Isolated (<1 kV) USB/DMX512 converter

October 31, 2018 | 12:08
Assembled USB/DMX512 converter,
mounted in the Bopla case for which
it has been designed (video below).
If you already know what USB-DMX converters are used for, skip directly to the video below. Otherwise, here are some answers. DMX 512 is a protocol for control of lights and lighting, very popular since its appearance twenty years ago.
It allows individual, remote, precise, synchronous and simultaneous control of a large number of lights, mobile projectors, lasers and the like. Programming, with the use of specific software, enables the integration of synchronised light effects into medium or large scale shows.

DMX, its universe, its frames and its jargon

The digital signals to control the lights and light effects are carried over an RS 485 unidirectional serial link at a rate of 250 Kb/s. 9 bit addressing allows control of 512 channels with 8 bits of data per channel. To designate such a system, one speaks of the DMX universe. Actually, all the 512 values (DMX frames) are received by all the devices at the same time. Initially, there was a limit of 32 devices on the same DMX line. Later extensions allow many more to be connected today.

As wireless communications techniques have become more common, DMX users are more and more using WiFi for the transmission of their commands. To remotely control chains of DMX projectors, other interfaces from the IT world have been combined with the DMX world using specific adapters: parallel port LPT/DMX, serial port COM/DMX and... USB/DMX.

Isolated converter – up to 1 kV

It is just such a USB-DMX512 converter, isolated up to 1 kV, which is described in the Elektor November-December 2018 edition just out. It supports a universe of 512 channels. Compatible with Windows and MacOS, it works with free DMX light programming software such as Freestyler and QLC+.

DJs and fans of amateur light shows are devotees of USB/DMX512 converters to control their projectors from their laptop PCs. Unfortunately, those found in the commercial world are often not (well) isolated from the mains voltage. Here, on the other hand, an isolated DC/DC converter (the WPMIB9200501S from Wurth) powers the isolated RS 485 transceiver (ADM2483BRWZ).

Like any DMX device worth of the name, this new converter has an XLR socket.
 
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