Why the far end dims or turns pink
Current flows out along the positive conductor and back along the negative, and the copper resists it both ways, so every dot sees a little less voltage than the one before. Blue and green LEDs need more voltage than red, so they fade first: white turns pink, then red, and below the dots' minimum the data can flicker too. The fix is to feed power in again before that point.
The formula
last dot voltage = supply − feed cable drop − string drop ≥ the dot's minimum
The resistances Pixel Designer uses, per conductor:
- Dot string cable: 0.0134 Ω per metre, plus each dot's own resistance.
- Feed and data-extension cable: 0.008 Ω per metre.
- Each connector mate: 0.004 Ω.
- Smart PXL60 RGBW at 24 V: at least 21 V at the last dot.
- Smart PXL60 RGBW at 48 V: at least 27 V at the last dot.
- No more than 10 A on any one feed.
Where Pixel Designer injects power
It feeds power at the ends of each line, and a turn between two lines feeds both ways. Each feed powers as many whole strings in a row as keep the last dot above its minimum and the feed within 10 A. Only where a line needs more than its two ends can feed does it add a point part-way along the line.
Worked example: a 20 × 8 m facade
1,809 Smart PXL60 RGBW dots in 27 rows at 300 mm, made as 216 strings of up to 9 dots:
Wiring rules for more than one supply
- Connect the 0 V (GND) of every supply together and to the controller's ground. Without a shared ground the data flickers in a way injection cannot fix.
- Never join the positive outputs of separate supplies: each supply powers its own section of the run.
- Use supplies of the same voltage on one run, and run each injection back to the supply as its own pair of wires.
Work it out for your own layout
Pixel Designer is ENTTEC's free online tool for planning pixel dot installations. Enter your layout's size and dot spacing and it applies every rule on this page: strings, controllers and ports, universes, power supplies, injection points and cabling, with a parts list. No account needed.
Questions
Why does the end of my pixel run turn pink?
Voltage drop. Blue and green LEDs need more voltage than red, so as the voltage sags along a run, blue and green fade first and white turns pink, then red. Feed power in again before the dots that change colour.
How often should I inject power into pixel dots?
It depends on the dots, their spacing, the voltage and the cable. For Smart PXL60 RGBW dots at 300 mm, Pixel Designer feeds at most 5 strings in a row at 24 V and 17 at 48 V, keeping the last dot above its minimum voltage and each feed within 10 A.
Does 48 V reduce voltage drop?
Yes. For the same power, 48 V carries half the current of 24 V, and the drop is current times resistance. On a 20 × 8 m facade at 300 mm, 48 V Smart PXL60 dots need 8 injection points where 24 V needs 32.
Can two power supplies feed the same pixel run?
Yes, if you connect the 0 V (GND) of every supply together and to the controller, and never join the positive outputs of separate supplies: each supply powers its own section of the run.
Do I need to inject the data as well?
No. Power injection feeds only V+ and GND. The data runs in one chain from the controller through every dot, re-driven by each dot.
More pixel planning guides
- LED pixel power calculator
- Pixels per universe and per controller port
- How far can pixel data run?
- LED media facade planner
The figures on this page come from Pixel Designer's own engine and settings, which follow the Smart PXL, OCTO, PIXELATOR and PLink manuals and datasheets. Background reading on the ENTTEC support site: Managing voltage drop and "pinking" in pixel runs, Pixel: power supplies, Design your Pixel Dot system with Pixel Designer.