ESP8266 - Solenoid Lock

The Solenoid Lock, also referred to as the Electric Strike Lock, can be used to lock and unlock cabinets, drawers, and doors. This tutorial will teach us how to control the solenoid lock using ESP8266.

An alternative to the Solenoid Lock is the Electromagnetic Lock. For more information, please refer to the ESP8266 - Electromagnetic Lock tutorial.

Hardware Preparation

1	×	ESP8266 NodeMCU ESP-12F
1	×	Alternatively, ESP8266 D1 Mini NodeMCU ESP-12F
1	×	Alternatively, ESP8266 NodeMCU ESP-12E (Uno-form)
1	×	Micro USB Cable
1	×	Alternatively, ESP8266 NodeMCU ESP-12F (SMD-form)
1	×	USB Cable Type-A to Type-C (for USB-A PC)
1	×	USB Cable Type-C to Type-C (for USB-C PC)
1	×	Solenoid Lock
1	×	Relay
1	×	12V Power Adapter
1	×	DC Power Jack
1	×	Recommended: Screw Terminal Expansion Board for ESP8266

Or you can buy the following kits:

DIYables Sensor Kit (18 sensors/displays)

Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables .

Overview of Solenoid Lock

The Solenoid Lock Pinout

The Solenoid Lock consists of two wires:

The Positive (+) wire (red) should be connected to the 12V of a DC power supply
The Negative (-) wire (black) should be connected to the GND of a DC power supply

How It Works

When supplying power to the solenoid lock, the lock tongue is extended, resulting in the door being locked.
When NOT supplying power to the solenoid lock, the lock tongue is retracted, resulting in the door being unlocked.

※ NOTE THAT:

The solenoid lock typically requires a 12V, 24V or 48V power source. Consequently, it CANNOT be connected directly to an ESP8266 pin. A relay must be used to link the solenoid lock to the ESP8266 pin.

If the solenoid lock is connected to a relay (in a normally open mode):

When the relay is not activated, the door is unlocked
When the relay is activated, the door is locked

Connecting ESP8266 to a relay enables programming for ESP8266 to control the solenoid lock. For more information on relays, please refer to the ESP8266 - Relay tutorial.

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

You can also build this circuit without a breadboard. Here is the same wiring:

The wiring diagram between ESP8266 NodeMCU and Solenoid Lock (No Breadboard)

This image is created using Fritzing. Click to enlarge image

ESP8266 Code

This code causes the door to be locked and unlocked every five seconds.

Detailed Instructions

To get started with ESP8266 on Arduino IDE, follow these steps:

Check out the how to setup environment for ESP8266 on Arduino IDE tutorial if this is your first time using ESP8266.
Wire the components as shown in the diagram.
Connect the ESP8266 board to your computer using a USB cable.
Open Arduino IDE on your computer.
Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
Copy the code and open it in the Arduino IDE.
Click the Upload button in the Arduino IDE to send the code to the ESP8266.
Check out the state of the lock tongue.

ESP8266 - Button Controls Solenoid Lock

Diagram of Wiring

This image is created using Fritzing. Click to enlarge image

If you do not use a breadboard, wire it like this:

This image is created using Fritzing. Click to enlarge image

See more in ESP8266's pinout and how to supply power to the ESP8266 and other components.

Writing code for an ESP8266 board.

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-solenoid-lock */ #include <ezButton.h> #define BUTTON_PIN D1 // The ESP8266 pin connected to button's pin #define RELAY_PIN D8 // The ESP8266 pin connected to relay's pin ezButton button(BUTTON_PIN); // create ezButton object for pin D8 void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(RELAY_PIN, OUTPUT); // set arduino pin to output mode button.setDebounceTime(50); // set debounce time to 50 milliseconds digitalWrite(RELAY_PIN, HIGH); // lock the door } void loop() { button.loop(); // MUST call the loop() function first if(button.isPressed()) { Serial.println("The button is pressed"); digitalWrite(RELAY_PIN, LOW); // unlock the door in 10 seconds delay(10000); // 10 seconds digitalWrite(RELAY_PIN, HIGH); // lock the door again } }

Detailed Instructions

Wire the components as shown in the diagram.
Connect the ESP8266 board to your computer using a USB cable.
Open Arduino IDE on your computer.
Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
Install the ezButton library. Refer to How To for instructions.
Copy the code and open it in the Arduino IDE.
Click the Upload button on the Arduino IDE to upload the code to the ESP8266.
Push the button once.
Check out the lock tongue's state for 10 seconds.

※ NOTE THAT:

In the code above, we used the delay function. As a result, we do not have to implement debouncing for the button. Nevertheless, we still included the code with debouncing in case you would like to carry out additional tasks without using the delay function. Check out How to use millis() instead of delay() for more information.

Relay vs MOSFET Module for the Solenoid Lock

This tutorial uses a relay to switch the solenoid lock. A 12V solenoid lock runs on DC, so a MOSFET module can also switch it.

	Relay	MOSFET Module
Lock control	lock or unlock	lock or unlock
Switching sound	a click every time	no sound
Switching time	slow (milliseconds)	very fast
Wear	the contacts get old with use	no moving parts to wear
Works with	AC and DC locks	DC locks only
Flyback diode	most relay modules do not need one	must add one (1N4007 or 1N5819)
Isolation	yes	yes, with a PC817 optocoupler
Choose it for	a simple, common setup	a silent lock, or a door that opens many times a day

A solenoid lock is only locked or unlocked, so the MOSFET module does not give extra control here. Its gains are: no click, and nothing wears out. Both turn on when the pin is HIGH, so the code stays the same. A 3.3V ESP8266 pin is enough, because it only pushes a few milliamps through the LED of the PC817 optocoupler. Do not keep the lock unlocked for a long time, or it gets hot. This is the same with a relay.

A solenoid valve works the same way as a solenoid lock. To see how to wire and code one with both a relay and a MOSFET module, see the ESP8266 - Water/Liquid Valve tutorial. The wiring for a solenoid lock is in the ESP8266 - MOSFET Module tutorial.

Video Tutorial

Learn More

※ OUR MESSAGES

As freelancers, We are AVAILABLE for HIRE. See how to outsource your project to us
Please feel free to share the link of this tutorial. However, Please do not use our content on any other websites. We invested a lot of effort and time to create the content, please respect our work!