NeoPixel Breakout Board Assembly Guide
Table of contents
Table of contents
Introduction
The NeoPixel Breakout Board is a key expansion in the LCC Fusion lighting and automation system, designed to drive up to eight NeoPixel LED strips (e.g., WS2812, SK6812). Each strip is connected via a 3-pin pixel header (Signal, 5 V, GND) and receives individual PWM signals through a network connection to the PWM Card.
The board regulates voltage from the accessory AC/DC/DCC PWR BUS using a KBL406 bridge rectifier and LM2596-ADJ step-down regulator, producing a clean, stable 5 V output. A TVS diode and a resettable PPTC fuse protect the rail and connected LEDs. Optional power may also be supplied from Line 8 on the PWM Card.
Built to match the modular design of all LCC Fusion PCBs, this board allows clean and distributed lighting control with built-in protection.
System Overview
The NeoPixel Breakout Board connects to the PWM Card using a standard network cable (RJ45), receiving up to eight PWM signals (lines 1–8). Each signal is routed to a separate 3-pin header for driving individual NeoPixel strips. Power is supplied by either the layout’s accessory bus or optionally by the PWM Card’s Line 8 via selector.
Each NeoPixel strip receives:
- Signal: 3.3 V PWM (1kΩ series resistor for protection)
- Power: Regulated 5 V from onboard LM2596-ADJ
- Ground: Common GND plane with source protection
flowchart LR
subgraph layout ["Train Layout"]
n["Node Card"]
c["PWM Card"]
bb["NeoPixel Breakout<br/>Board"]
p["NeoPixel Strips (1–8)"]
acc["PWR BUS<br/>(12–45 V DC/AC)"]
end
can["CAN Network"] --> n
n <--> c
n <--> |"PWM Lines"| bb
c <--> |"PWM Lines"| bb
bb -.- |"PWM Signal + 5 V Power"| p
acc -.- |"Via Bridge + Regulator"| bb
classDef layoutStyle fill:#f5f5f5,stroke:#888,stroke-width:2px;
classDef boardStyle fill:#FFE4B5,stroke:#333,stroke-width:2px;
class bb boardStyle;
class layout layoutStyle;
Assembly Instructions
This section combines both the component specifications and the assembly instructions to ensure a smooth assembly process. Below is a comprehensive list of components, their placement on the PCB, and orientation details to assist you during assembly.
High-Level Steps for Assembly:
- PCB for the card can be ordered from any PCB fabricator using these Gerber Files.
- Clean PCB with alcohol to remove residue. See Cleaning_PCB for details.
- See also: Soldering Tips
- PCB Components - listing of components used for PCB assembly
- PCB Parts - listing of parts used for PCB assembly
Required Components
| Reference | Count | Type | Value | Package | Purpose | Orientation |
|---|---|---|---|---|---|---|
| Bridge Rectifiers | ||||||
| BR1 | 1 | Bridge Rectifier | KBL406 | PTH | Handles up to 4 A input from AC/DC/DCC accessory bus | Position the rectifier’s clipped corner (pin 1) toward PCB right edge |
| Capacitors | ||||||
| C1 | 1 | Capacitor (Ceramic) | 0.1 µF | 1206 X7R | Regulator noise suppression | None |
| C2–C3 | 2 | Capacitors (Electrolytic) | 100 µF | 6.3x5.8mm , SMD | Input/output filtering (regulator) | Anode positioned toward PCB top edge |
| C4 | 1 | Capacitor | 1 nF | 1206 X7R | LM2596 FB noise suppression | None |
| Diodes | ||||||
| D1 | 1 | TVS Diode | SMAJ5.0A | SMA SMD | Protects 5 V output rail from spikes | Cathode end has a white line and positioned towards PCB left edge |
| Connectors | ||||||
| J1–J8 | 8 | Connectors | 3-pin headers | PTH | Pixel strip connections (SIG / 5V / GND) | None |
| J9 | 1 | JST XH Socket or 2-Position Spring Terminal Connector | 2P, 2.54mm | PTH, vertical or horizontal | PWR input via accessory bus | None |
| J10 | 1 | RJ45 Socket | 8P8C | PTH | Network cable from PWM Card | Fits only one way |
| Indicators | ||||||
| LED1 | 1 | LED | Red | 1206 SMD | Power indicator | Reference back of LED, position cathode towards PCB left edge |
| Fuse | ||||||
| F1 | 1 | PTC Polymer Fuse | JK30, 3 A, 16 VDC (or more) | 5.1mm pitch, PTH | Resettable 3 A fuse for 5 V output protection | None |
| Resistors | ||||||
| R1–R8 | 8 | Resistors | 1kΩ | 1206 SMD | Series resistors for each NeoPixel signal (DIN lines) | None |
| R9 | 1 | Resistor | 1kΩ | 1206 SMD | LED current limit resistor | None |
| R10 | 1 | Resistor | 3.3kΩ | 1206 SMD | LM2596 feedback resistor | None |
| Inductors | ||||||
| L1 | 1 | Inductor | 330 µH | 8x10mm, PTH | Required for LM2596 switching circuit | None |
| Voltage Regulators | ||||||
| VR1 | 1 | Voltage Regulator | LM2596-ADJ | SMD | Step-down switching regulator | Fits only one way |
Connector Assignments
| Header | Description | Connected Components |
|---|---|---|
| J1–J8 | Pixel Strip Outputs | NeoPixel strips (SIG/5V/GND) |
| J9 | Power Input | 12–45 V AC/DC/DCC |
| J10 | PWM Card Input | 8 signal lines via CAT5/6 |
PCB Assembly Image
Click to enlarge or print.
