So I needed to be able to get temperature in to the computer, and also have the computer turn a switch on and off to control the power to the heater. You'd think everyone wants to measure stuff and turn things on and off with their computer wouldn't you? No? It's just me then... A long search revealed that a nice small, simple and cheap 'box' didn't seem to be available until I discovered 3 companies who sold to the education sector in the UK. They supplied boxes complete with software for use in classroom projects like simulating traffic lights or measuring the temperature of the long-suffering class hamster. Only one of the companies was prepared to spend any time talking to me or even made available the programming information required to talk directly to the box however, so it was from Deltronics I bought "The Junior Serial Interface" (I wish they hadn't called it that). It also transpired they didn't provide a K-type thermocouple (required to measure the high temperatures in the roaster) so I resigned myself to a very small amount of electronic construction to build one myself.

I have since found out there may be cheaper alternatives to the serial box, though the one I have seen from the States is USB not serial, which for me, makes it more complex to write software for. In addition, a small group of coffee enthusiasts is designing their own board and writing software that may never be "productionised" but will be available as a design to anyone who wants to use it. This might use a technology called 1-wire which looks very interesting for building a cheap and simple box, so what follows isn't a step by step guide to how to do it yourself, but shows how I went about it in the first instance and I now believe it can be done better and cheaper!