off heater before fans Prevent residual heat buildup

🚀 Installation & Setup

Prerequisites

  • Arduino IDE: Version 1.8.19 or newer (or PlatformIO)
  • ESP32 Board Support: Install via Arduino Board Manager
  • Required Libraries:

Installation Steps

1. Clone Repository

git clone https://github.com/qppd/fish-dryer-v2.git
cd fish-dryer-v2

2. Install Arduino Libraries

Via Arduino IDE Library Manager:

  1. Open Arduino IDE
  2. Go to Sketch → Include Library → Manage Libraries
  3. Search and install:
    • PID by Brett Beauregard
    • Adafruit SHT31 Library
    • HX711 Arduino Library by Bogdan Necula

Via PlatformIO:

[env:esp32dev]
platform = espressif32
board = esp32dev
framework = arduino
lib_deps = 
    br3ttb/PID@^1.2.1
    adafruit/Adafruit SHT31 Library@^2.2.0
    bogde/HX711@^0.7.5

3. Configure Hardware Pins

Review src/esp/FishDryer/PINS_CONFIG.h and adjust GPIO assignments to match your hardware:

// Example: Change SSR1 pin from 16 to 23
#define SSR1_PIN 23

4. Upload Firmware

  1. Open src/esp/FishDryer/FishDryer.ino in Arduino IDE
  2. Select Board: "ESP32 Dev Module"
  3. Select Upload Speed: 115200
  4. Select COM Port: (your ESP32 port)
  5. Click Upload ⬆️

5. Verify Operation

  1. Open Serial Monitor at 115200 baud
  2. Reset ESP32
  3. Verify initialization messages: 
    SSR_CONFIG loaded. SSR1_PIN, SSR2_PIN, and SSR3_PIN set as OUTPUT.
SHT31 sensor initialized.
HX711 load cell initialized.
Buttons initialized with INPUT_PULLUP.
PID controller initialized.

📡 Serial Command Interface

The system provides a comprehensive serial command interface for testing, calibration, and remote control.

Command Reference

Relay Control

Command Function Response
SSR1:1 Turn ON Heating Element (GPIO 16) SSR1_PIN set HIGH
SSR1:0 Turn OFF Heating Element SSR1_PIN set LOW
SSR2:1 Turn ON Convection Fan (GPIO 17) SSR2_PIN set HIGH
SSR2:0 Turn OFF Convection Fan SSR2_PIN set LOW
SSR3:1 Turn ON Exhaust Fan (GPIO 18) SSR3_PIN set HIGH
SSR3:0 Turn OFF Exhaust Fan SSR3_PIN set LOW

Sensor Readings

Command Function Response Example
SHT31:READ Read temperature and humidity SHT31 Temp: 58.2 C, Humidity: 45.3 %
LOADCELL:READ Read raw load cell value Load cell reading: 823456
BUTTONS:READ Read all button states BTN1: RELEASED BTN2: PRESSED ...

PID Control

Command Function Response Example
PID:START Enable PID thermostat control PID thermostat control ENABLED. System will maintain temperature automatically.
PID:STOP Disable PID control PID thermostat control DISABLED.
PID:SET:65.0 Set temperature setpoint to 65.0°C Temperature setpoint set to: 65.0
PID:READ Read PID status and values PID Status: ENABLED | Current Temp: 58.2 | Setpoint: 60.0 | PID Output: 3245

Usage Examples

Test Heating Element

> SSR1:1
< SSR1_PIN set HIGH
(Wait 10 seconds)
> SHT31:READ
< SHT31 Temp: 35.2 C, Humidity: 42.1 %
> SSR1:0
< SSR1_PIN set LOW

Calibrate Load Cell

> LOADCELL:READ
< Load cell reading: 823456
(Remove all weight)
> LOADCELL:READ
< Load cell reading: 8203
(Add known weight, e.g., 1kg)
> LOADCELL:READ
< Load cell reading: 431287

Start Automatic Drying

> PID:SET:60
< Temperature setpoint set to: 60.0
> PID:START
< PID thermostat control ENABLED. System will maintain temperature automatically.
> PID:READ
< PID Status: ENABLED | Current Temp: 28.5 | Setpoint: 60.0 | PID Output: 4523

⚙️ Configuration

PID Tuning

The PID controller can be tuned for different drying chamber characteristics by modifying PID_CONFIG.h:

// PID tuning parameters
#define PID_KP 4.0   // Proportional gain
#define PID_KI 0.0   // Integral gain
#define PID_KD 22.0  // Derivative gain

Tuning Guidelines:

Parameter Effect Increase If Decrease If
Kp Immediate response Slow to reach setpoint Oscillates rapidly
Ki Eliminates steady-state error Persistent offset error Overshoot/instability
Kd Damping/smoothing Overshoot on changes Too sluggish

Recommended Starting Points:

  • Small chamber (< 0.5 m³): Kp=2.0, Ki=0.5, Kd=10.0
  • Medium chamber (0.5-2 m³): Kp=4.0, Ki=0.0, Kd=22.0 (current)
  • Large chamber (> 2 m³): Kp=6.0, Ki=0.2, Kd=30.0

