The project is all about temperature monitoring and displaying with a twist. Instead of using a costly Arduino with a boot loader, the author used Arduino Nano as it’s cheap but it doesn’t have an on-board boot loader. He used a Bus Pirate V3B to flash the boot loader and save on some extra-bucks. In the initial phase, the author started with a DHT11 sensor which is a SPI based temperature and humidity sensor having digital output. However, since he wanted an accuracy in decimals, he shifted to DS18B20 which is again a SPI based temperature sensor from Maxim. It has an accuracy of +/- half degree Celsius.
For displaying the graphs of temperature variations along the day, he used an old Nokia 5110 lcd which Is again very cheap to buy. He also decided to make small circular buffer for DS18B20 readings and draw that as scrolling graph, RRD style. At last step he also added PWM driven back-light to display which is off if value didn’t change, half-dimmed if current temperature is lower than previous one or full brightness if it’s higher than the previous one.