Large-scale LED build request for advice? Answered
As I was putting up my Christmas lights over the Thanksgiving weekend, I had an idea (cue ominous background music). The idea evolved from a wish to simplify installing the lights on the 2nd storey roofline into a set of fully-addressable RGB C7 lights that would make Clark Griswold proud. As a proof of concept, I want to replace the boring string of 25 multi-color LED lights over the peak of my garage (24 ft of roofline). I looked at some available products that could be used as a starting point.
From the adafruit store:
12mm Diffused Digital RGB LED Pixels – 4 strings = $180
20mm Clear Digital RGB LED Pixels – 6 strings = $270
Available many places:
GE Color Effects™ 50 LED Color Changing Light Show - $99
The Color Effects strings would be expensive when you consider the 200+ feet of roofline and guttering that I want to cover, and would difficult/impossible to sequence across the whole house. While the RGB pixels from adafruit would give me the most flexibility in creating animated sequences, the prices work out to $2.00 - $2.50 per light. To make this a reality, I need to do this on a $1.00 per light budget for the pilot project. Preferably $0.80 per light for the whole house.
So, I want to light the peak of my garage with 48 RGB LEDs spaced out over 24 feet (6 inch spacing between lights). The string would be controlled by an Arduino and a handful of TLC5916 constant-current sink drivers. Each group of 8 RGB LEDs would have a group of 3 TLC5916 chips, so I am looking at 18 chips. I am not worried about the programming, and there are plenty of examples to look at for the TI chips. I plan to use a power supply from an old computer to provide the juice (up to 3 amps with every LED lit). If this was something that fit on my desk, I would dive right in and start experimenting. However…
I am worried about the 24 foot run from the first light to the last. That is a long way for a signal to run to latch the chips. Do I need some sort of repeater for the latch signal? That is a long run for 5V power. If I am switching 144 channels on and off quickly, will there be voltage drops that could introduce bugs into the system?
Does anyone have experience with the sort of large-scale installation I have in mind? Please help a newbie by offering any cautions, advice, and examples to build on. I will definately document the build and post instructions if I manage to sneak this past the wife. Thank you!