ReflowOven controller

Reflow Oven Controller

An open-source controller for converting a kitchen toaster oven into a reflow oven.

Overview

This project consists of a PCB and firmware to convert a classic toaster oven into a temperature-controlled oven for PCB reflow.

Oven Modes

• Reflow - Follows a predefined temperature curve for optimal PCB reflow.
• Dry - Maintains a defined temperature for a set duration (useful for drying components, filaments, etc.).

The oven used in this build is a budget-friendly (40€) 9L toaster oven with two quartz heating elements (BROCK TO9001B). Despite initial concerns about heating speed, the small chamber allows it to reach the required temperatures quickly. The oven has been additionally insulated for improved performance.

A solid-state relay (SSR) is used for controlling the heating elements, and a 12V 5A power supply powers the entire electronics system.

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PCB

The PCB is a two-layer board with components on only one side (except for the LCD connector, which is on the opposite side). The board has the same dimensions and mounting hole positions as the LCD, allowing them to be stacked using a 3D-printed spacer.

The LCD used in this build is a 3.5-inch TFT LCD Display Module (320x480) with SPI Interface and Touch Screen (ILI9488 v2).

PCB Features

• Safety switch for 12V
• Voltage measurement (input and buck output)
• Overtemperature protection via NTC sensor
• Input protection (fuse and reverse polarity protection)
• Max input voltage: 23V
• AUX1 and AUX2 (can handle up to 45V and 500mA, but limited by PCB input voltage)
• Supports up to two solid-state relays (SSRs) (PWM amplitude matches input voltage)
• Supports up to two K-type thermocouples (MAX31855)
• Raw USART output & USB output (CH340G) for monitoring and calibration
• USB OTG support (requires core clock adjustment, affecting timer parameters)
• External 2MB flash (W25Q16JVSNIQ) for GUI and fonts
• SWD port for programming
• Buzzer
• MCU: STM32F411CEU6

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3D Models

All parts are printed from PC plastic using an FDM 3D printer. Alternative plastics can be used, but they must withstand high temperatures. There are two different options for electronics assembly mounting:

• Inside the oven as is in my case. For that you only need to print Front_frame

• On the side of the oven. For that you need to print three parts with external at the end of model names. Base that screws to the frame has teeth that allows preset angles. For rigit mount use only screw and nut, but you can add a spring under screw head. That will allow setting the angle later.

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External Loader

The External Loader is a necessary part of the program. It allows CubeIDE to upload data (GUI and fonts) to the external flash chip. If you use a different flash chip, modifications are required to meet the new chip's recommendations. The loader program must be included in the main firmware/IDE.

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Firmware

The firmware is not fully compatible with the latest version of the PCB. This update addresses mistakes found in the initial version of the board.

Missing Features

• Read input voltage
• Read buck voltage
• Read NTC sensor
• Safety switch (implemented in code but not tested)

For the GUI, TouchGFX with standard elements is used. The only custom file is the background.

External Libraries Used

The libraries for LCD (with touch) and external flash (External Loader) are not originally written by me but include minor modifications to fit this build. The original work was done by maudeve-it:

LCD Library:

• YouTube Video
• GitHub Repository

Flash Library:

• YouTube Video 1
• YouTube Video 2
• GitHub Repository

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License

This project is open-source and available under the MIT License.

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Contributing

Contributions are welcome! Feel free to submit issues or pull requests to improve the project.

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