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

The KY-028 is a temperature sensor module designed for measuring ambient temperature. It features the LM35 temperature sensor, which provides an analog output proportional to the temperature in degrees Celsius. The module also includes a digital output that can be triggered when the temperature exceeds a user-defined threshold, adjustable via an onboard potentiometer.

• Environmental temperature monitoring
• Home automation systems
• Industrial temperature control
• Educational projects and prototyping
• Arduino and microcontroller-based projects

• Sensor Type: LM35 Temperature Sensor
• Operating Voltage: 3.3V to 5V DC
• Temperature Range: -55°C to +150°C
• Analog Output Voltage: 10mV per °C
• Digital Output: High/Low signal based on threshold
• Dimensions: 32mm x 14mm x 8mm

The KY-028 module has four pins, as described in the table below:

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 on your microcontroller to measure the temperature.
3. Use Digital Output: Connect the DO pin to a digital input pin on your microcontroller to detect when the temperature exceeds the threshold.
4. Adjust Threshold: Use the onboard potentiometer to set the temperature threshold for the digital output.

• Ensure the power supply voltage matches the module's operating range (3.3V to 5V).
• Avoid exposing the sensor to temperatures beyond its specified range (-55°C to +150°C).
• For accurate readings, place the sensor in a stable environment and avoid sudden temperature changes.

Below is an example code to read both the analog and digital outputs of the KY-028 module using an 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

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

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
  
  // Read digital value from DO pin
  int digitalValue = digitalRead(digitalPin);

  // Print results to Serial Monitor
  Serial.print("Temperature (°C): ");
  Serial.println(temperature);
  Serial.print("Digital Output: ");
  Serial.println(digitalValue);

  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 (5V in this case).
• The digital output is HIGH when the temperature exceeds the threshold set by the potentiometer.

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. Inaccurate Temperature Readings

   • Verify that the sensor is not exposed to sudden temperature changes or heat sources.
   • Ensure the analog-to-digital conversion formula matches the operating voltage.

3. Digital Output Always HIGH or LOW

   • Adjust the potentiometer to set an appropriate temperature threshold.
   • Confirm that the temperature is within the sensor's measurable range.

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 calibration for negative values.

Q: How do I calibrate the sensor for more accurate readings?
A: Use a known temperature source (e.g., an ice bath or boiling water) to compare the sensor's output and adjust the formula or scaling factor in your code.

Q: Can I use the KY-028 with a 3.3V microcontroller?
A: Yes, the module operates at 3.3V. Ensure the analog-to-digital conversion formula in your code reflects the 3.3V reference voltage.

Q: What is the purpose of the potentiometer on the module?
A: The potentiometer adjusts the temperature threshold for the digital output (DO pin). Rotate it to increase or decrease the threshold.

By following this documentation, you can effectively integrate the KY-028 temperature sensor module into your projects for reliable temperature monitoring and control.