Ultrasonic Sensor: Working, Uses & DIY Arduino Projects

Table of Content

• The Working Principle of an Ultrasonic Sensor
  
• Internal Elements of an Ultrasonic Sensor
  
• Ultrasonic Sensor with Arduino: Getting Started
  
• Real-life uses of an ultrasonic sensor
  
• STEM/School projects with Ultrasonic Sensor
  
• Conclusion
• FAQs

The ultrasonic sensor is one of the most straightforward and useful electronic devices used in modern-day robotics, electronics, and even science education. It works by sending out sound pulses and measuring the time it takes to detect the pulse that bounces off a detected obstacle. Although it may seem simple at first, ultrasonic sensors are used in a variety of applications in a multitude of fields. They are even quite useful as an introduction to basic electronics and programming to students in all areas, ranging from the high school level to the professional level.

There are a multitude of reasons as to why this particular sensor is very appealing. Not only are these sensors very inexpensive, but they are also very easily connected to an Arduino microcontroller, even with no electronics knowledge! A student who needs to make an experiment for the science fair that uses distance measurement or who is working on a robot science project, or a robot that requires a proximity sensor, will find this component to be a time and money-saving addition to their project. This tutorial explains the principles behind this sensor, the various components inside, real-world applications, and projects.

The Working Principle of an Ultrasonic Sensor

An ultrasonic sensor works on the property of the sound waves that travel at frequencies above the range of human hearing (commonly 40 Khz). The sensor comprises two cylindrical components that look like a small speaker or microphone; one is a transmitter, and the other is a receiver. The process of ultrasonic sensing takes place in a cyclic manner, as follows:

1. The transmitter sends a pulse or burst of ultrasonic sound waves in a particular direction.

2. This sound wave then travels through the air, bounces off the nearest solid object, and returns towards the sensor as an echo.

3. The receiver detects this reflected wave.

4. An internal clock measures the total time the sound wave has taken from being transmitted and returning to be received by the receiver.

5. Using this value for the time taken, a calculation can then be made for the distance to the object.

This calculation is a simple one, and the formula to work it out is: Distance = (Speed of Sound x Time) / 2. Division by two is because the sound wave has travelled to the object and then back from it. Sound waves travel at roughly 343 meters per second at room temperature (although this can vary with ambient temperature for many sensors), so Distance = (343 m/s × time) / 2.

Some Key parameters to be aware of:

When deciding on which ultrasonic sensor for the project to use, these specifications are to be taken into account:

●     Detection range - The standard HC-SR04 module uses 2 cm to 400 cm for its range of detection.

●     Accuracy - Standard 3mm accuracy is to be expected for the sensor within a stable environment.

●     Operating Voltage - Standard HC-SR04 modules run on 5V, so they would work with any of the Arduino boards.

●     Trigger pulse - The module requires 10 microsecond high pulse on the trigger pin.

Internal Elements of an Ultrasonic Sensor

If you have an idea of what goes on inside the transducer, it's easier to understand its behaviour in various circumstances.

●     Piezoelectric transducers- Used in both the transmitter and receiver. When a voltage is applied to a piezoelectric crystal, it vibrates at an ultrasonic frequency, producing sound, but when it receives a sound wave, a small voltage is produced across the crystal.

●     Oscillator circuit- Used to control the transmitter. This produces the correct frequency to produce pulses of ultrasonic sound powerful enough to be detected by an object at the desired distance.

●     Control IC- a microcontroller is used to switch the transmitter on at a required interval, time when the receiver receives an echo, and produce a time-pulsed output to the echo pin proportional to the distance.

●     Grille and casing- a cylinder housing the transducers and directing the ultrasonic pulse in a cone within a range of approximately

Ultrasonic Sensor with Arduino: Getting Started

New electronic hobbyists and students who try to play with circuits for the first time encounter an Arduino with an ultrasonic sensor. The HC-SR04 ultrasonic sensor module has 4 pins, namely, VCC, Trig, Echo, and GND. Wiring this module up with an Arduino Uno only takes slightly less than 5 minutes.

Wiring HC-SR04 to Arduino Uno:

●     VCC to 5V on Arduino.

●     GND to any of the GND pins on Arduino.

●     Connect Trig to one of the digital output pins, typically 9.

●     Connect the Echo to one of the digital input pins, typically 10.

Basic Arduino sketch logic:

●     Clear the residual signal from the Trig pin by putting it in a LOW state for 2 microseconds.

●     Put the Trig pin into a HIGH state for precisely 10 microseconds.

●     Put Trig back into a LOW state.

●     Use the pulseIn() function on the Echo pin to measure how long it stays HIGH.

