How to Use KY-004 Key Switch Module: Examples, Pinouts, and Specs

The KY-004 Key Switch Module is a small, versatile component designed for detecting button presses in various electronic projects. It features a push-button switch that outputs a digital signal when pressed, making it an ideal choice for simple user input in microcontroller-based systems. This module is commonly used in DIY electronics, prototyping, and educational projects due to its ease of use and reliability.

• User Input: Ideal for projects requiring a simple button press input.
• Prototyping: Useful in breadboard setups for testing and development.
• Educational Projects: Great for teaching basic electronics and microcontroller interfacing.
• Interactive Devices: Can be used in interactive installations and devices requiring user interaction.

1. Connect the Pins:

   • Connect the S pin to a digital input pin on your microcontroller (e.g., Arduino).
   • Connect the - pin to the ground (GND) of your microcontroller.
   • The middle pin is not connected and can be left unconnected.

2. Power the Module:

   • Ensure the module is powered with a voltage between 3.3V and 5V, which is typically provided by the microcontroller.

3. Read the Button State:

   • When the button is pressed, the S pin outputs a digital HIGH signal.
   • When the button is not pressed, the S pin outputs a digital LOW signal.

• Debouncing: Mechanical switches like the KY-004 can produce noise or "bounce" when pressed. Implement software debouncing in your code to ensure reliable button press detection.
• Pull-down Resistor: If your microcontroller does not have internal pull-down resistors, consider adding an external pull-down resistor (e.g., 10kΩ) between the S pin and GND to ensure a stable LOW signal when the button is not pressed.

// KY-004 Key Switch Module Example Code for Arduino UNO

const int buttonPin = 2;  // Pin connected to the S pin of KY-004
const int ledPin = 13;    // Pin connected to the onboard LED

void setup() {
  pinMode(buttonPin, INPUT);  // Set button pin as input
  pinMode(ledPin, OUTPUT);    // Set LED pin as output
  Serial.begin(9600);         // Initialize serial communication
}

void loop() {
  int buttonState = digitalRead(buttonPin);  // Read the button state

  if (buttonState == HIGH) {  // If button is pressed
    digitalWrite(ledPin, HIGH);  // Turn on the LED
    Serial.println("Button Pressed");  // Print message to serial monitor
  } else {
    digitalWrite(ledPin, LOW);  // Turn off the LED
  }

  delay(50);  // Small delay for debouncing
}

1. Button Not Responding:

   • Solution: Check the wiring connections. Ensure the S pin is connected to the correct digital input pin on the microcontroller and the - pin is connected to GND.

2. Unstable Button Press Detection:

   • Solution: Implement software debouncing in your code to filter out noise and ensure reliable detection of button presses.

3. No Output Signal:

   • Solution: Verify the operating voltage is within the specified range (3.3V to 5V). Check for any loose connections or damaged components.

• Check Connections: Ensure all connections are secure and correctly oriented.
• Use Serial Monitor: Utilize the serial monitor to print debug messages and verify the button state.
• Test with Multimeter: Use a multimeter to check the voltage levels at the S pin when the button is pressed and not pressed.

By following this documentation, users can effectively integrate the KY-004 Key Switch Module into their projects, ensuring reliable and accurate button press detection.