What you need

• A MindStorms NXT intelligent brick
• RobotC
• Paint.NET, a free image creation/ editing software which you’re going to use to create your image, with this plugin [LINK] installed. Don’t know how to install Paint.NET plugins? Refer to this page here [LINK].

Step 1: Creating or Importing your image

For creating your own image: open Paint.NET, click the “Image” menu, and then open the “Canvas size…” option. In the wizard, specify any image size, up to 100 pixels wide and 64 pixels high. Then use the pencil or any of the other tools to create your image.

For importing an image: open Paint.NET, click “open,” navigate to the desired image, and double click it. Then, go to the “Image” menu, open the “Image size…” option, and, in the wizard, specify any image size, up to 100 pixels wide and 65 pixels high.

Step 2: Making your image black and white

First, open the “Adjustments” menu and click “Black and White.” Then, again in the “Adjustments” menu, open “Brightness/ Contrast,” and, in the wizard that pops up, set the contrast to 100.

You can play around with the brightness to change how dark a color needs to be to become black, and how light a color needs to be to end up white. Once you’re satisfied with your results, hit the “OK” button and your image is ready for the next step.

Step 3: Saving your image

Open the “File” menu and click “Save as…”. You can save your image under any name, anywhere, as long as you make sure you select “Portable Bit Map Files (*.pbm)” from the “Save as Type” drop down menu. If this option is not available, you didn’t install the plugin right, so re-install it and try again. Click image to enlarge.

Step 4: Reformatting your image’s code

Next up, you need to turn the image you just created into something the NXT can actually use. Go to the folder you saved your image in, right click the picture, and hit “Edit with Notepad++”. In the code you end up with, remove everything before the 1′s and 0′s (usually the top two lines).

Then, hit ctrl and f on your keyboard to open the “Find” wizard. The next steps are very important, so pay close attention:

1. In the wizard, go to the second tab, which should say “Replace”
2. In the “find what” box, type ” ” [hit the space bar once], and in the “Replace with” box, type nothing. Hit “Replace all.”
3. In the “find what” box, type “1″, and in the “Replace with” box, type “1,”. Hit “Replace all.”
4. In the “find what” box, type “0″, and in the “Replace with” box, type “0,”. Hit “Replace all.”
5. Finally, turn the code into a single line by going to the end of every line of code and hitting delete

Step 5: Displaying the image on your NXT

First of all, copy this code into your program somewhere:

int i, j;
int image[HEIGHT][WIDTH] = {PUT 1'S AND 0'S HERE};
for(i=0; i<HEIGHT; ++){
  for(j=0; j<WIDTH; j++){
    if(image[i][j] == 0){
      nxtSetPixel(j,-i+HEIGHT-1);
    }
  }
}

Replace “WIDTH” with the width of your image, “HEIGHT” with the height of your image, and “PUT 1′S AND 0′S HERE” with your image code (copy and paste it between the curly brackets).

And there you have it: you can now display any image you want on your NXT screen using RobotC and some freeware

It’s got three motors, one color sensor to show what it’s doing, and a touch sensor for calibration. Also, I bundled all three motor cables together for the first time, which actually improved the robot’s performance a lot more than I initially expected it to. Moving on, here are the power paths (how the motors’ power goes to the place it needs to go to) for all three motors, seen from the bottom of the moving printer head:

• Green: This motor drives the Y axis of the printer using the two  small outer gears as wheels on a track of gear racks
• Blue: This motor drives the X axis of the printer by, after quite a lot of gears, spinning an extended worm wheel hooked up to a single gear rack. When the axle spins, the gear rack goes from side to side, pulling the pen along with it
• Orange: This motor makes the pen go up and down. Again, after a lot of gears, it drives a big rod up and down, pulling the pen along with it.

So yeah, there you have it. I’ll start programming it ASAP. Follow me on Google Plus (+Leon Overweel) for progress updates on that, and much more interesting stuff.

More coming soon!

So, here’s a link to my profile:

https://plus.google.com/106671218963420759042/posts

Add me to your circles for updates!

