Arduino Project

Arduino Automatic Soap Dispenser with Ultrasonic Sensor

Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

2.webp__PID:7d088a16-8752-49fb-8b1f-f9bba7297987

Name	Includes Arduino board	PURCHASE LINK
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
3 in 1 Ultimate Starter Kit	Arduino Uno R4 Minima	BUY
Ultimate Sensor Kit	Arduino Uno R4 Minima	BUY
Universal Maker Sensor Kit	×	BUY

Course Introduction

In this lesson, you’ll learn how to use an OLED display, a button, and a buzzer with the Arduino R4 UNO to create a Slot Machine game.

The sensor is used to detect the presence of an object.

When an object is detected, the water pump is activated to dispense liquid (liquid hand soap).

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

1.1 Install Arduino IDE(Important)
1.2 Introduction of Arduino IDE

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Wifi	1	BUY
2	USB Type-C cable	1	×
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	Power Supply	1	BUY
6	Ultrasonic Sensor Module	1	BUY
7	TA6586 - Motor Driver Chip	1	×
8	Centrifugal Pump	1	×

Wiring

Auto_Pour_bb.webp__PID:e8ac75fb-2bae-4a21-ac7f-7cb5f5f7ce63

Common Connections:

Ultrasonic Sensor Module
Trig: Connect to 3 on the Arduino.
Echo: Connect to 4 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.

TA6586 - Motor Driver Chip
BI: Connect to 10 on the Arduino.
FI: Connect to 9 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.

Centrifugal Pump
Connect to TA6586 B0.
Connect to TA6586 F0.

Writing the Code

Note
You can copy this code into the Arduino IDE.
Don’t forget to select the board(Arduino UNO R4 Minima/WIFI) and the correct port before clicking the Upload button.

#include <Arduino.h>

/*
  UNO R4 + Ultrasonic (Echo=D4, Trig=D3) + TA6586 Pump Control
  Behavior:
    - Turn pump ON when distance < ON_THRESHOLD_CM
    - Turn pump OFF when distance > OFF_THRESHOLD_CM (hysteresis)
    - Median-of-5 sampling; pulseIn timeout; min ON/OFF hold times to avoid chattering
*/

// -------- Pins --------
// Ultrasonic (you asked to swap): Echo -> D4, Trig -> D3
const uint8_t ECHO_PIN = 4;
const uint8_t TRIG_PIN = 3;

// TA6586 motor driver pins (adjust as wired)
const uint8_t MOTOR_BI = 9;    // IN1 / Backward input
const uint8_t MOTOR_FI = 10;   // IN2 / Forward input

// -------- Tuning --------
const float    ON_THRESHOLD_CM   = 10.0f;    // pump ON below this
const float    OFF_THRESHOLD_CM  = 12.0f;    // pump OFF above this (hysteresis)
const uint8_t  SAMPLES           = 5;        // median-of-5
const uint32_t PULSE_TIMEOUT_US  = 30000UL;  // 30ms (~5m max), avoid long blocking

// Minimum hold times to protect the pump from rapid toggling
const uint32_t MIN_ON_HOLD_MS    = 1500;     // keep ON for at least this long
const uint32_t MIN_OFF_HOLD_MS   = 800;      // keep OFF for at least this long

// Optional: ambient temperature (°C) for speed-of-sound correction
const float AMBIENT_TEMP_C       = 20.0f;

// -------- State --------
enum PumpState { PUMP_OFF = 0, PUMP_ON = 1 };
PumpState pumpState = PUMP_OFF;
uint32_t lastToggleMs = 0;

// -------- Pump helpers --------
void pumpForward() {  // preferred ON direction (swap with pumpReverse() if needed)
  digitalWrite(MOTOR_FI, LOW);
  digitalWrite(MOTOR_BI, HIGH);
}
void pumpReverse() {  // alternative ON direction
  digitalWrite(MOTOR_BI, LOW);
  digitalWrite(MOTOR_FI, HIGH);
}
void pumpStop() {     // stop (coast). For brake, set both HIGH if datasheet recommends.
  digitalWrite(MOTOR_BI, LOW);
  digitalWrite(MOTOR_FI, LOW);
}

