Wiring & Cable Runs
How the signal system works — cable-run physics, the SmartReceiver architecture, and the placement rules. This page holds the principles; the specifics live in the Build Guide:
- Which cable plugs into which box → SR Boxes (generated from the wiring database)
- Cable routes and the order list → Cables & Runs
- Which PSU feeds what → Power Map
Source of truth: per-connector wiring (strand → box → socket → universe/channel) is the wiring database
wiring-db/strands.db, machine-checked against the controller config (F48V5-config-runbook.md) bypixel-map/validate.py. The Build Guide pages and printed labels are generated from it. Decision history lives in the projectprocess_notes.md.
Cable Run Limits
F48V5 → SmartReceiver (Cat6 differential)
Working limit: 90 m (300 ft). The Falcon differential system uses RS-485-style signaling over Cat6; Falcon rates it 300+ feet. The structure is ~20 m across — even the longest diagonal run is under 30 m. Not a constraint. The controller can reach any SR with margin to spare.
SmartReceiver → LED strip first pixel (data wire)
This is the critical placement constraint.
| Distance | Verdict |
|---|---|
| ≤5 m | Reliable without special measures |
| 5–10 m | Works with AWG18 or heavier + doubled ground return |
| >10 m | Signal degradation — needs null pixels or a booster |
Key insight: ground wire gauge matters more than data wire gauge — voltage drop on the return path is what kills the signal. On 4-core cable, use the spare wire as a doubled ground.
Why the limit only applies to the first pixel: every WS2811/WS2815 IC regenerates the data signal — the constraint is only the passive wire from SR output to the strip’s first pixel.
Null pixels: a dummy pixel inserted mid-wire as a signal repeater, for runs that must exceed 10 m.
Scaffold rule of thumb: a scaffold box is 1.98 m per side (2.02 m diagonal), so a 2-scaffold-length run is ~4 m — comfortably inside 5 m. Keep every strip entry within two scaffold lengths of its SR and placement can be eyeballed without measuring.
24 V note: higher strip voltage doesn’t change data limits — the data signal is 5 V logic regardless of strip voltage.
Power Wire Sizing — 24 V runs
Target < 1 V drop at the strip far end. V_drop = Current × 2 × Length × Ω/m:
| AWG | Ω/m round trip | 5 A max run | 10 A max run |
|---|---|---|---|
| 10 | 0.0066 | 30 m | 15 m |
| 12 | 0.0105 | 19 m | 9.5 m |
| 14 | 0.0166 | 12 m | 6 m |
| 16 | 0.0264 | very short runs only | — |
Dual-End Power Injection — safety rule
When a strip needs power at both ends, feed both ends from the same PSU — one source, no conflict. If two different PSUs must feed opposite ends of one continuous strip, the V+ line must be cut at the midpoint (data and GND stay intact): even a slight voltage difference between PSUs drives current through the strip traces (heat, noise, PSU damage).
Where each rule applies per zone — and every injection point — is on the Power page and the Power Map. The short version: major arches cut V+ at the crown (two PSUs per arch); minor arches, quads, and rose petals are single-PSU (no cut).
Rose window — tested 2026-06-25
Dual-end injection on every 9 m petal is empirically required, not optional: with single-end power the strip visibly failed past the halfway point at higher brightness (worst with warm whites). Both ends of each petal are fed by the same PSU.
Power vs. Data — why LED power never comes from the SR (24 V zones)
All Falcon SmartReceivers accept 5–13 V only — every SR on a 24 V tower runs on a 12 V buck converter. A 24 V fixture therefore cannot draw LED power through the SR. At every 24 V strip:
| Wire | Source |
|---|---|
| V+ (24 V) | Fused bus from the PSU — bypasses the SR entirely |
| GND | Common — PSU, SR, and fixture grounds bonded |
| Data | SR output |
In practice, inside each enclosure: the strip plugs into a normal 3-pin pigtail, but the pigtail’s V+ conductor lands on the fused 24 V bus, not the SR board. Dual-end zones add a far-end power-only tap. The rose window (12 V) is the only exception — its SRx1 boards run at 12 V, matching the strips, so petal power legitimately flows through the board (near end only).
Common ground is mandatory everywhere — without it the data signal has no reference. This is the silent failure mode of split power/data.