Basically, I’m building a printer out of Mindstorms NXT (hence the name, “PriNXT”). I know it’s probably been done before, so I’ve purposely not gone looking for how other people did it – I wanted this to be more of a challenge. And, so far, a challenge it has been. I’m pretty sure that it’s the most complex build I’ve done yet, mainly because I had to fit three motors, a bunch of gears, three long wires, and support beams all into a restricted place that has to be able to move around freely; it also can’t rest on the paper it’s printing on, so all the weight had to be distributed to the sides. I’m not going to try to explain how I got it working until I shoot some nice closeups of it, so there will be a whole post dedicated to PriNXT’s hardware sometime later this week.

Now, here’s a list of things: (very descriptive name for a list, I know)

• I’m going to try to write a basic text editing program in RobotC, so you can “type” something on one NXT and then transfer it to PriNXT to get it printed. That would probably use Bluetooth.
• I’m considering to add functions for underlining text, making it bold, and even italicizing it.
• The color scheme for PriNXT itself: White, light gray, dark gray and red.

In other news: I made a Technic camera jib for my iPhone, which, combined with the video editing software I got for Christmas, will make for some nice footage in the video for PriNXT.

Views per day; graph provided by the goo.gl (see link below)

As of today, the robot has been driven more than 700 times, with an average connection time of about 4 minutes! It’s been used from countries all over the world, including the US, Canada, Australia, Germany, Denmark, Spain, Hong Kong, Ireland, Belgium, South Korea, Bazil, the UK, Malaysia, Puerto Rico, Taiwan, Mexico, France, Switzerland, Iceland, India, and many more. The most popular OS was Windows, followed by Mac, and the most popular browsers were Chrome and Firefox.

If that’s not enough for you, you can hit the goo.gl stats link right here for lotsa more juicy numbers: http://goo.gl/info/7LLaU#all_time

A lot of stuff has been going on around this project, so here’s a timeline with all the highlights:

• 1/4/2012: Project launch, with a post here, a video on YouTube, and posts on the MindBOARDS and RobotC forums;
• 1/6/2012: Took the robot offline for the night and better part of the day to solve an issue with the battery’s wire getting tangled and ripping the robot apart – went wireless.
• 1/7/2012: Featured on the NXT STEP;
• 1/7/2012: Got asked to become a contributor on the RobotC blog and wrote my first post a few days later;
• 1/9/2012: Featured on the Make Magazine blog;
• 1/10/2012: Featured on Engadget! reblogged a load from there;
• 1/12/2012: Featured on first international website (great article, too);
• 1/13/2012: Got a YouTube PM from a tech writer for M3, Sweden’s largest gadget magazine, who asked me for HQ photos of my Skype car for their next print issue!

I also had a blast looking at what people thought of my robot, and even messaging with random people who had tried it out – one was a dad, who showing his son what Mindstorms NXT was all about (which was exactly what this project was for), and another one asked me if this was my bachelor project (it’s not), just to name two.

So yeah I hope you all liked it and expect more stuff soon – I’ve got an awesome sensor coming my way.

PS: I’m thinking about entering it into the Google Science Fair. Good idea?

Some of you might have noticed that my Skype car has been offline since last night. Why, you wonder? I was trying to solve the issue with the wire tangling around the robot all the time – first, I tried putting it on a high pole, but that just made it worse. Then I remembered an amazing Mindstorms NXT robot I once read about: Pulito, a floor cleaning robot that could look for its own power source using infrared light, and then plug itself in.

Since I do not have any equipment to read infrared light, I had to find another way for the robot to plug in. Here’s what I did:

• Because the environment my robot was in was way more controllable (a square lined with cardboard boxes), I decided to use the sonar sensor, and make the robot follow the walls.
• I then made a gap in one part of the wall, so the robot wouldn’t know where the corner was. That causes it to just keep on driving forwards, until it hit the wall on the other side.
• This is where I got lucky: when I ordered the charger for my new battery, I got the wrong one (the one for the other kind of battery, which was hooked up to my other NXT). Having a spare one, I decided to cut it in half:

• So when the car hits the wall, it’ll automatically start charging
• For the programming, I added some code for the ultrasonic sensor and the touch sensors, and wrote some sequences to happen when the robot needs to start charging, and when it’s done.

