How to make a secret knock detector to trigger anything with only an Arduino and a few cheap components

Learn Programming and Electronics with Arduino

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After taking a four year break on his Oklahoma ranch, Blake Shelton is back on the road and riding the high of his new album, For Recreational Use Only . After 29 number one hits, and a detour into Hollywood, Blake’s scorching hot single “Texas” proves he’s still got it. Country Thunder CEO Troy Vollhoffer recalls meeting Blake Shelton during a crazy storm that really put the “thunder” in Country Thunder. After 23 seasons on The Voice , Blake opens up about spreading himself thin and making the choice to be “a TV guy or a touring guy.” The two reminisce about Toby Keith and why being a road dog is the best way to learn how to entertain a crowd. Blake reveals how his worst on-stage “ass-kicking” taught him how to be himself in front of a crowd. After taking so much time away from the spotlight, Blake shares that it was Post Malone who reminded him that he’s still a country singer at heart.…

לפני 8 שנים 12:57

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There are a couple good use-case scenarios for making a secret knock detector using an Arduino.

You are a spy who needs to authenticate your cohorts
You are a super hero who wants a secret knock to open the entrance to your lair

Whatever the reason - by the end of this tutorial you will know how to use an Arduino, a piezo transducer and a couple other cheap components to make secret knock detector.

Here is an overview of exactly what we will talk about in this lesson:

The components you will need and how to set up this simple circuit.
The concept of operation of this secret knock detector
A thorough description of each block of code in the Arduino sketch
Why North American grizzly bears love piezo transducers

For this secret knock detector circuit you need:

Arduino (I use the Arduino Uno) [1]
Solderless breadboard [1]
1 Mohm Resistor [1]
Piezo transducer (aka buzzer) [1]
Jumper wires [4]
5.1V Zener diode (for extra protection) [1]
No spill stopper for a “to-go” coffee cup

How to set up the Circuit:

This is a really simple circuit to setup, below are step-by-step instructions and a breadboard diagram.

Place the piezo transducer on the breadboard, with the positive lead and the negative lead on separate rails.
Connect the positive lead to pin A0 on the Arduino and the other lead to ground.
Finally, use the 1Mohm resistor to connect the leads of the piezo transducer.
As an additional level of protection, you might consider adding a 5.1V zener diode between the leads to protect against high voltage spikes from frying your input pin - you might call it a cheap insurance policy.

An Overview of this Secret Knock Detectors operation

Here is the basic concept of how this will work.

We want something to happen when you tap out a secret code.

We will create a sequence of soft and hard taps - this will be our secret code which will be represented as 0’s and 1’s in an array.

For example:

secretKnock[secretKnockLength] = {0, 0, 1, 0};

The code above represents a secret code of soft , soft , hard, soft .

The piezo transducer will turn the mechanical pressure created by the tap into a signal that the Arduino analog pin can read. The level of the signal will determine whether a tap gets characterized as soft or hard.

The threshold of a soft vs hard tap need to be determined empirically, once you have the circuit built - it will depend on what you have the piezo transducer attached to - I have mine taped to a piece of paper.

You should start with the default threshold values provided in the sketch and change them to suit your specific setup.

Once a tap signal is picked up by the Arduino, the sketch will compare the entered sequence of taps to the secret code, one tap at a time.

If the code is entered correctly, then we will trigger an action on the output pin. In this code below, we trigger an LED to turn on for a couple seconds - but you could trigger a servo arm, a pump, or whatever you might need.

If the code is entered incorrectly - nothing happens.

