Reader [Will R] sent in a thermostat mod for his brew fridge. His friends had found a perfectly fine bar refrigerator and wanted to repurpose it for brewing beer. A previous batch of microbrew had been mangled by the Australian heat so they wanted something that could maintain the perfect temperature. The fridge’s built-in thermostat wouldn’t rise above 5 degrees so they had to build their own. [Will] used a 10K NTC thermistor to measure the temperature. It’s connected to an ATtiny25 microcontroller that does the comparison and determines whether to turn on the compressor. He referenced SparkFun’s relay tutorial for the switching side. Although he didn’t etch a board for this project, the design file is included along with all the code on the project site.

[Bob] has a USB page hit counter that uses an ATtiny25 to run a MAX7219 which drives eight 7-segment displays. It is easy to implement USB on an AVR using just firmware, eliminating the need for any USB to RS232 conversion. The host software is written in Delphi and sits in the Windows tray. The code examples seem simple enough to expand upon into your own display programs.