Arduino Nano - Touch Sensor - Solenoid Lock

This tutorial instructs you how to use the Arduino Nano and touch sensor to control the solenoid lock.

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

Arduino Nano turns on the solenoid lock when the touch sensor is being touched.
Arduino Nano 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 Arduino Nano 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	×	Arduino Nano
1	×	USB A to Mini-B 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	×	(Recommended) Screw Terminal Expansion Board for Arduino Nano
1	×	(Recommended) Breakout Expansion Board for Arduino Nano
1	×	(Recommended) Power Splitter For Arduino Nano

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	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 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 The best way to supply power to the Arduino Nano and other components.

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

Arduino Nano Code

/* * This Arduino Nano code was developed by newbiely.com * * This Arduino Nano code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano/arduino-nano-touch-sensor-solenoid-lock */ #define TOUCH_SENSOR_PIN 3 // The Arduino Nano pin connected to the touch sensor #define RELAY_PIN 2 // The Arduino Nano pin 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); // set arduino pin to input mode pinMode(RELAY_PIN, OUTPUT); // set arduino pin to 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

Connect an Arduino Nano 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 Arduino Nano.

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

Arduino Nano Code - Touch Sensor toggles Solenoid Lock

/* * This Arduino Nano code was developed by newbiely.com * * This Arduino Nano code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano/arduino-nano-touch-sensor-solenoid-lock */ #define TOUCH_SENSOR_PIN 3 // The Arduino Nano pin connected to the touch sensor #define RELAY_PIN 2 // The Arduino Nano pin 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); // set arduino pin to input mode pinMode(RELAY_PIN, OUTPUT); // set arduino pin to 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 Arduino Nano 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 Arduino Nano.
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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