Arduino: How to use KY-034 Automatic Flashing Color LED

Arduino Tutorial: KY-034 Automatic Flashing Color LED

Abstract

Learn how to use the KY-034 Automatic Flashing Color LED Module with Arduino. This unique module contains a single integrated circuit (IC) that causes the LED to automatically cycle through various colors and flash patterns when simply supplied with power. This tutorial focuses on using a digital output pin to act as a software switch to control the ON/OFF state of the module.

1. Introduction

Unlike standard LEDs (like the KY-016 or KY-029) that require complex PWM code to change color, the KY-034 has its control logic built-in. When the circuit receives power, the internal IC takes over, generating the flashing, fading, and color-cycling effects automatically.

In this episode, you’ll learn:

The principle of a self-flashing LED (integrated control logic).
How to use a digital output pin to control the module’s power.
How to use digitalWrite() to turn the flashing sequence ON and OFF.
How to combine this simple output with a timing sequence to create a controlled visual alert.

This project demonstrates how a complex visual effect can be achieved with the simplest of digital controls.

2. Prerequisites

Make sure you have:

An Arduino Uno or compatible board.
One KY-034 Automatic Flashing Color LED Module.
Jumper Wires.
Arduino IDE

3. Wiring and Setup for Arduino

The KY-034 module is essentially a specialized LED and resistor/IC on a board. It only requires a power source and ground.

Step 1 – Identify Pins

The module typically has three pins: Signal (S or OUT), VCC (+), and Ground (− or GND).

Step 2 – Connect the Module

Wire the module to the Arduino as follows. Since the module is self-flashing, we use a standard digital pin to supply the 5V power (treating the pin as a switch).

Connect the – / GND pin of the KY-034 to the GND pin on the Arduino.
Connect the + / VCC pin of the KY-034 to the 5V pin on the Arduino.
Connect the S / Signal pin of the KY-034 to Arduino Digital Pin 10.

This image was created with Fritzing

Note: For the KY-034, the signal pin (S) often directly controls the LED’s power. Supplying HIGH to the S pin turns the module ON, and LOW turns it OFF.

Step 3 – Initialize Pin Mode

The signal pin must be initialized as an OUTPUT in the setup() function:

pinMode(10, OUTPUT);

4. Writing Timed Control Code

Open main.ino and implement the following code. This program uses the Arduino to control when the self-flashing LED is allowed to operate, creating a pulsed sequence of color effects.

				
					const int FLASH_LED_PIN = 10;

void setup() {
  pinMode(FLASH_LED_PIN, OUTPUT);
  Serial.begin(9600);
  Serial.println("KY-034 Flashing LED Test Ready!");
}

void loop() {
  // 1. Activate the Flashing Sequence (Signal HIGH)
  digitalWrite(FLASH_LED_PIN, HIGH);
  Serial.println("Flashing ON...");
  delay(1500); // Allow flashing for 1.5 seconds

  // 2. Deactivate the LED (Signal LOW)
  digitalWrite(FLASH_LED_PIN, LOW);
  Serial.println("Flashing OFF...");
  delay(1500); // Wait for 1.5 seconds
}

Code Explanation

digitalWrite(FLASH_LED_PIN, HIGH): Sends 5V to the module’s control pin, allowing the internal IC to power up and begin its pre-programmed color cycling and flashing routine.
digitalWrite(FLASH_LED_PIN, LOW): Cuts the control voltage, immediately shutting down the module and stopping all color and flashing effects.
Autonomous Effect: Crucially, the color changing and flashing is handled entirely by the KY-034 module; the Arduino is only acting as a basic timer switch.

5. Creating a Short Burst Alert

This module is excellent for quick visual alerts. You can implement a function to create rapid bursts of the color effect.

				
					// Function to generate a short, rapid burst of the flashing color sequence
void burstFlash(int duration_ms) {
  digitalWrite(FLASH_LED_PIN, HIGH);
  delay(duration_ms);
  digitalWrite(FLASH_LED_PIN, LOW);
}

void loop() {
  // 1. Wait
  delay(3000);
 
  // 2. Alert: 500ms burst of flashing color
  Serial.println("Alert Burst!");
  burstFlash(500);
}

6. Uploading and Running the Project

Step 1 – Build

Click the Verify (checkmark icon) button in the Arduino IDE to compile the sketch.

Step 2 – Upload

Connect your Arduino board via USB.
Select the correct board and COM port.
Click the Upload (arrow icon) button.

Step 3 – Test

The LED on the KY-034 module should exhibit its full, complex color-changing and flashing pattern only when the digital pin is set to HIGH.
If you run the code from Section 4, the LED should turn ON and display the effect for 1.5s, then turn completely OFF for 1.5s, repeating the cycle.

7. Hands-On Lab Recap

You’ve learned:

How to control a component with integrated intelligence (internal IC).
That a complex visual effect can be controlled with a simple digital HIGH/LOW switch.
How to use the Arduino as a master timer for a sub-module’s behavior.

This module is useful for creating highly visible status indicators without consuming the Arduino’s processing power for complex PWM routines.

8. Common Issues & Fixes

Issue	Cause	Solution
LED is always ON and flashing.	Wiring error: Signal pin is shorted to VCC, or logic is wrong.	Check that the S pin is correctly connected to the Arduino output pin and not accidentally touching 5V.
LED never turns ON.	Wiring error (GND/VCC reversed or no connection).	Double-check that 5V and GND are connected correctly and the Signal pin is set to OUTPUT.
LED is always a single color, not flashing.	Module is damaged or is a standard RGB LED, not a KY-034.	Verify the part number. If it is a standard LED, you must use PWM (analogWrite) for color changes.