Plastic or Beer Bottles?

Blinkdom

A few months ago some architect friends visited the lab to see our robot and accidentally stumbled into our LED wonderland. That lead to being asked to do pixel wall in a conference room.

The Start

The original idea was to do a large grid of recycled beer bottles as the lenses for RGB LEDs. Working through the design, beer bottles present some challenges. How much does a thousand glass bottle weigh? How do you mount them? How do you wire LEDs to them? How do you control that many LEDs?

The projects our friends saw was a PixelInvader (64 LEDs), a StripInvader (240 LEDs), and the beginning of the Mega Pixel (572 LEDs). Now we were asked to scale up a project 2-3x bigger than anything we’ve done. We were already maxing out the Arduino system we’ve been using - each pixel needs needs three pieces of data to be sent over the network. Packet size/color data = ~1500/3 => ~500 pixels.

Get It Under Control

A new controller needed to be found. Since so many people are experimenting with LEDs, the search didn’t take long since we knew what we were looking for. PixelPusher by Heroic Robotics had recently been Kickstarted and checked all the boxes so we ordered one to test.

RGB LEDs, used mostly for outdoor signage, come in many form factors, have different power requirements, and are controlled by different software libraries. To best work with a beer bottle, we looked at the “thin” 12mm diffused RGB LEDs that would fit in the neck of the bottle. They run on 5V DC, use the WS2801 library, and provide 16 million colors (24-bit).

After some initial experiments with the bottles, the PixelPusher, a 5V power supply, and the LEDs things were looking good. The problems left were connecting the LEDs to the bottle and supporting the grid.

How Far Now?

The first issue is the distance between the Pixels. It is determined by the type of LED strands. The Thin 12mm strand samples we had all measured about 3.25-3.5in between pixels. When planning the grid layout on sheets of plywood, there was not enough material between the bottles to support them all safely. Increasing that distance would mean cutting and re-splicing 4-conductor cable - times hundreds of pixels!

Staying with the bottle idea and trying the “flat” 12mm RGB LEDs, we found that those pixels were spaced at 4.25-4.5in giving us another inch to work with. Attaching them to a beer bottle then gets tricky and would require more parts to figure out…

Ah Ha!

Working in the lab, drinking our favorite water - Hint honeydew-hibiscus, we noticed an empty bottle in the recycle bin. There was an interesting pattern left on the bottom from their manufacturing process. This pattern happens to catch LED light very nicely. It is plastic so it is lightweight and easily modifiable. The body of the bottle provides natural affordances between the base and the neck which means we can secure them between dimensional lumber which has longer spans versus expensive plywood.

And finally, the mouth of this bottle is larger than normal and happens to fit a Flat 12mm Diffused RGB LED. Grabbing a pair flush cutters, we were quickly able to snip tabs in the bottle cap. The cap when screwed down holds the LED in place and the wires can be locked in place with small zip ties.

Seems like we have stumbled onto the new path!