Liquid Level indicator using Ultrasonic Sensor HC-SR04
with Arduino, Node MCU, ESP32 and Displayed on OLED
Ultrasonic sensor HC-SR04 is used to measure distance in range of 2cm-400cm with accuracy of 3mm. The sensor module consists of ultrasonic transmitter, receiver and the control circuit.
The ultrasonic sensor module works on the natural phenomenon of ECHO of sound. A pulse is sent for about 10us to trigger the module. After which the module automatically sends 8 cycles of 40 KHz ultrasound signal and checks its echo. The signal after striking with an obstacle returns back and is captured by the receiver. Thus the distance of the obstacle from the sensor is simply calculated by the formula given as
Distance= (time x speed)/2.
Here we have divided the product of speed and time by 2 because the time is the total time it took to reach the obstacle and return back. Thus the time to reach obstacle is just half the total time taken.
We know that speed of sound is around 340 m/s. so we can calculate distance by using given formula:
Distance= (travel time/2) * speed of sound
Where speed of sound is approximately 340m per second.
By using this methods we gets distance from sensor to water surface. After it we need to calculate water level.
Now we need to calculate the total length of water tank. As we know the length of water tank then we can calculate the water level by subtracting resulting distance coming from ultrasonic from total length of tank. And we will get the water level distance. Now we can convert this water level in to the percent of water, and can display it on LCD or OLED. The working of the complete water level indicator project is shown in below block diagram.
In this circuit Ultrasonic sensor module is placed at the top of bucket (water tank) for demonstration. This sensor module will read the distance between sensor module and water surface, and it will show the distance on LCD screen with message “Water Space in Tank is:”. It means we are here showing empty place of distance or volume for water instead of water level. Because of this functionality we can use this system in any water tank.