The **IRS-B340ST02-R1** is a high-sensitivity pyroelectric infrared (PIR) sensor manufactured by Murata. It is primarily used for non-contact temperature measurement and human presence detection. --- ## 1. Core Technical Specifications The device is characterized by its surface-mount design and high sensitivity to infrared radiation in the specific wavelengths emitted by the human body. | Feature | Specification | | :--- | :--- | | **Type** | Dual Type (Differential) | | **Element Size** | 1.1mm x 1.1mm (x2) | | **Package** | SMD (Surface Mount Device) | | **Dimensions** | 5.0mm x 4.7mm x 2.4mm | | **Operating Voltage** | 2.0V to 15.0V | | **Operating Temperature** | -40°C to +70°C | | **Field of View (FOV)** | 80° x 70° | --- ## 2. Internal Components & Structure The IRS-B340ST02-R1 is not just a simple piece of material; it is an integrated electronic assembly: ### A. Pyroelectric Ceramic Element The heart of the sensor is a lead zirconate titanate (PZT) ceramic. When exposed to infrared radiation, the temperature of the ceramic changes, causing a spontaneous polarization that generates an electric charge. ### B. Optical Filter (Window) The sensor is capped with a silicon-based optical window. This window acts as a **band-pass filter**, typically allowing wavelengths between **5µm and 14µm** to pass through. This range corresponds to the infrared heat signatures emitted by humans. ### C. Internal FET (Field Effect Transistor) Because the charge generated by the ceramic element is extremely small and has a very high impedance, the sensor includes an internal **JFET**. * **Role:** Acts as an impedance converter (buffer). * **Function:** It converts the high-impedance signal from the pyroelectric element into a low-impedance voltage signal that a standard Microcontroller (MCU) or Op-Amp circuit can process. --- ## 3. Pin Configuration (Typical) The device generally follows a 3-terminal setup standard for SMD PIR sensors: | Pin Number | Name | Description | | :--- | :--- | :--- | | 1 | **VDD** | Drain of the internal FET (Supply Voltage) | | 2 | **OUT** | Source of the internal FET (Output Signal) | | 3 | **GND** | Ground / Common | --- ## 4. Application Circuitry Requirements To use the IRS-B340ST02-R1 effectively, additional electronic components are required: 1. **Amplification:** The output signal is in the millivolt range. An operational amplifier (Op-Amp) with a gain of roughly 60dB to 80dB is usually required. 2. **Band-pass Filtering:** Since PIR signals are very slow (0.1Hz to 10Hz), a filter is needed to remove high-frequency noise and DC offset. 3. **Fresnel Lens:** While the sensor works alone, a plastic Fresnel lens is typically placed over it to concentrate IR light and increase the detection range. ---