ESP8266 - Touch Sensor - Solenoid Lock

This tutorial instructs you how to use the ESP8266 and touch sensor to control the solenoid lock. By connecting the solenoid lock to a soleniod lock, light bulb, LED strip, motor, or actuator..., we can use a touch sensor to control the them. We will learn two different applications:

Application 1 - The solenoid lock state is synchronized with the touch sensor state. In detail:

ESP8266 turns on the solenoid lock when the touch sensor is being touched.
ESP8266 turns off the solenoid lock when the touch sensor is NOT being touched.

Application 2 - The solenoid lock state is toggled each time the touch sensor is touched. More specifically:

If ESP8266 detects that the touch sensor has been touched (changing from a HIGH state to a LOW state), it will turn ON the solenoid lock if it's currently OFF, or turn OFF the solenoid lock if it's currently ON.
Releasing the touch sensor does not affect to the solenoid lock state.

Hardware Preparation

1	×	ESP8266 NodeMCU
1	×	Micro USB Cable
1	×	Touch Sensor
1	×	Relay
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) Solenoid Lock
1	×	(Optional) 12V Power Adapter
1	×	(Optional) DC Power Jack
1	×	(Optional) 5V Power Adapter for ESP8266
1	×	(Optional) Screw Terminal Expansion Board for ESP8266

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

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Additionally, some of these links are for products from our own brand, DIYables.

Overview of Solenoid Lock and Touch Sensor

If you are unfamiliar with solenoid lock and touch sensor (including pinout, operation, and programming), the following tutorials can help:

Wiring Diagram

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.

Application 1 - The solenoid lock state is in sync with the touch sensor state

ESP8266 Code

/* * 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-touch-sensor-solenoid-lock */ #define TOUCH_SENSOR_PIN D5 // The ESP8266 pin D5 connected to touch sensor's pin #define RELAY_PIN D7 // The ESP8266 pin D7 connected to the solenoid lock via relay module void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(TOUCH_SENSOR_PIN, INPUT); // Configure the ESP8266 pin to the input mode pinMode(RELAY_PIN, OUTPUT); // Configure the ESP8266 pin to the output mode } void loop() { int touch_state = digitalRead(TOUCH_SENSOR_PIN); // read new state if (touch_state == HIGH) { Serial.println("The sensor is being touched"); digitalWrite(RELAY_PIN, HIGH); // turn on } else if (touch_state == LOW) { Serial.println("The sensor is untouched"); digitalWrite(RELAY_PIN, LOW); // turn off } }

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.
Connect an ESP8266 to your computer with a USB cable.
Launch the Arduino IDE, and select the correct board and port.
Copy the code and open it in the Arduino IDE.
Click the Upload button on the Arduino IDE to compile and upload the code to the ESP8266.

Touch the touch sensor and hold it for a few seconds.
Check out the change in the solenoid lock's condition.

You will see that the solenoid lock state is in sync with the touch sensor state.

Code Explanation

Check out the line-by-line explanation contained in the comments of the source code!

Application 2 - Touch Sensor toggles Solenoid Lock

ESP8266 Code - Touch Sensor toggles Solenoid Lock

/* * 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-touch-sensor-solenoid-lock */ #define TOUCH_SENSOR_PIN D5 // The ESP8266 pin D5 connected to touch sensor's pin #define RELAY_PIN D7 // The ESP8266 pin D7 connected to the solenoid lock via relay module int solenoidLockState = LOW; // The current state of relay int prev_touch_state; // The previous state of touch sensor int touch_state; // The current state of touch sensor void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(TOUCH_SENSOR_PIN, INPUT); // Configure the ESP8266 pin to the input mode pinMode(RELAY_PIN, OUTPUT); // Configure the ESP8266 pin to the output mode touch_state = digitalRead(TOUCH_SENSOR_PIN); } void loop() { prev_touch_state = touch_state; // save the last state touch_state = digitalRead(TOUCH_SENSOR_PIN); // read new state if (prev_touch_state == LOW && touch_state == HIGH) { Serial.println("The sensor is touched"); // toggle state of relay solenoidLockState = !solenoidLockState; // control relay according to the toggled state digitalWrite(RELAY_PIN, solenoidLockState); } }

Code Explanation

You can locate the explanation in the comment lines of the ESP8266 code above.

In the code, the expression solenoidLockState = !solenoidLockState is equivalent to the following code:

if(solenoidLockState == LOW) solenoidLockState = HIGH; else solenoidLockState = LOW;

Detailed Instructions

Copy the code and open it in the Arduino IDE.
Upload the code to the ESP8266.
Touch and release the touch sensor several times.
Check out the change in the solenoid lock's state.

You'll notice that the solenoid lock will switch on or off one time whenever you Touch the touch sensor.

Video Tutorial

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