Electronics

Electric Longboards and Adrenaline Rushes

Electric Longboards and Adrenaline Rushes

  1. Why pursue this madness?
  2. The parts
  3. Putting it all together
  4. The results
The final board

A side shot of the final board.

 

Why pursue this madness?

Like many of my projects, it all started when I stumbled upon something interesting on the internet. In this case it was a video of the Board of Imagination. Now, a mind controlled skateboard is pretty cool, and arguably the main point of interest in that project. But it was the motorization of the board that really captivated me. Motorizing skateboards is really nothing new, in fact the use of a normal DC motor and gears in the Board of Imagination is pretty old school. It’s essentially all Brushless DC motors (BLDC) and timing belts now. There are also entire communities built around achieving and refining the goal of motorized anything. And it was that little bit of research that did me in. I no longer just wanted one; I needed one.

I spent a lot of time working out the logistics of motorizing a longboard, and explored all of the options. There was the expensive but very slick looking LaGrange L1 truck. The pretty venerable looking Alien Drive System and Alien Power System combo. Last of all, there was the very sturdy looking one piece Paris truck with welded on motor mount provided at http://diyelectricskateboard.com/. The DIY Electric Skateboard kit looked to be the newest kid on the block, and didn’t really have as much in the way of reviews. But it looked like it was the most approachable in terms of repairs and tinkering, and that’s what sold me on it. Or on the design at least.

Originally my plan had been to weld a similarly styled, but self designed and fabricated motor mount to a set of Paris Trucks. I knew the equipment at Protospace (the local makerspace) was capable of it, but I lacked the skill set to use any of those tools. It became obvious to me that I would need to simply buy the pre-made trucks if I wanted to have my board running before the end of summer. It was a good call, because with that part of the project taken care of, the rest of it quickly progressed, and I now have a functioning motorized longboard.

But enough talking, lets look at the process of building such a toy. Seriously though, this board has an insane amount of power. It can accelerate way too fast and reach a top speed well above my current comfort level of about 30km/h. Don’t treat it like a toy.    

 

The parts:

  1.  A longboard deck. I used the Earthwing Big Hoopty. It’s a super solid and awesome board at an easy $107 from a local board shop.
  2. The trucks and drive mechanism from DIYelectricskateboard.com.
  3. Some bearings, as they don’t come with the DIY Electric kit.
  4. A brushless DC motor.
  5. An Electronic Speed Controller to run the motor. I took a risk on this Boat ESC. The braking is a little soft, but it runs well, barely gets warm even without proper cooling, and doesn’t make excess noise.
  6. At least one battery pack. A 5000 mAh 6S (22.2V) provides plenty of speed and power. I used two 3S batteries in series to make a 6S battery with a lower profile. 
  7. A receiver and transmitter of some sort. I used the all too common Quanum (nope, not a typo) pistol grip combo.
  8. RC connectors. I used HXT4mm to be consistent with the existing connectors.
  9. Some way to attach the parts to the deck. I used industrial strength Velcro tape.
  10. Some way to shield the LiPo batteries from damage by debris. I tried using ABS, gave up, and resorted to a box made from 22 gauge galvanized steel sheet.

 

Putting it all together:

The process of putting together isn’t all that difficult. With the step requiring the welding of a motor mount to a truck eliminated, the most difficult part was definitely the construction of the battery shield. But we get ahead of ourselves. Lets start with the deck and trucks.
IMG_2460

The longboard deck with trucks and wheels attached.

The first step of mounting the trucks is very straight forward. If you have ever assembled a normal skateboard or longboard before, then you already know what to do. For those who haven’t put together a board, I’ll cover the basics. The easiest place to start is inserting the bearing into the ABEC 11 Flywheel clones. This is just a matter of putting one bearing onto the axle, then pressing the wheel down onto it. Repeat this process for each side of each wheel. Once the wheels are set up, you can fasten them to the trucks with the appropriate nut. Ensure the wheel with the plastic timing belt pulley goes on the correct side of the truck with the motor mount. Tighten the nuts just enough to remove any play along the axle. Finally, you can bolt the trucks to the long board deck. This is very straight forward, you just need to use provided bolts and nylon lock nuts, and ensure that the kingpin is facing outward.

IMG_2461

The motor pulley. Note the two holes for set screws.

With the basic hardware mounted, we can set up the motor too. Notice that the provided timing belt pulley for the motor has two bolts to tighten it to the motor shaft. It’s very helpful to have a couple  of flat spots on the motor shaft for these bolts to fasten against.

IMG_2462

The brushless DC motor shaft has been dremeled down to make flat spots for the set screws.

I achieved this by using a Dremel tool with a carbide bit. I recommend that you punch the motor shaft through a piece of paper towel before grinding the flat spots in, as the metal filings are going to be magnetized and get stuck to the shaft. The paper towel allows you to easily wipe them all away.

IMG_2464

The BLDC motor has been attached to the mounting bracket. It’s still loose enough to slide in the slots.

Attaching the motor pulley is pretty easy, but first we need to losely fit the motor to the motor mount. You want to attach the motor so that it’s flush with the motor mount, but still just lose enough to slide in the slots. We need it loose to tension the motor after we put the pulleys and belt on. The motor pulley is really easy. Just line the bolts up with the Dremelled down spots and tighten them using an Allen Key.  Once that is done, the timing belt can be added. If everything is still a little lose, then it will be as simple as just slipping it over the wheel and then the motor pulley.

IMG_2465

The belt is now in place and ready for tensioning.

Finally, we need to tension the belt. This is achieved by pulling the motor along the mount until the belt is firm, but not excessively tight, then tightening the four M4 socket head bolts that hold the motor to the mount. This is also not a bad time to adjust the tightness of the bushings on the trucks (the plasticy coloured parts on the kingpin). Just loosen them until you find it steers well, but without any contact between the wheels and the board.

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The belt has been pulled taught and the motor has been tightened onto the mounting bracket.

And that’s it for the Mechanical side of things. Next up is the electronics and the protective shield for the electronics.

IMG_2467

The ESC has had the connectors soldered on and is plugged into the motor.

The electronics are also pretty straight forward. For the most part it is all just plug and play, with the exception of the ESC, which requires one to solder on the connector of their choice. Since everything else I ordered is using the HXT4 mm bullet connectors, I simply stuck with those. I hacked three of them apart to create three stand alone female connectors for the motor, and used a full one for the power connection. It’s important to make sure you get the polarity right, so match up the wire colours with one of the batteries to be sure you solder it on the right way. The insulation on the wire is also too large for the red plastic housing, so I stripped it back a little bit to solder the connector on before putting it back in place and taping the insulation back up. I used tape because I forgot to put some heat shrink tubing on before the connector. Don’t make the same silly mistake, and remember the heat shrink tubing!

Now it’s just a matter of plugging everything together and attaching it to the bottom of the board. I hooked everything together and made sure the motor worked first, then I set to work planning the layout of the components on the underside of the board. Once I was satisfied I used the industrial strength adhesive Velcro tape to hold everything in place. It has a 2 inch width which is exactly the right width for the ESC and batteries. At this point the board is technically ridable, but LiPo batteries have a reputation for being a little “explodey” if they are damaged, so I wanted to play it safe and put a shield of sorts over them.

DSCF0230

The failed ABS plastic shield. ABS is a finicky material.

Building the shield was the hardest and most frustrating part. I had originally planned to construct it out of .25″ ABS sheet, but that failed spectacularly. Apparently ABS plastic is renowned for its tendency to warp as it cools (it’s why 3D printers using ABS need heated base plates), and may not be the ideal material to learn on the fly without prior experience. I tried to make it work with just a heat gun, but that wasn’t going to work, so I resorted to slump forming the sheet in an oven.That also didn’t work. ABS is a pain, it’s no wonder it is usually moulded to a form using a vacuum.

After the failure of the ABS shield, I decided to try my hand at making a box out of sheet metal. I was able to get 8 inch wide 22 gauge galvanized steel from the local Home Depot, and I figured that I could pick up the sheet metal skill set a lot more easily.

SCAN0002a

The front panel that faces the direction of motion.

SCAN0001a

The main body of the sheet metal shield.

I designed a pattern, and cut it out of the sheet using some straight snips. Unfortunately my 8 inch wide sheet wasn’t wide enough to construct the box as a single piece as I had hoped, but I figured I could compensate  by making the forward facing panel separately, and attaching it to the rest of the box with flat lock seams. I didn’t even bother soldering the pieces together.

IMG_2488

The front panel cut out of the sheet metal.

IMG_2485

Bending the main body of the box into shape.

For the most part it worked. The shield isn’t beautiful, but it is sturdy. The front panel rattles a little on rough roads, but I can’t see any circumstances in which it would fall off. In retrospect, a 22 gauge steel box is probably overkill as far as shielding goes, but there’s also some risk of the metal causing a short if it didn’t stand up to an impact, so over kill is probably good in this case.

