You can made a cheap thermometer using few components: clone Arduino board (in my case, I use Arduino Nano board with uC ATmega 168, but work with Arduino nano with ATmega328, Arduino Uno, leonardo, etc), a 1N4148 diode, 4-digit 7-segment led display with common cathode or common anode (just few changes in sketch), an breadboard and some wires.
Schematic is very simple:
diode_thermometer_display_1.ino and on dissplay temperature is as integer:
diode_thermometer_display_2.ino sketch, value is with decimal value:
https://www.hackster.io/microst/thermometer-diode-based-524613 and I test sketch:
1N4148 diode as temperature sensor movie:
- DIODE-BASED TEMPERATURE MEASUREMENT (Burr-Brown)
- Accurate Temperature Sensing with an External P-N Junction (Linear Technology)