Toaster ovens are great for two things: making cheese toasties and re-flowing PCBs. While it is entirely possible to reflow boards without the use of a controller, automated control will make the process more consistent especially if you are doing several boards at a time. The Toast-R-Reflow Power board contains two opto-isolated triac control circuits to cater to the most common oven which contains a top and bottom heating element.
Note that this is only a power control board, connect the heating elements to the outputs and you can control them based on DC voltages you send to the inputs. To add in a controller you’ll need some way of sensing the temperature inside the oven, a k-type thermocouple is the most common way to do this. Since the thermocouple only outputs a few milli-volts it is a little tricky to get this temperature information directly to the controller. Thankfully, the MAX31855 IC makes this process extremely simple. Just connect the thermocouple to it and it will send the temperature over SPI to your microcontroller of choice. Now that your controller knows the internal temperature of the oven and has the ability to control the heating elements, you can do cool things like following the re-flow profile of your solder paste!
If you don’t feel like rolling your own controller, Geppetto Electronics also sells a controller board which consists of an ATMEGA328P microcontroller (used in several Arduino boards), an LCD screen and the aforementioned MAX31855 IC. Solder pastes come with a data sheet specifying the optimal reflow profile. This control board comes with enough flash to save several different temperature profiles.