To read more about my Skype car, click here.

Disclaimer: The Skype name, associated trade marks and logos, the Skype “Call Me” button and the “S” logo are trade marks of Skype.

Today was the first day my robot was online, and, as with any project, problems came up:

• The wire got tangled
• People didn’t know how to shut the robot off properly (which is probably why other people weren’t able to connect)
• The ball caster came off

These are some changes I made:

• I added a long, flexible rod to the back of the car to hold up the wire, so it’s less likely to drive over it too easily. This should also help against the caster issue, because it mostly came off because the wire was pulling it
• I put some extra protection around the caster, to make it less likely to come off
• Towards the bottom of the page with the arrows, you can now read about how to shut the robot down, so people won’t do it wrong anymore
• In case they do, an alarm will now sound if the robot has been driving in the same direction for longer than 60 seconds.

So thanks for the feedback everybody, and I’ll keep on improving this thing further. To see the changes, go to http://www.goo.gl/7LLaU (you might need to refresh your page).

To read more about my Skype car, click here.

Disclaimer: The Skype name, associated trade marks and logos, the Skype “Call Me” button and the “S” logo are trade marks of Skype.

If you want to get going right away, here is the link for driving this car: http://www.goo.gl/7LLaU.

This is going to be a pretty lengthy post, so I’ve broken it up into the following categories: Introduction/ General Explanation, Hardware, Program-ming, Computer Tweaks, and How YOU Can Drive This Car. Click any of the categories to jump forward to it.

Introduction/ General Explanation

I’ve been creating websites for a while now, and I was trying to think of a way to combine it with Mindstorms NXT, and this project is the result of that. The webpage is fairly simple – it’s got three arrows (one forward, two to the sides) and a start and a stop button. Clicking the start arrow will begin a Skype conversation with my computer, after which the user should share their screen; the NXT standing in front of my computer (called “Jeeves”) can then “see” the webpage the user is viewing.

That’s where the cool part kicks in – when the user clicks any one of the arrows or the stop button, the page will change to a different shade of gray. This shade of gray is then picked up by Jeeves, who turns it into a Bluetooth message for the other NXT (called “Alfred”). The car then drives in the direction the user tells it to, while remaining within a fenced off area where the webcam can see it.

So, the user can drive a LEGO Mindstorms NXT car, from the comfort of his or her home, without having to install any kind of software (provided that they have Skype).

Hardware – the Car

The car was fairly simple to build – it’s got two motors on the sides with the wheels attached directly (no gears), and a big ball caster attached at the back. It looks quite a bit like my line follower, actually, except for the fact that the caster is a lot bigger because the car needs to be able to drive over the power cable and because it’s on a carpet. Also, it’s got front bumpers so you all can’t break anything while driving it, a color sensor that turns on when the robot is in use, or has been in use the past minute, and a rechargeable battery that’s always plugged in. Some pictures:

The first one is a side view, and the second one is an upside down view.

Hardware – the Receiver

The receiver was a bit more tricky to build because it needed to be a specific height so its light sensor could “see” the right area of the user’s screen. The structure itself is fairly simple – the light sensor is on a big pole attached to the NXT, and it’s got a rechargeable battery that’s always plugged in at the bottom. Here’s a picture of it (without the battery; hence the delay):

Programming

For all of the coding in this project, I’ll provide a basic description of how it works, and then a download link in case you’re interested in trying to build this project yourself sometime. The first two pieces of code (for the car and the receiver) were made using RobotC, and the third (for the website) is in HTML. All of the code will be on Sourceforge.

Programming – the Car

There’s a small function for turning the motors’ PID control on or off  at the beginning of the program to get rid of the peeping noise the motors make when the car is not moving.

In the main task, here’s what happens: the variables are created, the Bluetooth is turned on, and the timer is cleared. In the main while-loop, the last received message is stored, so the robot can later use that information( along with the timer) determine whether it’s been active the last minute and decide to turn the signal light on or off. Then, the robot reads the message last sent to it and plugs it into a switch. Depending on which message it received from the receiver (ah, the irony), it will move the motors. At the end of the while loop, there is a 50 millisecond wait to save battery power.

