Interactive “Jack in the Box” design: Perpetual Cat Machine.
Interactive “Jack in the Box” design: Perpetual Cat Machine.
Laser cut wooden components.
In theory, when cats fall, they always land on the ground with their four legs, and when you drop a toast on the ground, the toast always lands with the side of butter on the ground.
<aside> 🐈 Someone came up with this brilliant idea (credit to the Flying Horse energy drink commercial), where they tied up a cat with a buttered toast on its back. When the cat tries to reach the ground with four legs, the toast will also try to reach the ground with the buttered side. A competition of power will then result in forever rotation movement.
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In my design, I tied the cat-toast combo to a LEGO rod that connects to a DC motor on one side (through a 3D printed connector) and rests on another LEGO structure with a hole in the middle. The DC motor is what causes the spinning motion of the Perpetual Cat (turns out the machine is not perpetual after all).
Right underneath the cap is the ultrasonic distance sensor. The sensor can automatically send 40 kHz and detect whether there is a pulse signal back. The shorter the duration is for the ultrasound to echo back, the closer the object is to the sensor. In this design, I use the duration output to calculate the distance using the formula: test distance = ( high level time * velocity of sound(340m/s) ) / 2. The resulting distance is then used to determine the spinning speed for the Perpetual Cat machine.
A schematics of the sensor and motor wiring using Arduino.
A cardboard model of the final design to test out functionality.
When the cap is lifted off the box and reaches a threshold distance, the ultrasonic sensor will detect it with its sensing duration, and the motor will start spinning the cat-toast. This is the trigger for box opening, meaning that an interaction has been detected. When the cap is lifted further off, the cat-toast will spin faster at a rate of (speed = distance * 2 + 180). This is a more complex interaction than just lifting up the box cap as an on-button, and the accelerating motion mimics the Perpetual Machine starting its work and warming up.
All other plywood components are built with my own laser cut designs. They incorporate both cut-through lines and engravings by mapping the line colors differently using Adobe Illustrator. Some engraving designs required using Fusion 360’s “Break” feature to sever up the entities of lines. The box walls are connected using the tooth-like shapes that interlace with each other. The ultrasonic sensor and its cables are held up using two wooden skewers so that the sensor is right underneath the cap. The cables connect to the breadboards hidden behind the box.
Perpetual Cat Machine done!