eFlow has been designed to be easily hand assembled using an off the shelf Solid State Relay with built in zero crossing detection. To keep the count and cost Bill of Materials as low as possible, we start with a NodeMCU development board. The NodeMCU development board is built with 0402 components and includes an ESP8266 and supporting hardware to make this easy. If this were to be built in quantity and the firmware is finalized, we can save about $5 in exchange for a few additional steps in the manufacturing and assembly process.
Any oven will work, but it’s important to purchase one with the highest rated wattage that you can find. The model I have is the Black & Decker TO3210SSD 1500 watt Toaster Oven with Quarts elements for $50. Quarts elements are helpful because they heat up quickly and don’t hold much heat once energy is disengaged.
Here’s the PCB design, with accompanying circuit schematic that can be found documented here:
Here’s a preview of the web interface and a shot of the thermocouples ‘installed’ in a toaster oven, as documented here:
The firmware is documented with additional screenshots here.
And lastly the entire hardware and software source are here on GitHub.
https://www.youtube.com/watch?v=AlXJRK3e7_I
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