Description:

HC-SR04 Ultrasonic Distance Module Sensor
This module performance is stable, measure the distance accurately. performance  nearly the same as SRF05, SRF02  SRF05, SRF02 ultrasonic distance measuring module and other comparable. Module High precision, blind spots (2cm) super close.

Main technical parameters:
    A: Voltage: DC 5V
    B: Static current: less than 2mA
    C: Electrical level output: 5V high
    D: Electrical level  output: at the end of 0V
    E: Induction angle: not more than 15 degrees
    F: Detection distance: 2cm-450cm
    G: High precision: 3mm

Wiring: VCC, trig (control side), echo (receiving end), GND

Module works:
    (A) using IO trigger distance, the high signal to at least 10us;

    (B) module automatically sends eight 40khz square wave, automatically detects whether a signal return;

    (C) a signal back, through the IO output a high electrical  level, high electrical  level duration is: the ultrasound time from launch to return. Test distance = (time of the high electrical  level *  speed of sound (340M/S))/2;