Glen Akins Brings a Little 802.3at to the Holidays with a Power-over-Ethernet Christmas Tree

The first in a series of PoE projects, Akins' WS2812 Christmas lights need nothing but an Ethernet cable for both power and data.

Biker and electronics enthusiast Glen Akins has created what may well be the first Ethernet-powered Christmas tree in the world, using a custom circuit board which pulls power for the lights and data down a single CAT5 cable.

"The lighted tree in the video [...] gets both the power and data for its RGB LED [WS2812] pixels using a single Ethernet cable," Akins explains. "Power for the pixels is supplied from an Ethernet switch using the 802.3at PoE+ standard. Data for the pixels comes from software running on a PC that generates Art-Net packets at 40 Hz. Each Art-Net packet contains the RGB levels for all the pixels on the tree.

"I’ve been wanting to build an 802.3af/at/bt Power over Ethernet design for a few years now and have always come up short on ideas and then it hit me, what if the Ethernet cable could connect closer to the pixels? With a small box of electronics between the Ethernet cable and the connector on the end of the pixels, the pixels could receive both power and data from the Ethernet switch. No more AC mains wiring and no more proprietary leader cables."

Given the time of year, it made sense for the project to be installed on a Christmas tree — offering power and control through a single Ethernet cable, based on a custom circuit board housed in a waterproof casing - which, handily, doubles as the electrical isolation required of the 802.3af/at/bt standards.

The finished design is built around the Texas Instruments TPS2378 802.3at Power over Ethernet+ Power Delivery (PoE+ PD) controller linked to a Microchip PIC18F67J60 microcontroller — which includes internal Ethernet MAC and PHY, simplifying the design and reducing the board area. While the PIC limits the Ethernet connection to 10-Base-T, a string of sixty 24-bit WS2812 operating at 40 Hz needs a mere 57.6Kb/s.

"I initially used the one meter strip of sixty WS2812 pixels rather than the string of 50 pixels because the strip fit entirely on my desk and it was very easy to look and see if the pixels were displaying the patterns from my PC properly or not," Akins notes. "Once the code was running properly, it was time to go bigger! I grabbed the five meter string of 50 pixels and a cheap $20 fake tree from Michael’s and proceeded to string the lights on the tree. I stuffed the board in the tree then shot the quick video. I’m pretty sure the tree is not an ESD-safe location for the circuit board."

A full write-up, including schematic, board design, and software, is available on Akins' blog, along with a look at two other in-progress PoE projects: A VFD tube clock and an LED floodlight.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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