PowerSource

I had a chance to talk with John Burne, chief engineer, special projects for Lighting Science Group, the company that designed the LED system  for the Times Square ball that will drop for the first time this New Year’s Eve. The old Times Square ball relied on incandescent bulbs and wasn’t capable of much in the way of a light show. There’s a youtube video of last year’s ball that purports be show the assembly of the old ball, and the lights look ancient – they could almost be a candidate for a steampunk project. Maintenance on those lights in a system that operates in the temperature extremes of a New York winter on a non-stationary display has got to be a real headache.

Not so with the new ball: Like the old, it’s 6 feet in diameter, but it uses 9,576 Philips Luxeon LEDs, each of which can be controlled independently. It weighs 1200lbs, much of which is in the Waterford crystals that face the triangular LED modules, and should be virtually-maintenance-free. A module is made up of four smaller triangular units, each acting as a pixel which can be red, green, blue, or white. These LEDs are Luxeon K2 and consume as much as 3-4W each. Along the edges of each pixel are delineating Luxeon Rebel LEDs, which don’t have to be as bright, and consume less than a watt. Here’s a picture of the larger triangular module.

Burne says that thermal management along with a very tight weight budget were their two biggest challenges. “We weren’t able to do a lot of extra heat sinking, so we used the aluminum-backed pc board for the majority of our heat-sinking area.” The ball itself has active cooling in the form of fans along the upper and lower portions of the ball to continuously circulate fresh air. The ambient air temp has a wide range – it might be as low as -10°F in the middle of a New York winter, or as high as 92° in their California development lab in the middle of summer. The ball can support such a wide temperature range with relatively little external cooling because every LED module its own thermistor that’s monitored by the module’s controller, a Cypress PSOC chip that will throttle back the LED brightness if the temperature goes too high.Here’s an IR photo of the ball’s hot and cold spots. 

And here’s a youtube video of the ball when it was on display at the Times Square Macy’s – in the Waterford crystal section.

And here’s a link to other very neat projects by Light Sciences Group, back when it was known as LED Effects .