Yet another reflow oven controller. I began this project about 5 years ago. Project files include a schematic for a custom controller, design files for the case, and the code.
The rear panel uses standard IEC connectors for AC in and out. There is a built-in fuse holder. For temperature sensing Open Vapors uses a K-style thermocouple and a MAX31855 breakout board from Adafruit. On the front I'm using a momentary pushbutton for manual relay override and a latching button for power.
Open Vapors does need a separate DC power supply. I was not comfortable powering the DC circuit from the AC in, so I kept it separate.
At the core is a PID library to control the relay. Parameters for the PID will vary by oven. The menu interface is based on a state machine. The screen is constantly being redrawn. The items shown is based on the current state. There is a I2C backpack in use, which required the "fast" LiquidCrystal library.