A very big Zeotrope

I got involved in this project a while back (2015). My friends over at Pirate called me up and told me a gent called Jim Le Fevre needed a strobe, a big strobe.

Jim is a BAFTA winning animator and director and had built Zeotropes before, but nothing anywhere close to this big. Who could resist?

This was a 2M diameter, 2.4M high, 3D printed monster Zeotrope and needed a strobe to illuminate it. He’d tried a conventional Xenon lab strobe, but that had nowhere near enough grunt. Also, the Zeotrope needed to be viewed from any direction.

To complicate things further, the mechanism for actually rotating the beast hadn’t been worked out so I couldn’t rely on stepper motors or any other tightly defined rotation.

In the end, I put a 3mm neodynium magnet embedded in the drum and used a Hall Effect sensor to time the period of rotation.

The drum itself was a 3 man lift, so there was a lot of inertia, which worked to my advantage. Any changes to rotational speed were pretty slow to take effect, and so just keeping a simple moving average of the rotation period and flashing the leds at 1/10th (there were 10 frames of animation) of that time worked very well.

I just used regular white led strips for illumination and a big bank of large electrolytic capacitors at the base of each column to allow a relatively modest power supply to power the whole thing. I think the leds were illuminated for 5ms at a time to give a good freeze frame, meant we were running at a 20% duty cycle.

All of which was fine, except that there was approximately 6 hours from the first time it worked until it was shipped to Miami. Needless to say, I wanted a week’s worth of soak test to make sure I’d got all my sums correct. I nearly had kittens when they just packed it up and took away immediately. To my relief, it apparently worked out of the box first time and kept running.

The thing I most remember was how cold it was in the warehouse we assembled the thing.

The rest is best told by the man himself…