How to Make a Tiny Thermocouple Thermometer with an ATtiny85

The Microchip ATtiny85 is, as the name suggests, pretty small. It’s an 8-bit microcontroller, and doesn’t have specs that you’re going to write home to mom about. But, it is very affordable and power efficient, which makes it ideal for simple projects like David Johnson-Davies’ Tiny Thermocouple Thermometer.

This is the kind of project that most people would turn to an Arduino for, but that’s actually overkill. An Arduino development board is bigger, more expensive, and uses more power, and that’s just not necessary. So, Johnson-Davies will walk you through how to use the humble ATtiny85 instead. In addition to that, you’ll need an I2C OLED display, a K type thermocouple, and some miscellaneous components like capacitors and resistors.

Johnson-Davies chose a thermocouple, like what a 3D printer’s hot end uses, for this project instead of a common temperature sensor because they can handle much hotter temperatures. Normally, you’d use a thermocouple with an amplifier chip to translate the output voltage to a digital signal that can be read by a microcontroller, but this circuit skips that and the analog signal is read directly by the ATtiny85.

That analog signal isn’t directly proportional to the changes in temperature, however. So, you’ll need to take advantage of some fancy math to get an accurate reading. The circuit is minimal, and should be pretty easy to wire up. From there, Johnson-Davies has provided the code to get everything working together. It may be a simple build, but it’s a great demonstration of why you might want to take advantage of an ATtiny85 in your next project.