How to Use Thermopile Infrared (IR) Sensor: Examples, Pinouts, and Specs

The Thermometrics ZTP135SR is a thermopile infrared (IR) sensor designed to detect infrared radiation and convert it into an electrical signal. This enables non-contact temperature measurement and presence detection. The sensor is highly sensitive to infrared radiation, making it ideal for applications requiring accurate temperature readings without physical contact.

• Non-contact temperature measurement (e.g., thermometers, HVAC systems)
• Human presence detection in smart home devices
• Industrial process monitoring
• Medical devices (e.g., ear and forehead thermometers)
• Consumer electronics (e.g., motion-activated devices)

The following table outlines the key technical details of the ZTP135SR thermopile IR sensor:

The ZTP135SR has a simple pinout configuration, as shown below:

1. Power Supply: Connect the VDD pin to a stable power source (2.7V to 5.5V) and the GND pin to the ground of the circuit.
2. Signal Output: The OUT pin provides an analog voltage signal proportional to the detected infrared radiation. This signal can be read using an analog-to-digital converter (ADC) on a microcontroller.
3. Placement: Ensure the sensor is positioned with a clear line of sight to the target object for accurate temperature measurement. Avoid obstructions or reflective surfaces that may interfere with the IR signal.

• Calibration: For precise temperature measurements, calibrate the sensor using known temperature references.
• Ambient Temperature Compensation: Use an external temperature sensor to account for ambient temperature variations, as they can affect the accuracy of the ZTP135SR.
• Noise Filtering: Add a capacitor (e.g., 0.1 µF) between the VDD and GND pins to reduce power supply noise.
• Field of View: Ensure the target object is within the sensor's 90° field of view for optimal performance.

Below is an example of how to connect and read data from the ZTP135SR using an Arduino UNO:

• VDD → 5V pin on Arduino
• GND → GND pin on Arduino
• OUT → A0 (Analog Input) pin on Arduino

// Thermopile IR Sensor (ZTP135SR) Example Code
// Reads the analog output from the sensor and converts it to a voltage value.

const int sensorPin = A0; // Analog pin connected to the OUT pin of ZTP135SR

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 baud
  pinMode(sensorPin, INPUT); // Set the sensor pin as input
}

void loop() {
  int sensorValue = analogRead(sensorPin); // Read the analog value from the sensor
  float voltage = sensorValue * (5.0 / 1023.0); // Convert to voltage (5V reference)
  
  // Print the voltage value to the Serial Monitor
  Serial.print("Sensor Voltage: ");
  Serial.print(voltage);
  Serial.println(" V");
  
  delay(500); // Wait for 500ms before the next reading
}

1. No Output Signal

   • Cause: Incorrect wiring or insufficient power supply.
   • Solution: Verify the connections and ensure the power supply voltage is within the specified range (2.7V to 5.5V).

2. Inaccurate Temperature Readings

   • Cause: Ambient temperature variations or improper calibration.
   • Solution: Use an external temperature sensor for ambient compensation and calibrate the ZTP135SR with known temperature references.

3. Noisy Output Signal

   • Cause: Power supply noise or electromagnetic interference.
   • Solution: Add a decoupling capacitor (e.g., 0.1 µF) between the VDD and GND pins to filter noise.

4. Sensor Overheating

   • Cause: Operating the sensor beyond its temperature range.
   • Solution: Ensure the sensor is used within the specified operating temperature range (-10°C to +85°C).

Q1: Can the ZTP135SR detect human presence?
A1: Yes, the ZTP135SR can detect human presence by sensing the infrared radiation emitted by the human body.

Q2: What is the maximum distance for temperature measurement?
A2: The effective distance depends on the size of the target object and its infrared emission. For small objects, the sensor should be placed closer for accurate readings.

Q3: Can I use the ZTP135SR with a 3.3V microcontroller?
A3: Yes, the ZTP135SR operates within a voltage range of 2.7V to 5.5V, making it compatible with 3.3V systems.

Q4: Does the sensor require additional components for operation?
A4: While the sensor can operate standalone, adding a decoupling capacitor and an ambient temperature sensor can improve performance and accuracy.