超声波介绍 HC SR04 Ultrasonic Module User Guide

HC-SR04_ultrasonic_module_user_guide

HC-SR04_ultrasonic_module_user_guide

HC-SR04_ultrasonic_module_user_guide

HC-SR04%20User%20Guide

hc-sr04_ultrasonic_module_user_guide

User Manual:

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HC-SR04 User Guide
1. Ultrasonic Distance Measurement Principles
The transmitter emits a 8 bursts of an directional 40KHz ultrasonic wave when
triggered and starts a timer. Ultrasonic pulses travel outward until they encounter
an object, The object causes the the wave to be reflected back towards the unit.
The ultrasonic receiver would detect the reflected wave and stop the stop timer.
The velocity of the ultrasonic burst is 340m/sec. in air. Based on the number of
counts by the timer, the distance can be calculated between the object and
transmitter The TRD Measurement formula is expressed as: D = C X T which is
know as the time/rate/distance measurement formula where D is the measured
distance, and R is the propagation velocity (Rate) in air (speed of sound) and T
represents time. In this application T is devided by 2 as T is double the time
value from transmitter to object back to receiver.

2. Product Features
Features

� Stable performance (Xtal.)
� Accurate distance measurement
� High-density SMD Board
� Close Range (2cm)
Uses
� Robotics barrier
� Object distance measurement
� Level detection
� Security systems
� Vehicle detection/avoidance

1

3. Product Views
BACK

FRONT

1

4

4

1

4. Module Pin Asignments

1
2
3
4

Pin Symbol
VCC
Trig
Echo
GND

Pin Function Description
5V power supply
Trigger Input pin
Receiver Output pin
Power ground

5. Electrical Specifications

WARARNING

Do Not connect Module with Power Applied! Always apply power after connecting
Connect "GND" Terminal first

Electrical Parameters
Operating Voltage
Operating Current
Operating Frequency
Max. Range
Nearest Range
Measuring Angle
Input Trigger Signal
Output Echo Signal
Board Dimensions
Board Connections

HC-SR04 Ultrasonic Module
5VDC
15mA
40KHz
4m
2cm
15 Degrees
10us min. TTL pulse
TTL level signal, proportional to
distance
1-13/16" X 13/16" X 5/8"
4 X 0.1" Pitch Right Angle Header Pins
2

6. Module Operation
Set Trig and Echo Low to initalize module. Place a minimum 10us High
level pulse to "Trigger" (module will automatically send eight 40KHz acoustic
bursts). At the same time, Gate the microcontroller timer to start timing.
Wait to capture the rising edge output of ECHO port to stop the timer. Now
read the time of the counter, which is the ultrasonic propagation time in the air.
According to the formula: Distance = (ECHO high level time X ultrasonic
velocity (Speed of Sound in air 340m/sec) / 2, you can calculate the distance to
the obstacle.

For best results and maximum range, the Object should be larger than 0.5M2
the nearer the target object, the smaller it may be

3

7. ModuleTiming

HC-SR04 ULTRASONIC MODULE
>50us
--10us--

Output of
ECHO Pin

~~
~~
~~

~~

40KHz
Reflected
Signal

8x40KHz

~~

40KHz
Acoustic
Burst

~~

Trigger

Propagation Delay
Dependent on Distance
Trigger 10us min. start measurement from microcontroller.
Max Rep. Rate: 50us
ECHO Output pulse to microcontroller, width is the time from last of 8 40KHz
bursts to detected reflected signal (microcontroller Timer gate signal)
Distance in cm = echo pulse width in uS/58
Distance in inch = echo pulse width in uS/148

Information obtained from or supplied by Mpja.com or Marlin P. Jones and Associates
inc. is supplied as a service to our customers and accuracy is not guaranteed nor is it
definitive of any particular part or manufacturer. Use of information and suitability for
any application is at users own discretion and user assumes all risk.
4



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