Low power digital thermometer on ATTINY13+LM35(TMP36) and Nokia 5110 LCD module. Works more than month on single 2xAA battery pack (3V). ATTINY will utilize watchdog for deep sleep and standby.

How to connect Nokia LCD to ATTINY13: LCD_MOSI to PINB2, LCD_SCK to PINB4, LCD_CD to PINB1, LCD_RESET to PINB0.

Connect LM35/TMP36 Vout to pin PB3 of ATTINY13. Connect CS and BL pins of Nokia LCD to GND.

Nokia LCD VSS/VCC/GND, VDD/VCC/GND of LM35/TMP36 and VCC/GND pins of ATTINY13 must be connected to +/- of 2xAA(1.5V) battery pack.

For TMP36 sensor ( which is capable to measure -50 - 100 Celsius ) there is a correction in the code to substract 0.5V from ADC reading. So if you want to use LM35 sensor you need to remove this line in the code.

Link to video how to program the chip : https://www.youtube.com/watch?v=7klgyNzZ2TI

to see how it works - look here https://www.youtube.com/watch?v=r6nF1iJ2r-M