IMG_2491

The finished box. It’s not going to win any competitions, but it will protect the batteries.


With the box complete, I drilled some holes in the base flanges, and then drilled some corresponding holes in the longboard deck when I had everything centred. Using 1.5″ long flat head bolts and some matching wing nuts I can easily replace and remove the shield as needed.

IMG_2493

The holes drilled in the flanges so the box can be attached to the longboard deck.

DSCF0229

The longboard deck has corresponding holes with bolts and wing nuts. Some foam has been added to the shield to cushion the batteries.

DSCF0228

The finished shield firmly bolted to the underside of the deck.

The results:

The final product of all this labour is an adrenaline rush. I’ve never taken a longboard downhill, so I really don’t have a taste for the high speed longboarding some people are accustomed to. But that’s okay because it means that I get a nice pleasant adrenaline rush when I manage to get this board above 30km/h .

Forgive the poor quality of the video, I lack a GoPro, so I had to film it with my phone. This also had the side effect that I didn’t really want to get up to speed, it’s nerve racking enough already without the additional filmography concerns.

In general, the acceleration has a ton of punch and the brakes are quite soft, especially at lower speeds. At higher speeds they work a lot better, and will certainly get you down to a speed at which you can toe drag to slow down. If you’re going down a really steep hill you may find that the brakes are too weak to prevent the acceleration due to gravity, so act accordingly. If that means toe dragging the whole way or walking the board down the hill, then do it. It also helps to reprogram the ESC to fit your riding style. You can find the instructions here: http://www.hobbyking.com/hobbyking/store/uploads/842133110X337002X22.pdf

I ended up keeping all the defaults except the startup acceleration, which I set to 9 levels. This makes the acceleration a lot smoother, so you’re less likely to over do it and fall over backwards as the board rockets forward.

Posted by Everett in Electronics, Kits, 4 comments
Experimenting with EL wire: A Stickfigure Costume

Experimenting with EL wire: A Stickfigure Costume

IMG_2396

Like most people on the internet, I saw this video leading up to this year’s Halloween. Unlike most people, I thought “I need to make one of those, but adult male sized!” A quick bit of research led me to realize that normal LED light strips as used in the video are a little impractical for a suit my size. They cost more than 4x as much per unit length compared to High brightness EL Wire and they appear to consume far more power as well. Not wanting to carry piles of spare batteries around when I go out for Halloween, I decided to use EL wire and settle for the few tradeoffs it has. The most major tradeoff is that EL wire doesn’t hold up as well to repeated flex in the joints or tight bends. I may regret the choice to use EL wire if it fails on the dance floor, but for now it seems like the smarter choice.

. . . . .

The Parts:

IMG_2369

. . . . .

The Basic Design:

SuitLayout

The suit consists of five separate strands of EL wire of varying lengths all connected to the inverter and power source. The hood of the suit is held into a circular shape using an aluminium ring that was salvaged from an old tomato cage. The inverter and battery pack is crammed into a small reusable container that has been cut up and modified to house the components.

ElectronicsBox

. . . . .

Preparing the Electronics:

The strands of EL wire that I purchased both come with jumpers preinstalled, but since I needed five separate strands it was necessary to cut off the extra strands from the ends and manually solder new connections to them. There were three of these new strands to be soldered using the male in-line connectors. A few images of my soldering efforts are included, but the adafruit guide to soldering EL wire is far superior to anything I could reproduce here.

IMG_2387 IMG_2390

After cutting the EL wire to size and soldering on the jumpers it was time to prepare some of the other wiring essentials, like a Y shaped extension cable for the arms. This was done by simply cutting the female end of the in-line extension cord off, and then resoldering it with a the second female connector attached. The junction was then sealed up tight with a little heat shrink tubing that I slid on before I soldered everything.

IMG_2391

And finally, as far as the electronics are concerned, all that needs to be done is assemble the power supply and inverter box. The box, contrary to my measurements, unfortunately didn’t quite fit the battery pack and inverter. To fix this I decided to modify the box with a little lighter and X-acto knife surgery.  After that, it was necessary to drill a hole for the toggle switch I planned to install. Technically I drilled the hole in the wrong place originally, and had to drill a second one. It’s not a mistake, just ventilation!

IMG_2372 IMG_2373

After getting the box ready to house the electronics, it was time to get soldering again. The connections are all really simple, I just soldered the two black leads together and then protected the joint with some more heat shrink tubing. After that the red leads were connected to the two terminals of the toggle switch I harvested from something too long ago to remember what it was. Once again, the connections were wrapped up tight with heat shrink tubing and then for good measure I placed a small bead of hot glue between them.

IMG_2382

With the soldering done, I just had to fit it all into my box. This was really just as simple as screwing the nut onto the threaded bit of the toggle switch after sticking it through the hole that I had drilled, then squeezing the battery pack and inverter into there. Everything fits so snug that I didn’t need to do any fastening of the components to the inside of the box. Lucky me.

IMG_2375 IMG_2383

. . . . .

Attaching it to the Clothes:

Okay so the electronics are done, and everything glows nicely. Now we jut need to sew it to the clothing. But before that, I decided I wanted a nice round stick person head. To achieve this I went and pulled a nice firm aluminium  ring from an old tomato cage then stuck it through the drawstring part of the hood.

IMG_2384 IMG_2385

To sew the EL wire on I used transparent thread, but that’s really just a fancy marketing gimmick used to sell 6 lb fishing line to the sewing demographic. I used a very simple rib stitch that wrapped around the EL wire then through the fabric over and over again. After this was done I decided to ensure the EL wire stayed put by further tacking it on using a few blobs of strategically placed hot glue. It’s okay, no one will notice in the dark.

I then started to sew on one of the arms, but due to my generally incompetent sewing skills, it failed to hold the EL wire in place after repeated movement. A little fed up, I resorted to the hot glue gun again. By putting little beads in places where the EL wire wasn’t moving too much and leaving high movement areas like the joints free I managed to get a solution that holds the EL wire onto the clothing well while still maintaining a good degree of freedom of movement. I repeated this process for the other arm and both legs, with the added benefit that it is much faster than sewing.

IMG_2394

All that remained to be done at this point is to hook up the EL wire to the power box. This is where the 1 to 4 splitter comes in handy to connect to the torso/head, two legs, and the Y extension to the arms. All of this wiring is hidden inside the hoodie and threaded through a hole on the inside of the front pouch pocket where I’ve hidden the power box.  That’s really all there is to it, and the costume is ready to go for Halloween.

IMG_2395

Posted by Everett in Electronics, 0 comments
Arduino: Super Graphing Data Logger

Arduino: Super Graphing Data Logger

The intensity of natural light in my basement.
Sections:

  1. Introduction
  2. The Results
  3. How to Make One For Yourself

Introduction

What is the Super Graphing Data Logger (SGDL)? It is an Arduino project that integrates data logging and the graphing of this data online using little more than an Arduino with the appropriate shields and sensors.   It differs from similar projects in that it doesn’t require a separate server or system to collect the data or to run script for the actual plot. Between the Arduino and the user’s browser, everything is taken care of.

If you just want to dive right in, the code is now posted on GitHub: https://github.com/evjrob/super-graphing-data-logger

Some time back I came across this neat javaScript based library for plotting and graphing called Highcharts JS. It didn’t take long for me to realize that charting with javaScript is very convenient for projects in which the server is limited in it’s capabilities, such as when using an Arduino with the Ethernet shield. Since the user’s browser does all the heavy lifting, the Arduino only needs to serve the files which is something it is perfectly capable of. This is especially true now that the Ethernet and SD libraries included in 1.0 support opening of multiple files simultaneously amongst other things. Thus the use of Highcharts allows us to create beautiful interactive charts based on data logged by the Arduino using nothing but the Arduino (and your browser, and a public javaScript CDN).

The Results

The best way to appreciate the final product is to actually play with it. While I’m not going to open up my home network and Arduino to the big wide internet, I have mirrored the pages and datafiles it produces on the webhost I used for my Has the World Ended Yet? project. You can find them here. These won’t be updated with new datapoints like the actual Arduino version will be, but they should at least give a fair impression of how the project looks and feels without the need to actually implement it.

For those who are unsure what they are looking at, I’ll offer a quick interpretation:

The list of data files available for graphing.

The list of data files available for graphing.

Going to the above page, we see that we are presented with a very basic list of the data files that can be selected from. Clicking any of them will cause  the graph for that datafile to be loaded (much more quickly than the Arduino can manage).

A graph for the first week of data collected.

A graph for the first week of data collected.

