Keeping with the “three groups” motif…three Fadecandy boards, three sets of power terminals…three identical wiring harnesses were built, each distributing power and data to 8 NeoPixel strips. Each block consists of:
- 1X USB cable
- 1X Fadecandy board
- 1X 2-row, 16-pin IDC header and plug
- 1X 16-conductor ribbon cable
- 8X JST female receptacle
- 8X 22 gauge wires for 5V
- 8X 22 gauge wires for GND
- 4X 18 gauge wires for 5V
- 4X 18 gauge wires for GND
- 1X 12 gauge wire for 5V
- 1X 12 gauge wire for GND
- 2X Power distribution bus bars (1 ea. for 5V and GND)
- Lots of heat-shrink tubing in various sizes (do not use electrical tape)
A 16-pin (8x2) header is soldered to each Fadecandy board.
A mating IDC header is assembled using 16-conductor ribbon cable, sufficiently long to bridge the anticipated distance between the Fadecandy board and strips. Use an IDC crimper or a vise for this. Do not use pliers.
Goal is to get pin 1 of the cable (usually marked with a dark stripe) connected to pin 0 on the Fadecandy board.
IDC cables can be a topological nightmare; accounting for the doubled-back strain relief always gets me.
Examine the header for a pin 1 mark (if any), align this end with pin 1 on the cable and the “0” pin on the Fadecandy board. You may need to try a dummy build and test with a multimeter.
For each receptacle, add an extension to the 5V wire, 22 gauge or heavier. Make sure they’re all oriented the right way, with the key in the same position.
Use a robust inline splice for the connection: twist the wires around each other, solder and cover with heat-shrink.
Take the first two conductors of the ribbon cable and peel away a few inches. The first conductor — pin 1 — gets connected to the data line for strip 0. Slide the heat-shrink tube over the wire before making the inline splice.
The second conductor — pin 2 — then goes to that strip’s GND wire…but, like was previously done for the 5V wires, this wire also needs a 22 ga. extension. It’s a three-way inline splice.
Repeat these steps, peeling pairs of wires off the ribbon cable and connecting to each receptacle’s data & GND wires.
The eight 5V and GND wires all need to meet up with 12 gauge wire to the power supply…that’s 9 wires total, but the power distribution bus bars only accommodate 7 wires each (and don’t take well to doubling-up). So pairs of 5V and GND wires were joined with 18 gauge pigtails (which can handle two strips worth of current) using three-way splices.
Conceptually, it’s similar to this:
Here’s one of the wiring harnesses nearly complete. The 18 gauge power pigtails haven’t yet been added.
If you have a label-maker, it’s extremely helpful to add strip number “flags” to each JST cable! They need to connect to strips in a specific physical order.
Being a stickler for details, I made these laser cut holders, but you DON’T need to go to such lengths! Fastening everything to a board would work just fine.
Each one holds a Fadecandy board, two power distribution bars (5V and GND) and the wiring harness for 8 NeoPixel strips.
With no strips attached and with the power supply switched off, each unit was wired in one at a time. Power up, confirm power supply is happy, power down and repeat with the next.