KY-034 Automatic Flashing Color LED Module
The KY-034 is an automatic flashing color LED module that emits a sequence of seven colors when powered. It's suitable for decorative and visual display applications, providing dynamic lighting effects without the need for external control.
KY-034 pinout
The KY-034 is a 3-pin automatic color-cycling LED module:
| Pin | Type | Description | Notes |
|---|---|---|---|
| - | Power | Ground connection | |
| middle | Power | Not connected | Leave unconnected |
| S | Communication | Power/control input | Connect to HIGH or GPIO pin |
Interface: Simple power control (no PWM/protocol needed)
LED: 5mm automatic color-cycling LED (7 colors)
Colors: Red → Green → Blue → Yellow → Cyan → Magenta → White (cycles automatically)
Power: 3.3V to 5V operation (via S pin)
Automatic: Self-cycling - no external control required
Control: Drive S pin HIGH to power LED, LOW to turn off
Applications: Decorative lighting, visual indicators, party effects, mood lighting
Wiring the KY-034 to ESP32
To interface the KY-034 with an ESP32 for automatic color-cycling LED:
| KY-034 pin | ESP32 pin | Purpose |
|---|---|---|
| - | GND | Ground |
| middle | NC | Not connected · optional |
| S | GPIO13 or 3.3V | Power control (any GPIO or direct power) |
Simple Control: Drive S pin HIGH to enable LED, LOW to disable
Direct Power: Can connect S directly to 3.3V for always-on operation
Auto-Cycling: LED cycles through 7 colors automatically (no code needed)
No PWM: This is NOT an RGB LED - colors change automatically via built-in IC
Low Current: ~20mA max - safe to drive directly from GPIO
No Configuration: Just power on and enjoy the color show
Middle Pin: Leave middle pin unconnected (NC)
KY-034 code examples
int led = 13; // Declaration of the LED input pin
void setup() {
pinMode(led, OUTPUT); // Initialization output pin for the LED
}
void loop() {
digitalWrite(led, HIGH); // LED is switched on
delay(4000); // Wait for 4 seconds
digitalWrite(led, LOW); // LED is switched off
delay(2000); // Wait for another two seconds
}This Arduino code initializes pin 13 as an output to control the KY-034 module. In the loop, it turns the LED on for 4 seconds and off for 2 seconds repeatedly, allowing the LED to cycle through its automatic color sequence during the on periods.
#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
#define LED_PIN GPIO_NUM_13
void app_main(void) {
gpio_config_t io_conf = {
.intr_type = GPIO_INTR_DISABLE,
.mode = GPIO_MODE_OUTPUT,
.pin_bit_mask = (1ULL << LED_PIN),
.pull_down_en = GPIO_PULLDOWN_DISABLE,
.pull_up_en = GPIO_PULLUP_DISABLE
};
gpio_config(&io_conf);
printf("KY-034 Automatic Flashing Color LED Test\n");
while (1) {
gpio_set_level(LED_PIN, 1); // LED on
vTaskDelay(pdMS_TO_TICKS(4000));
gpio_set_level(LED_PIN, 0); // LED off
vTaskDelay(pdMS_TO_TICKS(2000));
}
}This ESP-IDF code configures GPIO13 as an output for the KY-034 module. It turns the LED on for 4 seconds and off for 2 seconds in a loop, allowing the LED to display its automatic color-changing sequence during the on periods.
light:
- platform: binary
name: "KY-034 Flashing Color LED"
output: ky034_output
output:
- platform: gpio
id: ky034_output
pin: GPIO13This ESPHome configuration sets up the KY-034 module as a binary light component on GPIO13. The light can be controlled via Home Assistant or other ESPHome-compatible interfaces, turning the LED on to display its automatic color sequence and off as desired.
[env:esp32]
platform = espressif32
board = esp32dev
framework = arduino#include <Arduino.h>
#define LED_PIN 13
void setup() {
pinMode(LED_PIN, OUTPUT);
Serial.begin(115200);
Serial.println("KY-034 Automatic Flashing Color LED Test");
}
void loop() {
digitalWrite(LED_PIN, HIGH);
Serial.println("LED ON");
delay(4000);
digitalWrite(LED_PIN, LOW);
Serial.println("LED OFF");
delay(2000);
}This PlatformIO code initializes GPIO13 as an output for the KY-034 module. It turns the LED on for 4 seconds and off for 2 seconds in a loop while printing status messages to the serial monitor.
import machine
import time
LED_PIN = machine.Pin(13, machine.Pin.OUT)
while True:
LED_PIN.on()
print("LED ON")
time.sleep(4)
LED_PIN.off()
print("LED OFF")
time.sleep(2)This MicroPython script configures GPIO13 as an output for the KY-034 module. It continuously cycles the LED on for 4 seconds and off for 2 seconds, printing status messages to the console.
KY-034 specifications
About the KY-034
The KY-034 is not an RGB LED, and there’s no way to make it behave like one. The color-changing part happens entirely inside the 5mm LED package itself, which has a tiny driver IC built in that free-runs through a fixed sequence - commonly described as red, green, blue, yellow, purple, cyan and white - the moment power is applied. The “module” around it is just a current-limiting resistor and a 3-pin header; there’s no PWM input, no data line, and no way to pick a color, hold on one, or change the sequence’s timing from the ESP32 side.
That makes the wiring and code about as simple as it gets: drive the signal pin HIGH to power the LED and let it cycle, or LOW to turn it off, and that’s the entire interface. It’s a fine, cheap way to add an eye-catching color-cycling indicator to a project, but anyone who actually needs specific colors on demand - a status LED that turns red for an error and green for OK, for instance - needs an addressable RGB LED like a WS2812B instead, not this module.
KY-034 troubleshooting
LED Not Lighting Up
›
Issue: The LED does not turn on when powered.
Solutions:
- Verify that the module is connected to the correct voltage (3.3V to 5V).
- Ensure proper wiring connections between the module and the microcontroller.
- Check for any damage to the LED or module components.
LED Not Changing Colors
›
Issue: The LED remains a single color and does not cycle through colors.
Solutions:
- Confirm that the module is receiving continuous power without interruptions.
- Ensure that the signal pin is set to HIGH to allow the LED to operate.
- Check for any firmware or code that might be interfering with the LED's operation.
Where to buy the KY-034
Resources
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