Automating the effect of a sail rippling in the wind

hi Pololu,

I’m a long time fan of your voltage regulators and wiring harnesses. Though I don’t build robots, I build other stuff, and your parts have been great.

I’m trying to build a light diffuser that ripples under microprocessor control. Diffuser screens create very different effects when they’re close to the lights vs when they’re farther from the lights. I want the effect to change under software control.

I’m imagining a thin nylon sheet mounted about 3" from the lights, with some slack that can be manipulated mechanically, pushing and pulling it away/toward the lights. I have a couple of design ideas for the devices controlling rippling, and I wonder if you have any thoughts.

  1. I could pull the sheet toward the lights with a number of small, light springs. A number of servo motors under the sheet could each rotate their horns upward, perhaps with a small wheel on the horn to roll under the sheet, pressing it up. The issue here is that the motor would be mounted near the lights and thereby cause shadows. Also I’m a little worried about strain on the sheet.

  2. I could mount springs that push the sheet up, away from the lights. On top of the springs would be some kind of small soft cap to press against and be attached to the sheet. Under the cap I’d fasten a small wire which would run down through the spring, through a hole in the board on which the lights are mounted, to the back of the board where it would be wound around a wheel attached to a motor. When the motor turns one direction, it retracts the wire, compressing the spring and pulling the sheet down. When the motor turns in the other direction, it releases the wire, allowing the spring to push the sheet back away from the lights.

There may be an even better way? What Pololu motors/gears/horns/wheels might you recommend? Any thoughts about springs or the design?

Thanks in advance – wylbur.

Hello, wylbur.

It sounds like you have a couple of ideas that might work, and the choice on which one you try is ultimately up to what you want from your project. I cannot suggest a gearmotor or servo from the information you provided (e.g. there is no scale mentioned). However, if you can determine what kind of torque your system would require, I can point you to any appropriate solutions we might carry.