Ws2812b controller

WS2812B LED Controller — Vinyl Record Shelf Finder

PCB for the hardware layer of the vinyl record shelf finder: a system that illuminates the correct cube of a Kallax 4×4 shelf when you look up a vinyl record. The shelf-finder application lives in vinyl-record-shelf-gopher and uses record metadata from discogsography.

Overview

A Raspberry Pi 4B queries a PostgreSQL database for a record's shelf location, then fires an HTTP call to WLED running on a Seeed XIAO ESP32C6. The ESP32C6 drives the correct WS2812B LED strip, lighting up the cube containing that record.

flowchart TD
    PI[Raspberry Pi 4B]
    ESP["XIAO ESP32C6<br/>(WLED)"]
    LS["74AHCT125<br/>3.3V → 5V level shift"]
    C1[Cube 1 LEDs]
    C2[Cube 2 LEDs]
    C16[Cube 16 LEDs]

    PI -->|WiFi HTTP| ESP
    ESP --> LS
    LS --> C1
    LS --> C2
    LS -.-> C16

PCB Specifications

Schematic

The signal path:

flowchart TD
    A["XIAO D1<br/>GPIO3 (3.3V)"]
    B[R1 470Ω series]
    C["U2 74AHCT125<br/>1A → 1Y<br/>3.3V → 5V shift"]
    D[J2 DATA pin]
    E[WS2812B Strip Din]

    A --> B --> C --> D --> E

Power:

• 5V in via J1 (CUI PJ-102AH barrel jack, center positive)
• 5V rail shared between LED strips (via J2) and XIAO VBUS
• 3.3V generated by XIAO's onboard regulator → decoupled by C4

Bill of Materials

See BOM.csv for the full sourced BOM with DigiKey part numbers.

LED Strip Wiring

16 × WS2812B strips (one per Kallax cube). All strips share the 5V/GND power bus. Data is a single daisy-chain through all 16.

J2 +5V ──────────────────────── ●  ●  ●  ... ●   (all 16 strip +5V pads)
J2 GND ──────────────────────── ●  ●  ●  ... ●   (all 16 strip GND pads)
J2 DATA → Strip1 Din
           Strip1 Dout → Strip2 Din
                          Strip2 Dout → ... → Strip16 Din

Cube numbering (top-left = 1, bottom-right = 16, row-major):

┌────┬────┬────┬────┐
│  1 │  2 │  3 │  4 │  ← Row 1
├────┼────┼────┼────┤
│  5 │  6 │  7 │  8 │  ← Row 2
├────┼────┼────┼────┤
│  9 │ 10 │ 11 │ 12 │  ← Row 3
├────┼────┼────┼────┤
│ 13 │ 14 │ 15 │ 16 │  ← Row 4
└────┴────┴────┴────┘

WLED Configuration

Each cube maps to one WLED segment. The vinyl-record-shelf-gopher service sends an HTTP request to activate the segment corresponding to the record's cube location. API specification: TBD.

J1 Barrel Jack Pinout

⚠️ Center positive only. Verify polarity with a multimeter before first power-up.

J2 Terminal Block Pinout

Assembly

See ASSEMBLY.md for the full step-by-step guide covering PCB population, LED strip installation, wiring, and system test.

Soldering order (shortest to tallest):

1. R1 (470Ω axial)
2. C2, C3, C4 (100nF ceramic disc)
3. C1 (100µF electrolytic — observe polarity)
4. ED14DT DIP socket (not the IC)
5. J1 barrel jack
6. J2 terminal block
7. XIAO female socket headers (1×7 × 2)
8. SN74AHCT125N into socket (after power test)
9. XIAO ESP32C6 module

Fabrication

Designed for OSH Park 2-layer service. Upload controller/ws2812b_controller.kicad_pcb directly.

To generate gerbers in KiCAD 7:

1. Open controller/ws2812b_controller.kicad_pcb
2. File → Fabrication Outputs → Gerbers
3. Output to controller/gerbers/
4. Also generate drill files from the same dialog

Software

WLED firmware is flashed to the XIAO ESP32C6 before installation. The shelf-finder application lives in vinyl-record-shelf-gopher, which consumes record metadata from discogsography and issues the WLED segment calls to this controller. API specification: TBD.

License

Hardware designs released under CERN OHL-P v2.