1. ELT-2720 Electrical Project by Patrick Schlott DMX-512 Data Splitter

2. Brief stage lighting history • Electronic control is about 40 years old • Digital control is not as old, at least for stage lighting • DMX-512 protocol standardized in 1985 by USITT • Digital MultipleX with 512 pieces of information • Conventionals were operated using rheostat boards or autotransformer boards • Large, heavy, inefficient, needed many hands to run

3. Resistance Dimmer

4. Background – what is DMX512? • Not the rapper… • Data protocol for theatrical lighting control • Allows consoles (controllers) to “talk” to dimmers, scanners, movers, LEDs, and similar devices • Based on RS-485 (250kbaud) • Unidirectional • Connections use 5-pin XLR

5. DMX-512: How it works • DMX uses differential signaling along 2 communication lines; 3 total (ground) • Voltage levels must be at least +/-200mV to drive device chips (+12/-7V max.) • Signal components shown here

6. Physical network requisites • Twisted pair cabling is common practice • Helps for noise immunity • 120Ω characteristic impedance of cables • Terminators for DMX and RS-485 devices are 120Ω.

7. Source-Device Operation • DMX devices (dimmers, LEDs, movers, etc.) are addressable on the network • They will only “listen” to the channels they are addressed to

8. Typical setup

10. DMX-controlled fixture configuration

11. My project: Data splitter

12. Data Flow Block Diagram

13. Circuit Diagram

14. Typical Bias and termination network

15. PCB Design

16. Why is an optosplitterhelpful? • DMX512 Optosplitters are used for theaters or other venues with large amounts of lights • Often in locations that would make linking fixtures a waste of cable • Fixtures are connected via “daisy chain”, opto allows for a star connection • Opto chip provides electrical isolation –also safety • Can only directly link 32 devices per universe

17. Features • DMX Splitters already exist • But, more rugged, high quality models will have a bigger price • Basic components • Simple construction • Replaceable ICs

18. More features • Sturdy 3-D printed plastic enclosure • Schottkey diode on power supply for reverse voltage protection • Power and DMX data LEDs on board • 3 outputs

20. Are there any questions?