The formula
amps = watts ÷ volts
supplies = watts ÷ (supply rating × 0.8), rounded up
Size for full white at full brightness: every colour of every dot on at once is the most current the installation can draw. Strobing all the dots can draw more than you expect, so leave at least 10% headroom on every supply. Pixel Designer loads each supply to 80% of its rating, which leaves 20%.
Power per dot
Current and power at full white, per dot, from the Smart PXL datasheets:
At 48 V a dot draws less current than at 24 V, but the same or more power. What 48 V buys is distance: less current means less voltage drop, so one feed reaches more dots. See voltage drop and power injection.
Worked example: a 20 × 8 m facade
- Dots: 27 rows of 67 dots at 300 mm spacing = 1,809 Smart PXL60 RGBW dots.
- Power at full white, 24 V: 1,809 × 2.11 W = 3,821 W, or 159 A.
- Supplies: 3,821 W ÷ (600 W × 0.8) = 7.96, so at least 8 × 600 W. Pixel Designer uses 9: it never splits one power feed across two supplies, so it packs whole feeds onto each one.
- The same facade at 48 V: 5,123 W from 16 × 480 W supplies, with 8 injection points instead of 32.
Supply sizes Pixel Designer chooses from: 150, 240, 320, 480, 600 W at 24 V; 240, 320, 480, 600 W at 48 V.
Choosing the supply
- Use a constant-voltage (CV) supply at the dots' voltage. A supply that switches between CV and CC must be set to CV.
- Look for short-circuit, overload, over-temperature and over-voltage protection, inrush-current limiting and good output filtering.
- Keep the cable from supply to first dot short and heavy enough that the first dot still sees its rated voltage.
- Where the installation must be UL Class 2, every power circuit is limited to 100 W; Pixel Designer's "Requires UL" option plans for that.
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
How many watts does an LED pixel dot use?
At full white on 24 V, an RGBW Smart PXL dot uses: Smart PXL40 1.80 W (0.075 A), Smart PXL60 2.11 W (0.088 A), Smart PXL100x25 2.11 W (0.088 A). Multiply by the number of dots for the total, and size the supplies with headroom on top.
How much headroom should a pixel power supply have?
At least 10%, because strobing every dot at full white can draw more than expected. Pixel Designer loads each supply to at most 80% of its rating.
How many amps do 1,000 pixel dots draw?
1,000 Smart PXL60 RGBW dots draw 88 A at 24 V at full white, which is 2,112 W.
Should I use 24 V or 48 V pixel dots?
48 V dots carry power further along a run. On a 20 × 8 m facade at 300 mm spacing, one 48 V feed powers 17 strings where a 24 V feed powers 5, so the facade needs 8 injection points instead of 32. Per dot, 48 V draws less current but the same or more power.
Does lower brightness reduce the power supply size?
Yes. If the show will never run brighter than a set level, Pixel Designer can size the supplies for 80, 60 or 40% brightness instead of 100%, which cuts the watts it plans for.
More pixel planning guides
- Pixels per universe and per controller port
- Voltage drop and power injection for pixel dots
- 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: Pixel: power supplies, Managing voltage drop and "pinking" in pixel runs, Design your Pixel Dot system with Pixel Designer.