Info
product url - HC-SR04 Ultrasonic Proximity Sensor R2
Buck order price 17% discount for 50pcs, auto update price in cart.
Board Map, Dimension, Pins, chip info, Use Guide, Setup Jumper, etc.
Voltage：DC 3.3 – 5V (R2 version now is 3.3V-5V compatible)
version new-top and old-bottom
Pins and Wiring
- VCC
- TRIG (trigger / control input)
- ECHO (echo / receive output)
- OUT (spare pin)
- GND
Note: The TRIG pin has an internal 10 kΩ pull-up resistor. To trigger the module from a microcontroller, pull the TRIG pin low with an MCU I/O pin, then send a pulse longer than 10 µs.
- OUT: When the module is used as an alarm/anti-theft module, the OUT pin provides a digital switch output. This pin is not used for distance measurement.
Power-up note:
- Insert the module onto the circuit board before applying power to avoid unwanted false high outputs. If a false high occurs, power-cycle the module to clear it.
Reference test firmware:
- Example test programs available for: C51, PIC18F877, and Yilong MCU.
Operation / Working Principle
-
Triggering
- The module is triggered by the TRIG pin. Provide a high pulse of at least 10 µs to start a measurement.
-
Transmission and detection
- After trigger, the module automatically transmits 8 cycles of 40 kHz square waves and listens for an echo.
-
Echo output and timing
- When an echo is detected, the ECHO output goes high. The duration of this high pulse equals the round-trip travel time of the ultrasonic pulse (transmit → reflect → receive).
Distance calculation
- Distance = (high_time * speed_of_sound) / 2
- Using speed of sound ≈ 340 m/s.
Examples and MCU integration
- Typical method: send a >10 µs high pulse on TRIG. Wait for ECHO to go high, start a timer when ECHO goes high, stop the timer when ECHO goes low. The measured timer value is the round-trip time.
- If the timer measures microseconds (us): distance (cm) = time_us * 0.017 (because 340 m/s = 0.034 cm/us, divide by 2 → 0.017 cm/us).
Continuous measurement
- Repeating this trigger–measure cycle periodically allows continuous distance tracking or motion detection.