Analog to DMX

Information on this page may be out of date or apply to old equipment. Use with caution.

This page covers an idea. It may not reflect current practice, but might help develop it.

Does

• 6 channels (expandable to 12)
• 0 to 10v input
• DMX512 out (3pin)
• DMX base channel selectable between 1 and 505

Guts

• Driven by ATmega 328
• RS485 line driver pushes DMX
• 120ohm line for DMX
• supplies 10v to OB board on pin 13, Gnd out on pin 14

Connection

• Power
  • external 12v PSU
  • via YSTV style 4pinXLR
• Analog
  • DA15 (15pins 2 rows)
  • Common ground on pin 15
  • channels on 1 to 6, 7 to 12
    • if soneone wants, they can then duplicate everything to get channels 7 to 12
• DMX
  • 120ohm, 3 pole, XLR for each set of six.
    • because that means we don't have to play around with chaining.
    • Also, if one Universe fails, we still have the other to run on.

Outboard

The analog to DMX outboard is going to be a little box for when you don't have a full lighting desk available. It gets power from the Analog to DMX box, and sends back different voltages, to control the Analog to DMX box, which then controls the DMX devices at the other end.

How

• ONE connection of DA15
  • channels on pins 1 to 12
  • 10v in from Analog to DMX on pin 13
  • Gnd in on pin 14
  • Gnd out on pin 15

Why are there two grounds?

• The Analog to DMX box expects a reference Gnd from wherever it gets it's signal, this can be used, in conjunction with the AREF of some microcontrollers, to boost or cut the difference between 'reference' and signal (channels), so that was given a separate line. Usually, just leaving this alone or common (i.e. pins 14 and 15 bridged) is fine - it's main reason for existance is to be used as part of a compensator for long cable runs making voltage drops.
• The Analog to DMX also sends 0v ground out to it's controlling devices, so they can operate - rather than being boxes of variable resistors.
• Compensation happens at the slave end. Doing it at the control end risks someone coming along sometime in the future, and splitting the channels off the lines - in a worst-case scenario, they then compensate for long lines, something gets more than 10v without expecting it...