🔥 Homemade SMD Reflow Oven 🔥

📑 Table of Contents

• Overview
• Project Demo
• Workflow
• Technical Challenges
• Repository Structure
• Requirements & Dependencies
• Installation & Usage
• To-Do List
• Possible Improvements
• Safety Considerations
• Contributing
• Reference Links
• License

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📝 Overview

The SMD Reflow Oven is an open-source project designed for precise SMD soldering. It utilizes configurable thermal profiles managed by an STM32F411 microcontroller and a web-based GUI hosted on an ESP01-S. Key features include real-time PID temperature control, smart power management, and robust safety systems.

✅ Functional Demo: All core features (PID control, temperature sensing, web GUI, and the reflow algorithm) are fully operational and ready for soldering SMD components. 🚧 Active Development: Both the firmware and hardware are under continuous improvement.

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📹 Project Demo

See the oven in action! This video demonstrates its current functionality and soldering capabilities.

Watch a video demonstration of the oven in action

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🔄 Workflow

Step-by-step SMD soldering process

1. 📋 PCB Preparation

• Apply solder paste evenly using a stencil.
• Carefully place the SMD components onto the pasted pads.

2. ⚙️ Oven Setup

• Power the oven (120V AC).
• Select the appropriate thermal profile for your solder type via the web GUI.
• Verify that all safety systems are active.

3. 🔥 Soldering Process

• Place the prepared PCB inside the oven chamber.
• Close the door securely and start the process from the interface.
• Monitor the temperature curve in real-time to ensure it follows the selected profile.

4. 🔍 Final Inspection

• Wait for the Cooldown phase to complete before opening the door.
• Allow the PCB to cool completely before handling.
• Inspect the solder joints with a magnifier or microscope for any defects.
• Perform electrical tests to check for shorts or open circuits.

📺 Watch the final results on YouTube

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🎯 Technical Challenges

Challenge	Solution Approach
Temperature Control	Ensure uniform heat distribution, implement adaptable thermal curves, and design profiles to prevent component microcracks.
Risk Management	Implement automatic overheating detection and shutoff, along with a system for filtering potentially toxic vapors.
Operational Precision	Calibrate sensors accurately and synchronize heating/cooling stages for reliable and repeatable results.

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📂 Repository Structure

The Serial Peripheral Interface (SPI) is crucial in this project for fast communication between the STM32 microcontroller and peripherals like the MAX6675 thermocouple sensors, ensuring precise, real-time temperature readings for the PID control loop.

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├── Firmware/                   # Firmware for all microcontrollers
│   ├── esp01/                  # ESP-01S firmware and related tools
│   ├── nextionGUI/             # Nextion HMI screen GUI files
│   └── stm32f411/              # STM32F411 firmware and related tools
├── Hardware/                   # Hardware design files (schematics, PCB)
│   ├── horno_no_modificado/  # Original, unmodified oven schematics
│   └── horno_reflujo/        # Custom reflow oven hardware
├── pictures/                   # Project images and photos
├── .gitignore                  # Git ignore file
├── LICENSE                     # Project license
└── README.md                   # This README file

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📦 Requirements & Dependencies

Software

• PlatformIO: Recommended for firmware development.
• Python 3.x: For data analysis and utility scripts.
• KiCad: For viewing and editing hardware schematics and PCB layouts.
• STM32CubeIDE: Optional, for STM32-specific development.

Hardware

• Refer to the Bill of Materials (BOM) located in the Hardware/horno_reflujo/ directory for a complete list of components.

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🛠️ Installation & Usage

1. Clone the Repository:

   git clone https://github.com/La-guajolota/Horno_reflujo.git
   cd Horno_reflujo

2. Setup Firmware:
   • Open the Firmware/ and stm32f411/ directories in PlatformIO.
   • Follow the specific setup instructions within each folder to compile and upload the firmware.
3. Assemble Hardware:
   • Use the schematics and PCB files in the Hardware/ directory as a guide.
   • Solder and assemble all components according to the BOM.
4. Calibrate & Test:
   • Before the first use, perform temperature sensor calibration.
   • Test all safety systems to ensure they are functioning correctly.

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📋 To-Do List

High Priority

• Complete the documentation for hardware assembly.
• Implement a physical emergency stop button.
• Create a detailed guide for sensor calibration procedures.
• Add unit tests for critical firmware functions.

Medium Priority

• Develop a mobile-friendly interface or a dedicated app.
• Add data logging and analysis features to track performance.
• Create 3D printable designs for the enclosure.

Low Priority

• Integrate with PCB design software for profile suggestions.
• Add cloud connectivity for remote monitoring.

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🚀 Possible Improvements

Firmware Enhancements

• Advanced PID Control: Implement auto-tuning algorithms and adaptive control for even greater precision.
• Enhanced Safety: Add redundant sensors and fail-safe mechanisms.
• Intuitive UI: Improve the user interface with a touchscreen, OLED display, or rotary encoder.
• IoT Integration: Allow for remote monitoring and control over the internet.
• Ventilation Control: Develop an automated system to manage toxic vapor extraction.

Hardware Upgrades

• Improved Insulation: Enhance thermal efficiency and user safety.
• High-Accuracy Sensors: Upgrade to more precise temperature sensors.
• Modular Design: Create a modular system to support different oven sizes.
• Power Efficiency: Optimize heating element control to reduce energy consumption.
• Electrical Isolation: Improve electrical isolation between high-voltage and low-voltage circuits.

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⚠️ Safety Considerations

• ⚡ High Voltage: This project involves 120V AC. Exercise extreme caution and ensure all connections are properly insulated.
• 🌡️ High Temperatures: The oven reaches temperatures capable of causing severe burns. Use protective equipment.
• 💨 Ventilation: Solder paste fumes can be toxic. Operate the oven in a well-ventilated area.
• 🔧 Grounding: Ensure the oven chassis is properly grounded to prevent electrical shock.
• 📏 Calibration: Regularly calibrate temperature sensors to maintain accuracy and prevent overheating.

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🤝 Contributing

Contributions are welcome! If you'd like to help improve this project, please follow these steps:

1. Fork the repository.
2. Create a new branch: git checkout -b feature/your-amazing-feature
3. Make your changes and commit them: git commit -m 'Add your amazing feature'
4. Push to your branch: git push origin feature/your-amazing-feature
5. Open a Pull Request and describe the changes you've made.

Please report any bugs or suggest features by opening an issue on GitHub.

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🔗 Reference Links

• Nextion HMI Displays – Official site for Nextion touchscreen displays.
• gerber_to_scad (GitHub) – Tool for generating 3D stencils from Gerber files.
• SMD Soldering Guidelines – Comprehensive guide to the reflow soldering process.
• Reflow Soldering Profiles (SMTA) – Industry resources and recommended thermal profiles.
• DIY Reflow Oven on Instructables – Step-by-step guide for building a reflow oven with open-source firmware.
• Hack Your Toaster Oven to Become a Thermocouple Measurement System (All About Circuits) – Reference for thermocouple integration and reflow process insights.
• Better SPI Bus Design in 3 Steps (DorkbotPDX) – Key considerations for reliable MAX6675 sensor communication.

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📄 License

This project is licensed under the MIT License. See the LICENSE file for more details. This means you are free to use, modify, and distribute the project, provided you include the original copyright and license notice.