The Arduino thermometer was originally built as a presentation model for education fairs. The base is an ATmega328P-AU (32pin SMD package). This way there are a few more pins for LEDs. As temperature sensor we used the LM35 in a SOIC-8 package.

Disclaimer: Everything is SMD here, because it was easier to build in a small quantity run. (About 20-30)

The LEDs are showing the temperature in whole degrees centigrade. A small transistor circuit is used to save power so the 9V battery in the back doesn’t drain too fast. Everything is activated with a button press. With a potentiometer you can adjust the temperature reading.

After the schematic was done, my boss wanted the thermometer to look a bit like the old glass thermometers, so I made the outline accordingly.

Schematic and thow pictures are following.