Arduino Project 5: Internet Control without Ethernet Shield

February 18, 2013 22 comments

I’m getting ready to start an Arduino home automation project, so I started looking at ways to interface with an Arduino across the internet. That way I’ll be able to control all of the lights, locks, etc. anywhere I have internet access.

Now, the obvious answer was to buy an Ethernet shield, but I already run a home web server so that seemed unnecessary. I saw a few solutions using Processing or Python scripts, but that seemed unnecessarily complicated. It took a fair amount of digging and brainstorming, but I’ve found an ultra-easy, ultra-flexible, and ultra-fast solution. Ultra.

There are a few major assumptions here.

  1. You have a computer running a web server that is accessible from the open internet, using a static IP address or a Dynamic DNS name. Your computer is either directly connected to your ISP and using a public IP address or your router is set up for port forwarding. If you don’t have this set up yet, just Google it – there are a lot of tutorials that explain how to set up a home web server.
  2. Your home web server has PHP. If not, this will still work, you’ll just have to re-write it in Java or whatever server-side language you’re using.
  3. The Arduino will be plugged into the web server via USB.

Here’s the basic concept: the Arduino can’t read files from the server via the USB serial connection, so the server will have to “push” the message. The server side code (PHP, Java, whatever you choose) cannot talk directly to the serial COM port, so we need a local script on the web server that can talk to the serial (USB) port. Last, the Arduino sketch has to be written so it can “catch” and process the message.

In this example, we’ll just create a barebones web page for controls that will turn an LED on and off via the Arduino. Let’s start with the sketch. The sketch is just listening on the serial connection for a 1 or 0. If it receives a 1 it will turn the LED on, if it receives a 0 it will turn the LED off.

Alex Glover
February 2013

void setup() {
//set the LED pin to OUTPUT
pinMode(13, OUTPUT);

void loop() {
//wait until the serial connection is open
while (Serial.available() ==0);

//read from the serial connection; the - '0' is to cast the values as the int and not the ASCII code
int val = - '0';

//print to the console for testing

//if we've recieved a '1', turn on the LED and print a message
Serial.println("Received a 1");
digitalWrite(13, HIGH);
//if we've recieved a '0', turn off the LED and print a message
Serial.println("Received a 0");
digitalWrite(13, LOW);

Pretty straightforward, right? OK, now we need two scripts, one to send a ‘1’ and one to send a ‘0’. In Windows, simply create a text file (call it whatever you want), and give it a .bat extension. In my setup, my files are called serial_out_0.bat and serial_out_1.bat. Each script has only one line of code.

ECHO 0 > COM3:


ECHO 1 > COM3:

Note that you might have to change the COM designation. You can check which COM your Arduino is connected to by looking in the Arduino IDE under Tools –> Serial Port. If you’re not using Windows, you should be able to do this pretty easily in a shell script. At this point you can test to see if the batch scripts will turn the LED off and on. Also ensure that the web server will be able to execute these scripts (don’t assign user-specific privileges or save them in protected directories). If you’re unsure, just put these scripts in the same web root directory where you’ll host your web page.

Easy right? Alright, the last piece is the web form. All you need are buttons within a form that will then execute the batch scripts we wrote earlier. Easiest solution is to use ‘submit’ buttons and then check for which post variables are set. The rest of the code is very straightforward so I’ll let it speak for itself.

if(isset($_POST[‘submitOn’])) {
else if(isset($_POST[‘submitOff’])) {
<form action=”control.php” method=”post”>
<input type=”submit” name=”submitOn” value=”Submit On”>
<input type=”submit” name=”submitOff” value=”Submit Off”>


You’ll have to change the paths to correspond with the location of your scripts, but otherwise that’s it. Add some CSS if you want to add some polish to your controls. This is a very simple example, but you should be able to adapt this code to any project.

