To put it simply, Jarvis consists of a remote control that tells the computer to open the door when pressed, the door controller that reads the RFID tags and send the information to the computer, and the computer that validates the RFID information, gets the remote’s messages, and sends a special ‘open the door’ message to the door controller when the remote button is pressed, or a valid RFID card is read. We even have the five last events on the website, so you can tell if any of your friends are in the hackerspace at the moment.

Yesterday, Jarvis was featured on Hack a Day, the most popular site for hardware and software hacks, MAKE/DIY projects. Suffice to say, we were all stunned! We even got some ideas on how to improve the system from the comments.

If you’d like to know more on how the system works, read the hackaday.com post and check out the project’s wiki. You can also

Anyone who has used high power LEDs to light a surface could tell you, these things need to be diffused, because the light isn’t distributed evenly to the surface and it looks like crap.

So I was sitting and trying to find something to diffuse the LEDs with, and then it hit me (ouch)! Rolling paper for cigarettes*! After some quick googling i found out that the thinnest one is the Rizla Silver brand, so I bought some from the 24/7 kiosk** down the corner, and voila! Awesome! You can see the difference below, but the photos really do it no justice. (coming soon, can’t upload the photos :P)

*Yes, you can buy rice paper at bookstores and get a much better price. But can you do that at 1.15am? Didn’t think so.
**περίπτερο

For those of you who have never heard of it, Growl is a notification system and framework for OS X. It’s highly configurable, yet easy to do so. The user can choose the notification style, the position of notification on the screen, set different notification styles and behavior for each program, etc. It’s even possible to have the notification emailed to you, or spoken out. It’s also the first notification system AFAIK, started back in 2004, which I believe was a really innovative idea at the time. Oh, and did i mention it’s open source too? And it’s no secret I love open source projects

One of the things I love most is how easy it is to use the framework as a developer. When I got accepted for GSoC 2010 to improve Pallet (a MacPorts GUI which is still in beta), adding Growl notification was amongst the first things i did, and it was so easy, even with my worthless Obj-C knowledge at that time, that I couldn’t believe it. When it came to developing Capster, it took me less than half an hour for the notification part.

Those of you who know Growl might have missed its companion app, Hardware Growler. hwGrowler (as we call it for short) is part of the Growl Extras, which include an iTunes Growl plugin, a command-line growl notification tool, a mail plugin (which is awesome and very, very useful*),  and of course, Harware Growler. It’s designed to run at the background and send you notifications for things like pluging a usb/firewire/bluetooth device, mounting a volume, connecting to a wifi network and networking in general (i.e. IP changes, ethernet cables geting unpluged, etc), power cord changes (on power, charging, on battery, on UPS) and device syncing using iSync.

Here’s what it looks like when you plug in the charging cable:

A plain Hardware Growler notification.

The reason I joined the Growl team was to improve Hardware Growler on a few places that bothered me. First of all, Hardware Growler had no reason for a Dock icon. It’s supposed to run on the background be forgotten. Therefore, I moved the icon to the status bar. I also removed the preference panel, since there was only one preference anyway (for now ;), and moved that preference to the statusbar icon menu. I’m also adding a second preference (which is disabled right now).

New Hardware Growler menu on the status bar.

Last, but not least, came notification coalescing. What is coalescing you say? The idea is simple enough. If a device disconnects and connects fast, the second notification will replace the first one on the screen. That way, instead of having both notifications shown at the same time, you’ll see the first notification, and when the second notification comes up, it replaces the first one. Imaging plugging and unplugging the power cord. Instead of this:

Old Hardware Growler. Notice the icon on the Dock and the two notifications.

You get this:

New Hardware Growler. Notice the status bar icon and the one notification.

There are also many exciting features we’re considering. Who knows, we may add so many features we’ll have to bring back the preference panel ;). I hope you’re as excited about this as I am (though I doubt it).

*The Growl team has recently stopped developping the GrowlMail plugin for Apple’s Mail.app, so it doesn’t come included in the extras anymore, but it’s been picked up as a personal project from Rudy Richter, who just so happens to be the Growl lead developer. You can download the last version here.

