B
BlackMamba
Guest
Project by Alfax
Source here
Function of this device is to signal if the refrigerator door is left open. Of course most of nowadays refrigerator has such signaling device, but there is a lot of older ones, without such protection.
Device start its action when refrigerator door will be open. After starting the microcontroller checks the time, set via time programming inputs (in my case 3 minutes is set) and starts counting that time interval. When counting ends the alarm begins. At the beginning of alarm cycle microcontroller generates one signal every seven seconds for a 30 seconds. next one signal every 3 seconds for a 10 seconds is initiated, Third phase generates double beep every two seconds for 10 seconds and in the last phase there is continuous sound silenced by closing the fridge door.
Devise has been placed in a enclosure of the lamp lighting the fridge interior. Small pcb was designed in EAGLE. Power unit is taken out from cell phone charger. At the side of lamp enclosure there is a small hole for buzzes sound. LED is a indicator of microcontroller actions during testing and a additional reminder for a person opening the fridge.