Ultra Sonic

HC-SR04 Ultrasonic Sensor

Block Diagram :-

Ultrasonic Sensor Pin Configuration:

Pin Number
Pin Name
Description

1
Vcc
The Vcc pin powers the sensor, typically with +5V

2
Trigger
Trigger pin is an Input pin. This pin has to be kept high for 10us to initialize measurement by sending US wave.

3
Echo
Echo pin is an Output pin. This pin goes high for a period of time which will be equal to the time taken for the US wave to return back to the sensor

4
Ground
This pin is connected to the Ground  of system

HC-SR04 Sensor Features

• Operating voltage: +5V
• Theoretical  Measuring Distance: 2cm to 450cm
• Practical Measuring Distance: 2cm to 80cm
• Accuracy: 3mm
• Measuring angle covered: <15°
• Operating Current: <15mA
• Operating Frequency: 40Hz.

HC-SR04 Ultrasonic Sensor :

An ultrasonic sensor is an electronic device that measures the distance of a target object by emitting ultrasonic sound waves, and converts the reflected sound into an electrical signal. Ultrasonic waves travel faster than the speed of audible sound (i.e. the sound that humans can hear). Ultrasonic sensors have two main components: the transmitter (which emits the sound using piezoelectric crystals) and the receiver (which encounters the sound after it has travelled to and from the target).

In order to calculate the distance between the sensor and the object, the sensor measures the time it takes between the emission of the sound by the transmitter to its contact with the receiver. The formula for this calculation is D = ½ T x C (where D is the distance, T is the time, and C is the speed of sound ~ 343 meters/second). For example, if a scientist set up an ultrasonic sensor aimed at a box and it took 0.025 seconds for the sound to bounce back, the distance between the ultrasonic sensor and the box would be:

D = 0.5 x 0.025 x 343

Working:

As shown above the HC-SR04 Ultrasonic (US) sensor is a 4 pin module, whose pin names are Vcc, Trigger, Echo and Ground respectively. This sensor is a very popular sensor used in many applications where measuring distance or sensing objects are required. The module has two eyes like projects in the front which forms the Ultrasonic transmitter and Receiver. The sensor works with the simple high school formula that
Distance = Speed × Time
The Ultrasonic transmitter transmits an ultrasonic wave, this wave travels in air and when it gets objected by any material it gets reflected back toward the sensor this reflected wave is observed by the Ultrasonic receiver module as shown in the picture below.

Ultrasonic Sensor Working:

Now, to calculate the distance using the above formulae, we should know the Speed and time. Since we are using the Ultrasonic wave we know the universal speed of US wave at room conditions which is 330m/s. The circuitry inbuilt on the module will calculate the time taken for the US wave to come back and turns on the echo pin high for that same particular amount of time, this way we can also know the time taken. Now simply calculate the distance using a microcontroller or microprocessor.

 Applications:

• Used to avoid and detect obstacles with robots like biped robot, obstacle avoider robot, path finding robot etc.
• Used to measure the distance within a wide range of 2cm to 400cm
• Can be used to map the objects surrounding the sensor by rotating it