ESP32 - Electromagnetic Lock

The electromagnetic lock (also known as magnetic lock, maglock, or EM lock) is an important component of the door lock system. This tutorial instructs you how to use ESP32 to control the electromagnetic lock.

Hardware Used In This Tutorial

1×ESP-WROOM-32 Dev Module
1×Micro USB Cable
1×Electromagnetic Lock
1×Relay
1×12V Power Adapter
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Introduction to Electromagnetic Lock

Electromagnetic Lock Pinout

The electromagnetic Lock is composed of two components:

  • Armature plate: this part is attached on the moving part of the door
  • Electromagnet: this part is attached on the door frame. it has two wires, which are connected to power source.

When the door is closed, two components are in contact with each other.

Electromagnetic Lock Pinout

How Electromagnetic Lock Works

  • When the electromagnet is powered ⇒ the electromagnet attracts to armature plate ⇒ lock
  • When the electromagnet is NOT powered ⇒ the electromagnet does NOT attract to armature plate ⇒ unlock

The electromagnetic lock uses high voltage (12V, 24V or 48V...) power supply. Therefore, we need to use a relay in between the electromagnetic lock and ESP32 pin. See ESP32 - Relay tutorial.

If we connect the electromagnetic lock to a relay in normally open mode and use an ESP32 pin to control the relay:

  • When the ESP32 pin is LOW ⇒ the relay is open ⇒ door is unlocked
  • When the ESP32 pin is HIGH ⇒ the relay is closed ⇒ door is locked

Wiring Diagram between Electromagnetic Lock and ES32

wiring diagram between esp32 electromagnetic lock

This image is created using Fritzing. Click to enlarge image

ESP32 Code

The below code lock/unlock the door every 5 seconds

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-electromagnetic-lock */ #define RELAY_PIN 27 // ESP32 pin GIOP27 connected to the IN pin of relay // the code in setup function runs only one time when ESP32 starts void setup() { // initialize digital pin GIOP27 as an output. pinMode(RELAY_PIN, OUTPUT); } // the code in loop function is executed repeatedly infinitely void loop() { digitalWrite(RELAY_PIN, HIGH); // lock the door delay(4000); digitalWrite(RELAY_PIN, LOW); // unlock the door delay(4000); }

Quick Instructions

  • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
  • Copy the above code and paste it to Arduino IDE.
  • Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
  • Put the armature plate close to electromagnet.
  • See the attraction between armature plate and electromagnet.

Video Tutorial

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ESP32 - Button Controls Electromagnetic Lock

See ESP32 - Button Controls Electromagnetic Lock tutorial

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