Justin Roberson’s annual holiday display looks like a triumph of electrical and computer technology. More than 30,000 LEDs blink, flash, and race around his parents’ Bismarck, North Dakota home each night from Thanksgiving to New Year’s. The lights are synchronized to music, which is broadcast via low power radio frequency, so that anyone can tune in from their vehicle and listen in as they watch the show from the street.
It’s a popular local attraction, and the cul-de-sac in front of the house is crowded with cars, trucks, and even limousines all season.
The lights are timed down to 0.05 seconds, with the entire program repeating every 12 minutes. It looks and sounds like this:
But surprisingly, neither electronics nor computers are Roberson’s first love. Mechanical engineering is.
He’s pursuing an ME degree at North Dakota State University, expecting to graduate December 2016. He also interns for a well-known equipment manufacturer (and PTC Creo customer) in Fargo.
With that in mind, I asked him to take us on an ME’s tour of the display. He started by urging me to look closer at the big tree.
Out in the synchronized lights community (they have forums, just like everybody else), the centerpiece of most displays is a giant tree, says Roberson. “The taller the better.” Roberson’s “mega tree” stands 20-feet tall, and holds about 50 strands of LEDs.
With the tree comes several design challenges. In North Dakota, for example, the wind often gusts at 50-70 mph, sometimes faster. To keep the structure from falling over, Roberson weighed a number of options for its center pole.
“A lot of people choose PVC pipe or even wood,” he says. “They quickly find out that doesn’t work.”
Galvanized pipe would provide the strength the tree needed, but too much weight.
In the end, Roberson devised his own solution: Double-walled electrical metallic tubing. EMT conduit is commonly found in commercial and industrial buildings for routing electrical wires. It’s lightweight and inexpensive–but not very sturdy on its own.
“EMT conduit can fold,” Roberson says, “So I put a tube within a tube and pinned them together. My calculations showed that would give me the structural integrity I needed, without too much weight.”
The pole sits loosely in a PVC base, with guide-wires supporting the structure, much like how radio towers stand up. The guide-wires are staked into the ground during warmer weather and usually frozen firmly in place by December.
The second major challenge is simply hauling the lights up to the top of the pole. For this, Roberson devised an ingenious cart.
With the cart at the base of the pole, Roberson hooks one end of all the LED strands to it, spreading their tails across the lawn. “When it’s ready, I use a wire and pulley system to pull the cart up, lifting all the LEDs with it,” he says. “Otherwise, I’d have to rent a bucket truck to raise the lights.”
This year, Roberson added a talking snowman. That is, a human-sized figure with a face made from LEDs. The snowman MCs the show as its mouth appears to move open and shut.
Finding the right material for the character took some research too. It had to be flexible, easy to pack up and store, and sturdy. In this case, Roberson used corrugated plastic sheeting, the same material often used in campaign yard signs.
Roberson modeled the snowman on PTC Creo first, to check the scale of the figure fit well with other objects in his display. Then he cut the “Coroplast” into strips to form the snowman.
You can see this year’s entire 12-minute show, without ever driving to North Dakota, by visiting Roberson’s website here: http://holidaylights4u.webs.com/christmasshowvideos.htm.
And if you’re a student, you can get your own seat of PTC Creo free–also without ever driving to North Dakota. Ready to amaze your friends and neighbors with your innovation and creativity? Download the student edition today.