HydroView: Ultrasonic Water Level Display with MAX7219

Overview

HydroView is a water level indicator that uses an HC-SR04 ultrasonic sensor to measure the distance between the water surface and the sensor, then displays the water level on a MAX7219 4-in-1 8×8 LED matrix in a dynamic bar format.The design is perfect for home water tanks, aquaponics setups, or industrial fluid containers.

Instead of relying on blinking LEDs or numeric displays, HydroView provides a real-time, graphical representation of the water level that’s instantly understandable at a glance.

Features

Non-contact measurement — Ultrasonic sensing means no physical contact with water.

• Non-contact measurement — Ultrasonic sensing means no physical contact with water.

Real-time visual display — LED matrix bar fills from right to left as the tank fills.

• Real-time visual display — LED matrix bar fills from right to left as the tank fills.

Customizable tank height — Easily set your tank’s depth in centimeters.

• Customizable tank height — Easily set your tank’s depth in centimeters.

Serial debugging — Built-in logging of distance, depth, and display columns.

• Serial debugging — Built-in logging of distance, depth, and display columns.

Scalable — Works with different MAX7219 configurations and display lengths.

• Scalable — Works with different MAX7219 configurations and display lengths.

Hardware Requirements

Component

Quantity

Notes

HC-SR04 Ultrasonic Sensor

1

Measures distance to water surface

MAX7219 4-in-1 LED Matrix (32×8)

1

For graphical display

ESP32-S3 (e.g., Seeed Studio XIAO ESP32-S3)

1

Main microcontroller

Jumper Wires

As needed

Female–female or female–male depending on modules

Breadboard or PCB

Optional

For neat wiring

USB Cable

1

For programming and power

Pin Connections

ESP32-S3 ↔ MAX7219 (Software SPI)

MAX7219 Pin

ESP32-S3 Pin

Code Name

DIN

D10

DATA_PIN

CLK

D8

CLK_PIN

CS

D9

CS_PIN

VCC

5V

—

GND

GND

—

ESP32-S3 ↔ HC-SR04

HC-SR04 Pin

ESP32-S3 Pin

Code Name

VCC

5V

—

GND

GND

—

TRIG

D2

TRIG_PIN

ECHO

D3

ECHO_PIN

Working Principle

The ESP32-S3 sends a 10µs HIGH pulse to the ultrasonic sensor’s TRIG pin.

• The ESP32-S3 sends a 10µs HIGH pulse to the ultrasonic sensor’s TRIG pin.

The HC-SR04 emits an ultrasonic pulse and waits for it to bounce back.

• The HC-SR04 emits an ultrasonic pulse and waits for it to bounce back.

The ECHO pin outputs the time taken for the echo to return.

• The ECHO pin outputs the time taken for the echo to return.

The ESP32-S3 calculates distance using the speed of sound.

• The ESP32-S3 calculates distance using the speed of sound.

Water depth is calculated as:

waterDepth = tankHeight - measuredDistance

• Water depth is calculated as:waterDepth = tankHeight - measuredDistance


The water depth is mapped to 0–32 columns of the LED display.

• The water depth is mapped to 0–32 columns of the LED display.

The LED matrix is updated to show the water level, filling right-to-left.

• The LED matrix is updated to show the water level, filling right-to-left.

Code

#include <MD_MAX72xx.h>
#include <SPI.h>

#define HARDWARE_TYPE MD_MAX72XX::FC16_HW
#define MAX_DEVICES 4  // 4 modules of 8x8 = 32 columns

#define DATA_PIN D10
#define CLK_PIN D8
#define CS_PIN D9

#define TRIG_PIN D2
#define ECHO_PIN D3

// Tank dimensions
#define TANK_HEIGHT_CM 12 // distance from sensor to bottom of tank

// Software SPI constructor (lets you use any pins)
MD_MAX72XX mx = MD_MAX72XX(HARDWARE_TYPE, DATA_PIN, CLK_PIN, CS_PIN, MAX_DEVICES);

void setup() {
  Serial.begin(115200);
  Serial.println("Water Level Indicator Starting...");

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  mx.begin();
  mx.clear();
}

long getDistance() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH, 30000); // Timeout 30ms
  return duration * 0.034 / 2; // cm
}

void displayLevel(int filledColumns) {
  mx.clear();
  for (int col = 0; col < filledColumns; col++) {
    int actualCol = 31 - col; // Reverse fill
    for (int row = 0; row < 8; row++) {
      mx.setPoint(row, actualCol, true);
    }
  }
}

void loop() {
  long distance = getDistance();
  
  Serial.print("Raw Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  if (distance > 0 && distance <= TANK_HEIGHT_CM) {
    int waterDepth = TANK_HEIGHT_CM - distance; // water height from bottom
    int levelCols = map(waterDepth, 0, TANK_HEIGHT_CM, 0, 32);
    
    Serial.print("Water Depth: ");
    Serial.print(waterDepth);
    Serial.print(" cm, Columns: ");
    Serial.println(levelCols);

    displayLevel(levelCols);
  } else {
    Serial.println("Out of range or no water detected.");
    displayLevel(0); // No water or out of range
  }
  delay(500);
}

Customization

Change TANK_HEIGHT_CM to match your tank’s depth.

• Change TANK_HEIGHT_CM to match your tank’s depth.

Adjust the delay(500) in loop() to update faster or slower.

• Adjust the delay(500) in loop() to update faster or slower.

Change the actualCol calculation if you want left-to-right fill instead.

• Change the actualCol calculation if you want left-to-right fill instead.

Possible Improvements

Add a buzzer alarm when the water level is too low or too high.

• Add a buzzer alarm when the water level is too low or too high.

Display numeric percentage on an additional OLED screen.

• Display numeric percentage on an additional OLED screen.

Use WiFi or Bluetooth to send water level data to a smartphone.

• Use WiFi or Bluetooth to send water level data to a smartphone.

Add low-power mode for battery operation.

• Add low-power mode for battery operation.

Demonstration