Fermentation temperature controller
I got an old freezer that was surplus to requirements and some heater wire and then made a control box with an Atmel ATMega32 controlling a relay board, talking to a serial port (made for microcontroller experimentation) which is connected to my WRT54G? (modded for serial ports :) It's a lot more complicated than necessary but I had all the bits and pieces on hand and it is quiet and low power (compare to, say, another PC). The basic idea is the same as Greg used here http://www.lemis.com/grog/brewing/temperature-control.html (same relay board, same sensor type). Since the WRT54G? runs OpenWRT I can SSH into it - this allows me to control the system from a proper machine and write the software in Python rather than fiddle around with C (which can be quite limiting and a PITA to develop on a micro). The microcontroller talks to 3 Maxim/Dallas 1-wire bus temperature sensors, one for the fermenter, one for fridge air and one for the ambient air. It is also connected to a relay board Here's a picture of the freezer layout
And an old one of the box internals
It looks better now, I have replaced the heavy transformer (which wasn't even used) and the black 5V/12V supply with a small 12V switchmode PSU and a 7805 board. The big ferrite has been replaced with a smaller one and tidier cabling.
The software on the micro side is written in C using AVR GCC but is fairly basic, I mainly wrote it as a tool for playing around with various bits and pieces. I have rejigged it so the microcontroller is now standalone and only logs to the serial port. It does this via a Maxstream ZigBee module to another one on a PC.
The code in the microcontroller is available here (Mercurial repo).
-- Main.darius - 30 Sep 2007
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