This chart for the 25-12-12.CSV file is already complete, and won’t have any new data added to it in the future, because the files for subsequent weeks have already been made. There is a lot to see though. The two data points that are at 1000 on the y-axis are from when I pointed a bright flashlight directly at the photo sensor. All of the data points between 300 and 400 on the y-axis are the result of the basement lights being on. The abnormally large gaps in the data are periods when the Arduino was powered off because I was still tweaking and developing it. Finally, the short humps that occur everyday are the result of natural light coming through one of the basement windows. By zooming in on one of them, we can see even more detail:

The intensity of natural light in my basement.

The intensity of natural light in my basement.

The first thing we notice is that the levels rise from zero to about 65 before falling and levelling out at close to 35 for two hours. This is followed by a another small increase before it ultimately decreases down to a value of ~10 where it levels out. That middle valley where the light levels are equal to 35 is due to the shadow cast  on the basement window by our neighbour’s house to the south of us. The levelling out of the light intensity at 10 after all the daylight has disappeared is because a light out in the hallway is usually on in the evening. It is eventually turned off for the night, causing the light levels to drop to zero where they will usually remain until the next morning. I must admit, I’m impressed that the cheap $1.00 photoresistor is capable of capturing this level of detail, and that these trends are so easily interpreted from the graphs.

How to Make One For Yourself

All of the code below is now conveniently hosted on GitHub (https://github.com/evjrob/super-graphing-data-logger) so you no longer need to copy and paste it if you don’t want to.

To replicate this project, a few things are necessary. You’ll obviously need an Arduino capable of connecting over Ethernet and storing files on an SD card. In my case, this is achieved through the use of an Uno with the Ethernet shield. Presumably an Arduino Ethernet model will also work fine, though I have not personally tested it. Other non official Ethernet shields and SD card adapters may also work if they use the same libraries, though I make no guarantees. For the more adventurous, it may be possible to adapt my code to achieve the same functionality using a Wifi shield. You will also need a data source of some sort. For my project I chose to use a very cheap photoresistor, which I rigged up on a small perf board to plug directly into the 5v, gnd, and A0 pins of my Arduino (or more precisely,  the headers on the Ethernet shield). It is set up in such a way that the minimum recordable light intensity is zero, while the maximum is 1024.

The photo sensor board fits like a charm.

The photo sensor board fits like a charm.

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One header is bent to reach A0.

The pins on the male headers don’t quite line up, so I intentionally used extra long ones and added a slight S-curve to the one that goes to A0. This can be seen in better detail above. For those who are interested, the circuit is very simple:

The circuit.

The circuit.

Before we get started, we need to make sure our SD card is good to go. It should be formatted as a FAT16 or FAT32 filesystem, the details of which are available on the official Arduino website. Once that is done, we need to ensure two things are present in the root directory of the card: the HC.htm file, and a data/ directory for our datafiles. The data directory is easily made with the same computer that was used to format the card provided one has an SD card reader of some sort. The HC.htm simply consists of the following code:

You will need to edit this file first to make sure it points towards the preferred  location of your highcharts.js files. You can leave this as the public CDN: http://cdnjs.cloudflare.com/ajax/libs/highcharts/2.3.5/highcharts.js, change it to point towards your own webhost, or it can even be on the Arduino’s SD card (this will be slow). It is not necessary to create a datafile before hand, the SGDL sketch will take care of that when it decides to record its first data point. Before we get that far though, it is necessary to make sure we have configured the EEPROM memory for the SGDL sketch. This is very easily accomplished using a separate sketch, which I have called EEPROM_config. This sketch (along with SGDL itself) requires an extra library called EEPROMAnything, which needs to be added to the Arduino’s libraries folder wherever one’s sketchbook folder is. While you’re at it, you should also add the Time library which we need for SGDL.

I have intentionally commented out the write line so that no one writes junk to the EEPROM by accident. While the EEPROM has a life of ~100,000 write cycles, I’d rather not waste any of them. Please review the sketch carefully and ensure you’ve adjusted it accordingly before uploading it to the Arduino. The most important thing is to ensure that your newFileTime is something sensible (in the near future most of all).

Now that that’s all taken care of, we’re ready to get SGDL all set up! The code will need a few adjustments for your own specific setup, mostly in regards to the Ethernet MAC and IP addresses. I trust that anyone making use of this code already knows how to configure their router to work with the Arduino, and that they can find the appropriate local IP address to update this sketch with. You may also wish to change the timeserver IP address to one that is geographically closer to yourself.

I currently have my code set up to make a measurement every 10 minutes, and to create a new data file every week. You are welcome to change those parameters, just be aware that the current data file management names files using a dd-mm-yy.csv date format, so the new file interval should be at least 24 hours. Another concern, is that the shorter the measurement interval and the longer the new data file interval is, the larger the files will be. Because the Arduino is not especially powerful, this will have consequences for the loading times of each chart.

Posted by Everett in Arduino, Electronics, Programming, Sensors and Data Logging, Web Applications, 75 comments
BeagleBone: Making a Home Media Server

BeagleBone: Making a Home Media Server

There are plenty of products available to the person who wants a functioning NAS out of the box, though I’ve never really been that type. By using a versatile board like the BeagleBone as a home media server, I can make a project that is more than a simple networked storage solution. It also affords me the opportunity to learn about administration of a Linux server. While I could teach myself these skills by implementing a home media server using an old desktop, the amount of electricity consumed would be at least an order of magnitude higher and in any case my old desktop recently gave up the ghost. The information contained here is specifically intended for use on a BeagleBone, though I wouldn’t be the least bit surprised if it was useful to someone trying to achieve the same effect with a different platform. It is also important to not that I accept no liability for damages or issues that occur as a result of following my directions either on a BeagleBone or other hardware. I am very sorry if such an event should take place however, and would appreciate knowing about it so that I could correct this guide asap.

This guide is broken into major steps for the convenience of anyone wishing to follow it:

  1. Installing Ubuntu and some basic configuration
  2. Locking down SSH
  3. Getting rtorrent and rutorrent running
  4. Installing and configuring Samba
  5. Updating and maintaining the system

*****

Installing Ubuntu and some basic configuration

To start it’s necessary to get your preferred Linux distribution running on the BeagleBone. I chose Ubuntu mainly because I found an easy and ready to install image, though the fact that it is compiled to take advantage of the hard float capabilities in this arm processor was also a factor. The following instructions were up to date when I utilized them, though it’s entirely possible that a newer image has been created in the meantime and you should use that one if possible. You will also need a microSD card to write the image to (I used a 4GB card, though a 2GB card or greater should work).

Credit goes to http://elinux.org/BeagleBoardUbuntu#Demo_Image as the basis for this portion of my guide.

The first thing we need to do is download the operating system image that we will write to the microSD card:

wget http://rcn-ee.net/deb/rootfs/precise/ubuntu-12.04-r1-minimal-armhf.tar.xz

This image needs to be unpacked before we write it to the SD card:

tar xJf ubuntu-12.04-r1-minimal-armhf.tar.xz
cd ubuntu-12.04-r1-minimal-armhf

We need to know where to install this image , and even though it is likely /dev/mmcblk0 we should check anyway:

sudo ./setup_sdcard.sh –probe-mmc

In the output a line like Disk /dev/mmcblk0: 3957 MB, 3957325824 bytes should be seen. If there is only one line starting with Disk /dev/mmcblk… then that is the SD card we want, and that’s the location you should use. If there are more than one of these /dev/mmcblk lines, then you must figure out which one belongs to the SD card you want to write to, otherwise you may overwrite something important.

Having figured out where the SD card is mounted, we will run the script to write the contents of our image to it:

sudo ./setup_sdcard.sh –mmc /dev/mmcblk0 –uboot bone

Where /dev/mmcblk0 may be something else if you found the SD card to be mounted somewhere else in the previous step.
At this point you only have to insert the microSD card and plug it into the BeagleBone to get started. Because the board lacks a way to hook up a display it is easiest to insert an ethernet cable and remotely SSH into it with the user “ubuntu” and the password “temppwd”

ssh ubuntu@<Local IP Address>

I have managed to use the DHCP reservation functionality on my home router to ensure that the BeagleBone has a fixed local IP address, and I strongly encourage you to do the same if possible. Because this process varies by router manufacturer and model, I cannot offer much guidance in this regard. This guide may be of some help.

Our first step after logging in should be to change the password for this account:

passwd

This will ask for the current password, and the one you wish replace it with twice. The next two steps will create a new user account with a better name (just replace <username> with your preference) and give it administrative privileges. These steps are cosmetic, and are unnecessary if you just wish to use the account “ubuntu”.

sudo adduser <username>

sudo usermod -aG admin <username>

The next two commands will allow us to change the host name for the BeagleBone to something other than “omap” and are also optional as they are purely cosmetic.

sudo nano /etc/hostname

You should change the first line of this file to whatever you’d like as a new host name (don’t use spaces) and then press CTRL-o to save the changes and CTRL-x to exit. We will also need to change the following file:

sudo nano /etc/hosts

The word omap in the second line of this file should be replaced with the same host name we just used.

