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The HC-SR04 Ultrasonic Sensor is a distance-measuring modules in electronics, known for its simplicity, affordability, and reliable performance. This article will discuss the HC-SR04 ultrasonic sensor in detail, including its working principle, usage, pinout, specifications, and more.
The HC-SR04 Ultrasonic Sensor is a low-cost distance-measuring module that uses ultrasonic sound waves to detect objects without physical contact. It works by sending a short ultrasonic pulse and measuring the time it takes for the echo to return, allowing accurate distance calculation even in dark or dusty environments.
This module typically operates at 5 V and features four pins: VCC, Trig, Echo, and GND, making it easy to connect to microcontrollers such as Arduino and similar development boards. With a measuring range of about 2 cm to 400 cm and stable performance, it is widely used in robotics, obstacle avoidance, level sensing, and basic automation projects.
If you are interested in purchasing the HC-SR04 Ultrasonic Sensor, feel free to contact us for pricing and availability.
| Pin Number | Pin Name | Description |
| 1 | VCC | Supplies power to the module. It typically requires a 5 V DC input to operate properly. |
| 2 | Trig | Trigger input pin. A short HIGH pulse (usually 10 µs) sent from the microcontroller starts the ultrasonic distance measurement. |
| 3 | Echo | Output pin that sends a pulse back to the controller. The pulse width represents the time taken for the ultrasonic wave to return, which is used to calculate distance. |
| 4 | GND | Ground pin. Connects to the ground of the power supply or microcontroller. |
| Sensor Model | Sensor Type | Typical Range | Notes |
| JSN-SR04T | Ultrasonic (Waterproof) | 20 cm – 600 cm | Waterproof probe, suitable for outdoor or liquid-level sensing |
| HY-SRF05 | Ultrasonic | 2 cm – 450 cm | Improved version of HC-SR04 with better stability |
| Parallax PING))) | Ultrasonic | 2 cm – 300 cm | High-quality ultrasonic sensor, single-pin control |
| URM37 | Ultrasonic | 4 cm – 500 cm | Industrial-grade ultrasonic module with serial output |
| Sharp GP2Y0A21YK0F | IR Analog Distance Sensor | 10 cm – 80 cm | Analog output, good for short-range indoor use |
| Sharp GP2Y0A02YK0F | IR Analog Distance Sensor | 20 cm – 150 cm | Longer range IR distance sensing |
| VL53L0X | Time-of-Flight (Laser) | Up to 200 cm | High-precision digital distance sensor (I²C) |
| E18-D80NK | IR Proximity Sensor | 3 cm – 80 cm | Adjustable digital output, simple obstacle detection |
| Parameter | Specification |
| Product Model | HC-SR04 Ultrasonic Sensor |
| Sensor Type | Ultrasonic distance measuring module |
| Operating Voltage | 5 V DC |
| Operating Current | < 15 mA |
| Ultrasonic Frequency | 40 kHz |
| Trigger Pulse Width | ≥ 10 µs |
| Echo Signal | TTL pulse output (5 V) |
| Measuring Distance (Theoretical) | 2 cm – 400 cm |
| Measuring Distance (Practical) | 2 cm – 80 cm |
| Distance Resolution | ~3 mm |
| Measuring Angle | < 15° |
| Interface Type | Digital (Trig & Echo pins) |
| Response Time | ~60 ms |
| Accuracy | ±3 mm |
| Operating Temperature | 0 °C to +70 °C |
| Storage Temperature | −40 °C to +85 °C |
| PCB Dimensions | ~45 × 20 × 15 mm |
| Mounting Holes | Yes (2 holes) |
| Weight | ~9 g |
| Compatibility | Arduino, ESP8266, ESP32, STM32, Raspberry Pi (with level shifting) |
• Non-contact ultrasonic distance measurement
• Operates at 5 V DC
• Measuring range from 2 cm to 400 cm
• High distance resolution (~3 mm)
• Narrow measuring angle (<15°)
• Uses 40 kHz ultrasonic frequency
• Simple 4-pin interface (VCC, Trig, Echo, GND)
• Digital TTL pulse output
• Easy integration with microcontrollers
• Compact and lightweight module
• Accurate distance measurement at low cost
• Works reliably in low-light or dark environments
• No physical contact, reducing wear and damage
• Simple wiring and control logic
• Widely supported with libraries and examples
• Suitable for beginners and educational projects
• Low power consumption
• Easily replaceable and widely available
• Minimal calibration required for basic use
The HC-SR04 ultrasonic sensor timing diagram shows the exact sequence of signals used to perform a distance measurement. The process begins when the microcontroller sends a short HIGH pulse, typically 10 microseconds, to the Trig pin. This trigger signal tells the sensor to start a new ranging cycle and prepares the internal circuitry to transmit ultrasonic waves.
