On some level, a brewer is a sort of a yeast god. Taking the infant yeast from their little Eden in a test-tube or packet and casting it into a world flowing with maltose and oxygen with the commandant "be fruitful and multiply!". We seek tribute from our creations in the form of alcohols, CO2, and flavors, and threaten damnation down the drain if they misbehave.
Of course yeast, unlike human, are kinda stupid and simple. Having only a single cell and a mare sixteen sets of chromosomes to the human 23, they haven't quite evolved complex skills such as language and writing. If you want yeast to do something, you have to give them the conditions to do it. One thing we as brewers often want from our yeast is to grow into more yeast. To do this we must give them two main things: Food (in the form of maltose and other complex sugars) and Air (Oxygen). Like most organisms, yeast will use up air long before they ran out of food. So if we are trying to get them to keep growing and multiplying we have to give them more and more Oxygen. In a yeast Starter (the place which we most want the yeast to multiply) we do this by shaking the beaker regularly or, preferably, by putting it on a stir plate where it can have a regular supply.
All of this is by way of long-winded introduction to the fact that I decided that I really want a stir plate at home so I can make good starter. Unfortunately, a basic stir plate in this country costs about 800NIS (over $200US), so I wasn't going to buy one. I decided to build one instead.
Building a stir plat is actually quite easy. All it involves is finding a computer cooling fan, sticking a couple of magnets on it, connecting it to an appropriate power source, and building a housing over the whole thing. I built my stir plate based on a page-long instruction which I found on a brewing forum. I wont share the the link here, as the instructions were not very good. The electronics were overly complicated and it lacked some important details. Instead I will tell you that there are plenty of YouTube videos about this, and they're fairly comprehensive.
This is the finished product. You can see the strong magnets mounted on the computer fan. They are the ones that engage the stir stick inside the Erlenmeyer flask that actually does the stirring. The whole thing is mounted in a makeshift enclosure that I built out of spare wood and clear plastic, and I use a variable resistor to control the speed of the fan and the speed of the stirring. Total cost for this fully functional plate: 6.80Nis for the Teflon-coated stir stick (Just under $2US).
Here's the stir plate in action. Screws all set and balanced, and the stir stick engaged. if you look carefully you can see that the wort inside is spinning and is pulling a nice vortex. Mission accomplished. The yeast can go forth and multiply.
There are a lot of random pieces of equipment involved in our craft. I have seen brewers make fermentors out of some mighty weird containers, build wort chillers out of garden hoses and copper tubing, bastardize laundry machine pumps and use innovation and creativity to create an endless array of useful appliances. It is one of the greatest aspects of our hobby, I think. We don't just make beer, we make the things that make things happen. We create the world in which water, air, and sugar combine to make a little drop of heaven for our yeast, and it rewards us with beer. We are yeast gods.