LightBoxPCB

LED-PCB-Controller

A custom ATmega328P controller board for WS2812B addressable LED strips, designed in KiCad and built for a light box. Three buttons and a brightness knob drive three lighting modes, from adjustable warm/cool white to six animated "party" effects, all running on a standalone Arduino-compatible board with no dev board required.

Features

• Standalone ATmega328P (DIP-28) running at 16 MHz, fully Arduino-compatible
• Three lighting modes selectable with a dedicated MODE button
• Analog brightness control via an on-board potentiometer, with smoothing to avoid flicker
• Six animated effects in Party mode: rainbow wave, color chase, twinkle, fire, bouncing ball, and meteor rain
• EMI-hardened button input: falling-edge detection, a confirm re-read to reject noise spikes from the LED data line, and release tracking to block repeat triggers
• Two programming paths: 6-pin ICSP header and FTDI serial header with DTR auto-reset
• Through-hole only, so it's easy to hand-solder
• Compact 2-layer board, roughly 44.5 × 100 mm

Repository Contents

The KiCad files were saved with KiCad 10, so open them with KiCad 10 or newer.

Controls

The MODE button cycles through White → Party → Color. Buttons A and B change behavior depending on the active mode. The potentiometer sets brightness in every mode.

Hardware

Pin Map

Connectors

Bill of Materials

Design Notes

• Decoupling: 100 nF caps on VCC and AVCC, a 100 nF cap on AREF, a 10 µF bulk cap near the MCU, and a 1000 µF reservoir cap on the 5 V rail to absorb inrush current when the strip powers up or changes brightness quickly.
• LED data line: the 470 Ω series resistor damps ringing and protects the first LED's data input.
• Auto-reset: DTR on the FTDI header couples to RESET through a 100 nF cap, so uploads over serial work like a normal Arduino.

Power

The barrel jack feeds the 5 V rail directly. There's no on-board regulator, so use a regulated 5 V supply. Feeding it 9 V or 12 V will damage the MCU and the LEDs.

Each WS2812B can draw up to about 60 mA at full white. The default 11-LED configuration needs up to about 0.66 A, so a 5 V / 1 A supply is plenty. Scale the supply up if you increase NUM_LEDS.

Fabrication and Assembly

1. Upload Gerbers.zip directly to a PCB fab (JLCPCB, PCBWay, OSH Park, etc.). The defaults are fine: 2 layers, 1.6 mm, HASL.
2. Solder components from shortest to tallest: resistors, ceramic caps, crystal, IC socket (recommended for the DIP-28), headers, electrolytics, buttons, potentiometer, barrel jack.
3. Watch the polarity on C8 and C9.
4. Before inserting the ATmega328P, power the board and check for 5 V between VCC and GND on the socket.

Firmware

Dependencies

• Arduino IDE or Arduino CLI
• FastLED library (install via Library Manager)

Configuration

Edit these defines at the top of Lights_For_lightbox.ino to match your setup:

#define NUM_LEDS       11     // number of LEDs on your strip
#define COLOR_ORDER    GRB    // change if colors look swapped
#define DEBOUNCE_MS    600    // raise if buttons still double-trigger
#define CONFIRM_MS     12     // noise-rejection re-check delay

Flashing

Set the board to Arduino Uno (ATmega328P, 16 MHz). Then use one of these methods.

Option A: ICSP (blank chip)

1. Connect an ISP programmer (USBasp, or another Arduino running the ArduinoISP sketch) to J1.
2. Run Tools → Burn Bootloader once to set the fuses for the 16 MHz external crystal.
3. Upload with Sketch → Upload Using Programmer, or switch to Option B now that the bootloader is installed.

Option B: FTDI (bootloader installed)

1. Connect a 5 V FTDI adapter to J2, matching GND to GND.
2. Select the adapter's port and click Upload. DTR resets the chip automatically.

You can also flash the chip in an Arduino Uno and move it to the board.

Troubleshooting

Author

Audrey — Computer Engineering, UC Riverside