| DMX splitter |
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So, to understand the DMX splitter, you'll need to understand DMX a bit. This lighting communications standard is based on another standard – RS485 (also known as EIA-485), which is an electronics communications protocol. The idea here is that electronics devices can get transmissions from a source on RS485 in a “multi-point” environment, which is another way of saying that you can daisy-chain multiple DMX devices along the same circuit, without having to have repeaters or amplifiers  But – and there’s always a but – while DMX will support 512 different channels, RS485 only supports 32 physical devices per line. Enter the Lynx DMX Splitter. It is designed to take the single DMX output of the Lynx DMX Dongle and split it into four different circuits. While the Lynx DMX Dongle will support only 32 physical devices, after the Lynx DMX Splitter enters into the environment, 128 physical devices can be located downstream from the Lynx DMX Dongle. The Splitter is fairly simple technology: it has a power supply that converts 110-volts AC (household current) and takes it down to five volts, changes it to DC and filters it so that it can drive electronics. The DMX signal comes into the device and is then changed from RS485 to straight serial signals and the serial signal is then in turn sent to three RS485 convertors, which then pass the signal back out of the device. Because RS485 is a daisy-chain environment, while there are only three convertors, the input signal itself can be daisy-chained, so you get four physical outputs from one input with this design. Initially, I didn't think I needed more than two outputs and was going to build a splitter of my own design. Then the proverbial light-bulb went off over my head (it was a C9, I think) and I realized that I would need to send signals in three directions from the show computer: to stage right (the garage), stage left and onto the roof (for the icicle lights). Once I realized I needed four circuits, the ease of using RJ’s printed circuit board outweighed the cost-savings of something I would build on stripboard. For the 2011 show, I decided I needed even further splitting and distribution, so the Lynx DMX Splitter was moved to the garage and an RPM Splitter was built. RPM’s design is slightly different — rather than three RS485 transmitters wired in parallel, RPM’s design uses an SN65172 chip, which has four legs out of RS485, giving the device a five-way split. Much like the hip bone being connected to the thigh bone, the next step is to connect the splitter to the Lynx DMX SSR4. |