DMX Cable
DMX is an acronym for Digital Multiplex. These cables have an impedance of 120Ω and a low capacitance, so each wire is not affected by the electromagnetic fields of the other wires. It also must be terminated with a 120Ω resistor to prevent reflections, although most lights have built-in terminators on them. Using a cable without a signal terminator, your DMX signal will reach the end of the line, and bounce back like a rubber ball off a wall. This is known as a reflection and it will interfere with your DMX signal.
It comes in 5', 10', 25', 50', and 100' lengths. The DMX specification states the maximum length is 3,281'—but every connection can degrade the signal. A good working practice is to limit your cable run to 1,000'. You are able to daisy chain multiple fixtures together, the DMX standard allows you to daisy chain up to 32 units in one run.
While some people may want to use 3 pin XLR cable in place of DMX along with 3 pin to 5 pin, an analog XLR cable is not rated at 120 ohms, which is based on the cable’s construction; so, transferring data may experience some interruptions, such as strobing or flickering lights since the cable can’t transfer the necessary voltage. This won’t damage the lighting equipment, but is simply signal degradation that can cause inconsistencies and frustration. XLR and 3 pin to 5 pin adapters are therefore not recommended.
This is used by the electric department.
Uses
DMX Cable is used to control lights with a lighting console or other DMX device.
Accessories
Some items commonly used with DMX are:
- Opti-Splitter
- Cintennas may be used to wirelessly connect to lights.
- Lighting Console, which can take many forms.
- DMX Terminator
Troubleshooting
If you are having issues gaining control of your lights you should:
- Check that the fixture address and profile match any labels that are on the unit. If no label exists, then confirm with the console programmer that it is addressed correctly.
- Check that the unit is receiving DMX, this can be done by tracing the cable back or with a DMX tool like the DMXcat. Some units will have a DMX indicator.
- Check the patch inside the console to confirm the light is patched correctly.
If your lights are flickering, check the following:
- The cable run is properly terminated
- The cable run does not exceed the standard of 3281' per DMX run.
- The cable does not exceed the standard of 32 devices in a daisy chain.
- Make sure there is no physical damage to the cable or conectors.