I encountered perl locale errors when I tried doing various things later on, which may still be an issue. To fix them you want to check that /etc/default/locale contains a few things:

sudo nano /etc/default/locale

You should find the following lines within, though they do not necessarily need to be US english:

LANG=en_US.UTF-8
LANGUAGE=en_US.UTF-8:en
LC_ALL=en_US.UTF-8

If any of these lines are not present, then you should add them (substituting in another language pack such as en_GB if you’re so inclined.)

Before proceeding, it is also a good idea to make sure all of the packages on your system are up to date:

sudo apt-get update
sudo apt-get upgrade

sudo reboot

*****

Locking down SSH

Credit goes to http://www.debian-administration.org/articles/530 as the basis for this portion of my guide.
We need to generate a set of public and private keys on the computer you wish to SSH into the BeagleBone from. It is important to make sure you are running this locally on the client computer, not through SSH on the BeagleBone:

ssh-keygen

You will then be prompted for a password to protect the key we just generated. This password is not transmitted in any way to the system were are using SSH to access, but rather to decrypt the key on your local machine. If you leave the password blank it will not encrypt this key and make it so that anyone with the right file permissions can see it.
Now we want to install the key on the BeagleBone:

ssh-copy-id -i .ssh/id_rsa.pub <username>@<local IP address>

If this was successful, we should be able to SSH into the BeagleBone without entering a password.
We should then check that we only installed the key we intended to:

nano ~/.ssh/authorized_keys

You should see only one line in the file.

Next, it is a good idea to disable password authentication and limit the users who can access the board via SSH.
You do not want to do this by disabling password authentication for the chosen account as outlined in the debian-administration.org article; this runs the risk of breaking your ability to use sudo and can leave you without root access. I may or may not have made this error first hand. It’s not fun. We achieve the desired effect by editing /etc/ssh/sshd_config .

sudo nano /etc/ssh/sshd_config

First things first, it’s never a bad idea to disable root login. This isn’t really necessary on an Ubuntu system since there is no functioning root password and everything is done using sudo, but we’re better safe than sorry. Find the line beginning with PermitRootLogin and change it to no:

PermitRootLogin no

We also want to disable password authentication by finding the line #PasswordAuthentication yes, changing it to no, and uncommenting it by removing the #:

PasswordAuthentication no

Because we do not need X11-forwarding for our purposes you may also wish to change that line to:

X11Forwarding no

And to limit the users allowed to SSH into the BeagleBone we want to add the following line to the end of the file, using the username we created earlier in the place of <username>:

AllowUsers <username>

Finally, to finish our lockdown of SSH, we need to restart it so that the changes can take effect:

sudo service ssh restart

*****

Getting rtorrent and rutorrent running

This portion of my guide has been mainly adapted from http://forums.rutorrent.org/index.php?topic=256.0.

First we want to install a large number of packages:

sudo apt-get install apache2 apache2.2-common apache2-utils autoconf automake autotools-dev binutils build-essential bzip2 ca-certificates comerr-dev cpp cpp-4.6 dpkg-dev file g++ g++-4.6 gawk gcc gcc-4.6 libapache2-mod-php5 libapache2-mod-scgi libapr1 libaprutil1 libc6-dev libcppunit-dev libcurl3 libcurl4-openssl-dev libexpat1 libidn11 libidn11-dev libkdb5-6 libgssrpc4 libkrb5-dev libmagic1 libncurses5 libncurses5-dev libneon27 libpcre3 libpq5 libsigc++-2.0-dev libsqlite0 libsqlite3-0 libssl-dev libstdc++6-4.6-dev libsvn1 libtool libxml2 linux-libc-dev lynx m4 make mime-support ntp ntpdate openssl patch perl perl-modules php5 php5-cgi php5-cli php5-common php5-curl php5-dev php5-geoip php5-sqlite php5-xmlrpc pkg-config python-scgi screen sqlite ssl-cert subversion ucf unrar zlib1g-dev pkg-config unzip htop screen libwww-perl curl

Several of these packages are probably already installed, though it does not hurt to make sure. Some of the packages in this long list have been updated to newer versions since the guide I have adapted thus from was written. If any appreciable length of time has passed since I wrote this, then you are well advised to check if any of these packages need to have their version numbers changed. If this is the case, then apt-get is likely to spit out some error messages about certain packages being missing. The specific packages I updated were: cpp-4.6, g++-4.6, gcc-4.6, libstdc++6-4.6-dev, libkdb5-6, and libneon27. Here’s a quick way to check the version numbers for packages in the ubuntu repository online.

Having everything we need, our next step is to configure apache:

a2enmod ssl
a2enmod auth_digest
a2enmod scgi

We need to make sure that apache has SCGI support enabled so that the rutorrent webui will work:

sudo nano /etc/apache2/apache2.conf

You then need to paste the following at the end of the file:

SCGIMount /RPC2 127.0.0.1:5000
servername localhost

To make sure everything we’ve done takes effect it is a good idea to restart the server:

sudo reboot

To make sure everything is working, on your client machine type the local ip address assigned to your BeagleBone into the address bar of your browser:

http:// < Local IP Address>

You should see the following:

Because our rutorrent front end to rtorrent will be password protected, we need to have HTTPS functionality eneabled. To achieve this we need an SSL certificate. This process will ask for a lot of information which you can fill in however you see fit, though it’s a good idea to use the domain name your BeagleBone will be connected to if you have one:

openssl req $@ -new -x509 -days 365 -nodes -out /etc/apache2/apache.pem -keyout /etc/apache2/apache.pem
chmod 600 /etc/apache2/apache.pem

This is a self signed certificate, meaning your browser will probably spit out a warning the first time you connect. Just ignore the warning and store the exception, and this won’t happen again. Our next step is to protect our apache webserver with a username and password:

sudo htdigest -c /etc/apache2/passwords gods <webusername>

This username, <webusername>, and password can be whatever you like. It can even be the same user and password we used earlier when setting sup the system. I personally decided to use a different username and password because it offers a slight security advantage in that if someone figures out the password to our rutorrent and apache setup, they still don’t have the password for root privileges through the operating system account we made earlier. It is unlikely that this scenario would ever happen since we made access through ssh only possible using key authentication, though it’s not much of a hassle for a little added security (Besides, I know you’ll just save the webusername and password in your browser anyway).

We also need to configure apache using the /etc/apache2/sites-available/default file:

sudo nano /etc/apache2/sites-available/default

You want to replace the contents of this file with the following, where the two instances of <Local IP Address> are replaced by the address of your BeagleBone on the local network:

<VirtualHost *:80>
	ServerAdmin webmaster@localhost

	DocumentRoot /var/www/
	<Directory />
		Options FollowSymLinks
		AllowOverride None
	</Directory>
	<Directory /var/www/>
		Options Indexes FollowSymLinks MultiViews
		AllowOverride None
		Order allow,deny
		allow from all
	</Directory>

	ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
	<Directory "/usr/lib/cgi-bin">
		AllowOverride None
		Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
		Order allow,deny
		Allow from all
	</Directory>

	ErrorLog /var/log/apache2/error.log

	# Possible values include: debug, info, notice, warn, error, crit,
	# alert, emerg.
	LogLevel warn

	CustomLog /var/log/apache2/access.log combined

	Alias /doc/ "/usr/share/doc/"
	<Directory "/usr/share/doc/">
		Options Indexes MultiViews FollowSymLinks
		AllowOverride None
		Order deny,allow
		Deny from all
		Allow from 127.0.0.0/255.0.0.0 ::1/128
	</Directory>

	<Location /rutorrent>
		AuthType Digest
		AuthName "gods"
		AuthDigestDomain /var/www/rutorrent/ http://<Local IP Address>/rutorrent

		AuthDigestProvider file
		AuthUserFile /etc/apache2/passwords
		Require valid-user
		SetEnv R_ENV "/var/www/rutorrent"
	</Location>

</VirtualHost>

<VirtualHost *:443>
	ServerAdmin webmaster@localhost

	SSLEngine on
	SSLCertificateFile /etc/apache2/apache.pem

	DocumentRoot /var/www/
	<Directory />
		Options FollowSymLinks
		AllowOverride None
	</Directory>
	<Directory /var/www/>
		Options Indexes FollowSymLinks MultiViews
		AllowOverride None
		Order allow,deny
		allow from all
	</Directory>

	ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
	<Directory "/usr/lib/cgi-bin">
		AllowOverride None
		Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
		Order allow,deny
		Allow from all
	</Directory>

	ErrorLog /var/log/apache2/error.log

	# Possible values include: debug, info, notice, warn, error, crit,
	# alert, emerg.
	LogLevel warn

	CustomLog /var/log/apache2/access.log combined

	Alias /doc/ "/usr/share/doc/"
	<Directory "/usr/share/doc/">
		Options Indexes MultiViews FollowSymLinks
		AllowOverride None
		Order deny,allow
		Deny from all
		Allow from 127.0.0.0/255.0.0.0 ::1/128
	</Directory>
	<Location /rutorrent>
		AuthType Digest
		AuthName "gods"
		AuthDigestDomain /var/www/rutorrent/ http://<Local IP Address>/rutorrent

		AuthDigestProvider file
		AuthUserFile /etc/apache2/passwords
		Require valid-user
		SetEnv R_ENV "/var/www/rutorrent"
	</Location>
</VirtualHost>

We then want to run the following to get apache running https:

sudo a2ensite default-ssl
sudo /etc/init.d/apache2 reload

If everything worked as intended, then going to https://< Local IP Address> should show us the same page we saw earlier.

