Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:3023804.
Here's one version of my dual stage temperature controller that I luckily saved before OnShape completely ruined my assemblies. Connect a refrigerator and a heating pad to the AC outputs, load/tune the code for your hardware, and you're good to go.
BOM:
Adafruit 2821 Feather HUZZAH with ESP8266: https://www.amazon.com/gp/product/B01BV3AU0Y 5v AC-DC stepdown module: https://www.amazon.com/gp/product/B01BV3AU0Y Dual 5A solid state relays: https://www.amazon.com/gp/product/B008BGLM02 10A Fused AC input: https://www.amazon.com/gp/product/B01LYMNQ2L/ or https://www.amazon.com/gp/product/B06XKBRT9M AC power sockets: https://www.amazon.com/gp/product/B008J80J1A
I know that some of these parts are no longer available, but the links have been provided to show the approximate shapes.
You can ignore the microSD card, as the data is now being stored on the cloud.
I'll share the code on github soon.