The Sensors – Part 4: Ultrasonic Proximity Sensor HC-SR04

   The Sensors – Part 4: Ultrasonic Proximity Sensor HC-SR04

   In the previous Part-2 and Part-3, we have been described a small part of Infrared-IR based Proximity Detectors – Sensors.

    They are based on a principle of detecting the IR Light, reflexes from the surface of any obstacle or subjects.


PIC. 1  Whole used by humans RF Frequency Spectrum – As a representation, related to Wavelength.

 The Beginning From Direct Current:

  • Radio waves Spectrum,
  • 300GHz – 430THz (Tera Herz):  Infrared Spectrum,
  • 430THz – 790 THz (Tera Herz):  VISIBLE Spectrum,
  • 790THz – 30 PHz (Peta Herz):  Ultraviolet Spectrum,
  • 30 PHz – 30 EHz (Exa Herz): X-Ray Spectrum.


PIC. 2 Details about metric Prefixes used in our description.

   More Details you can see following the Wikipedia Link.

  Now, it’s time to move on to the essence of today’s topic. We present you the Ultrasonic sensor for measuring the distance to a near or coming object.

  We present you:  the Ultrasonic sensor for measuring the distance to a near or coming object. Nowadays in the market have two basic kinds of ultrasonic sensor

  • Two Component System,
  • Single Component System.


  The First of them has two independent Parts – One For Sending the Ultrasonic signal, and second for Receiving the reflexed wave.

  Let we describe a member of the two-component system. 



PIC. 3   HC-SR04: PCB Top & Bottom Side View  

HC-SR04 – Key Features:

  • Working Frequency: 40 KHz,
  • Detection Distance : 2cm ~ 500 cm,
  • Minimal step or Resolution: 3 mm,
  • HC-SR04 Power Supply: DC 5V,
  • Quiescent Current : < 2mA, 
  • Controlling Signal – Active High Logical Level,
  • Effective Angle of Ultrasonic Beam: ~ 15°.

   HC-SR04 Distance measurement method: high-level time velocity of sound (343.2 m/s) /2 (related to a signal twice path to, and from the object ).

  HC-SR04 Ultrasonic Sensor Distance Module Start: Need IO trigger to have the high logical level for at least 10 microseconds. 

   The HC-SR04 ultrasonic sensor can send eight pulses filled with 40 kHz carrier frequency signal and detect if there is any reflected signal back.

   If there is a reflected back pulse, an I/O pin drives high-level signal with a duration, proportional to time from sending the ultrasonic pulse to returning reflected signal.

  See the Package:

  HC-SR04 – 5 pcs. in an electrostatic shield bag. 


Don’t Stop To Reinvent Yourself, Dear Explorers!




Amazon Gift Ideas  Affiliate Link

Amazon Hot New Releases  Affiliate Link

Amazon Best Sellers  Affiliate Link


Leave a Reply