How to Use KY-028: Examples, Pinouts, and Specs

The KY-028 is a temperature sensor module that utilizes the LM35 temperature sensor to measure ambient temperature. It provides both analog and digital outputs, making it versatile for a wide range of applications. The analog output corresponds to the temperature in a linear fashion, while the digital output can be used for threshold-based temperature detection. This module is commonly used in temperature monitoring systems, home automation, weather stations, and educational projects.

• Sensor Type: LM35 Temperature Sensor
• Operating Voltage: 3.3V to 5V DC
• Output Types:
  • Analog Output (proportional to temperature)
  • Digital Output (based on adjustable threshold)
• Temperature Range: -55°C to +150°C
• Accuracy: ±0.5°C (at 25°C)
• Dimensions: 32mm x 14mm x 8mm (approx.)
• Adjustable Threshold: Via onboard potentiometer

The KY-028 module has 4 pins. The table below describes each pin:

1. Power the Module: Connect the VCC pin to a 3.3V or 5V power source and the GND pin to ground.
2. Read Analog Output: Connect the AO pin to an analog input pin of your microcontroller to measure the temperature.
3. Use Digital Output: Connect the DO pin to a digital input pin of your microcontroller to detect when the temperature crosses the threshold set by the potentiometer.
4. Adjust Threshold: Use the onboard potentiometer to set the desired temperature threshold for the digital output.

• Ensure the module is powered within its operating voltage range (3.3V to 5V).
• The analog output voltage is directly proportional to the temperature in °C. For the LM35, the output is typically 10mV per °C.
• Avoid exposing the sensor to extreme conditions (e.g., high humidity or corrosive environments) to maintain accuracy and longevity.

Below is an example of how to use the KY-028 module with an Arduino UNO to read both analog and digital outputs:

// KY-028 Temperature Sensor Example with Arduino UNO

// Define pin connections
const int analogPin = A0; // Connect AO pin to A0 on Arduino
const int digitalPin = 2; // Connect DO pin to digital pin 2 on Arduino
const int ledPin = 13;    // Built-in LED for threshold indication

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

void loop() {
  // Read analog value from AO pin
  int analogValue = analogRead(analogPin);
  float temperature = (analogValue * 5.0 / 1023.0) * 100.0; 
  // Convert analog value to temperature in °C
  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.println(" °C");

  // Read digital value from DO pin
  int digitalValue = digitalRead(digitalPin);
  if (digitalValue == HIGH) {
    digitalWrite(ledPin, HIGH); // Turn on LED if threshold is crossed
    Serial.println("Threshold exceeded!");
  } else {
    digitalWrite(ledPin, LOW);  // Turn off LED if below threshold
  }

  delay(1000); // Wait 1 second before next reading
}

• The analog value is converted to temperature using the formula:
  Temperature (°C) = (Analog Value * Vcc / 1023) * 100
  where Vcc is the operating voltage (typically 5V for Arduino UNO).
• The onboard LED on the KY-028 module will also light up when the temperature exceeds the threshold.

1. No Output from the Module:

   • Ensure the module is powered correctly (3.3V to 5V).
   • Check all connections for loose wires or incorrect pin assignments.

2. Incorrect Temperature Readings:

   • Verify the formula used to convert the analog value to temperature.
   • Ensure the sensor is not exposed to external heat sources or airflow that could affect readings.

3. Digital Output Not Triggering:

   • Adjust the potentiometer to set the correct threshold.
   • Verify the digital pin connection and ensure it is configured as an input.

Q: Can the KY-028 measure negative temperatures?
A: Yes, the LM35 sensor can measure temperatures as low as -55°C. However, the analog output may require additional processing to interpret negative values correctly.

Q: How do I calibrate the sensor?
A: The LM35 is factory-calibrated, so no additional calibration is required. However, you can adjust the threshold for the digital output using the onboard potentiometer.

Q: Can I use the KY-028 with a 3.3V microcontroller?
A: Yes, the KY-028 operates within a voltage range of 3.3V to 5V, making it compatible with 3.3V microcontrollers like the ESP32 or Raspberry Pi Pico.

Q: What is the purpose of the onboard LED?
A: The onboard LED lights up when the temperature exceeds the threshold set by the potentiometer, providing a visual indication of the digital output state.