A piezo buzzer is used to detect the vibrations inside the drum, each hit triggering a different color combination. The LEDs fade to off after each impact as if dying along with the sound ...

It runs on mains power and uses a 100dB piezo buzzer for ear-splitting effectiveness to alert [Adam] whenever the freezer is at 32°F/0°C or above. If the Arduino loses sight of the DHT22 ...