Update: I was informed by Rudy that the iTunes Plugin has been discontinued as a Growl project and picked up by him as well. You can get the source code on GitHub. There an iTunes Growl app though, called GrowlTunes, which is part of the Extras and essentially does the same thing. Check it out, t’s pretty neat!

First of all, I need to make a small introduction. Using the Stackable Headers from Sparkfun, I made it possible to add and stack shields to an Arduino Pro Mini, just like you would on a normal Arduino Uno. Here is a picture of an Arduino Pro Mini with the stackable headers:

Arduino Pro Mini with stackable headers

Using these headers, we can add shields/boards both on the top and below the Arduino Pro Mini board. It’s also much easier to program the Arduino Pro Mini using an FTDI Basic Breakout board, and you can easily add an XBee module on the Arduino with an XBee Explorer Regulated board if you want to (I do. all the time). Here’s another pic:

Arduino Pro Mini with XBee module

And now on to the good part. First of all, I made a relay shield because as I said, I use relays a lot! The shield includes all the circuitry needed to control a relay from one of the Arduino’s digital output pins. All the necessary headers to make it stackable are there, as well as the necessary components, relay and 2 screw terminals. I wanted to be able to select which digital I/O pin the relay would be connected to, so I’ve added a header to make it easy to connect the relay control (SEL) pin to any of the Arduino digital 2-9 pins using nothing more than a cable. I’ve also added a 0.1″ standard 2-pin Molex connector (you can also use a standard 0.1″ header if you want to make it more breadboard-friendly) to make it easy to power the Arduino with a regulated 5V power supply.

Relay Board. Notice the header on the left. It’s easy to set which pin controls the relay, by simply using a cable to short the SEL pin to the digital pin of your choice.

The 2 most common stuff someone will need to use an Arduino Pro Mini for are I/O and reading sensor values from the Analog In pins. So I made a digital I/O shield with space for 4 digital I/O slots, using the same header to select which Arduino pin you want to connect to each slot. In addition to the 2-pin connector for power, I’ve added 2 more 3-pin connectors (since there was unused space) so you can power it with 7-12V in the RAW pin.

I’ve brought out the GND rail as well, to be used both for Output (i.e. controlling a LED) as well as an input. For buttons and switches, you should use the internal pull-up resistor in the microprocessor and the GND rail to detect a button press (if the pin state is LOW, it’s pressed, if HIGH, it’s not pressed). That way you don’t even need any external resistors for your buttons. You can either use screw terminals, or the standard 0.1″ header to connect your I/O, and I’ve also added a 0.1″ 2-pin molex connector for each of the four I/Os. Of course, if you need more I/Os, all you need to do is stack another shield ;)

Digital I/O Shield. Notice the selection header and the 2-pin connector for each I/O.

In regards to Analog Input, the usual way to use them is to connect a sensor in series to a resistor in order to make a voltage divider (image taken from ladyada’s excellent tutorial on how to use photoresistors). So I made a board that you can use to make up to 4 voltage dividers. There are slots for each resistor, so that you can use any resistor value you want, and there is one connector for each of the sensors. There’s also a header for breadboard-friendly connectivity. Of course, the usual power connectors are still there :)

Analog Input Shield. Notice the resistor slots, and the 2-pin header for each sensor.

Of course, if you know me, you know I love open source stuff, so here are all the EAGLE files for all 3 of the boards.

I hope I’ve wet your appetite. If you’re hungry for more, here’s a video of me explaining each circuit, and showing how to stack them and connect them to the Arduino Pro Mini.

If you just want to take a look at some action, here’s a quick demo of the system in action with 2 relay shields and an I/O shield. You can get the code for the demo here.

Till then, take care, and take some vacations for yourself. They’re the best thing for unleashing your creativity :)

Long story short, a friend of mine and me wake up at my place after a long night of drinking, and start making coffee, and more specifically, the Greek favorite, Frappé. This includes shaking the coffee into a shaker, or using a device like this to stir the coffee. But the batteries were dead, and I had no replacements!!!!! We were left with 3 choices:

• Use the shaker. (No way! Did i mention the drinking?)
• Go out and buy some goddamn batteries (HELL NO! Hangover, you know?)
• Improvise! (Bingo!) √

What did I do? Easy. Everyone is always making fun of me saying ‘use an Arduino’ every time I have a problem. Well, this time I did. We take an Arduino, plug it in, take the 5V and Gnd pins, and connect them to the stiring-device-thingy (no idea what the official name is), and this is what you get. I like to think of myself as a moder Odysseus. lol, NOT.

