12/17/2023 0 Comments Ilift tm ultrasonicGreater the distance, the higher the time it will take by the Ultrasonic wave to reflect to the receiver circuit. As you know that the time duration for which the output signal remains high depends on the distance between the ultrasonic sensor and the object under test. Now let’s see how to measure the output signal time or pulse duration of the HC-SR04 sensor. Measure HC-SR04 Output Pulse width using TM4C123 The figure below shows the timing diagram and it illustrates all the steps metioned above. Hence, the measured distance will be zero. Hence, if the width of the output pulse is 38ms, that means there is no object in the range of the obstacle sensor. In this case, the echo output signal will go high for 38ms. Note: If there is no obstacle or out of the range of the maximum range of the sonar sensor ( 400cm), the transmitted signal will not reflect back. More the distance, the more time the sonar sound wave takes to receive after reflecting back. The pulse width can vary between 150 µS to 25 mS depending on the distance between the sensor and the obstacle. By measuring the width of the output pulse, we can measure the distance.As soon as the ultrasonic signal received by the receiver circuit after striking with an object, the echo pin goes low.The echo pin remains active high until the ultrasonic sound wave does not reflect back to the receiver circuit after striking the object Under test.In other words, the output echo pin makes transition from an active low to active high level. As soon as all eight pulses are transmitted through the air, the echo pin goes high.As a result, the transmitter circuit produces 8 pulses burst of ultrasound waves and each pulse has 40KHz frequency. First of all, we apply 10 microseconds pulse to the Trigger pin of HC-SR04 sensor from general purpose input output pin of TM4C123 microcontroller.Now let’s see the steps to initiate distance ranging or get echo pulse output: The width of this pulse or pulse duration can be used to measure the distance. On the other hand, an ultrasonic receiver listens to these ultrasonic sound waves and if the receiver circuit receives these ultrasonic sound waves, it produces a pulse on the output pin. The ultrasonic transmitter circuit converts the electrical signals into 40kHz ultrasonic sound waves. As you mentioned earlier, it consists of one ultrasonic transmitter circuit and one ultrasonic receiver circuit. In this section, we will see how HC-SR04 ultrasonic sensor work. Therefore, you must connect an external 5 volt supply to power HC-SR04. Additionally, TM4C123 Tiva Launchpad does not have an onboard 5 volts signal. Note: This sensor does not work properly on a 3.3 volts power supply. Trigger pin is used to initiate the sensor to start ranging. The echo output pulse pin is used to get output from the sensor. The other two pins are Trigger and echo pin. Two of them are power supply pins such as +5V and ground.
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