Here is the code for your hacking enjoyment:

/* A simple sketch to detect a secret knock using a piezo transducer Created JUL 2015 by Michael James http://www.programmingelectronics.com/ This code is in the public domain */ const int outputPin = 6; // led indicator connected to digital pin const int knockSensor = A0; // the piezo is connected to an analog pin const int thresholdHIGH = 150; // threshold value to decide when the detected knock is hard (HIGH) const int thresholdLOW = 120; // threshold value to decide when the detected knock is gentle (LOW) const int secretKnockLength = 4; //How many knocks are in your secret knock /* This is the secret knock sequence * 0 represents a LOW or quiet knock * 1 represents a HIGH or loud knock * The sequence can be as long as you like, but longer codes increase the difficulty of matching */ const int secretKnock[secretKnockLength] = {0, 0, 1, 0}; int secretCounter = 0; //this tracks the correct knocks and allows you to move through the sequence int sensorReading = 0; // variable to store the value read from the sensor pin void setup() { //Set the output pin as an OUTPUT pinMode(outputPin, OUTPUT); //Begin Serial Communication. Serial.begin(9600); } void loop() { // read the piezo sensor and store the value in the variable sensorReading: sensorReading = analogRead(knockSensor); // First determine is knock if Hard (HIGH) or Gentle (LOW) //Hard knock (HIGH) is detected if (sensorReading >= thresholdHIGH) { //Check to see if a Hard Knock matches the Secret Knock in the correct sequence. if (secretKnock[secretCounter] == 1) { //The Knock was correct, iterate the counter. secretCounter++; Serial.println("Correct"); } else { //The Knock was incorrect, reset the counter secretCounter = 0; Serial.println("Fail - You are a spy!"); }//close if //Allow some time to pass before sampling again to ensure a clear signal. delay(100); //Gentle knock (LOW) is detected } else if (sensorReading >= thresholdLOW) { //Check to see if a Gentle Knock matches the Secret Knock in the correct sequence. if (secretKnock[secretCounter] == 0) { //The Knock was correct, iterate the counter. secretCounter++; Serial.println("Correct"); } else { //The Knock was incorrect, reset the counter. secretCounter = 0; Serial.println("Fail - You are a spy!"); }//close if //Allow some time to pass before sampling again to ensure a clear signal. delay(100); }//close if else //Check for successful entry of the code, by seeing if the entire array has been walked through. if (secretCounter == (secretKnockLength) ) { Serial.println("Welcome in fellow Illuminante!"); //if the sececret knock is correct, illuminate the LED for a couple seconds digitalWrite(outputPin, HIGH); delay(2000); digitalWrite(outputPin, LOW); //Reset the secret counter to 0. secretCounter = 0; }//close success check }//close loop

If you enjoyed this lesson, you should join our free Arduino Crash Course - it has 19 Video Training lessons all about using Arduino (you can sign up below).

61 פרקים

#Tech #Higher Education #Programming Electronics Academy #Podcasting Education

How to make a secret knock detector to trigger anything with only an Arduino and a few cheap components

Learn Programming and Electronics with Arduino

published לפני 8 שנים

שתפו

MP4•בית הפרקים

There are a couple good use-case scenarios for making a secret knock detector using an Arduino.

You are a spy who needs to authenticate your cohorts
You are a super hero who wants a secret knock to open the entrance to your lair

Whatever the reason - by the end of this tutorial you will know how to use an Arduino, a piezo transducer and a couple other cheap components to make secret knock detector.

Here is an overview of exactly what we will talk about in this lesson:

The components you will need and how to set up this simple circuit.
The concept of operation of this secret knock detector
A thorough description of each block of code in the Arduino sketch
Why North American grizzly bears love piezo transducers

For this secret knock detector circuit you need:

Arduino (I use the Arduino Uno) [1]
Solderless breadboard [1]
1 Mohm Resistor [1]
Piezo transducer (aka buzzer) [1]
Jumper wires [4]
5.1V Zener diode (for extra protection) [1]
No spill stopper for a “to-go” coffee cup

How to set up the Circuit:

This is a really simple circuit to setup, below are step-by-step instructions and a breadboard diagram.

