🔐 SMART DOOR LOCK SYSTEM (ESP32 + Servo + Solenoid + Relay)

✅ 1) Introduction (Project Idea)

This project is a Smart Door Lock System where:

• ESP32 is the brain (controller)

• A Servo motor rotates to open/close a latch (like knob turning)

• A Solenoid lock works as a strong locking mechanism (push/pull lock)

• A 1-channel relay is used to turn ON/OFF the solenoid lock safely

This is a very strong and real-world door lock system.

✅ 2) Component List (Complete)

🧠 Main Controller

1. ESP32 Dev Board

🔩 Locking Devices

2. Servo Motor (SG90 / MG90S / MG996R)

3. 12V Solenoid Door Lock

⚡ Power & Switching

4. 1-Channel Relay Module (5V)

5. 12V Adapter (for solenoid)

6. 5V Adapter (for ESP32 + servo)
   (or one 12V adapter + buck converter)

🔌 Extra Safety Components (Highly Recommended)

7. 1N4007 diode (for solenoid protection)

8. Jumper wires

9. Breadboard / PCB

10. Screw terminals / connectors

✅ 3) Component Details (Simple Explanation)

🧠 ESP32

• Works like Arduino but much faster

• Has WiFi + Bluetooth built-in

• Controls servo and relay signal pin

Why ESP32?
Because it can later connect to:

• Blynk

• WiFi App

• Bluetooth app

• Fingerprint

• RFID

• Keypad

🔧 Servo Motor

Servo rotates to a specific angle like:

• 0° = Lock

• 90° = Unlock

📌 Servo is used for mechanical latch movement.

✅ Best for Door Lock:

• MG90S (metal gear)

• MG996R (heavy duty)

🔒 Solenoid Lock

Solenoid lock is like:

• When power ON → pin pulls/pushes

• When power OFF → returns back

📌 Works like an electric lock used in real doors.

⚠️ Most solenoid locks are 12V and need good current.

🔥 1-Channel Relay Module

Relay works like a switch.

ESP32 gives small signal → relay turns ON/OFF → solenoid gets power.

📌 Relay protects ESP32 from high voltage and high current.

✅ 4) Connection / Wiring (Very Clear)

🔌 SERVO Connection to ESP32

Servo has 3 wires:

⚠️ Do NOT power servo from ESP32 3.3V
Use external 5V.

🔌 RELAY Connection to ESP32

Relay has 3 pins:

🔌 SOLENOID Lock Connection with Relay

Relay output side has:

• COM

• NO

• NC

Use COM and NO.

Wiring:

12V Adapter + → Relay COM
Relay NO → Solenoid +
Solenoid – → 12V Adapter –

✅ 5) IMPORTANT: Common Ground Rule (Very Important!)

If you use:

• 12V for solenoid

• 5V for ESP32/servo

You MUST connect:

✅ GND of 12V supply + GND of 5V supply + ESP32 GND together

Otherwise relay/servo may behave wrongly.

✅ 6) Working Logic (How It Works)

When Unlock Command comes:

1. ESP32 rotates servo to open latch (example 90°)

2. ESP32 turns ON relay

3. Relay powers solenoid

4. Solenoid pulls pin → door unlocks

When Lock Command comes:

1. ESP32 turns OFF relay

2. Solenoid returns to lock

3. Servo rotates back to lock angle (0°)

⭐ Recommended Power Setup (Best Option)

Instead of 2 adapters, use:

✅ 12V Adapter (2A or 3A)
and use:

✅ Buck Converter (LM2596) to make 5V for ESP32 + servo.

This is the cleanest setup.