What Is A 3D Printed Zoetrope?

Here’s one I found on YouTube that I like:

Ever since I saw my first 3D printed Zoetrope (a spinning disk with 3D printed figures on it, spun to a synchronized light which simulates a smooth animation) I set out plans to make one myself

The basis is easy – 3D print a group of figures, each frozen in a single frame of a looping animation, stuck to a spinning wheel and a strobe light set to synchronize to the rotation until you see a perfect animation.

However, there are complications, the largest being how to synchronize the light so it always aligns to the figures on the disk at an exact angle. You can spin it at a variable rate with a potentiometer on the motor and then use a variable strobe and hand-sync the two until they work, or fall out of sync due to variations in current, etc… but what I really wanted is an absolute sync, and I think I figured out a good method:

The Arduino

I intend to use an Arduino Micro to synchronize the light to the spinning disk. This should be easy, but some experimentation has to happen first.

First, I purchased several infra-red light emitter/detector pairs. These are LEDs, one of which emits an infra-red light, and the other detects that light. Using the pair, I should be able to trigger a circuit whenever the light is detected (or not detected) by the detector.

There are numerous examples of how to do this on the web, but it’s fairly easy. Simply hook up the emitter to an Arduino output (with an appropriate resistor to ramp down the voltage so as not to blow the LED) and the detector to an Arduino input.

Next, I will write a simple piece of Arduino code that registers the input strength (the detector is analog, so it can detect any amount of light the emitter emits.) I will use that with a variable threshold to trigger another output that I have hooked up to a very bright LED light (and perhaps even to the switch of a third-party LED flashlight).

This way I can light the LED whenever the detector sees the emitted Infrared light.

I can trigger the light to turn on and stay on only for a very short time.

Synchronization

To synchronize, I intend to print a small hole (or tab) near each 3D printed figure “frame” and then, no matter how fast I spin the disk, it will itself trigger the Emitter/Detector to flash the LED flashlight. So I should be able to spin an unmotored disk and have it sync, and as it naturally slows down, the sync will remain solid.

But of course I will use a motor to keep it going, and hopefully a motor which speed I can adjust, so I can speed up and slow down the animation.