Place the piezo transducer on the breadboard, with the positive lead and the negative lead on separate rails.
Connect the positive lead to pin A0 on the Arduino and the other lead to ground.
Finally, use the 1Mohm resistor to connect the leads of the piezo transducer.
As an additional level of protection, you might consider adding a 5.1V zener diode between the leads to protect against high voltage spikes from frying your input pin - you might call it a cheap insurance policy.

An Overview of this Secret Knock Detectors operation

Here is the basic concept of how this will work.

We want something to happen when you tap out a secret code.

We will create a sequence of soft and hard taps - this will be our secret code which will be represented as 0’s and 1’s in an array.

For example:

secretKnock[secretKnockLength] = {0, 0, 1, 0};

The code above represents a secret code of soft , soft , hard, soft .

You should start with the default threshold values provided in the sketch and change them to suit your specific setup.

Once a tap signal is picked up by the Arduino, the sketch will compare the entered sequence of taps to the secret code, one tap at a time.

If the code is entered incorrectly - nothing happens.

Here is the code for your hacking enjoyment:

If you enjoyed this lesson, you should join our free Arduino Crash Course - it has 19 Video Training lessons all about using Arduino (you can sign up below).

61 פרקים

#Tech #Higher Education #Programming Electronics Academy #Podcasting Education

כל הפרקים

לפני 8 years8:11

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לפני 8 years14:04

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This lesson discusses what to do when you open an existing program and realize that you simply don't understand all the stuff that is going on. It also talks about using the ADXL345 triple axis accelerometer breakout board to control the hue of a Red-Green-Blue (RGB) LED.

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3 Ways to Use Acceleration in an Arduino Sketch 17:37

