Using Ultrasonic Sensor for Distance Measurement

ABSTRACT

An ultrasonic sensor to detect the distance measurement system is introduced in the literature. In this literature consists of the working principle of ultrasonic distance measurement, the structure properties of ultrasonic sensors, the ultrasonic sensors in the transmitter and receiver. Ultrasonic sensor is a component of detecting the distance. The system consists of; software is written using Ardunio, ultrasonic ranging module, the ultrasonic transmission circuit, the ultrasonic receiving circuit, the serial monitor and the alarm and LEDs circuit. This system can be used level measurement, parking sensor, presence, position and other areas.

Ultrasonic Sensors
Ultrasonic sensors are used in many applications. One of their most common applications is in robotics. That is because they are easy to interface and comprehend. Ultrasonic sensors contain ultrasonic transducers. A transducer can convert one energy form to another. The transducer is the reason why a sensor can emit a sonic pulse. An echo is then created once the emitted pulse reflects off an entity. The original sonic pulse and the echo determine how far the entity is from the sensor. The value of the distance is based on the amount of time that the pulse has travelled from the sensor and back.

Ultrasonic Ranging Module HC - SR04
Ultrasonic ranging module HC - SR04 provides 2cm - 400cm non-contact measurement function, the ranging accuracy can reach to 3mm. The modules includes ultrasonic transmitters, receiver and control circuit. The basic principle of work:

• Using IO trigger for at least 10us high level signal,
• The Module automatically sends eight 40 kHz and detect whether there is a pulse signal back.
• IF the signal back, through high level , time of high output IO duration is the time from sending ultrasonic to returning [3].

The Speed of Sound

The speed of sound is not always the same. The closer the molecules are to each other and the tighter their bonds, the less time it takes for them to pass the sound to each other and the faster sound can travel. It is easier for sound waves to go through solids than through liquids because the molecules are closer together and more tightly bonded in solids. Similarly, it is harder for sound to pass through gases than through liquids, because gaseous molecules are farther apart. The speed of sound is faster in solid materials and slower in liquids or gases. The velocity of a sound wave is affected by two properties of matter: the elastic properties and density. The relationship is described by the following equation. Cij is the elastic properties and p is the density [6].

 

Distance Calculation

•  40 kHz frequency an audio signal is sent to the environment with the help of a special speaker.
• Echo of transmitted signal is taken with the help of a special microphone.
•  Time difference between the received signals with the transmitted signal is measured.
•  The measured time is divided in half (t/2) then the distance between the sensor with the object is found by multiplying the speed of sound with time (t/2).

RESULTS
Software in the system works for certain distances differently. If distance is for bigger than 15cm, then Green LED is been ON and Red LED and buzzer is been OFF as seen as Picture. It is considered as simple parking sensor.

If distance is for equal to and smaller than 15cm, for example “4cm” then Green LED is been OFF and Red LED and buzzer is been ON as seen as Picture. This system can provide what a car don’t hit an obstacle.

 

REFERENCES

[1]http://www.bjultrasonic.com/ultrasonic-technical-info/ultrasonic-transducers-and-ultrasonic-sensors/
[2] http://jrzp.files.wordpress.com/2011/04/renesas_app_note_ultrasonic_range_finder.pdf
[3] Ultrasonic Ranging Module HC - SR04, Datasheet [4]http://www.finemech.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=F&Category_Code=ultrasound_applications
[5] http://www.kerrywong.com/2011/01/22/a-sensitive-diy-ultrasonic-range-sensor/
[6] https://www.nde-ed.org/EducationResources/HighSchool/Sound/speedinmaterials.htm