ESP32 - Button Solenoid Lock

This tutorial instructs you how to use ESP32 with the button and solenoid lock. In detail, we will learn how to use the button to control solenoid lock without debouncing and with debouncing. Each time button is pressed, unlock the door for 10 seconds and then lock the door.

Hardware Used In This Tutorial

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

Or you can buy the following sensor kit:

1×DIYables Sensor Kit 30 types, 69 units
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Introduction to Button and Solenoid Lock

We have specific tutorials about solenoid lock and button. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:

Wiring Diagram

ESP32 Button Solenoid Lock 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 - Button Controls Solenoid Lock Without Debouncing

/* * 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-button-solenoid-lock */ #define BUTTON_PIN 22 // ESP32 pin GPIO22 connected to button #define RELAY_PIN 27 // ESP32 pin GPIO27 connected to the solenoid lock relay // variables will change: int prev_button_state; // the previous state of button int button_state; // the current state of button void setup() { Serial.begin(9600); // initialize serial pinMode(BUTTON_PIN, INPUT_PULLUP); // set ESP32 pin to input pull-up mode pinMode(RELAY_PIN, OUTPUT); // set ESP32 pin to output mode digitalWrite(RELAY_PIN, HIGH); // lock the door button_state = digitalRead(BUTTON_PIN); } void loop() { prev_button_state = button_state; // save the last state button_state = digitalRead(BUTTON_PIN); // read new state if (prev_button_state == HIGH && button_state == LOW) { 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 } }

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
  • Press button one time.
  • See the the lock tongue's state

Line-by-line Code Explanation

The above ESP32 code contains line-by-line explanation. Please read the comments in the code!

In practice, we need to debounce for the button. The next part will show how to debounce for the button.

ESP32 Code - Button Controls Solenoid Lock With Debouncing

Why need to debounce for the button? ⇒ see ESP32 - Button Debounce tutorial

/* * 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-button-solenoid-lock */ #include <ezButton.h> #define BUTTON_PIN 22 // ESP32 pin GPIO22 connected to button #define RELAY_PIN 27 // ESP32 pin GPIO27 connected to the solenoid lock relay ezButton button(BUTTON_PIN); // create ezButton object that attach to pin 7; void setup() { Serial.begin(9600); // initialize serial pinMode(RELAY_PIN, OUTPUT); // set ESP32 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 } }

Quick Instructions

  • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
  • Install ezButton library. See How To
  • Copy the above code and paste it to Arduino IDE.
  • Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
  • Press button one time.
  • See the the lock tongue's state

※ NOTE THAT:

Since the above code used the delay() function, we do not need to do debouncing for the button. However, We still provide the code with debouncing in case you modify this code and do not use the delay() function

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