NFC_temp - passive thermometer for your keychain

NFC_temp is a passive open-source NFC thermometer based on an ATtiny microcontroller, a TMP117 temperature sensor, and the NXP ntag NFC IC. The device harvests part of the NFC field from a generic NFC reader for power and enables temperature measurements with up to 0.1 °C accuracy. The result is output by the NXP ntag as an URL and can be read using any smartphone. With a size of only 35 mm × 18 mm, the system design enables maintenance-free, location-independent, and accurate temperature measurements on your keychain without a dedicated battery.

The entire hardware was created using freely available software (KiCAD, FreeCAD).