But talk is cheap. Let me elaborate on the article. Basically, it focuses on Arduino (ofc), and how you can use it to control a lamp (or your entire house ;)) from a computer, setting automated scripts to take care of repetitive tasks, such as automatically turning on the lights, and more. I have also included an introduction to Arduino, since most people haven’t even heard of it, and I take care to describe every step in ridiculous detail so that everyone can keep up :) I hope it will inspire some people to try it, experiment with Arduino, and then come up with their own fabulous ideas :)

P.S. Speaking of fabulous ideas, for the next issue, I’m preparing an article on using Arduino and XBee to communicate wirelessly with a computer, and other Arduinos. You have no idea how awesome it can get ;)

As chance would have it, I was the only one left in charge of the arduinoproject.gr booth, since the 2 other guys who were supposed to come couldn’t. For those who don’t know, arduinoproject.gr is a work-in-progress in creating a Greek Arduino community, since we all know a lot of people interested in it (I personally know more than 50 people who are constantly asking me questions in our hackerspace, P-Space), and we felt the need to create a common place for everyone to ask questions, get help, and get in touch with each other. I was glad that a lot of people stopped by to ask about Arduino, most of them leaving with the impression that Arduino rocks, which, after all, is true :) I was also glad to meet a LOT of cool people, who are too many to be named here, and also had the chance to finally meet Eleftherios Kosmas, who is a great guy, and has a great blog regarding open source.

Last but not least, I finally made it to the melissi project’s presentation by Giorgos Logiotatidis, which was truly great, and I already have a lot of ideas on how to use his API, which we discussed with Giorgos. I wish him the best in his work, and who knows, I am even considering helping him :)

Now, that’s all for now, I gotta go prepare my presentation for tomorrow.

First things first, if you’re planning to organize a conference, don’t take it lightly. It’s a HUGE job, and if you decide to do so, do it with a team of awesome great guys, like we did this year. I can honestly say it was thanks to everyone’s hard work, passion, and determination that we managed to make everything work and overcome all the setbacks. I ‘d like to thank all of the co-organizers for not killing me while planning the conference. And a lot of thanks go to our volunteers from the Computer Center of the Computer Engineering and Informatics Department (University of Patras, Greece) and from the Patras Linux Users Group for helping out. We never could have done it with out you.

I’d also like to extend a big thank you to our sponsors, for giving us the ability to organize and host this conference, get the necessary equipment, and keep things running. And last but not least, thank you all for coming.

In regards to the conference itself, I was really glad that so many people attended, and I am still thrilled by the number of people who came to congratulate us for the good work, and the quality of the presentations. This only goes to show that the Greek FOSS community has a lot to offer. I personally loved being there, even in the heat of troubles, and I’m happy I had one more chance to meet new people, and get in touch with old friends. I hope next year’s FOSSCOMM will be even better, and I know I’m gonna enjoy it much more ;)

Recently, a friend of mine just commented on Capster, saying he prefers the Bezel notification. Could I support that as well, as a choice for the user? Well, sure thing, fella! See, the thing is, I don’t even have to. Growl has a lot of customization options, one of which is the display style. And on top of the general display type for all applications, you can customize the style per-application as well.

And guess what, one of those styles is Bezel. You can even configure it to play a sound when a specific notification is sent. It’s also faster in updating the notification when you press Caps Lock twice. So, in my opinion, Capster is better than CapSee* even in what CapSee does. Showing bezel notifications.

Personally, I also think it looks better. Take a look:

*Don’t get me wrong. I’m not saying CapSee is bad. I respect its developers, and I honestly love the idea. If it was open source, I would have submitted a patch instead of creating something similar to it, but I just thing Growl has so much power, it’s perfect for the job.