Brewery controller & stir plate

Over the summer I took advantage of my workplace's extensive tool collection and put together couple of gadgets for the brewery, a brewery controller, and a magnetic stir plate.

The brewery controller is basically just a Sestos PID controller and a solid state relay for the HLT, and a switch for my pump. I put it all in a big box so when I want to add something extra there's space.

I got the panel mount sockets from Jaycar, and the IEC socket was lying around work. i decided to go for a 2.5mm audio socket for the sensor input. I only have two of the power sockets wired up currently, with one spare.

The guts inside. Note the grounding post - very important!

For the stir plate I basically glued some rare earth magnets to a 12V computer fan, and experimented with different ways to vary the speed of the fan. I tried a few different circuits to vary the amount of energy being delivered to the fan: Potentiometer, PWM generator, and a voltage regulator. The voltage regulator method totally works the best, and is relatively simple to implement.

I would put up a picture of it stirring water, but both my stir bars were tipped into my fermentors, along with the yeast staters!

One thing I noticed was that it was much easier to get the small stir-bars to catch and spin rather than the larger ones, so I set the magnets really close together.

I put the circuit together with stripboard. It's based on an LM317 voltage regular IC, and I found it here: http://seanterrill.com/2010/04/26/build-a-better-stirplate/

To raise the fan I found some random bits of scrap prototyping plastic and tapped threads in them. I then screwed the fan onto the improvised posts and epoxied them down to the box.