Arduino Project 4: Tilt To Unlock

February 7, 2013 10 comments

This is my favorite Arduino project to date. After some basic experimenting with an accelerometer, I had an idea. What if you used the accelerometer to look for a combination of movements? Instead of using a combination lock or a traditional key lock, you could just tilt the object in a set pattern to unlock it. Here’s what I ended up with:

Pretty sweet if you ask me.

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WordPress: Twenty Eleven Child Theme with Galleria Slider

January 28, 2013 Leave a comment

OK – I’ve been spending the last few hours getting acquainted with the WordPress backend (that sounds more risque than I had intended) and making my first custom ‘child’ theme.

If you have an interest in making custom themes and you’re just getting started, I’ve got a few very generic tips:

  • Don’t underestimate how complex some of the themes and frameworks can be
  • Start by creating a child theme or modifying an existing theme
  • Check out this tutorial on PressCoders

The tutorial on PressCoders is very clear, so I won’t re-invent the wheel and write a tutorial on making child themes. Instead, I wanted to share the child theme that I made. Basically, I’ve taken the Twenty Eleven theme and replaced the static header image with a dynamic image slider (using Galleria). You can check out a live demo, otherwise here’s a quick screenshot:


Anyways, as simple as it is, I’ve learned a lot from the exercise. If you want to use the theme or take a look at the code, here’s the package.

Thanks for reading.

Arduino Project 3: Accelerometer Primer

January 21, 2013 2 comments

This project is more of a warm-up than a full-blown project. I wanted to get a feel for the basic workings of an accelerometer in preparation for a larger undertaking (no spoilers!). I borrowed this project idea from a forum about Arduino and accelerometers but can’t remember which forum, so I can’t credit back to the original poster – sorry about that.

Before we get to the how, let’s take a look at the what. Basically we have an accelerometer and 5 LEDs mounted on a breadboard. Four of the LEDs are mounted to correspond with the X and Y accelerometer axes and one LED is in the middle.   When the accelerometer is level, only the middle LED is illuminated. If you tilt the accelerometer to the side, the LED on that side is illuminated.

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Bootable USB with UNetbootin

January 14, 2013 Leave a comment

OK, so you have a netbook or ultrabook with no optical drive. Or maybe your optical drive is dead. Or maybe you’re smart enough to not use optical drives in general. Whatever the situation is, you want to run or install something from a bootable USB drive.

There are lots of solutions out there, but nothing beats the Universal Netboot Installer, or UNetbootin. UNetbootin has a simple GUI and never gives any grief. You can use your own ISO that you’ve downloaded or use one of the 42 ISOs UNetbootin provides, including BackTrack, CentOS, Ubuntu, as well as several rescue and recovery utilities.

Using UNetbootin is stupid easy. Grab a USB flash drive with enough storage to hold your ISO. Better yet – pick up a 16GB flash drive for $10 and it will be big enough to hold any ISO you could ever want. Got your USB flash drive? Let’s get started.

  1. Plug your USB flash drive into your computer. Note the drive assignment; in Windows, it will probably be D:\ or E:\, or some other letter. For the Unix users, your drive designation will probably be sda, sdb, sdc… sdx. Remember the drive assignment.
  2. Go to UNetbootin’s page and download the correct version for your OS.
  3. If you have a particular ISO you want to use, download it. Otherwise if you want to use one of the included ISOs, skip this step.
  4. Open UNetbootin. If you want to use one of the ISOs they provide, check the “Distribution” radio button and choose an ISO from the dropdown

    Thanks to UNetbootin for this image.

    If you want to use your own ISO, click the “Diskimage” radio button, click the browse button ” … ” and find your ISO that you downloaded.

  5. Change the drive to correspond with your USB flash drive. If you can’t find your drive, make sure it’s mounted and then restart UNetbootin.
  6. Click OK. If you chose a distribution provided by UNetbootin, it will take a fair amount of time to download the ISO before it can write to your USB drive. This is normal.
  7. Once the USB has been formatted and the ISO written to it, UNetbootin will restart your computer in an attempt to boot from the USB drive. If it doesn’t work, go into your BIOS settings and try changing the boot order.

Donezo. Hope you found this useful.

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