After receiving the trigger pulse, the sensor generates an ultrasonic burst made up of several cycles at a frequency of about 40 kHz. These sound waves are emitted from the transmitter and travel through the air toward the target object. During this time, the sensor waits for the reflected sound to return and does not yet output a distance signal.
Once the ultrasonic waves hit an object and bounce back, the sensor detects the echo and sets the Echo pin HIGH. The duration of this HIGH pulse represents the total time taken for the sound to travel from the sensor to the object and back again. The farther the object is, the longer the Echo pulse remains HIGH.
By measuring the width of the Echo pulse, the microcontroller can calculate the distance using the known speed of sound. A short delay between measurements is recommended to avoid signal overlap and ensure stable, accurate readings.
The HC-SR04 Ultrasonic Sensor measures distance by sending and receiving ultrasonic sound waves. When a microcontroller sends a short pulse to the Trig pin, the sensor activates its transmitter and emits a brief ultrasonic burst at around 40 kHz. These sound waves travel through the air until they encounter an object, where they are reflected back toward the sensor.
The returning sound waves are detected by the sensor’s receiver through the Echo pin. The sensor then outputs a signal whose duration represents the total time taken by the sound to travel to the object and return. Because the speed of sound in air is known, the microcontroller can calculate the distance by processing this time value and dividing it by two to account for the round trip.
To use the HC-SR04, supply a stable 5 V power source and connect the Trig and Echo pins to digital I/O pins on the microcontroller. By repeatedly sending trigger pulses and measuring the echo response in software, the sensor can provide continuous and reliable distance readings for real-time applications.
• Obstacle detection and avoidance in robots
• Distance measurement in DIY and educational projects
• Object detection in automation systems
• Water or liquid level monitoring (non-contact)
• Parking assistance and proximity sensing prototypes
• Smart trash bins and automatic lid system
• Security and intrusion detection setups
• Industrial position and spacing measurement
• Interactive electronics and IoT projects
• Motion-based triggering systems
| Specification | HC-SR04 | HY-SRF05 |
| Sensor Type | Ultrasonic distance sensor | Ultrasonic distance sensor |
| Operating Voltage | 5 V DC | 5 V DC |
| Operating Current | <15 mA | <15 mA |
| Ultrasonic Frequency | ≈40 kHz | ≈40 kHz |
| Measuring Range | 2 cm – 400 cm | 2 cm – 450 cm |
| Practical Range | 2 cm – 80 cm (more stable) | Extended stable range |
| Distance Resolution | ~3 mm | ~3 mm |
| Measuring Angle | <15° | <15° |
| Pins / Interface | 4-pin (VCC, Trig, Echo, GND) | 4-pin (VCC, Trig, Echo, GND) |
| Trigger Input | 10 µs pulse | 10 µs pulse |
| Echo Output | TTL pulse | TTL pulse |
| Response Time | ~60 ms | ~60 ms |
| Temperature Range | 0 °C – +70 °C | 0 °C – +70 °C |
| Dimensions | ~45 × 20 × 15 mm | ~45 × 20 × 15 mm |
| Weight | ~9 g | ~9 g |
| Compatibility | Arduino, ESP32, Raspberry Pi | Arduino, ESP32, Raspberry Pi |
| Special Notes | Most widely used beginner module | Improved range, tighter echo reliability |
| Best for | Budget projects, education | Projects requiring wider detection range |
The HC-SR04 ultrasonic sensor simple working principle, clear timing behavior, and easy integration with microcontrollers make it a reliable choice for obstacle detection, level sensing, and automation systems. By understanding its features, technical specifications, working operation, and how it compares with similar sensors like the HY-SRF05, you can confidently select and apply the HC-SR04 for your specific needs.
Catalogue
FPGA / CPLD
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MCU 
DSP
OCEP
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