Unlike the guide I adapted these instructions from, I have decided not to install the Webmin configuration utilities for a couple of reasons. The first is that I wanted this project to help develop my skills as a Linux administrator, and a graphical GUI to change everything does not really fit that goal. The second reason is that the BeagleBone is not a powerful computer, and so I would prefer not to weigh it down with things that are not absolutely necessary.

Now that we have apache up and running with all the necessary bells and whistles, we can proceed to install and configure rtorrent and the rutorrent webui. At the time the guide I used as my starting point was written, the version of rtorrent in the Ubuntu repositories wasn’t complied with xmlrpc support, which was needed for rutorrent to work. This has long been fixed, and so you can probably just install the packages libxmlrpc-core-c3-dev and rtorrent. I can’t offer any guidance in this regard because I decided to compile the latest versions of these packages from source, mostly because I could. The compilation process will take a fair amount of time; likely more than an hour.

First things first, we need the sources for each of these packages:

cd ~/
mkdir source
cd source
svn co https://xmlrpc-c.svn.sourceforge.net/svnroot/xmlrpc-c/advanced/ xmlrpc-c
wget http://libtorrent.rakshasa.no/downloads/libtorrent-0.13.2.tar.gz
wget http://libtorrent.rakshasa.no/downloads/rtorrent-0.9.2.tar.gz
tar -xvzf libtorrent-0.13.2.tar.gz
tar -xvzf rtorrent-0.9.2.tar.gz
rm *.tar.gz

This simply downloads the sources, unpacks the archives and deletes the archive files once we have. These packages may be updated to newer versions by the time you read this, and you can change version numbers accordingly.

The first package we need to build is xmlrpc-c:

cd xmlrpc-c
./configure –disable-cplusplus
make
sudo make install

Once this has completed we will do the same for libtorrent, the backend of rtorrent:

cd ../libtorrent-0.13.2
./autogen.sh
./configure
make
sudo make install

And finally, we will compile rtorrent itself:

cd ../rtorrent-0.9.2
./autogen.sh
./configure –with-xmlrpc-c
make
sudo make install

sudo ldconfig

Next we need an rtorrent configuration file, which we will save as ~/.rtorrent.rc:

nano ~/.rtorrent.rc

and replace any contents with the following:

# This is an example resource file for rTorrent. Copy to
# ~/.rtorrent.rc and enable/modify the options as needed. Remember to
# uncomment the options you wish to enable.
#
# Based on original .rtorrent.rc file from http://libtorrent.rakshasa.no/
# Modified by Lemonberry for rtGui http://rtgui.googlecode.com/
#
# This assumes the following directory structure:
#
# /Torrents/Downloading - temporaray location for torrents while downloading (see "directory")
# /Torrents/Complete - Torrents are moved here when complete (see "on_finished")
# /Torrents/TorrentFiles/Auto - The 'autoload' directory for rtorrent to use.  Place a file
#           in here, and rtorrent loads it #automatically.  (see "schedule = watch_directory")
# /Torrents/Downloading/rtorrent.session - for storing rtorrent session information
#

# Maximum and minimum number of peers to connect to per torrent.
#min_peers = 40
max_peers = 100

# Same as above but for seeding completed torrents (-1 = same as downloading)
min_peers_seed = -1
max_peers_seed = -1

# Maximum number of simultanious uploads per torrent.
max_uploads = 10

# Global upload and download rate in KiB. "0" for unlimited.
download_rate = 0
upload_rate = 0

# Default directory to save the downloaded torrents.
directory = <directory torrents will download to by default>

# Default session directory. Make sure you don't run multiple instance
# of rtorrent using the same session directory. Perhaps using a
# relative path? (We disregard this because of our startup script later)
session = /home/<username>/.session

# Watch a directory for new torrents, and stop those that have been
# deleted.
#schedule = watch_directory,5,5,load_start=/home/downloads/<username>/watch/*.torrent
#schedule = untied_directory,5,5,stop_untied=

# Close torrents when diskspace is low. */
schedule = low_diskspace,5,60,close_low_diskspace=100M

# Stop torrents when reaching upload ratio in percent,
# when also reaching total upload in bytes, or when
# reaching final upload ratio in percent.
# example: stop at ratio 2.0 with at least 200 MB uploaded, or else ratio 20.0
#schedule = ratio,60,60,stop_on_ratio=200,200M,2000

# When the torrent finishes, it executes "mv -n  ~/Download/"
# and then sets the destination directory to "~/Download/". (0.7.7+)
# on_finished = move_complete,"execute=mv,-u,$d.get_base_path=,/home/downloads/<username>/complete/ ;d.set_directory=/home/downloads/<username>/complete/"

# The ip address reported to the tracker.
#ip = 127.0.0.1
#ip = rakshasa.no

# The ip address the listening socket and outgoing connections is
# bound to.
#bind = 127.0.0.1
#bind = rakshasa.no

# Port range to use for listening.
port_range = 55995-56000

# Start opening ports at a random position within the port range.
#port_random = yes

scgi_port = 127.0.0.1:5000

# Check hash for finished torrents. Might be usefull until the bug is
# fixed that causes lack of diskspace not to be properly reported.
#check_hash = no

# Set whetever the client should try to connect to UDP trackers.
#use_udp_trackers = no

# Alternative calls to bind and ip that should handle dynamic ip's.
#schedule = ip_tick,0,1800,ip=rakshasa
#schedule = bind_tick,0,1800,bind=rakshasa

# Encryption options, set to none (default) or any combination of the following:
# allow_incoming, try_outgoing, require, require_RC4, enable_retry, prefer_plaintext
#
# The example value allows incoming encrypted connections, starts unencrypted
# outgoing connections but retries with encryption if they fail, preferring
# plaintext to RC4 encryption after the encrypted handshake
#
encryption = allow_incoming,try_outgoing

# Enable DHT support for trackerless torrents or when all trackers are down.
# May be set to "disable" (completely disable DHT), "off" (do not start DHT),
# "auto" (start and stop DHT as needed), or "on" (start DHT immediately).
# The default is "off". For DHT to work, a session directory must be defined.
#
dht = disable

# UDP port to use for DHT.
#
# dht_port = 6881

# Enable peer exchange (for torrents not marked private)
#
peer_exchange = no

#
# Do not modify the following parameters unless you know what you're doing.
#

# Hash read-ahead controls how many MB to request the kernel to read
# ahead. If the value is too low the disk may not be fully utilized,
# while if too high the kernel might not be able to keep the read
# pages in memory thus end up trashing.
#hash_read_ahead = 10

# Interval between attempts to check the hash, in milliseconds.
#hash_interval = 100

# Number of attempts to check the hash while using the mincore status,
# before forcing. Overworked systems might need lower values to get a
# decent hash checking rate.
#hash_max_tries = 10

# Max number of files to keep open simultaniously.
#max_open_files = 128

# Number of sockets to simultaneously keep open.
#max_open_sockets =

# Example of scheduling commands: Switch between two ip's every 5
# seconds.
#schedule = "ip_tick1,5,10,ip=torretta"
#schedule = "ip_tick2,10,10,ip=lampedusa"

# Remove a scheduled event.
#schedule_remove = "ip_tick1"

There are a couple of lines you must replace with your own specific information. The first is directory = <directory torrents will download to by default> and the second is session = /home/<username>/.session . I also encourage you to do a little research so that you can change other settings to suit your purposes.

