Arduino LED Signage

Pan and zoom to explore the wiring. Remix the project to edit it in your own workspace.

1. 01

   Lay out the word

   On a breadboard or sign panel, place five LEDs in positions that form the word HELLO. Label them H, E, first L, second L, and O so the wires stay identifiable.

   • Tip: Use the same LED colour for a consistent-looking sign.
   • Tip: For a panel, make letter shapes from several LEDs later; this starter build uses one LED as each letter indicator.

   • ⚠ The longer LED leg is normally the anode (+); the shorter leg and flat edge mark the cathode (–).
2. 02

   Connect the LED cathodes to ground

   Connect the cathode (short leg) of every LED to an Arduino GND pin. A shared ground rail on the breadboard is convenient.

   • Tip: All five LED cathodes may share the same ground rail.

   • ⚠ Keep the Arduino disconnected from USB while changing wiring.
3. 03

   Add a resistor to every LED anode

   Connect one separate 220 Ω resistor in series with the anode (long leg) of each LED. Never connect an LED directly to an Arduino output pin.

   • Tip: A 220 Ω to 330 Ω resistor is suitable for typical red, yellow, or green LEDs on an Uno.
   • Tip: The resistor may be placed on either side of an LED electrically, but placing it between the Arduino pin and anode makes the wiring easier to check.

   • ⚠ Each LED requires its own resistor; do not share one resistor among multiple LEDs.
4. 04

   Connect the five letter inputs

   From the free end of each resistor, connect H to D2, E to D3, the first L to D4, the second L to D5, and O to D6 on the Arduino Uno.

   • Tip: Avoid D0 and D1 because they are used for USB serial communication.
   • Tip: Check each connection against the letter label before powering the board.

   • ⚠ Do not connect LEDs to the 5 V rail for this animated design; the Arduino digital pins control them.
5. 05

   Power and observe the sign

   Connect the Arduino Uno to its USB port. Use Schematik’s Deploy button to flash the project. The LEDs will light H-E-L-L-O one at a time, remain on as a complete word, then repeat.

   • Tip: If a letter does not illuminate, unplug USB and first reverse that LED; LEDs are polarity-sensitive.

   • ⚠ USB power is sufficient for these five indicator LEDs with the specified resistors.

#include <Arduino.h>
// Fixed-word LED sign: H E L L O
// Each LED anode is connected through its own 220-ohm resistor.


// Forward declarations
void setAllLetters(uint8_t state);

const uint8_t H_LED_PIN = 2;
const uint8_t E_LED_PIN = 3;
const uint8_t L1_LED_PIN = 4;
const uint8_t L2_LED_PIN = 5;
const uint8_t O_LED_PIN = 6;

const uint8_t letterPins[] = {
  H_LED_PIN, E_LED_PIN, L1_LED_PIN, L2_LED_PIN, O_LED_PIN
};
const uint8_t LETTER_COUNT = sizeof(letterPins) / sizeof(letterPins[0]);

void setAllLetters(uint8_t state) {
  for (uint8_t i = 0; i < LETTER_COUNT; i++) {
    digitalWrite(letterPins[i], state);
  }
}

void setup() {
  for (uint8_t i = 0; i < LETTER_COUNT; i++) {
    pinMode(letterPins[i], OUTPUT);
  }
  setAllLetters(LOW);
}

void loop() {
  // Light H-E-L-L-O in sequence to attract attention.
  for (uint8_t i = 0; i < LETTER_COUNT; i++) {
    digitalWrite(letterPins[i], HIGH);
    delay(250);
  }

  // Keep the completed word visible briefly.
  delay(1500);

  // Turn the sign off before repeating the animation.
  setAllLetters(LOW);
  delay(500);
}

“Deploy to device” opens this project in Schematik, where you can flash it to your board over USB.