Fridge/Freezer Door Alarm

Description

Fridge Freezer alarm using Arduino Nano and AA batteries. Printed with Elegoo Saturn 2 Switch is wired Normally Closed to the positive terminal of the battery and the 5v DC-DC step up converter, so the device only draws power when the fridge door is open. Used cheap parts from AliExpress: https://www.aliexpress.com/item/1005003932299815.html https://www.aliexpress.com/item/1005005955954266.html https://www.aliexpress.com/item/1005002976480289.html https://www.aliexpress.com/item/1005008157344660.html https://www.aliexpress.com/item/1005006085607858.html (KW11-3Z-C) Additionally: 2x M2x12mm screws 4x M2x16mm screws 6x M2 Nuts 0.2mm enamel coated copper wire or appropriate substitute (for buzzer) 0.5mm enamel coated copper wire or appropriate substitute (for power) Instructions: Solder battery terminals at the far end together. Wire buzzer to D3 and ground, ensuring the wires are long enough to reach when everything's packed in (approx 8cm). Bend switch lever at approx 5mm from the end (or whatever works for your use case) Remove middle terminal from the switch with Side cutters (optional) Solder 0.5mm wire to switch terminals, leaving enough length to be cut down later (40mm?) Solder Arduino 5v to Vo on the DC-DC module (50mm) Solder Arduino GND to GND on the DC-DC module, so that it passes though and can also be soldered to the neutral battery terminal (80mm) Solder switch terminal closest to the arm to the Vi on the DC-DC module (test fit first, approx 2cm) Solder switch terminal furthest from the arm to the positive battery terminal. Test fit Install the switch. Place 2 nut inside the hex shaped slots (fiddly), screw in 12mm M2 screws Shove everything else back in Affix lid with 16mm screws and nuts Devices is held on the side of the fridge with Command Strips Arduino code: const int buzzer = 3; //buzzer to arduino pin 3 void setup(){ pinMode(buzzer, OUTPUT); // Set buzzer - pin 3 as an output } void loop() { delay(60000); // Wait 60 seconds do{ tone(buzzer, 2349.32); // Send sound signal... delay(100); // ...for 0.1 sec tone(buzzer, 1975.53); // Send 2KHz sound signal... delay(200); // ...for 0.2 sec noTone(buzzer); // Stop sound delay(8000); // ...Wait 8 seconds } while(true); }

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