Coming soon to an LED near you, VLC provides a means of transmitting information by modulating the light at a frequency too high to be perceptible to the human eye. A simple conceptual analogy would be using a torch to flash a message in Morse code. Unlike a torch, however, VLC is exciting because of the high data rates that can be achieved and the fact that LED is a huge growth market. Other benefits relate to security and/or safety in environments where radio frequency transmissions are undesirable, such as hospitals.
Aiming for the highest possible data transmission speeds, companies such as pureLiFi are exploiting VLC as an alternative to Wi-Fi - a clever move that side-steps the problem of dwindling radio spectrum bandwidth in a world ever-more dependent on cloud data storage.
At lower speeds, VLC has the advantage of being compatible with existing technology infrastructure. For example, the LED display lighting in a museum could transmit text information or video URLs about the exhibits to visitors' smart devices. Customers in a large retail store could opt to share their phones' GPS location with VLC enabled lighting to better navigate the aisles or find special offers.
Another concept is that of a VLC beacon, which transmits a repeated message. For example, this could be the identity of a zone in a building, such as a hotel foyer. An installer could then use a smartphone control app to auto-configure the lighting levels throughout the building.
Given the opportunities afforded by VLC, there was a pressing need to incorporate it into the lighting protocols in common use today. One of the most ubiquitous is Art-Net, the ethernet based protocol that enables transmission of DMX512 data.
Accordingly, Howell and Archenhold have worked together to devise a standard method of controlling VLC via Art-Net and DMX512 (the newer sACN standard is also supported). Within the Art-Net specification, there is now a packet identified as ArtVlc, which can be used for both Art-Net and DMX512.
For developers, the supporting network analysis programme, DMX-Workshop (available as a free download from the Artistic Licence website) includes an option for viewing and dissecting this packet. There is also a transmitter function that includes the ability to adjust the parameters of the packet and test receivers.
(Jim Evans)
