The HC-SR05 (often cross-referenced or identical to the HY-SRF05) is a high-precision, non-contact ultrasonic distance sensor that provides reliable distance tracking regardless of an obstacle’s color or lighting conditions. It serves as an upgraded, more versatile alternative to the popular HC-SR04 module, notably adding a 5th pin which allows it to alternate between a dual-pin or a single-pin control configuration.Technical Specifications

• Measurement Range: 2 cm to 4.5 meters
• Measurement Precision/Resolution: Up to 0.3 cm
• Operating Voltage: 4.5V to 5.5V DC (5V nominal)
• Working Frequency: 40 kHz
• Measuring Angle: Up to 15 degrees
• Supply Current: 10 mA to 40 mA
• Interface: Breadboard-friendly 5-pin male connector

Pin ConfigurationUnlike standard 4-pin sensors, the HC-SR05 features 5 pins:

1. VCC: +5V Power Supply
2. Trig (Trigger): Input pin used to trigger the ultrasonic pulse initiation.
3. Echo: Output pin that emits a digital pulse whose length is proportional to the distance.
4. OUT: Internal state/switching pin (often used to configure single-pin mode on compatible microcontroller hardware).
5. GND: Ground connection.

How It Works

1. Triggering: The host microcontroller sends a short 10-microsecond high pulse to the Trig pin.
2. Emission: The sensor automatically responds by emitting an 8-cycle burst of 40 kHz ultrasonic sound waves.
3. Echo Return: The waves travel through the air, hit an object, and bounce back to the receiver.
4. Calculation: The Echo pin goes high the moment the pulse is sent and goes low when the bounce-back is received. The duration of this high signal is the Time-of-Flight (t).

Common Applications

• Robotics: Obstacle avoidance and path routing for autonomous rovers.
• Automation: Non-contact liquid or material level sensing in containers.
• Security Systems: Proximity alarms and movement triggers.