The **HRS-04-R** is a specific variant of the HC-SR04 ultrasonic distance sensor family. It is widely used in robotics and automation for non-contact distance measurement. The "R" variant often signifies specific design tweaks or pinout orientations (like right-angle pins) depending on the manufacturer. --- ### 1. Key Technical Specifications The table below outlines the electronic characteristics of the module: | Parameter | Value | | :--- | :--- | | **Operating Voltage** | 5V DC | | **Operating Current** | 15mA | | **Operating Frequency** | 40kHz | | **Max Range** | 400cm (4 meters) | | **Min Range** | 2cm | | **Measuring Angle** | 15 degrees | | **Trigger Input Signal** | 10µs TTL pulse | | **Output Echo Signal** | TTL pulse (duration proportional to distance) | --- ### 2. Main Components (Electronic Parts) The module consists of several critical components on a single PCB: 1. **Ultrasonic Transmitter (T):** A ceramic transducer that converts electrical energy into 40kHz sound waves. 2. **Ultrasonic Receiver (R):** A transducer that detects the reflected sound waves and converts them back into small electrical signals. 3. **Control Integrated Circuit (IC):** Usually a microcontroller (like an EM78P153 or similar) that handles the timing logic, pulse generation, and signal processing. 4. **Signal Amplifier:** Operational amplifiers (often an LM324) are used to amplify the tiny signal received from the "R" transducer so it can be interpreted by the logic chip. 5. **Crystal Oscillator:** Provides a stable clock frequency for precise timing calculations. --- ### 3. Pin Configuration The HRS-04-R typically features four pins: * **VCC:** +5V Power supply. * **Trig (Trigger):** Input pin. When pulled HIGH for at least 10µs, the sensor initiates a measurement. * **Echo:** Output pin. It goes HIGH when the sound is sent and LOW when the reflection is received. * **GND:** Ground. --- ### 4. How It Works (The Logic) 1. **Triggering:** The host (Arduino/MCU) sends a **10µs pulse** to the `Trig` pin. 2. **Transmission:** The module emits an **8-cycle sonic burst** at 40kHz. 3. **Echo High:** The `Echo` pin goes **HIGH** immediately after transmission. 4. **Detection:** If the sound hits an object and returns, the `Echo` pin goes **LOW**. 5. **Calculation:** The distance is calculated using the formula: `Distance = (Time Echo was HIGH × Speed of Sound) / 2` *(Speed of sound is approximately 340 m/s or 0.034 cm/µs).*