Mapped per LED, moving in blocks. Pixel length on SPI LED strip

The chase looked smooth in the mock-up. On site, it moves in blocks, and the colours come out in the wrong order. The content was built for one LED per pixel; the strip isn't wired that way.

A pixel isn't always one LED

On addressable strips, a pixel is the smallest part of the strip that can be controlled on its own. On SPI strips, one control IC drives that pixel, and one IC can drive several LEDs. So the pixel length depends on the model: it might be one LED, or a group of three or six, or a fixed length of strip.

If the content is mapped per LED but the strip has, say, three LEDs per pixel, every step of the animation lands on a block of three. The line moves in blocks, and a design meant for fine detail looks coarse.

As our technology page puts it: pixel length is model-specific, not necessarily one LED.

The other things that go wrong

• The IC. Different SPI ICs use different data formats. The controller has to support the exact IC on the strip.
• Data and clock. Some SPI strips use a data line only; others use data and clock. The wiring and controller settings must match.
• Channel order. If the controller sends red-green-blue and the strip expects green-red-blue, the colours come out wrong even though everything "works".
• Pixel count. The controller's output capacity and the number of pixels per run need to fit together.

What helps

1. Confirm the exact IC, data/clock configuration and channel order before ordering. For SPI, confirm the exact IC, data/clock configuration, channel order and controller compatibility.
2. Build the content on the real pixel length of the chosen model, not the LED pitch.
3. Run the actual controller on a sample of the actual strip before the full installation and before the content is finished.
4. Record a commissioning brief. Zones, pixel count, scene behaviour, power-feed locations and signal runs. Confirm refresh behaviour, fault response and replacement addressing with the actual controller and LED model.

DMX works differently

For DMX512 systems, define the addressing and the number of channels per pixel. A DMX decoder converts the DMX signal for the strip, and its channel count and addressing need to match the content too.

Where it matters most

Mall atriums, façades, hotel features and retail windows with pixel animation. Anywhere the content team and the lighting team work separately, the pixel map is the document that has to connect them.

If you're planning a pixel feature, tell us the controller and the content and we'll help match the strip, IC and controller.