// -------- Ultrasonic helpers --------
float usPerCm() {
  // Speed of sound (m/s) ≈ 331.4 + 0.6*T(°C)
  float v = 331.4f + 0.6f * AMBIENT_TEMP_C; // m/s
  float us_per_m = 1e6f / v;                // µs per meter (one-way)
  return (us_per_m * 0.01f) * 2.0f;         // round-trip µs for 1 cm (~58 at ~20°C)
}

float measureOnceCm() {
  // Send 10us trigger pulse
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Read echo pulse width with timeout
  unsigned long dur = pulseIn(ECHO_PIN, HIGH, PULSE_TIMEOUT_US);
  if (dur == 0) return NAN; // timeout -> invalid reading

  return dur / usPerCm();   // convert to cm
}

float readDistanceMedianCm() {
  float vals[SAMPLES];
  for (uint8_t i = 0; i < SAMPLES; i++) {
    vals[i] = measureOnceCm();
    delay(5); // small gap between pings to avoid cross-talk echoes
  }
  // insertion sort (small N) - NANs float to the end
  for (uint8_t i = 1; i < SAMPLES; i++) {
    float key = vals[i];
    int j = i - 1;
    while (j >= 0 && (isnan(vals[j]) || vals[j] > key)) {
      vals[j + 1] = vals[j];
      j--;
    }
    vals[j + 1] = key;
  }
  return vals[SAMPLES / 2]; // median
}

// -------- Setup / Loop --------
void setup() {
  // Ultrasonic
  pinMode(ECHO_PIN, INPUT);
  pinMode(TRIG_PIN, OUTPUT);
  digitalWrite(TRIG_PIN, LOW);

  // Pump driver
  pinMode(MOTOR_BI, OUTPUT);
  pinMode(MOTOR_FI, OUTPUT);
  pumpStop(); // safe default

  // Debug serial
  Serial.begin(115200);
  Serial.println("Ultrasonic + Pump (Echo=D4, Trig=D3) ready.");
}

void loop() {
  float d = readDistanceMedianCm();
  uint32_t now = millis();
  bool valid = !isnan(d);

  // Simple state machine with hysteresis and min hold times
  switch (pumpState) {
    case PUMP_OFF:
      if (valid && d < ON_THRESHOLD_CM && (now - lastToggleMs >= MIN_OFF_HOLD_MS)) {
        pumpForward();              // switch to pumpReverse() if direction is wrong
        pumpState = PUMP_ON;
        lastToggleMs = now;
        Serial.println("Pump -> ON");
      }
      break;

    case PUMP_ON:
      if (valid && d > OFF_THRESHOLD_CM && (now - lastToggleMs >= MIN_ON_HOLD_MS)) {
        pumpStop();
        pumpState = PUMP_OFF;
        lastToggleMs = now;
        Serial.println("Pump -> OFF");
      }
      // Optional safety: if invalid for long time, you may force OFF after MIN_ON_HOLD_MS
      // else keep last state to avoid chattering on occasional timeouts.
      break;
  }

  // Debug print
  if (valid) {
    Serial.print("Distance(cm): ");
    Serial.print(d, 1);
    Serial.print(" | State: ");
    Serial.println(pumpState == PUMP_ON ? "ON" : "OFF");
  } else {
    Serial.println("Distance: INVALID (timeout)");
  }

  delay(60); // moderate loop rate
}

Recover password

Create my account

Arduino Project

Arduino Automatic Soap Dispenser with Ultrasonic Sensor

Kit purchase

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino Automatic Soap Dispenser with Ultrasonic Sensor

Kit purchase

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Subscribe to our newsletter