Posted by JEC on September 17th, 2009
About a month ago, I was contacted by a lighting designer who wanted to use 7,000 Tripix as part of an outdoor installation. The show would run for about six weeks. The nodes needed to be very bright, very durable, and also waterproof.
He’d checked with several commercial vendors and received quotes as high as $110,000 for the nodes, controllers & cabling.
Wowzers. Plus, he needed something viewable (and evenly lit) over 360 degrees, and there didn’t appear to be an existing product on the market with that feature.
So, I mailed out a short string of Tripix for him to evaluate. After much testing, he determined that 2 Tripix, mounted back to back (if you’re counting, that’s 6 SMD RGB LEDs) would be bright enough for his purposes.
However, the RJ45 connectors were very expensive. And we weren’t sure how reliable that junction would be if asked to bear weight. The strings of 25-50 nodes were meant to hang vertically.
After much discussion, we decided to totally re-work the design. We settled on two variants: one based on a six wire, ‘shift register’ PWM processor and a second based on a three wire ‘power ground data’ (similar to DMX) controller.
We researched potting compounds, waterproof dips, UV-cured clear resins (awesome, but $$) and more. I’d finished the circuit board layouts and was about to send off for prototype boards.
Then, late one night I discovered a Source in Asia who specializes in this sort of thing.
Their net-to-me, out-the-door pricing for waterproof nodes – pre-wired and built to our specifications – was phenomenally good.
So I immediately ordered a whole box of goodies as samples.
They arrived this morning.
Let’s start with the ‘dumb’ bits:
These little bars measure about .75″ x 4″. They come in strings of nearly any length and board spacing. Each bar contains R, G & B emitters, evenly spaced in groups of three. Each string of bars can be controlled together via PWM / constant current / whatever to generate any needed color.
These round assemblies are similar to the bars, but they only contain a single emitter of each color. They too can be daisy chained together. The entire chain can be controlled simultaneously.
These point source dots are even more fun. They contain an 8mm RGB LED inside an injection molded, waterproof (!) plastic blob. My sample string contained 50 emitters on 10 cm spacing. Again, the entire chain can be set to any color.
Here’s where it gets more interesting… This next handful of goodies have a built-in brain and can be controlled discretely. Any node can be set to any color, regardless of what the neighboring node may be doing.
These bars are identical to the first (dumb) ones, except that they have an in-built PWM controller. They’re chained together on a four-wire bus (power, ground, clock and data). I grabbed 10 with discrete LEDs and 10 with all-in-one SMD RGB emitters.
These point source dots are awesome. Again, I got a string of 50 on 10 cm spacing. They are very, very similar in intensity and function to my Point Source design from last year. Except that all the environmental problems of wiring harnesses, waterproofing, etc, seem to have been completely solved.
Then, I grabbed a handful of ‘cubes.’ These are waterproof, discretely controlled and daisy-chainable. Size is ~ 2″ per side. Mounting holes under the black bezel for making a wall-sized grid. Nice.
The built-in driver chip has 5 bit resolution for each color. 32 levels * 32 levels * 32 levels = ~ 32K different shades of color available. Maybe not enough for HD video, but certainly adequate for the task at hand.
Here’s the wrinkle…
The datasheet for the PWM controller is written in Chinese. There appears to be no English version anywhere on the entire Internet. The factory won’t release any further details, so I’ve got to spend a few days reverse-engineering the control protocol.
When the dust settles, we’ll have a nifty DMX bridge and a nifty Art-Net interface for driving the ‘smart’ nodes. Probably in about two weeks.
Plus I’ll probably throw together a quick driver – based on the classic RGB pixel design, probably – which can drive one or two strings of the ‘dumb’ nodes.
Here’s two quick video clips of the RGB string. They’re grainy & overexposed, but sufficient for previewing. I also purchased a small stand-alone controller from the factory. It reads show files stored on an SD card, then loops them indefinitely. The factory sent me a demo file with a single demo show loaded. It runs for about 30 seconds, it seems.
The effects are a bit frantic, but the overall look is nice.
Next week we’ll be able to speak with these over regular DMX.