ETC Unison Mosaic Show Control - Manual (Page 47)

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LED
Colour changing fixtures just have multiple instances of these LED arrangements, one for each
colour, typically three (RGB) so requiring three driver/DMX channels to control. Note that
with colour changing LED fixtures the anodes (+) are connected together and the cathodes (-)
individually driven since LED current switching occurs on the negative side. Beware colour
coded cables as there is no standard coding system.
FIXTURE GANGING
It is often desirable to gang fixtures together onto one driver/DMX channel and here again the
fixture type determines how this is done and what needs to be determined:
LED MODULE - GANG IN SERIES
CxD VERSION & POWER SUPPLY SELECTION
Once you have determined the fixture types, drive characteristics and ganging requirements you
can select the appropriate drivers & power supplies:
LED MODULE - GANG IN SERIES - CONSTANT CURRENT
That all being said, ganging is an iterative process based on zoning requirements and driver &
power supply choices with the highest system efficiency and lowest cost being the overall target.
It is often sensible to start with the constant voltage power supply requirement and use that for
the constant current supply as well to standardise on a power supply but this is not a
requirement. You should also not balk at selecting the LED fixtures themselves to fit into your
overall system.
Further, consider distributing the LED drivers & power supplies to be close to the fixtures
themselves to minimise cabling and cable losses (constant voltage) and maximise flexibility,
particularly when it comes to refits. Finally it is advisable to use multiple low-power power
supplies, perhaps one per 6 channel driver, rather than a centralised high-power approach.
• All modules must have the same forward current If(module) to be ganged
• Determine the total forward voltage drop Vf(total) by summing the Vf(module)s
• It is helpful to end up with similar Vf(total)s for each gang of modules
LED ARRAY - GANG IN PARALLEL
• All arrays must have the same supply voltage Vs(array) to be ganged
• Determine the total power load Ps(total) by summing the Ps(array)s
• It is helpful to end up with similar Ps(total)s for each gang of arrays
• Use the LED-C350, C500 or C700 for 350, 500 or 700mA If(module) drive respectively
• Choose a power supply such that Vin is slightly greater (2-3V) than the maximum Vf(total)
• The more that Vin exceeds Vf(total) per channel then the worse the efficiency
LED ARRAY - GANG IN PARALLEL - CONSTANT VOLTAGE
• Use the LED-V ensuring that each channel load is 40W maximum or 180W in total
• Choose a power supply such that Vin equals Vs(array)
• Choose a power supply capable of supplying the total load, the sum of each Ps(total)
• Long cables decrease efficiency, split up large arrays to avoid visible drooping