●     Use the formula to convert the pulse duration to centimeters.

This block repeats continuously within the loop function, which provides readings of distance from the ultrasonic sensor. The output can be shown on the serial monitor, or fed into components such as motors, LED’s, or buzzers. Anyone attempting a new DIY electronics kit for the first time will have no problem with the logical structure of this program and the sensor setup.

Real-life uses of an ultrasonic sensor

The ultrasonic sensor is implemented in more places than one would first imagine. Its ability to measure distances without direct contact makes it useful in a variety of situations that a mechanical switch or IR sensor cannot operate in.

Industrial and Commercial Applications:

Parking sensors on cars:

Nearly all modern vehicles today use ultrasonic sensors on their bumpers to detect surrounding objects while in reverse. If the distance falls under a certain value, an audio alarm will be emitted by the sensor.

 Monitoring of liquids

In water treatment plants, chemical companies, and even food production facilities, the distance is measured between a liquid surface and an ultrasonic sensor above the surface (submerging any components is not feasible).

 Conveyor belt systems

Factories use this technology to sense the presence and position of items moving along belts and to trigger sorting and packaging machinery as necessary.

 Automatic doors

Many automatic sliding doors around public buildings are used as safety devices. The sensors are located on each side of the door, waiting for a person to approach, and the door slides open before contact.

Medical and Scientific Applications:

 Medical ultrasounds

Although at much higher frequencies and with much more advanced signal processing, medical ultrasounds utilize a similar principle by transmitting sound waves into the body and using the reflected signals.

Laboratory robotics

Ultrasonic sensors can be used by laboratory robotics science experiments to correctly position sample trays and pipettes.

STEM/School projects with Ultrasonic Sensor

Perhaps one of the most rewarding pieces of equipment in any electronics science kit for students and teachers. The types of projects this sensor allows you to make are numerous, interesting and satisfying.

1. Digital Ruler

Couple the HC-SR04 to an Arduino and get an LCD screen to display the distances it measures. Students are introduced to how sensors work, real-time data output, and the connection between code and physical measure.

2. Obstacle Avoiding Robot

Place the arduino ultrasonic sensor onto a basic robot with two motorized wheels and program the Arduino to stop and then turn around when the sensor is around 20 cm from any object. This project is one of the most used school science experiments relating to robotics and covers coding, electronics, and mechanical thinking.

3. Parking Distance Indicator

The projects are not restricted to displaying digital numbers, with a model car park with different color LED lights based on how close you are: green for 'far', yellow for 'close', and red for 'stop'. This is an ideal demonstration piece for school science projects.

4. Water Tank Level Monitor

Affix the sensor just above the container, and you have an automated water tank level monitor (percentage shown on a digital screen). This introduces students to basic engineering projects and to how engineers would deal with data presentation.

5. Intruder Alarm System

The sensor can easily be programmed to turn on a buzzer if anything is in range of it. This STEM projects for school, working like a security system, will cover how conditional logic operates within the program in a clear way.

Conclusion

In conclusion, the ultrasonic sensor is a small, inexpensive, reliable, and truly versatile electronic component and is therefore considered a "must-have" component in electronics, professional, and educational spheres. Its mechanism of operation is easy to grasp, and an Arduino ultrasonic sensor circuit is simple for anyone to implement.

The number of projects that can be undertaken with the use of ultrasonic sensor component ranges from a simple school science project to complex real-world robotics systems. It should be toward the very top of any list of useful components to have when assembling a collection of science kit parts or building a classroom STEM project. It is something the more you use, the more you will see value in.

FAQs

1. What is the maximum distance of a typical ultrasonic sensor?

The maximum range of the HC-SR04 is listed as 400cm, however it is best to obtain reliable measurements no further than 300cm, soft and angled surfaces can absorb/deflect sound waves.

2. Can an ultrasonic sensor work under water?

 Typically they are used for use with air only, waterproof variations, such as the JSN-SR04T are used for liquids level sensing or where the environment can be wet.

3. Why is my ultrasonic sensor returning erratic readings?

Poor performance may be caused by soft surfaces or angled surfaces, temperature variations or running the sensor too frequently with insufficient delay between pulses.

4. Can a transparent object be detected by the sensor?

 Yes. A standard infrared sensor can only detect a surface if it has color. An ultrasonic sensor will work irrespective of color as it depends on reflecting a physical surface.

5. What is the difference between ultrasonic and infrared distance sensors?

Ultrasonic sensors are different from infrared distance sensors in that infrared ones work with light, ultrasonic with sound waves. This means infrared sensors work differently with colored/reflective materials whereas ultrasonic ones do not but are generally slower at extremely short distances.