Uploaded June 2018 | Updated September 2026, 1 week ago

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Simple project with modified Arduino Pro Mini, thermistor and Nokia 5110 LCD

Features:
- extremely low power with modded Pro Mini
- ATMEGA clock speed reduced to 4MHz
- display is refreshed every 80 seconds
- most optimal power option: any lithium cell or 3xNiMH AA/AAA, at battery capacity 2000mAh thermometer should work for about 500 days
- there is no lithium protection in hardware, but current cell voltage is displayed and in case of less than 3V warning message is shown and everything enters deep sleep mode to avoid further discharging
- thermistor isn't connected directly between ADC and VCC to avoid constant power consumption
- own low level/low resource N5110 library used
- temperature min/max and battery level are displayed
- min/max alternatively can be stored/read from EEPROM

Connections - N5110 LCD from left:
#1 RST - Pin 9
#2 CS/CE - Pin 10
#3 DC - Pin 8
#4 MOSI/DIN - Pin 11
#5 SCK/CLK - Pin 13
#6 VCC 3.3V
#7 LIGHT (not used here)
#8 GND
Thermistor between A0 and D7
Balance resistor 10k from A0 to GND

Source code is available here:
github.com/cbm80amiga/N5110_lowpower_thermometer

N5110 lib:
github.com/cbm80amiga/N5110_SPI