| DMX transmitter (dongle) |
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Between the computer that runs the show and the rest of the stuff is an interface, the DMX USB Dongle. From 2008-2010 I used a model designed by electronics hobbyist Robert Jordan of DIY Light Animation and Avon Park, Fla. In 2011, I used a similar device designed by Robert P. Martin (aka “RPM”) of Pomona, Calif. The DMX dongle connects to the computer via the USB port and interprets the code that xLights sends out, turning it into DMX-512 packets (for more information on how DMX-512 works, see this explanation). The packets are then sent out over a twisted-pair wire. The DMX Christmas light crowd has agreed to standardize on using computer cabling, called Cat5, and RJ45 connectors. (The official DMX-512 standard connector – a five-pin XLR – is very expensive and so was rejected by the DIY Christmas light community.)  The brains of the Lynx Dongle is the PIC18f2450 microcontroller from Microchip; it is aided and abetted by a USB-UART adapter board from DLP Design. The adapter board fits onto the printed circuit board as though it is a 24-pin, through-hole microchip, cutting down a lot of time in building the Lynx Dongle.The RPM version uses an Atmel ATMega88 as its brains and uses the same DLP USB-UART adapter. (I chose the RPM version of the dongle over the Lynx version for 2011 because I thought I was going to add a new show feature that would have required me to use the Lynx for another function; that didn’t come to pass, but I had moved far enough along on the dongle conversion not to want to move back.) The microcontroller brings in the signal from the USB adapter board and converts it into DMX and then sends it back out on an RJ45 connector. The DMX dongle uses the power from the computer’s USB port, so it doesn’t require a separate power supply. While neither are a clone of the Enttec DMX USB Pro – neither support RDM among other things – both were inspired by that device and these dongles use the Enttec Pro Vixen plug-in. The only downside to a DMX Dongle is that it has only one output – but that’s why RJ invented the DMX Splitter (and RPM designed a slightly different one too). |