לפני 8 years17:37

17:37

This lesson covers three easy ways to implement some form of acceleration in your Arduino sketches. It will cover the following: Linear Acceleration Exponential Acceleration Messing Around with the Square Root function What is Acceleration? Acceleration is the rate of change of something over time. Acceleration would help describe things like: Have fast can a stopped car get to 88mph? If I do a wing-suit jump from the top of Mount Everest, how fast will I be when I am gliding over base camp? How can I gently slow down the movement of a mechanical servo before it comes to rest? We can implement acceleration when programming Arduino quite easily with just a couple lines of code. The basic concept is that a variable will need to change - how it changes over the course of the sketch is what we are interested in. Below are three examples of how we can code change in variables so they display acceleration. Linear acceleration Linear acceleration is a constant rate of change. It can be represented by a sloped line on an x-y axis. A simple way to use it is to increment or decrement a variable every time through a loop like below... for (int i = 0; i < 10; i++) { //accel gets increasingly smaller as for loop continues accel = accel - 100; }//close for You can see in the code above, that each time through the 'for loop', the accel variable is decreasing by 100. If accel started at 1000, this is what accel would look like with respect to the number of iterations of the for loop. You can see that the accel variable decreases at a set rate over time in a linear fashion. Exponential Acceleration Exponential acceleration changes over time too, but it does so more dramatically (It's basically a drama queen). At first the rate of change in the variable is small, but once it begins to increase it really takes off! You can use the power function built into the Arduino IDE to make a variable change exponentially. The power function syntax is quite easy. pow( base, exponent ) The parameter base is the number that get raised to the power of the exponent . Like 2 to the 5th power. Below is an example of how you might code it to change a variable exponentially over the course of a 'for loop'. for (int i = 0; i < 10; i++) { //accel grows exponentially as the for loop continues accel = pow(2, i); }//close for Looking at a chart of accel over the course of the 'for loop', we can see that the way it changes is much different than linear acceleration: The theme for exponential growth is that is starts out slow, but once it starts going it really get's going! Using the Square Root Function for Acceleration The square root function can also provide some flavor to the output from your Arduino. It's syntax is simple: sqrt( x ) It returns the square root of the number or variable that you put in the parenthesis. Below is an easy way to use it in a 'for loop': for (int i = 0; i < 6; i++) { //accel quickly decreases through the loop accel = sqrt(accel); }//close for Let's look at how accel changes over the course of the for loop(let's say it started at 10,000): You can see the a rapid deceleration in the value of the accel variable of the 'for loop'. Practice With Acceleration: If you want to take a look at what these types of acceleration will do in "real" life, then set up the circuit below. You Will Need: (10) LEDs (10) 220 Ohm Resistors (1) Jumper Wire Arduino Board Bread Board Black Marker Set Up The Circuit: Start by by placing one resistor at pin 2 on your Arduino. Connect the other end of the resistor to the breadboard and then connect the long leg of the LED to the resistor. Place the short leg of the LED in the outer ground rail of the bread board. Then add 9 more resistors and LEDs across - you should stop at Pin 11 on the Arduino. Then add a jumper wire from GND on the Arduino to the shared ground on the breadboard. (All LEDs not pictured). That is pretty much it for the circuit. Below are the code examples for the different ways to program acceleration that we talked about: Here is the code for the linear acceleration: /* Linaer ( Constant ) Acceleration The circuit: * LEDs from pins 2 through 11 to ground created 2006 by David A. Mellis modified 30 Aug 2011 by Tom Igoe Modifeid 21 Jul 2014 by Michael James This example code is in the public domain. http://www.arduino.cc/en/Tutorial/Array */ //Declare and initialize variables // The higher the number, the slower the timing. int timer = 1000; // an array of pin numbers to which LEDs are attached int ledPins[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 }; // the number of pins (i.e. the length of the array) int pinCount = 10; void setup() { // the array elements are numbered from 0 to (pinCount - 1). // use a for loop to initialize each pin as an output: for (int thisPin = 0; thisPin < pinCount; thisPin++) { pinMode(ledPins[thisPin], OUTPUT); } //Start Serial Communication Serial.begin(9600); }//close setup void loop() { // loop from the lowest pin to the highest: for (int thisPin = 0; thisPin < pinCount; thisPin++) { // turn the pin on: digitalWrite(ledPins[thisPin], HIGH); delay(timer); // turn the pin off: digitalWrite(ledPins[thisPin], LOW); //decrement timer (EASY WAY) timer = timer - 100; //let's take a look at the numbers via the serial monitor window (Tools > Serial Monitor) Serial.print("Back ... LED #"); Serial.print(thisPin); Serial.print(" = "); Serial.println(timer); }//close for //reset timer for next for loop timer = 1000; // loop from the highest pin to the lowest: for (int thisPin = pinCount - 1; thisPin >= 0; thisPin--) { // turn the pin on: digitalWrite(ledPins[thisPin], HIGH); delay(timer); // turn the pin off: