HC-SR04 Ultrasonic Module

Main Technical Parameters:

1. Operating Voltage: DC 5V
2. Quiescent Current: < 2mA
3. Output High Level: 5V
4. Output Low Level: 0V
5. Sensing Angle: ≤ 15 degrees
6. Detection Distance: 2cm - 450cm
7. High Accuracy: Up to 0.3cm

Pin Connections on Board:

• VCC: Power Supply
• Trig: Control Signal (Trigger Pin)
• Echo: Receive Signal (Echo Pin)
• OUT: (Empty Pin) - Used as a digital output when the module functions as an anti-theft sensor.
• GND: Ground

Note on Pins:
The TRIG pin has an internal 10kΩ pull-up resistor. To trigger, the microcontroller's IO port should pull the TRIG pin low, then provide a high-level pulse signal of at least 10µs.
The OUT pin serves as a switch output for anti-theft applications. Do not use this pin for distance measurement.

Important Usage Notes:

• Always plug the module into the circuit board before powering it on to prevent false high-level triggering. If a false trigger occurs, simply power cycle the module to resolve it.
• This module can provide reference testing programs for distance measurement on three types of MCUs: C51, PIC18F877, and Yilong microcontroller.

HC-SR04 / URF04 Module Operating Principle:

1. Trigger: Use an IO pin to trigger distance measurement by sending a high-level signal of at least 10µs to the Trig pin.
2. Transmission: The module automatically sends eight 40kHz square wave pulses and automatically detects if a signal returns.
3. Echo Reception: If a return signal is detected, the module outputs a high level on the Echo pin. The duration of this high level corresponds to the time elapsed from transmission to return of the ultrasonic wave.
4. Distance Calculation:
   Distance = (High-level Echo Time * Speed of Sound (340 m/s)) / 2

Summary of Use:
This product is simple to use. Send a high-level pulse longer than 10µs from a control pin to the Trig pin. Then, wait for a high-level output on the Echo pin. Once the Echo pin goes high, start a timer. When this pin goes low, read the timer value. This time value is the duration for this measurement cycle, which can then be used to calculate the distance. By continuously cycling this process, you can achieve real-time distance readings for moving objects.