The HC-SR04 ultrasonic sensor is a popular distance measurement device that uses ultrasonic sound waves to determine the distance to an object. It has two main pins: the Trigger (Trig) pin and the Echo (Echo) pin. These pins play a crucial role in generating and measuring the ultrasonic pulses used for distance calculation.
1. Trigger (Trig) Pin:
The Trigger pin is responsible for initiating the measurement process. Here’s how it works:
- Pulse Generation: To start a distance measurement, you send a short pulse to the Trigger pin. This pulse serves as a trigger for the sensor to emit an ultrasonic pulse.
- Pulse Duration: The pulse should have a minimum duration of 10 microseconds. The sensor’s datasheet often provides information about the pulse duration and voltage levels required.
- Initiating Ultrasonic Pulse: When the Trig pin receives the pulse, the sensor emits an ultrasonic pulse consisting of high-frequency sound waves.
- Ultrasonic Pulse Propagation: The emitted ultrasonic pulse travels through the air and hits an object. It then reflects off the object and starts its journey back to the sensor.
2. Echo (Echo) Pin:
The Echo pin is used to measure the time taken for the ultrasonic pulse to travel to the object and back. This time is used to calculate the distance between the sensor and the object. Here’s how the Echo pin functions:
- Receiving Echo Pulse: When the ultrasonic pulse returns to the sensor after reflecting off the object, it’s detected by the Echo pin.
- Pulse Duration Measurement: The microcontroller connected to the sensor measures the duration for which the Echo pin remains in the high state. This duration is directly proportional to the time taken for the ultrasonic pulse to travel to the object and back.
- Distance Calculation: Using the known speed of sound in the air and the measured time, you can calculate the distance to the object using the formula: Distance = (Time × Speed of Sound) / 2. Since the ultrasonic pulse travels to the object and back, you need to divide the total time by 2.
Summary:
In summary, the Trigger pin initiates the emission of an ultrasonic pulse, while the Echo pin receives the reflected pulse and measures the time it takes to return. By calculating the time of flight and applying the appropriate formula, you can accurately determine the distance from the ultrasonic sensor to the object.