Digital LED Thermometer with Microcontroller AVR ATtiny13

Each book of this series deals with a microcontroller project. Hardware (electronics circuitry) and software (microcontroller program) are described in detail. Following the author's ideas, you will build a useful device, have fun and learn a lot.

Topic of this volume is constructing a digital Celsius/Fahrenheit thermometer from only a few, inexpensive parts which are readily available. The device measures temperatures ranging from -55 up to +125 °C (-67 … 257 °F) with great accuracy and may be used for many purposes. Even people with little experience in assembling electronics projects should be able to build this circuitry successfully. The key components are a microcontroller of type Atmel AVR ATtiny13 (also suited in the versions with additional letter A or V) and a digital temperature sensor DS18B20 from manufacturer Dallas / MAXIM.

The temperature is displayed by flashing of two light-emitting diodes (red and blue) in very elementary manner, either in half degree or tenth degree resolution. Beside the easy realization for the hobbyist, the advantage of this simple method is that reading the temperature is possible from greater distance. In complete darkness, the blinking device is visible over several hundred metres.

The circuitry can easily be built up on a piece of perfboard so small that it fits into a so-called PETling (raw form for PET bottles) leaving room enough for a lithium battery or a LiIon accumulator. This construction gives a compact, robust and watertight thermometer for all sorts of applications.

This book contains detailed assembly instructions and an in-depth description of the other features of the digital thermometer, because it offers more functions than you recognize at first sight. For instance, additional temperature sensors can be connected for measurement of inside and outside temperature et cetera. The thermometer switches off automatically when the battery voltage falls below 3 volts in order to prevent damage to rechargeable accumulators due to over-discharge.

Difficulty level: Making this circuitry is easy. You need basic knowledge in electronics soldering or help by an expert.

The computer file required to program the microcontroller (hex file) is available for download on the author's internet site. Alternatively, you may assemble this file from the program listed in this book.