My “combination lock” as a whole is a toy cat. When you interact with it, it can meow.
The first “combination number” is made of a potentiometer. It symbolizes the tail of the toy cat. And in order to make it meow, the first step is to “play” with its tail.
The second “combination number” is made of a photoresistor (Ideally, it should be a touch sensor. But I do not have one yet. So I used a photoresistor to symbolize the “touch”.) It is one hand of the toy cat. The second step to make the cat meow is to touch that hand.
The third “combination number” is made of an ultrasonic sensor. It is the eyes of the toy cat. The last step to make the cat meow is to wave your hand in front of the cat’s eyes.
And the final output is the meow sound coming out from a piezo element (The meow sound is kind of rough though.)
Video: https://drive.google.com/open?id=0Bxu-j9eOkv5XLWFCWjZ0TjJEX0U