Click here for the code (first version).

UPDATE: Since the robot is now wireless, the code has changed to support some more sensors for plugging itself in. Read more about these changes here:

http://wp.me/p10flW-l9.

Click here for the code (second version w/ wireless charging capabilities).

Programming – the Receiver

The receiver also starts by initializing its variables and turning on Bluetooth, after which it connects itself with the other NXT – also using Bluetooth. The program then enters its main while loop, in which there is a series of if/ else switches designed to determine what shade of gray the screen is. The if/ else switches then plug this message into the “messageToSend” variable, which is sent out afterwards. The loop ends with a 100 millisecond wait, again to preserve battery.

Click here for the code.

Programming – the Website

There isn’t really much to explain about this one, so I’ll just give you the download link. Please note that the images on the page aren’t included, so you won’t be able to view it correctly in your browser. Screenshot below.

Click here for the code.

Computer Tweaks

There were quite a few tweaks I had to make to my computer, so I decided to list them here in case, again, you want to build this project yourself someday. Keep in mind that I might be missing/ forgetting some things, so if you ever have a problem just leave a comment below.

• Turned off sleeping mode on both my screen and the computer itself;
• Skype:  in the general > video settings menu, I changed the first option (“Automatically receive video and screen sharing from…”) to “anyone”;
• Skype: in the privacy > privacy settings menu, I changed everything to anyone. I also checked all the boxes;
• Skype: in the calls > call settings menu, I changed “Allow calls from…” to “anyone”, and again checked all the boxes;
• Skype: in the IM & SMS > IM settings menu, I changed “Allow IMs from…” to “anyone”;

I’m also keeping the Skype window open 24/7, so my background won’t confuse the light sensor.

How YOU Can Drive This Car

Here’s how:

• Go to http://www.goo.gl/7LLaU
• Make sure your window is maximized
• Click the “Start” button
• Go through the dialog windows you get (there will be more on IE and Firefox than on Google Chrome)
• Wait for my video to start (this can take up to 20 seconds)
• Open the “call menu” at the top bar
• Click “Share Your Screen” – it’s about 3/4th of the way down the menu
• Click “Share Full Screen”
• You should now be brought back to the webpage with the arrows. Once you see the car stop, use the arrows to drive it around.
• To stop, hover your mouse over the little screen where you see the car, and click the red phone button

This project has successfully been tested on the following operating systems:

• Windows 7

With the following browsers (newest version as of 12/31/2011):

• Google Chrome (tested best)
• Firefox
• Internet Explorer

Conclusion

So there you have it: a LEGO Mindstorms NXT car that you can drive using Skype. If you like this project and want to see more, subscribe to my YouTube page and this blog for the latest updates. Once this project ends, I’ll put some statistics on how many people tried this project up down here. Feel free to use anything on this page (the robots, the code, the website, etc.) non-commercially, as long as you give credit where it’s due.

To read more about my Skype car, click here.

Disclaimer: The Skype name, associated trade marks and logos, the Skype “Call Me” button and the “S” logo are trade marks of Skype.

So, if I’m really, really lucky, I’ll still be able to launch before school starts (read: before January 3rd), but otherwise it’ll probably be the weekend after. To leave on a more positive note, here is a little spoiler:

There is a webcam involved.

UPDATE: I checked the FedEx tracking system thing and the charger should be here Tuesday January the 3rd. I have everything (the post, the movie, etc.) finished, so I’ll launch it January 4th.

I know I haven’t posted anything lately (sorry), but worry-you-not — I’m finishing something very exciting right now, and I think it’ll will be up and running by the end of the year.

In other news, you might’ve noticed that my blog’s url has changed to worldofmindstorms.com, instead of the old dimastero.wordpress.com. Why? Because ‘dimastero’ doesn’t relate to MindStorms NXT in any way, and because I think the url looks better this way. Again, worry-you-not: all the old links to specific posts and pages still work (thx WP!).

So, once again, merry christmas and a happy new year!