We need to make sure the directories we just told rtorrent to use exist. Because it would be silly to have your media stored on the same SD card containing the OS, I’ve attached an external USB hard drive to the BeagleBone and set my directory = <directory torrents will download to by default> line to point towards there. Since this is external media, we’ll need it to auto mount whenever the board reboots so that rtorrent will always be able to find it. We’ll start by making the directories for rtorrent and for the drive to be mounted to:

cd ~
sudo mkdir .session
sudo mkdir /media/<mount directory name>

I am mounting it in /media because that is the standard place to place such things in ubuntu, though you could just as well mount it in /mnt or another directory you have made. To achieve automagical mounting we will edit /etc/fstab after backing up the original:

sudo cp /etc/fstab /etc/fstab.backup

We’re going to mount the usb hard drive using the uuid rather than the /dev/sda path because it is a better way of identifying the drive we actually want. To find this uuid we need to run:

ls -l /dev/disk/by-uuid

One of the lines should have something like ../../sda1 listed in yellow, and a corresponding alphanumeric code in blue. The blue code is the uuid, which you should copy. We can now go ahead and edit /etc/fstab :

sudo nano /etc/fstab

We want to add a specific line to the end:

UUID=<uuid>     /media/<mount directory name> auto defaults 0 0

where <uuid> is the value we copied earlier, and /media/<mount directory name> is where we decided to mount the drive. If you happen to know the file system in use on your usb drive you may wish to change the auto in the above line to the proper filesystem. For ext4 this is just “ext4” and for ntfs (oh god, why?) it would be “ntfs-3g“, each without quotes. If using ntfs it may be necessary to install the ntfs-3g package.

Now that fstab has been modified, we want Ubuntu to recognize the changes:

sudo mount -a

And we will also make ourselves the owner of the external drive mount point:

sudo chown -R <username>:<username> /media/<mount directory name>

If everything went well, then we should find that rtorrent starts up without any issues:

rtorrent

Any problems should be noted in rtorrent with an error that should help direct you towards a solution. I got a warning about xmlrpc, though a little research showed this was just an advisory and nothing to actually be worried about. You can now quit rtorrent by pressing CTRL-q.

We also want rtorrent to start up automatically in such a way that it will also keep running when we are not logged in via ssh. This is accomplished using a startup script (which I have left unmodified for the original guide) that makes use of screen.

sudo nano /etc/init.d/rtorrent

Paste the follwing into that file. The only change necessary is to replace <username> in the line user=”<username>” with the user we created earlier:

#!/bin/sh
#############
###<Notes>###
#############
# This script depends on screen.
# For the stop function to work, you must set an
# explicit session directory using ABSOLUTE paths (no, ~ is not absolute) in your rtorrent.rc.
# If you typically just start rtorrent with just "rtorrent" on the
# command line, all you need to change is the "user" option.
# Attach to the screen session as your user with
# "screen -dr rtorrent". Change "rtorrent" with srnname option.
# Licensed under the GPLv2 by lostnihilist: lostnihilist _at_ gmail _dot_ com
##############
###</Notes>###
##############

#######################
##Start Configuration##
#######################
# You can specify your configuration in a different file
# (so that it is saved with upgrades, saved in your home directory,
# or whateve reason you want to)
# by commenting out/deleting the configuration lines and placing them
# in a text file (say /home/user/.rtorrent.init.conf) exactly as you would
# have written them here (you can leave the comments if you desire
# and then uncommenting the following line correcting the path/filename
# for the one you used. note the space after the ".".
# . /etc/rtorrent.init.conf

#Do not put a space on either side of the equal signs e.g.
# user = user
# will not work
# system user to run as
user="<username>"

# the system group to run as, not implemented, see d_start for beginning implementation
# group=`id -ng "$user"`

# the full path to the filename where you store your rtorrent configuration
config="`su -c 'echo $HOME' $user`/.rtorrent.rc"

# set of options to run with
options=""

# default directory for screen, needs to be an absolute path
base="`su -c 'echo $HOME' $user`"

# name of screen session
srnname="rtorrent"

# file to log to (makes for easier debugging if something goes wrong)
logfile="/var/log/rtorrentInit.log"
#######################
###END CONFIGURATION###
#######################
PATH=/usr/bin:/usr/local/bin:/usr/local/sbin:/sbin:/bin:/usr/sbin
DESC="rtorrent"
NAME=rtorrent
DAEMON=$NAME
SCRIPTNAME=/etc/init.d/$NAME

checkcnfg() {
    exists=0
    for i in `echo "$PATH" | tr ':' '\n'` ; do
        if [ -f $i/$NAME ] ; then
            exists=1
            break
        fi
    done
    if [ $exists -eq 0 ] ; then
        echo "cannot find rtorrent binary in PATH $PATH" | tee -a "$logfile" >&2
        exit 3
    fi
    if ! [ -r "${config}" ] ; then
        echo "cannot find readable config ${config}. check that it is there and permissions are appropriate" | tee -a "$logfile" >&2
        exit 3
    fi
    session=`getsession "$config"`
    if ! [ -d "${session}" ] ; then
        echo "cannot find readable session directory ${session} from config ${config}. check permissions" | tee -a "$logfile" >&2
        exit 3
    fi
}

d_start() {
  [ -d "${base}" ] && cd "${base}"
  stty stop undef && stty start undef
  su -c "screen -ls | grep -sq "\.${srnname}[[:space:]]" " ${user} || su -c "screen -dm -S ${srnname} 2>&1 1>/dev/null" ${user} | tee -a "$logfile" >&2
  # this works for the screen command, but starting rtorrent below adopts screen session gid
  # even if it is not the screen session we started (e.g. running under an undesirable gid
  #su -c "screen -ls | grep -sq "\.${srnname}[[:space:]]" " ${user} || su -c "sg \"$group\" -c \"screen -fn -dm -S ${srnname} 2>&1 1>/dev/null\"" ${user} | tee -a "$logfile" >&2
  su -c "screen -S "${srnname}" -X screen rtorrent ${options} 2>&1 1>/dev/null" ${user} | tee -a "$logfile" >&2
}

d_stop() {
    session=`getsession "$config"`
    if ! [ -s ${session}/rtorrent.lock ] ; then
        return
    fi
    pid=`cat ${session}/rtorrent.lock | awk -F: '{print($2)}' | sed "s/[^0-9]//g"`
    if ps -A | grep -sq ${pid}.*rtorrent ; then # make sure the pid doesn't belong to another process
        kill -s INT ${pid}
    fi
}

getsession() {
    session=`cat "$1" | grep "^[[:space:]]*session[[:space:]]*=" | sed "s/^[[:space:]]*session[[:space:]]*=[[:space:]]*//" `
    echo $session
}

checkcnfg

case "$1" in
  start)
    echo -n "Starting $DESC: $NAME"
    d_start
    echo "."
    ;;
  stop)
    echo -n "Stopping $DESC: $NAME"
    d_stop
    echo "."
    ;;
  restart|force-reload)
    echo -n "Restarting $DESC: $NAME"
    d_stop
    sleep 1
    d_start
    echo "."
    ;;
  *)
    echo "Usage: $SCRIPTNAME {start|stop|restart|force-reload}" >&2
    exit 1
    ;;
esac

exit 0

Finally we will make the owner of the file the root, make it executable, and have it startup at boot.

sudo chown root:root /etc/init.d/rtorrent
sudo chmod a+x /etc/init.d/rtorrent
cd /etc/init.d
sudo update-rc.d rtorrent defaults

If everything has worked out then running the following should startup rtorrent in a screen session:

sudo /etc/init.d/rtorrent start

Which we will verify by running htop. We should find a few rtorrent processes and a screen process which belong to the user we created earlier. To quit htop hit the “q” key on your keyboard.

The last step is to get rutorrent up and running. rutorrent is just a web interface, and so we will put it in /var/www so that the apache webserver we installed and configured earlier can serve it up to us.

cd /var/www
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/rutorrent

We will also install a bunch of plugins to extend to functionality of rutorrent and to make it more like a native program running on the client machine itself:

cd rutorrent/plugins
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/erasedata
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/create
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/trafic
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/edit
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/retrackers
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/cookies
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/search
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/scheduler
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/autotools
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/datadir
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/tracklabels
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/geoip
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/ratio
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/seedingtime
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/diskspace
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/data
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/rss
sudo svn checkout http://rutorrent.googlecode.com/svn/trunk/plugins/throttle

The diskspace plugin watches the root directory by default, and that is no good since we’re using an external drive for our torrent download location. To fix this we need to edit one line in the file /var/www/rutorrent/conf/config.php:

sudo nano /var/www/rutorrent/conf/config.php

We need to find the line that begins $topDirectory and change it to the following:

$topDirectory = '/media/<mount directory name>';

Finally, we have to change the ownership of these files and folders so that the web server can make use of them:

cd /var/www
sudo chown -R www-data:www-data rutorrent
sudo chmod -R 777 rutorrent

If everything went as expected, then going to https://<local IP Address>/rutorrent should prompt us for a username and password (this is the one we created for the webserver, <webusername>, and is not necessarily the user account we created for the OS). After logging in, we should see the empty rutorrent webgui:

At this point we’re essentially finished with this part of the guide unless you wish to install an FTP server. For my purposes I am content with using sftp, which is built into SSH, though the original source for this portion of the guide also includes instructions for setting up a true FTP server using Pure-FTPd. There are also instructions to enable a multi-user rtorrent setup, though I have not pursued those either since I don’t have any need for it. Since we are finished with rtorrent and rutorrent, you can now start adding your torrents to it. You should make sure to point rutorrent to the right directory  if you add any torrents that you already have the data for and are seeding so that it won’t redownload the entire thing.

