IoT Engineering Course using ESP32 with 12 Real-World Projects

💧 Project Overview

In this lesson, we will connect an Ultrasonic Sensor with ESP32 to measure water level in a tank and control a water pump using a relay.

This system will:

Measure water level using ultrasonic distance
Detect LOW and FULL tank condition
Control motor automatically
Prevent overflow
Prevent dry running

📦 Components Used in This Project

🔹 1️⃣ ESP32

Main microcontroller
Reads ultrasonic data
Controls relay
Handles automation logic

🔹 2️⃣ HC-SR04 Ultrasonic Sensor

Measures distance to water surface
Calculates water level
Non-contact measurement

🔹 3️⃣ Single Channel Relay Module

Controls high voltage motor
Electrically isolates ESP32

🔹 4️⃣ DC Water Pump

Pumps water into tank
Controlled via relay

🔹 5️⃣ 12V Power Supply

Powers water pump
External supply required

🔌 Circuit Connections

🔹 Ultrasonic Sensor → ESP32

Ultrasonic Pin	ESP32 Pin
VCC	5V
GND	GND
Trig	GPIO 5
Echo	GPIO 18

⚠ IMPORTANT:
Echo pin gives 5V output.
Use a voltage divider (10k + 20k resistor) to reduce to 3.3V for ESP32 safety.

🔹 Relay Module → ESP32

Relay Pin	ESP32
VCC	5V
GND	GND
IN	GPIO 26

⚠ Relay Active LOW
LOW → Motor ON
HIGH → Motor OFF

🔹 Relay → DC Pump Wiring

Relay Terminal	Connection
COM	12V Supply +
NO	Pump +
Pump –	12V Supply –

When relay activates:
COM connects to NO → Pump turns ON

📐 How Ultrasonic Sensor Measures Water Level

1️⃣ Sensor sends ultrasonic pulse
2️⃣ Pulse hits water surface
3️⃣ Echo returns
4️⃣ ESP32 calculates distance

Formula used:

Distance = Duration × 0.034 / 2

If tank height = 30 cm:

Water Level = Tank Height – Measured Distance

Example:

Distance	Tank Condition
25 cm	Tank Low
5 cm	Tank Full

⚡ Power Distribution

ESP32 powered by USB
Ultrasonic powered by 5V
Relay powered by 5V
Pump powered by 12V external supply

⚠ Always connect all GND together (Common Ground)

🚨 Important Safety Notes

✔ Use voltage divider for Echo pin
✔ Never connect pump directly to ESP32
✔ Use proper insulated wiring
✔ Keep ultrasonic sensor dry
✔ Mount sensor firmly at tank top

🎯 What Students Learn in This Lesson

Ultrasonic sensor interfacing
Distance measurement concept
Relay module wiring
Motor control circuit
Power isolation
Industrial-style wiring

📌 Lesson Summary

In this lesson, we successfully:

Connected HC-SR04 ultrasonic sensor with ESP32
Connected relay module safely
Designed pump control circuit
Built a complete hardware foundation for Smart Water Management System

This makes the system:

✔ More accurate
✔ Non-contact measurement
✔ Industry-ready
✔ Long-lasting solution