Fridge open door detector

cults3d

Our fridge door occasionally refuses to close fully. To become immediately aware when this happens instead of waiting until morning, I built an open-door detector. This device also alerts you with a beep notification whenever your selection takes too long while the door is still open. A micro switch is used for the door open detection. When the door opens, it closes and powers the circuit containing an Arduino-based microcontroller (ATmega328) and a spare piezo speaker. Note that instead of using a complete Arduino board, I'm using just the ATmega328P on a breadboard. See Julian Ilett's video for details on how to do this. However, I needed an extra 10 kOhm pull-up resistor on the reset pin during data transfer. The program in "ArduinoToneMelody.ino" includes the following steps: * When the door opens, the LED starts blinking. * After 10 seconds, one beep is played. * After 20 seconds, two beeps are played. * After 30 seconds, three beeps are played. * After 40 seconds, a siren sound is repeated once. * After 50 seconds, a siren sound is repeated twice. * After 60 seconds, a siren sound is repeated thrice. * After 70 seconds, a short melody plays. * Then all steps will repeat. Refer to the circuit picture for the used parts. The ATmega328P came with an Arduino bootloader already programmed, making it easy to get started. The piezo speaker was salvaged from a broken device. The microswitch closes when the fridge door opens, so the circuit doesn't require power while the door is closed. It's soldered onto a piece of veroboard for stability. The OpenSCAD files are included, including my own battery box design.