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Safety and Testing
Safety Precautions
- See Safety Tips
- Ensure 5 V output is disconnected from NeoPixel strips during initial testing.
Initial Testing
- Verify continuity and polarity from bridge to regulator.
- Power with 12–20 V on J9.
- Confirm LED1 illuminates (5 V rail live).
- Test output voltage on J1–J8 = 5.0 V.
- Validate PWM signal with logic analyzer (optional).
Appendences
Specifications
| Characteristic | Value |
|---|---|
| Supported Strips | 1–8 NeoPixel |
| Output Voltage | 5 V Regulated |
| Max Output Current | 2 A (with PPTC limit) |
| Input Voltage Range | 12–45 V AC/DC |
| Strip Connector Format | 3-Pin (SIG/5V/GND) |
| Data Source | PWM Card via RJ45 |
How It Works
The NeoPixel Breakout Board is designed to distribute signal and regulated 5 V power to up to eight NeoPixel-compatible LED strips, typically WS2812 or SK6812. Each strip connects to a dedicated 3-pin output header (Signal, 5 V, GND) and receives a unique PWM signal from the PWM Card via a network cable.
Power Input and Regulation
Power is supplied from the Accessory Bus (AC/DC/DCC, 12–45 V) through a KBL406 bridge rectifier, which ensures proper polarity. The rectified DC feeds the LM2596-ADJ switching regulator, which steps down the voltage to a stable 5 V rail. This rail is filtered with 100 µF bulk capacitors and protected using a SMAJ5.0A TVS diode and a JK30-300 resettable fuse (PPTC). This regulated 5 V supplies all eight NeoPixel headers.
Signal Distribution and Protection
Each strip receives an individual PWM signal from the PWM Card via an RJ45 connector on the breakout board. The signal lines are protected with 1 kΩ series resistors to suppress transients and prevent overshoot from damaging the first pixel in each strip.
The PWM signal on Line 7 controls strip 7, Line 8 controls strip 8, and so on — all routed directly to each output header. The breakout board assumes the PWM Card is configured with PWM mode (not 12 V output) on these lines.
Shared Power Rail
The regulated 5 V is shared across all eight strip outputs. A SMAJ5.0A TVS diode is placed across the 5 V rail to protect against surges caused by inductive cable bounce or hot-plugging. A resettable fuse (JK30) provides short-circuit and overcurrent protection, tripping around 3 A and resetting automatically after cooldown.
Optional Configurations
- If Line 8 from the PWM Card is misconfigured as 12 V output, the onboard 1 kΩ resistor and TVS on the signal input line help limit damage to the first strip’s signal input.
- Additional breakout boards can be supported via PWM signal expansion and power wiring if required.
Protection Overview
| Protected Component | Protection | Purpose |
|---|---|---|
| 5 V Rail to Strips | TVS (SMAJ5.0A) | Clamps power spikes on shared rail |
| Regulator Output | PPTC (JK30) | Cuts output current >3 A, resets when cool |
| NeoPixel DIN Lines (1–8) | 1 kΩ Resistors | Protects first pixel inputs from overvoltage and overshoot |
| Regulator Input | KBL406 Rectifier | Allows AC/DC/DCC input, blocks reverse polarity |