This project was inspired by Cooking for Geeks author Jeff Potter’s quick DIY sous-vide hack. My plan, initially, was to just hack the controller into an enclosure with an A/C outlet, the idea being that you could just plug any heater you wanted into the outlet.
Looking around for cheap temperature controllers, however, I happened across the STC-1000 on eBay for $25. It’s not PID, but it has proven to be accurate enough for almost any practical purpose. And since the STC-1000 has both heating and cooling functions built-in, the logical next step seemed to be to split a single A/C outlet so that you could plug a heater or a cooler (or both) into it and use it for all kinds of stuff.
The STC-1000 will regulate at any temperature between the freezing and boiling points of water, which opens up all kinds of potential applications in chemistry, aquaculture, zymurgy, hydroponics, cooking, etc., etc. And unlike most other water temperature controllers I’ve seen around, this one can operate in heat only, cool only, and heat-or-cool-as-necessary modes.