digitalWrite(ledPins[thisPin], LOW); //decrement timer timer = timer - 100; //let's take a look at the numbers via the serial monitor window (Tools > Serial Monitor) Serial.print("Forth ... LED #"); Serial.print(thisPin); Serial.print(" = "); Serial.println(timer); }//close for //reset timer for next for loop timer = 1000; }//close loop Here is the code for the exponential acceleration: /* Exponential Acceleration The circuit: * LEDs from pins 2 through 11 to ground created 2006 by David A. Mellis modified 30 Aug 2011 by Tom Igoe Modifeid 21 Jul 2014 by Michael James This example code is in the public domain. http://www.arduino.cc/en/Tutorial/Array */ //Declare and initialize variables // The higher the number, the slower the timing. float timer = 1000; // an array of pin numbers to which LEDs are attached int ledPins[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 }; // the number of pins (i.e. the length of the array) int pinCount = 10; void setup() { // the array elements are numbered from 0 to (pinCount - 1). // use a for loop to initialize each pin as an output: for (int thisPin = 0; thisPin < pinCount; thisPin++) { pinMode(ledPins[thisPin], OUTPUT); } //Start Serial Communication Serial.begin(9600); }//close setup void loop() { // loop from the lowest pin to the highest: for (int thisPin = 0; thisPin < pinCount; thisPin++) { // turn the pin on: digitalWrite(ledPins[thisPin], HIGH); delay(timer); // turn the pin off: digitalWrite(ledPins[thisPin], LOW); //decrement timer timer = pow(2, thisPin); //let's take a look at the numbers via the serial monitor window (Tools > Serial Monitor) Serial.print("Back ... LED #"); Serial.print(thisPin); Serial.print(" = "); Serial.println(timer); }//close for //reset timer for next for loop // loop from the highest pin to the lowest: for (int thisPin = pinCount - 1; thisPin >= 0; thisPin--) { // turn the pin on: digitalWrite(ledPins[thisPin], HIGH); delay(timer); // turn the pin off: digitalWrite(ledPins[thisPin], LOW); //decrement timer timer = pow(2, thisPin); //let's take a look at the numbers via the serial monitor window (Tools > Serial Monitor) Serial.print("Forth ... LED #"); Serial.print(thisPin); Serial.print(" = "); Serial.println(timer); }//close for //reset timer for next for loop timer = 1000; }//close loop Here is the code for messing around with the square root: /* square root The circuit: * LEDs from pins 2 through 11 to ground created 2006 by David A. Mellis modified 30 Aug 2011 by Tom Igoe Modifeid 21 Jul 2014 by Michael James This example code is in the public domain. http://www.arduino.cc/en/Tutorial/Array */ //Declare and initialize variables // The higher the number, the slower the timing. float timer = 1000; // an array of pin numbers to which LEDs are attached int ledPins[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 }; // the number of pins (i.e. the length of the array) int pinCount = 10; void setup() { // the array elements are numbered from 0 to (pinCount - 1). // use a for loop to initialize each pin as an output: for (int thisPin = 0; thisPin < pinCount; thisPin++) { pinMode(ledPins[thisPin], OUTPUT); } //Start Serial Communication Serial.begin(9600); }//close setup void loop() { // loop from the lowest pin to the highest: for (int thisPin = 0; thisPin < pinCount; thisPin++) { // turn the pin on: digitalWrite(ledPins[thisPin], HIGH); delay(timer); // turn the pin off: digitalWrite(ledPins[thisPin], LOW); //decrement timer timer = sqrt(timer); //let's take a look at the numbers via the serial monitor window (Tools > Serial Monitor) Serial.print("Back ... LED #"); Serial.print(thisPin); Serial.print(" = "); Serial.println(timer); }//close for //reset timer for next for loop timer = 1000; // loop from the highest pin to the lowest: for (int thisPin = pinCount - 1; thisPin >= 0; thisPin--) { // turn the pin on: digitalWrite(ledPins[thisPin], HIGH); delay(timer); // turn the pin off: digitalWrite(ledPins[thisPin], LOW); //decrement timer timer = sqrt(timer); //let's take a look at the numbers via the serial monitor window (Tools > Serial Monitor) Serial.print("Forth ... LED #"); Serial.print(thisPin); Serial.print(" = "); Serial.println(timer); }//close for //reset timer for next for loop timer = 1000; }//close loop I hope the lesson was helpful. The idea of adding acceleration to a sketch can seem a bit intimidating at first, but as you can see, it turns out to be a rather simple addition of code. Try on Your Own Challenge: Can you make the fade amount of an LED accelerate/deccelerate? Can you add a potentiometer to the circuit above and find a way to control the amount of acceleration - either linear, exponential or otherwise.…

לפני 8 years5:45

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I want to get you excited about the possibilities when you learn some basic programming and electronics that drive the Arduino. It is literally amazing what you can do.

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The premise of our course is that Arduino is a tool to assist in prototyping your imagination.

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לפני 8 years2:22

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This is the introduction for the following lessons on the programming and electronics of Arduino. Michael talks about the following lessons, the Arduino Crash Course, and the premium Arduino Course for Absolute Beginners.

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How to make a secret knock detector to trigger anything with only an Arduino and a few cheap components

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How to make a secret knock detector to trigger anything with only an Arduino and a few cheap components