I'm looking for a serial-port temperature controller thingie for a bizarre cooling system I'm building, for a beer fermenter.
The Problem: Beer needs to be kept around 65-70 degF in order to ferment properly; too cold and everything slows down, too hot and the yeasts die.
The Tools: I have a mini-fridge, a very small computer with only a serial port and 3 network ports, and not a lot of money.
The Solution so far: I'm going to have the beer fermenting in a glass carboy
, and the mini-fridge running right beside it. Inside the fridge will be a tank of water, and inside the tank will be an aquarium pump.
The aquarium pump is connected to some plastic hose which attaches to a copper coil (refrigeration grade) that circles around the carboy, then dumps the water back inside the fridge container. Basically, when the aquarium pump turns on, it cycles a new length of cold water into the copper tubing and cools the carboy. The whole carboy will be inside of a styrofoam box or something to insulate it.
To control the pump, I'm going to have a thermistor or some other temperature sensor floating in the beer, or even better a couple of them at different positions inside the carboy. This is where my question comes in:
I can either try and build a circuit to switch on the aquarium pump when the temperature hits a certain trigger, using a prototype board and solder. Or, since I have this tiny computer sitting un-used, I can just find a temperature sensor that will plug into the serial port, then write a program to read the temperature and...I guess somehow use it to turn on the aquarium pump.
Basically I want to know if anyone can think of a better setup than this (keeping in mind that i'm poor,) or suggest another way to do it?