No level shifter needed: the SRs output a 5 V data signal; the WS2811’s logic input wants ≥3.5 V, regardless of strip voltage. (A bare 3.3 V ESP32 would need a shifter; the SRs don’t.)
SR Architecture — ports, sub-addresses, chaining
The fundamental unit: 4 ports per Cat6
Each Cat6 from the F48V5 carries 4 ports of pixel data; the controller’s 48 ports = 12 Cat6 differential outputs. (Ports 1–4 also mirror the controller’s onboard connectors — kept reserved for that.)
How SRs break ports into sockets
The ID dial letter is a sub-address that multiplies sockets per port:
| SR model | Sockets | How |
|---|---|---|
| SRx1 | 4 | 4 ports × 1 letter |
| SRx2 | 8 | 4 ports × 2 letters (e.g. dial E exposes E + F) |
| SRx4 | 16 | 4 ports × 4 letters (dial A exposes A–D) |
Chaining: boxes daisy-chain on one Cat6, each set to a different dial letter — same 4 ports, different sockets. A chain of boxes is functionally one big receiver distributed across the scaffold.
Connector notation: socket ID = <port><letter> — 5A is port 5 on the dial-A board; 5E is port 5 on the chained dial-E board. An installer reads 8F as: box SR 5-8 (E), second letter-row, socket 4. (See the Build Guide primer.)
Ports vs. universes
- Ports are hardware — 48 physical outputs, ≤704 px each.
- Universes are software — 510-channel blocks (⚠️ never 512 — 510 divides by 3 so no RGB pixel straddles a boundary; a 512 setting would misalign the whole show).
Universe block allocation (stable; full per-socket detail is in the SR Boxes tables):
| Block | Zone |
|---|---|
| u1–u2 | Rose window design cells (xLights-internal — no port reads these) |
| u7–u16 | Minor arches |
| u39–u48 | Major arches (full resolution) |
| u50–u75 | Towers: spires, spirelets, canopy, chained quads |
| u76–u139 | Rose window physical pixels (expanded FSEQ; 4 universes per petal) |
Current chain layout (see Build Guide for details)
- Front towers: SRx4 (dial A) → SRx2 (dial E, exposes E+F)
- Back towers: SRx4 (dial A) → SRx1 (dial E)
- Arches: one SRx2 (dial A) per group — left minors, right minors, majors
- Rose: 4× SRx1 (dial A), one Cat6 each, at the hub
Port map: 5–8 FR tower · 9–12 FL · 13–16 BL · 17–20 BR · 21–24 minors LEFT · 25–28 minors RIGHT · 29–32 majors · 33–48 rose (one petal per port) · 1–4 reserved.
SR units: 15 — 4× SRx4 (towers) + 5× SRx2 (2 front-tower corners + 3 arch groups) + 6× SRx1 (4 rose + 2 back-tower corners). Spares on hand of every type.
SR Placement Principles
- SRs live on the scaffold, within 5 m of the strips they serve — not at ground level
- Cat6 runs long — never let Cat6 routing constrain SR placement
- Group strips by proximity — SRx4 for dense clusters, SRx1 for small/isolated zones
- Every SR needs 12 V — buck converter off the local 24 V PSU (rose: direct 12 V)
- Weatherproof enclosures required — playa dust and weather at height
SRx4 board layout
The SRx4 has 4 physical rows labeled ID, ID+1, ID+2, ID+3, each with sockets 1–4. Each row holds one socket from each of the 4 incoming ports; each port column runs down the rows as sequential sub-strands of that port’s stream:
Port 5 Port 6 Port 7 Port 8
Row ID: 5A 6A 7A 8A
Row ID+1: 5B 6B 7B 8B
Row ID+2: 5C 6C 7C 8C
Row ID+3: 5D 6D 7D 8D
Reference: Falcon SR port numbering · SRx1 chaining
xLights controller configuration
Port/universe/brightness values are entered on the physical controller per F48V5-config-runbook.md (in the NYC lab, then backed up — never configured on-playa). xLights sequences are built against universes; the port config maps them to hardware.
Cable labels
Moved to the Build Guide: Cables & Runs → Cable labels.
Recommended hardware
WAGO solderless push-in connectors for all wire-to-wire junctions inside enclosures, at V+ cuts, and anywhere a reliable re-openable connection is needed: WAGO 221 (lever, mixed gauges) and WAGO 2273 (push-in).