*****

Installing and configuring Samba

Samba is a very convenient application to have running for a home media server as it allows us to have very easy access to the files from other computers on the local network. To install samba:

sudo apt-get install samba

We also need to make a samba password for our samba user (the same Ubuntu user we made earlier):

smbpasswd -a <username>

The next step in setting samba up is to change some things in the configuration file, /etc/samba/smb.conf:

sudo nano /etc/samba/smb.conf

The first thing to ensure is that the following line is present and uncommented (it should be below ####### Authentication #######):

security = user

This will ensure that the only people who can access samba shares are those with a valid ubuntu account on the BeagleBone. The next step is to ensure that only people on the local network can access the samba shares which we achieve by adding the following lines under #### Networking ####:

# Added for extra security, only addresses on the local network can connect.
    hosts allow = 127.0.0.1 192.168.1.0/24
    hosts deny = 0.0.0.0/0

You may need to change 192.168.1.0/24 to something else depending on your router and local area network addresses (192.168.0.0/24 is another common one).

The last things we need to do in this config file are to setup the shares themselves. We will comment out any of the lines pertaining to printers because the BeagleBone is not attached to any. The end result is that those lines should appear as follows:

;[printers]
;   comment = All Printers
;   browseable = no
;   path = /var/spool/samba
;   printable = yes
;   guest ok = no
;   read only = yes
;   create mask = 0700

# Windows clients look for this share name as a source of downloadable
# printer drivers
;[print$]
;   comment = Printer Drivers
;   path = /var/lib/samba/printers
;   browseable = yes
;   read only = yes
;   guest ok = no

We also want to enable a share for our attached usb drive by adding the following lines to the end of the file with <mount directory name> and <username> are replaced by the appropriate values we used earlier:

# Share for the external media hard drive
[media]
        comment = External Drive connected to BeagleBone.
        path = /media/<mount directory name>
        read only = no
        browseable = yes
        valid users = <username>

This makes the entire usb hard drive available to the user we created earlier and no one else.

That’s it for samba, and we can enable the changes by restarting the samba processes:

sudo restart smbd
sudo restart nmbd

*****

Updating and maintaining the system

There are a few basic things we need to do to keep our new home media server functioning in tiptop shape, and the first is keeping it up to date. For the most part, this can be done through the ubuntu repositories:

sudo apt-get update
sudo apt-get upgrade

The kernel is a slightly more difficult matter because the one that works with the TI omap processors isn’t upstreamed to the repositories yet. To update the kernel you need to get the one built by Robert C Nelson. Luckily you shouldn’t need to do this very often, except in the case of security patches and important bug fixes. To make this process as easy as possible someone has already created a simple script to do all of the work for you. I have made the necessary changes to configure it to work with the BeagleBone running Ubuntu 12.04.
First we will create a scripts directory to store it, then create the file using nano:

mkdir ~/scripts
cd scripts
nano update-kernel-bone.sh

You then want to paste the following into this file:

############################################################################
## This is a script obtained from http://elinux.org/BeagleBoardUbuntu     ##
## It updates the kernel on the BeagleBone using Robert C Nelsons Sources ##
## https://github.com/RobertCNelson/stable-kernel                         ##
############################################################################

export DIST=precise #(options are lucid/maverick/natty/oneiric/precise/squeeze/wheezy)
export ARCH=armhf   #(options are armel/armhf (armhf only for precise))

#Beagle/Panda
#export BOARD=omap

#BeagleBone
export BOARD=omap-psp

wget http://rcn-ee.net/deb/${DIST}-${ARCH}/LATEST-${BOARD}
wget $(cat ./LATEST-${BOARD} | grep STABLE | awk '{print $3}')
/bin/bash install-me.sh

Using this script is a simple as moving into the scripts directory and running it:

cd ~/scripts
sudo bash update-kernel-bone.sh

Before updating the kernel, it is a good idea to make a backup of the system so it can be restored if something goes amiss. The easiest way I have found of backing up the operating system itself is to use dd to clone the microSD card. To do this you need to remove the microSD card from the BeagleBone after shutting it down:

sudo poweroff

After removing the card you want to insert it into another computer, the one you used to write the card in the first place should work just fine. Running the following command will copy the entire contents of the card to a file called sdcard.img into the home directory of this computer:

sudo dd if=/dev/mmcblk0 of=~/sdcard.img

If there are other SD cards inserted into this computer, then the location /dev/mmcblk0 may be incorrect. Make sure you are copying the contents of the correct SD card before you assume you have a valid backup. You can also change the location the image is copied to some other directory if you wish. This process will take a few minutes to complete, and when it is done you should have an image that can be copied back to the card using the command:

sudo dd if=~/sdcard.img of=/dev/mmcblk0

Hopefully this will never be necessary, though we’re always better off safe than sorry.

If you have another USB hard drive, you may wish to backup the contents of the one on the BeagleBone to it. The easiest way to do this is through rsync using SSH. On your computer (not the BeagleBone, the one we use to ssh into it) you just run the following command with necessary changes to fit your system:

rsync -avv –progress -e ssh <username>@<Local IP Adress>:/media/<mount directory name>/ <the path to the backup drive on the local computer>

The amount of time this takes will depend on the amount of data that is present on the BeagleBone’s drive but not on the destination drive.

*****


And with all that we should be done. I’ve tried my very best to keep this guide free of any errors, but some are sure to have snuck through. If you notice any, then I will be very grateful if you point them out so I can get them fixed. Once again, I accept no liability for damages or issues that occur as a result of following my directions either on a BeagleBone or other hardware.

*****

Posted by Everett in BeagleBone, Electronics, Linux, 17 comments
Beaglebone: Making a Case

Beaglebone: Making a Case

I recently purchased a BeagleBone with the intent of using it to make a home server and media box that could run constantly without costing a small fortune when the power bill arrived. I originally intended to make this project using a raspberry pi, though they’re having serious issues satisfying the demand, and I have other projects a raspberry pi can be put to use on that would make better use of its video capabilities.

The first thing I wanted to tackle when my BeagleBone arrived was creating some sort of enclosure. For those who’d rather shop than build, there are options available, though I’ve always been a more DIY kind of person. In regards to DIY BeagleBone cases, there are obvious solutions like an Altoids tin which the board fits into perfectly. This is not necessarily as simple as it seems though, since the Altoids tin can conduct electricity and could cause a short circuit if one isn’t careful. I considered this, and decided to pursue a different approach inspired by these computers. This had the added benefit of reusing the shipping box my BeagleBone arrived in, and effectively eliminates the risk of a short occurring. In summary; it is simply several layers of corrugated cardboard glued together with plain white glue, a set of self adhesive rubber feet, and some 1/2 inch 4-40 screws, nuts and nylon standoffs. At each step I also traced a rough template for that layer (seen below) which may be of use to anyone who wishes to replicate this project.

The Basic Template

Rough guide for layers 1 – 4

Rough guide for layers 5 – 7

The beginning of my template

I started by cutting the shipping box into several pieces for each of the layers in the case. I used the outline of an Altoids tin as the basis of my template since I knew the BeagleBone would fit snugly within that. This outline was scanned into my computer and modified it to create a general template with an inner area large enough for the BeagleBone.

For the base we need two layers; the bottom piece with large holes cut which will accommodate the tips of the screws and the nuts, and the upper piece which has holes just large enough for the screws and a notch for the USB client. I did not realize this notch was necessary until after I had already glued these two pieces together, and had to cut it in with an Xacto knife after the fact.

The two bottom most layers of the case, along with a couple template stencils.

To make the upper layer, I used my base template to trace both the outlines onto the cardboard, but did not cut out the inner area. Instead I centred the BeagleBone in the centre with the screws and nylon standoffs attached and firmly pressed down on the screws until they made light indentations on the cardboard. Using a nail with the same approximate diameter as the screws I then punched holes into the cardboard at these points so that the computer could be firmly attached when the case was finished.

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Letting the glue set

Next, it was necessary to glue these two pieces together, which was accomplished with a judicious amount of white glue (the kind you’ve probably used in elementary school). Once the glue became tacky, I wrapped a few elastic bands around them to keep them firmly pressed together and left them to dry for about half an hour.

