What's going on? Who's sneaking into the fridge?
Build this simple alarm circuit to catch the midnight snacker in the act! When the refrigerator door is closed, the alarm is quiet. When the refrigerator door is open, the inside light switches on and activates the alarm, which emits a shrill tone. Even if the tone fails to wake you, it just might cause the fridge invader to quickly close the door and return to bed.