ESP32 - Solenoid Lock

The Solenoid Lock is also known as the Electric Strike Lock. It can be use to lock/unlock cabinet, drawer, door. This tutorial instructs you how to use ESP32 to control the solenoid lock.

An alternative to the Solenoid Lock is Electromagnetic Lock. You can learn more in ESP32 - Electromagnetic Lock tutorial

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	Solenoid Lock
1	×	Relay
1	×	12V Power Adapter
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) DC Power Jack
1	×	(Recommended) ESP32 Screw Terminal Adapter

Or you can buy the following sensor kit:

DIYables Sensor Kit 30 types, 69 units

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Introduction to Solenoid Lock

Pinout

Solenoid Lock includes two wires:

Positive (+) wire (red): needs to be connected to 12V of DC power supply
Negative (-) wire (black): needs to be connected to GND of DC power supply

How It Works

When the Solenoid Lock is powered, the lock tongue (strike) is extended ⇒ the door is locked
When the Solenoid Lock is NOT powered, the lock tongue (strike) is retracted ⇒ the door is unlocked

※ NOTE THAT:

The solenoid lock usually uses 12V, 24V or 48V power supply. Therefore, we CANNOT connect the solenoid lock directly to ESP32 pin. We have to connect it to ESP32 pin via a relay

If we connect the solenoid lock to a relay (normally open mode):

When relay is open, door is unlocked
When relay is closed, door is locked

By connecting ESP32 to the relay, we can program for ESP32 to control the solenoid lock. Learn more about relay in ESP32 - Relay tutorial.

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

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-solenoid-lock */ #define RELAY_PIN 16 // ESP32 pin GPIO16, which connects to the solenoid lock via the relay // the setup function runs once when you press reset or power the board void setup() { // initialize digital pin as an output. pinMode(RELAY_PIN, OUTPUT); } // the loop function runs over and over again forever void loop() { digitalWrite(RELAY_PIN, HIGH); // unlock the door delay(5000); digitalWrite(RELAY_PIN, LOW); // lock the door delay(5000); }

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Do the wiring as above image.
Connect the ESP32 board to your PC via a micro USB cable
Open Arduino IDE on your PC.
Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
Copy the above code and paste it to Arduino IDE
Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
See the the lock tongue's state

ESP32 - Button Controls Solenoid Lock

See ESP32 - Button Controls Solenoid Lock tutorial

※ NOTE THAT:

In the above code, we used the delay function. Therefore, we do not need to debouncing for button. However, We still provide the code with debouncing just in case you want to do more tasks without using delay function. See How to use millis() instead of delay()

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