Learn Programming and Electronics with Arduino Programming Electronics Academy

Have you seen some really cool stuff being made with a thing called Arduino? What is Arduino anyway?
It sounds like an Italian sandwich with extra cheese or something...
Well - it's that and a lot more. I hope this video can help explain some the basic premise of the Arduino!
 

Have you ever wanted to change the font color in the Arduino IDE?
Maybe it is hard for you to read the light grey comments in the Arduino IDE, or maybe you prefer something a little bolder.
Whatever your reason, in this short video, I demonstrate a relatively easy way to change the font color of comments.

In many cases while using an Arduino, you will want to see the data being generated by the Arduino. One common method of doing this is using the Serial.print() function from the Serial library to display information to your computer’s monitor.

In this week’s episode we will talk about the intricacies of the Serial.print() function.  This is the second part of a two part series on the Serial.print() function (Click here for the first part).
Here are the exact topics we will cover in this lesson:
Adjusting the number of digits to be displayed after the decimal point with the Serial.print() function. Adjusting the format to display with the Serial.print() function Formatting the output with text and tabs If you enjoyed this video, you should consider signing up for our free Arduino Crash Course - it has 19 high quality video training classes to help build your imagination with Arduino.

In many cases while using an Arduino, you will want to see the data being generated by the Arduino. One common method of doing this is using the Serial.print() function from the Serial library to display information to your computer’s monitor.
In this week’s episode, we will talk about the intricacies of the Serial.print() function.
This is the first part, of a two part series on the Serial.print() function. Here are the specific topics we will cover in this lesson:
Why would you want to use the Serial.print() function? A brief overview of the Serial library The basic use of the Serial.print() function
Like this video?  Sign up for our FREE Arduino Crash Course to get more videos that don't assume you have a PhD. Why Would You Want to Use the Serial.print() Function?
You may know that a function is a programming tool - it performs a specific task for you. The Serial.print() function’s task is to send information from your Arduino to your computer, so you can see the value displayed on your computer’s monitor.
There are an endless number of reasons you may want to send information from the Arduino to a computer display, but two reasons really stand out to me:
The first reason is being able to see information that you are generating with your Arduino.
For example, if you have a temperature sensor hooked up to your Arduino and you want to see the value that the temperature sensor is recording, then you can use the Serial.print() function to send the data to a computer monitor via the USB cable. If you open up the serial monitor window (Tools > Serial Monitor), you will see the values streaming in from the Arduino.

The other big reason to send information to a computer display using the Serial.print() function is for developing and debugging Arduino sketches.
Very often, when you are developing an Arduino sketch, what you end up coding does something differently than what you expected it to do. Maybe you have a variable that gets incremented every so often and blinks an LED when it reaches a threshold. When you upload the code to the Arduino, you notice that the LED is blinking more often than it should.
You can look at the code until your eyes bleed, but actually visualizing the variable being incremented [via the Serial.print() function], to see its values every time through the loop() can help explain what is happening very quickly.
A Brief Overview of the Serial Library We can’t talk about the Serial.print() function, without briefly talking about the Serial library.
Generally speaking, a library is simply a collection of functions that all have something in common.
The print() function is part of a library called the Serial library. Now, it's not cereal like Cheerios or Captain Crunch we're talking about - it's serial as in “one after another”.

The serial library allows us to interface the Arduino with other hardware, like a computer.
In order for us to use the functions of the Serial library, we have to initiate serial communication - to do this we use the Serial.begin() function. Serial.begin() needs to go in the setup().
void setup() { //Initiate Serial communication. Serial.begin(9600); } Now for reasons beyond the scope of this discussion, it is convenient to use the number 9600 in the Serial.begin() function. The value 9600 specifies the baud rate. The baud rate is the rate at which information will pass from the Arduino to the computer, or in the other direction.
The Basic Use of the Serial.print() Function Let's talk about how to use the Serial.print() function.
Say we have a sketch. This sketch has a variable called coolFactor.
I want to be able to monitor the value of the coolFactor variable – that is, I want it displayed on my computer screen. A perfect use for the Serial.print() function!
The first thing we must do in the Arduino sketch is begin serial communications. Like we just said, we use the Serial.begin() function and place it within the setup()

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