LED Word Clock: Tell Time with Illuminated Words

A word clock tells the time using illuminated words instead of numbers. ‘IT IS HALF PAST SEVEN’ glows through a beautifully designed face plate, making it both a functional clock and a piece of art. This project combines addressable LEDs, an RTC module, and careful design to create a stunning display piece for your home or office.

What Is a Word Clock

A word clock uses a grid of letters with LEDs behind them. At any given time, specific letters light up to spell the current time in words:

• IT IS TEN PAST THREE — at 3:10
• IT IS QUARTER TO EIGHT — at 7:45
• IT IS TWENTY FIVE MINUTES PAST TWELVE — at 12:25

The standard design uses a 11×10 or 16×16 letter grid with an LED behind each letter.

Designing the Letter Grid

The letter grid must be carefully designed so all possible time phrases can be spelled:

I T L I S A S T H P M
A C Q U A R T E R D C
T W E N T Y F I V E X
H A L F S T E N F T O
P A S T E R U N I N E
O N E S I X T H R E E
F O U R F I V E T W O
E I G H T E L E V E N
S E V E N T W E L V E
T E N S E O C L O C K

Each word occupies consecutive positions in a row. The Arduino maps time values to specific LED positions.

Laser Cutting the Face Plate

The face plate can be made from:

• Laser-cut MDF or acrylic: Most precise. Use 3mm MDF painted black with letters cut through.
• 3D printed: Print in black PLA with letter openings. Multiple pieces for larger grids.
• Vinyl sticker on glass: Black vinyl with letter cutouts on a picture frame glass.

Behind the face, add a sheet of white diffuser paper or tracing paper to spread the LED light evenly behind each letter.

WS2812B LED Matrix Behind the Grid

Use WS2812B LED strip cut into rows:

• Cut the strip into segments matching your grid rows
• Route in a serpentine pattern (left-to-right, then right-to-left)
• Create dividers between each letter cell using cardboard or 3D-printed grids to prevent light bleed
• Connect all segments in series for single-wire control

For a 10×11 grid, you need 110 LEDs — about 2 metres of 60 LED/m strip.

Arduino RTC Programming

#include <RTClib.h>
#include <Adafruit_NeoPixel.h>

void showTime() {
  DateTime now = rtc.now();
  int hour = now.hour() % 12;
  int minute = now.minute();

  clearAll();
  lightWord("IT");
  lightWord("IS");

  if (minute >= 5 && minute = 10 && minute = 15 && minute = 5 && minute = 35) lightWord("TO");

  lightHourWord(hour);
  strip.show();
}

Adding Colour Themes and Effects

• Warm white: Classic, elegant look — perfect for living rooms
• Rainbow words: Each word in a different colour
• Seasonal themes: Red/green for Christmas, orange for Diwali
• Breathing effect: Active words gently pulse in brightness
• Birthday mode: Special animation on configured dates

Building the Frame and Diffuser

The frame assembly:

1. Build or buy a shadow box frame (15-25 cm depth)
2. Mount the LED matrix on the back panel
3. Add the cell divider grid (prevents neighbouring letter light bleed)
4. Place the diffuser sheet
5. Attach the face plate with letter cutouts
6. Mount the Arduino and RTC module on the back with easy access for USB programming

Recommended LED and RTC Modules