Arduino - Touch Sensor - Solenoid Lock

We are going to learn how to use Arduino to control the solenoid lock in two use cases:

Hardware Required

1×Arduino UNO or Genuino UNO
1×USB 2.0 cable type A/B
1×Touch Sensor
1×Solenoid Lock
1×Relay
1×12V Power Adapter
1×DC Power Jack
1×Jumper Wires
1×(Optional) 9V Power Adapter for Arduino
1×(Recommended) Screw Terminal Block Shield for Arduino Uno
1×(Optional) Transparent Acrylic Enclosure For Arduino Uno

Or you can buy the following sensor kit:

1×DIYables Sensor Kit 30 types, 69 units
Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

About Touch Sensor and Solenoid Lock

If you do not know about solenoid lock and touch sensor (pinout, how it works, how to program ...), learn about them in the following tutorials:

Wiring Diagram

Arduino Touch Sensor Solenoid Lock Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Arduino Code - Touch Sensor controls Solenoid Lock

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-touch-sensor-solenoid-lock */ const int TOUCH_SENSOR_PIN = 8; // Arduino pin connected to touch sensor's pin const int RELAY_PIN = A5; // Arduino pin connected to the solenoid lock via relay void setup() { Serial.begin(9600); // initialize serial pinMode(TOUCH_SENSOR_PIN, INPUT); // set arduino pin to input mode pinMode(RELAY_PIN, OUTPUT); // set arduino pin to output mode } void loop() { int touchState = digitalRead(TOUCH_SENSOR_PIN); // read new state if (touchState == HIGH) { Serial.println("The sensor is being touched"); digitalWrite(RELAY_PIN, HIGH); // turn on } else if (touchState == LOW) { Serial.println("The sensor is untouched"); digitalWrite(RELAY_PIN, LOW); // turn off } }

Quick Steps

  • Connect Arduino to PC via USB cable
  • Open Arduino IDE, select the right board and port
  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to Arduino
Arduino IDE Upload Code
  • Touch and keep touching the touch sensor several seconds
  • See the change of solenoid lock's state

Code Explanation

Read the line-by-line explanation in comment lines of source code!

Arduino Code - Touch Sensor Toggles Solenoid Lock

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-touch-sensor-solenoid-lock */ const int TOUCH_SENSOR_PIN = 8; // Arduino pin connected to touch sensor's pin const int RELAY_PIN = A5; // Arduino pin connected to solenoid lock via relay // variables will change: int solenoidLockState = LOW; // the current state of relay int lastTouchState; // the previous state of touch sensor int currentTouchState; // the current state of touch sensor void setup() { Serial.begin(9600); // initialize serial pinMode(TOUCH_SENSOR_PIN, INPUT); // set arduino pin to input mode pinMode(RELAY_PIN, OUTPUT); // set arduino pin to output mode currentTouchState = digitalRead(TOUCH_SENSOR_PIN); } void loop() { lastTouchState = currentTouchState; // save the last state currentTouchState = digitalRead(TOUCH_SENSOR_PIN); // read new state if(lastTouchState == LOW && currentTouchState == HIGH) { Serial.println("The sensor is touched"); // toggle state of relay solenoidLockState = !solenoidLockState; // control relay arccoding to the toggled state digitalWrite(RELAY_PIN, solenoidLockState); } }

Quick Steps

  • Connect Arduino to PC via USB cable
  • Open Arduino IDE, select the right board and port
  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to Arduino
  • Keep touching the touch sensor several seconds and then release it.
  • See the change of solenoid lock's state

Code Explanation

Read the line-by-line explanation in comment lines of code!

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

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

Video Tutorial

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