Control data link
15
Control data link
The Alien LED Downlight system can be operated using a standard DMX dynamic lighting
control system if driver units are connected to a DMX controller via a control data link. Unlike the
combined power/data cables from driver units to the heads, the control data link from a DMX
controller to driver units carries data only.
Planning the data link
Before planning the data link, study Figure 2 on page 10 and the guidelines below. If you are
unsure about any aspect of installation, contact your Martin supplier for assistance.
Alien LED Downlight control principles
• Downlights are controlled by sending color and intensity commands from the DMX controller
over the data link to driver units. The driver units then relay these commands to the heads over
combined power/data cables.
• A head consists of one transformer that must be connected to either one high-power or two
standard downlight luminaires. Two standard luminaires connected to one transformer will
behave identically.
• A maximum of 10 heads may be connected to one driver unit. A driver unit can control up to 4
heads – or groups of heads – independently. This means for example that you can control one
head and 3 groups, each containing 3 heads, as four independent groups that show four
independent lighting effects. To give another example, you can also put all 10 heads into one
group and control them together, so that they all show the same lighting effects.
• One DMX universe has 512 DMX control channels available in the data signal. Channels 1 -
479 are available for use in an Alien LED Downlight system.
• The driver unit uses 4 DMX control channels to control a head:
- one channel for red, one for green, one for blue and one for white in RGBW mode, or
- one channel for hue, one for saturation, one for intensity and one redundant channel in HSI
mode.
• Since the driver unit can control up to 4 heads independently, it uses up to 16 DMX channels in
total (4 groups x 4 channels = 16).
Cable and link details
• Use RS-485 (also known as EIA-485) data cable for the data link. RS-485 cable has low
capacitance and a characteristic impedance of 85 to 150 Ohms. It is electrically shielded and
has at least 1 twisted pair of conductors. The minimum recommended wire size is 0.25 mm
2
(24 AWG) for runs up to 300 meters (1000 ft.) and 0.32 mm
2
(22 AWG) for runs up 500 meters
(1640 ft). CAT 5 network cable conforms to the RS-485 specification and is suitable for the data
link.
• The maximum permitted control data cable length before a control signal amplifier is required is
500 meters (1640 ft.).
• Devices that are connected to a controller via a data link must be ‘daisy-chained’, i.e. the data
cable must be connected in one single chain.
• Each chain may contain a maximum of 32 Alien LED Downlight driver units or similar devices.
• An optically isolated amplifier-splitter such as the Martin RS-485 Opto-Splitter (P/N 90758060)
must be used to:
- extend a control data link beyond 500 meters (1640 ft.), or
- branch the link into further single chains, each containing a maximum of 32 devices. The
Martin Opto-Splitter allows a link to be branched into four new chains, or
- extend the link if the maximum of 32 devices is reached.
• Each chain on the link must be terminated with a DMX termination plug in the output of the last
device in the chain.