Drawing Letters with LEDs

Overview

This tutorial builds a reusable LedLetter component. Give it a capital letter, a power net, and a ground net, and it places a 5x7 bitmap letter on the PCB with one 0603 LED and one current-limiting resistor for every lit pixel.

The same component handles all capital letters from A to Z. Change the letter prop in the snippet to generate a different letter without manually placing each LED again.

Complete Snippet

const LED_FONT = {
A: ["01110", "10001", "10001", "11111", "10001", "10001", "10001"],
B: ["11110", "10001", "10001", "11110", "10001", "10001", "11110"],
C: ["01111", "10000", "10000", "10000", "10000", "10000", "01111"],
D: ["11110", "10001", "10001", "10001", "10001", "10001", "11110"],
E: ["11111", "10000", "10000", "11110", "10000", "10000", "11111"],
F: ["11111", "10000", "10000", "11110", "10000", "10000", "10000"],
G: ["01111", "10000", "10000", "10111", "10001", "10001", "01111"],
H: ["10001", "10001", "10001", "11111", "10001", "10001", "10001"],
I: ["11111", "00100", "00100", "00100", "00100", "00100", "11111"],
J: ["00111", "00010", "00010", "00010", "10010", "10010", "01100"],
K: ["10001", "10010", "10100", "11000", "10100", "10010", "10001"],
L: ["10000", "10000", "10000", "10000", "10000", "10000", "11111"],
M: ["10001", "11011", "10101", "10101", "10001", "10001", "10001"],
N: ["10001", "11001", "10101", "10011", "10001", "10001", "10001"],
O: ["01110", "10001", "10001", "10001", "10001", "10001", "01110"],
P: ["11110", "10001", "10001", "11110", "10000", "10000", "10000"],
Q: ["01110", "10001", "10001", "10001", "10101", "10010", "01101"],
R: ["11110", "10001", "10001", "11110", "10100", "10010", "10001"],
S: ["01111", "10000", "10000", "01110", "00001", "00001", "11110"],
T: ["11111", "00100", "00100", "00100", "00100", "00100", "00100"],
U: ["10001", "10001", "10001", "10001", "10001", "10001", "01110"],
V: ["10001", "10001", "10001", "10001", "10001", "01010", "00100"],
W: ["10001", "10001", "10001", "10101", "10101", "10101", "01010"],
X: ["10001", "10001", "01010", "00100", "01010", "10001", "10001"],
Y: ["10001", "10001", "01010", "00100", "00100", "00100", "00100"],
Z: ["11111", "00001", "00010", "00100", "01000", "10000", "11111"],
} as const

type LetterName = keyof typeof LED_FONT

type LedLetterProps = {
name: string
letter: LetterName
power: string
gnd: string
color?: "red" | "green" | "blue" | "yellow" | "white"
pcbX?: number
pcbY?: number
schX?: number
schY?: number
}

const getLitCells = (letter: LetterName) => {
const rows = LED_FONT[letter]

return rows.flatMap((row, rowIndex) =>
  row.split("").flatMap((cell, colIndex) =>
    cell === "1" ? [{ rowIndex, colIndex }] : []
  )
)
}

function LedLetter({
name,
letter,
power,
gnd,
color = "red",
pcbX = 0,
pcbY = 0,
schX = 0,
schY = 0,
}: LedLetterProps) {
const ledPitch = 2.4
const resistorYOffset = -0.95
const schematicPitch = 1.3
const litCells = getLitCells(letter)

return (
  <>
    {litCells.map(({ rowIndex, colIndex }, index) => {
      const ledName = name + "_D" + (index + 1)
      const resistorName = name + "_R" + (index + 1)
      const x = pcbX + (colIndex - 2) * ledPitch
      const y = pcbY + (3 - rowIndex) * ledPitch
      const sx = schX + (colIndex - 2) * schematicPitch
      const sy = schY + (3 - rowIndex) * schematicPitch

      return (
        <group key={ledName}>
          <led
            name={ledName}
            color={color}
            footprint="0603"
            pcbX={x}
            pcbY={y}
            schX={sx}
            schY={sy}
          />
          <resistor
            name={resistorName}
            resistance="1k"
            footprint="0603"
            pcbX={x}
            pcbY={y + resistorYOffset}
            schX={sx + 0.55}
            schY={sy - 0.55}
          />
          <trace from={"." + resistorName + " .pos"} to={power} />
          <trace from={"." + resistorName + " .neg"} to={"." + ledName + " .pos"} />
          <trace from={"." + ledName + " .neg"} to={gnd} />
        </group>
      )
    })}
  </>
)
}

export default () => (
<board
  width="26mm"
  height="24mm"
  pcbStyle={{ silkscreenFontSize: 0.6 }}
>
  <pinheader
    name="J1"
    pinCount={2}
    pinLabels={{ pin1: "V5", pin2: "GND" }}
    connections={{ pin1: "net.V5", pin2: "net.GND" }}
    pcbX={-10}
    pcbY={0}
    schX={-6}
    schY={0}
  />

  <LedLetter name="LETTER_A" letter="A" power="net.V5" gnd="net.GND" pcbX={2} />
</board>
)

How It Works

LED_FONT stores every letter as seven strings of five characters. A 1 means the component should place an LED at that row and column; a 0 leaves the cell empty. The getLitCells helper turns that bitmap into row and column coordinates.

Inside LedLetter, the row and column are converted into pcbX and pcbY positions. The formula centers the 5-column letter around the component origin, then flips the row index so the first bitmap row appears at the top of the PCB.

Each lit cell contains:

• one 0603 <led />
• one 0603 <resistor />
• a trace from the power net to the resistor
• a trace from the resistor to the LED positive pin
• a trace from the LED negative pin to ground

That keeps every LED current-limited independently. It is simple to fabricate and easier to debug than sharing one resistor across a mixed LED pattern.

Drawing Another Letter

Change the letter prop to any capital letter:

<LedLetter name="LETTER_Z" letter="Z" power="net.V5" gnd="net.GND" />

Use a different name when you place more than one letter on the same board so the generated LED and resistor names remain unique.

Tuning the Layout

The layout math lives in a few constants:

Constant	What it controls
ledPitch	LED spacing in millimeters on the PCB
resistorYOffset	How far each resistor sits below its LED
schematicPitch	Spacing between symbols in schematic view

Increase ledPitch for a larger display or change the LED footprint to 0402 if you want a tighter letter.