Load Cell Calibration

To calibrate the HX711 load cell for accurate weight readings:

  1. Tare (Zero) Calibration:

    scale.tare();  // Add to setup() after initLoadCell()

  2. Scale Factor Calibration:

    scale.set_scale(2280.f);  // Calibration factor (adjust based on testing)
float weight = scale.get_units(10);  // Average of 10 readings

  3. Calibration Procedure:

    • Remove all weight from platform
    • Call scale.tare()
    • Place known weight (e.g., 1.000 kg)
    • Read raw value with scale.read_average(10)
    • Calculate factor: calibration_factor = raw_value / known_weight
    • Update set_scale(calibration_factor)

Button Function Customization

Edit BUTTON_CONFIG.h to customize button actions:

void handleShortPress(int buttonIndex) {
  switch(buttonIndex) {
    case 0: // Button 1
      PID_ENABLED = !PID_ENABLED;
      Serial.println(PID_ENABLED ? "PID Started" : "PID Stopped");
      break;
    case 1: // Button 2
      TEMPERATURE_SETPOINT += 5.0;
      Serial.print("Setpoint: ");
      Serial.println(TEMPERATURE_SETPOINT);
      break;
    // ... add your custom actions
  }
}

📈 Project Roadmap

Current Version: v2.0.0

  • ✅ Modular configuration architecture
  • ✅ PID temperature control
  • ✅ Load cell integration
  • ✅ Button input system
  • ✅ Serial command interface

Planned Features (v2.1.0)

  • ⬜ HMI display integration (Nextion/ESP-NOW)
  • ⬜ SD card data logging
  • ⬜ Battery voltage monitoring
  • ⬜ Automatic water loss calculation

🤝 Contributing

Contributions are welcome! Please follow these guidelines:

Development Workflow

  1. Fork the repository
  2. Create a feature branch: git checkout -b feature/amazing-feature
  3. Commit your changes: git commit -m 'Add amazing feature'
  4. Push to branch: git push origin feature/amazing-feature
  5. Open a Pull Request

Code Standards

  • Follow Arduino/C++ style conventions
  • Comment all hardware-specific configurations
  • Include docstrings for new functions
  • Test on real hardware before submitting
  • Update README.md if adding user-facing features

Reporting Issues

Use GitHub Issues with the following labels:

  • bug - Software defects
  • hardware - Hardware compatibility issues
  • enhancement - Feature requests
  • documentation - Docs improvements

📄 License & Contact

License

This project is licensed under the MIT License. See the LICENSE file for full terms.

Project Information

Contact & Support

Acknowledgments

Built with:

  • ESP32 by Espressif Systems
  • Arduino framework and community libraries
  • PID_v1 by Brett Beauregard
  • Adafruit SHT31 library
  • HX711 library by Bogdan Necula

🔍 Troubleshooting

Common Issues

Issue: SHT31 Sensor Not Found

Symptoms:

Couldn't find SHT31 sensor!

Solutions:

  1. Check I2C wiring (SDA:21, SCL:22)
  2. Verify sensor I2C address (default 0x44, alternative 0x45)
  3. Add pull-up resistors (4.7kΩ) to SDA and SCL lines
  4. Test with I2C scanner sketch

Issue: Load Cell Returns Erratic Values

Symptoms:

Load cell reading: 823456
Load cell reading: 11234
Load cell reading: 923487

Solutions:

  1. Check wiring connections (loose wires cause noise)
  2. Move HX711 away from high-power lines (EMI interference)
  3. Add ferrite bead on load cell cable
  4. Use shielded cable for load cell wiring
  5. Increase averaging: scale.read_average(20)

Issue: PID Oscillates Wildly

Symptoms:

  • Temperature swings ±10°C around setpoint
  • Relay chatter (rapid on/off cycles)

Solutions:

  1. Reduce Kp gain (try Kp=2.0)
  2. Increase Kd gain (try Kd=30.0)
  3. Increase PID update interval to 5000ms
  4. Check for poor thermal contact between sensor and chamber

Issue: ESP32 Won't Boot After Upload

Symptoms:

  • Brown-out detector triggered
  • Continuous restart loop

Solutions:

  1. Check power supply capacity (minimum 2A)
  2. Add bulk capacitor (100-1000µF) near ESP32 VIN
  3. Ensure SSRs are not back-feeding voltage to ESP32
  4. Try different USB cable (some have high resistance)

📚 Additional Resources

Technical Documentation

Related Projects

Community Support

Fish Dryer v2 — Built with ❤️ by the QPPD Dev Community

⭐ Star this repo if you find it useful!

About

Fish Dryer v2 is an advanced, modular ESP32-based control system designed for automated fish drying applications. The system combines precision temperature control, real-time weight monitoring, and intelligent automation to achieve optimal drying conditions while ensuring safety and energy efficiency.

Topics

fish automation monitoring esp32 smart pid-control heating-control dryer loadcell-control fishdryer

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