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Cutting out the next set of layers

While the glue set, I went to work cutting out several pieces for the remaining layers, which were all derived from the base template with the inner area also removed. To remove the centres, I simply used the Xacto knife again with extra care around the rounded corners. I then cut out portions of these to make layers 3 and 4. Only one copy of the 3rd layer was necessary, while layer 4 needed to be repeated several times (the number of times will depend on the thickness of the cardboard used).

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Building up the walls of the case

Like the two base layers, each of these remaining layers was glued to the base one at a time and the glue was allowed to set before the next layer was added. A set of plastic clamps were used because these layers have significant portions cut out it is not possible to use the elastic bands to hold them in place. This process should be repeated until the walls of the case come high enough to clear the Ethernet port on the BeagleBone.

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The case with the fifth layer added

After all this had been accomplished it was necessary to add a copy of the fifth layer to the top, which was simply one of the pieces I cut out earlier without any modifications. In my haste I neglected to double check that the walls of my case were high enough, and the fifth layer did not quite clear the Ethernet jack. I fixed this by cutting out the portion of layer 5 that stretched across the open area for these ports. This modification of the case can be seen in the image at the top of this post. It was also necessary to create a lid for the case, which was made by gluing together one copy of layer 6 and one of layer 7. I also had to cut a notch out of layer 6 to accommodate the Ethernet jack. If the correct number of copies of layer 4 are added, these modifications should be unnecessary.

Some basic hardware holds the board firmly in place.

After finishing the case the last step was to firmly attach the BeagleBone to it using the nuts and washers. The nuts should be gently hand tightened so that they will not come undone while at the same time not crushing or damaging the cardboard where they connect. At this time I also added the rubber feet to the bottom of the case so that it would lift the cardboard off the surface and prevent it from sliding around.

Below are several images of the finished case, including a little bit of decoration I added to the lid a couple days later. I made it using a stencil based on this image, which I simply shaded in using a green felt marker. At the end of it all The case is not the most beautiful or elegant way to house a BeagleBone, though the fun I had designing and making it myself all while recycling the packing material makes up for that in strides. I also enjoy the texture the corrugated cardboard gives to the case, which is best seen in the profile view below. Lastly, the ease with which it can be decorated and customized to your liking is definitely another nice touch. All things considered, I am extremely pleased with how this project turned out.

A side profile of the case

With the lid on

The case and board in action

Decorative elements can be added too

Posted by Everett in BeagleBone, Electronics, 1 comment
Vetinari’s Clock – A Clock that Ticks Irregularly

Vetinari’s Clock – A Clock that Ticks Irregularly

I saw this sort of project posted on Hackaday a few months ago, originally using an Arduino, and quickly went to work building my own. It worked well when plugged into the USB port of my computer, and I was excited to hook it up to some batteries and see how long it would run (knowing full well that the Arduino was probably going to run them dry fairly quickly). It made it about 36 hours before the clip of 5 AA batteries was drained, and so I decided to try and rig it up with a 9V wall adapter power supply. Unfortunately, for reasons I am still unsure of, the whole thing would stop ticking after exactly 38 seconds and I quickly gave up in frustration. Luckily for me, Simon Inns came up with a version using a PIC microcontroller that runs much longer on only 2 AA batteries. Having never used PIC microcontrollers, I decided this was a good opportunity to learn something about them and used some money received at Christmas to order the parts and tools necessary for my own version of this clock.

The components necessary to make it work

Each clock requires a PCB, a PIC 12F683 microcontroller, two Schottkey diodes (1N5819), two 47Ω resistors, two 22pF capacitors, one 100nF capacitor, a 32.768 kHz crystal, and a 6 pin 0.1″ header of some sort for programming (I used a male right angle header). It is also a good idea to use a DIP socket for the PIC microcontroller, so that it can easily be removed if necessary. Using the Cadsoft Eagle schematics and board files supplied by Simon Inns, I slightly rerouted one of the traces so that it would pass the DRC Bot (an automated program to check that prototype boards conform to the rules) at BatchPCB.com and ordered a couple of the boards. I was pleasantly surprised when they arrived and I found 4 boards, all of which appeared to be in perfect condition. Altogether, the materials necessary for a single clock cost less than $20 (not including the tools to program the PIC or the shipping fees).

The PCB with components soldered in plac

I started by soldering everything to the PCB which was straight forward, though the capacitors I purchased were different from the ones originally used by Simon Inns, and I had to bend the leads to make them fit. The picture to the right shows all of the components soldered into place, with the exception of the leads for the clock and battery clip. It is also important to make sure the Diodes are installed in the correct direction, or else they will not properly protect the microcontroller from the flyback voltage that is generated by the solenoid in the clock mechanism.

Next it is necessary to dissect the clock, and hook up the solenoid that drives it to our circuitry instead of the little board that normally drives it. In theory this is simply done by cutting the traces to the little pads near the bottom where the solenoid attaches, and then soldering our own wires to it, though the board inside the clock is cheap, and the copper pad itself delaminated from the board almost immediately upon trying this.

The left copper pad has delaminated from the board

The guts of the clock mechanism

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Everything rewired to the battery contacts, and hot glued

Not to be defeated, I simply rerouted the thin wires of the solenoid to the large copper pads that were formerly the contact points for the battery, and made all of my connections there. I followed that with plenty of hot glue to keep everything firmly in place, and then went about putting the clock mechanism back together. Unfortunately for me I neglected to double check that everything was functioning before I glued it, which caused some issues later. Lesson learned: check your solder joints BEFORE you smother them in glue.

All of the clockwork put back in place.

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In order to reassemble the clock, I had to cut a notch in the housing to make space for the leads I had just soldered on, and I also trimmed off most of the plastic that formed the original battery holder, since it was no longer necessary. After replacing the back plate and soldering the battery leads (make sure the polarity is correct!) and the clock leads in place on the PCB, I then hot glued everything to the back of the clock and stuck in a couple of batteries.

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The original clock used with the arduino, now being run by the same circuit on a breadboard

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This was the point at which I realized something had gone wrong, since the clock was not ticking like the one I had already assembled using a breadboard. At first I was worried that one of the components on the PCB had been fried, but my trusty multimeter assured me otherwise when I saw pulses of voltage at the point where the clock leads had been soldered onto the PCB. This was were I realized that the problem must exist at the solder joints in the clock, which I had already hot glued. Oops! Luckily I already had a functioning clock mechanism from back when I assembled my power hungry Arduino version, which I had already hooked up to the breadboard version seen left. I cut the leads between the clock and the PCB, and swapped out the broken clock mechanism for the functioning one. Since both clocks were the same, this was a trivial task (thankfully).

The functioning clock, with swapped clock mechanism

Finally the clock was assembled and functioning, and I used some more hot glue to hold everything in place, including all of the wires. I also strategically positioned the PCB so the 6 pin programming headers would face downwards for easy access. Uploading the program the PIC is fairly easy, and I accomplished it without any issues by using the PICKit 3 with Microchip’s MPLAB X IDE. At the same time, I decided to re-brand the clock (no name dollar store brands don’t cut it) using some stickers I got when I ordered the components. I have had the clock running on a fresh pair of AA batteries since January 11th, 2012, and while it fell behind the clock on my computer by 10 seconds in the first two days, it has maintained accurate time since. My plan now is to leave it on my wall and test how long it runs on a pair of batteries and to compare that to the back of the envelope calculation I did earlier, which predicted at least 60 days for lower capacity batteries. While I have not yet noticed any brain mushification as a result of the clock, it seems like it disrupts my sleep slightly by causing me to wake more often during the night. We’ll see whether the batteries or my patience for poor sleep give out first.

Re-branded and fully functioning!

While over simplified, the circuit is basically 2 47Ω resistors in series, for a total of 94Ω. It operates at 3V, so the current draw is 3V/94Ω = 0.0319A = 31.9mA. But the clock mechanism is only powered for 30ms for each tick, which on average occur once per second, so the average current draw is 31.9mA * 30ms/1000ms = 0.957mA. The PIC microcontroller draws 11μA at 32kHz, which is essentially negligible in such a rough calculation. Rounding the average current draw up to 1mA, and assuming a cheap set of AA batteries with 1500mAh capacity, the clock should theoretically run for 1500 hours, which works out to 62.5 days. For a  better set of batteries with 2500mAh capacity, we get 2500 hours of operation, or about 104 days. In either case, two AA batteries every 2 to 3 months is far better than 5 AA batteries every 36 hours. EDIT: The clock managed to go for about 5 months on a pair of batteries before it became noticeably slow. It was 10 minutes behind the correct time when I finally replaced its batteries.

Posted by Everett in Clocks, Electronics, 5 comments
Solar Powered Robot Bugs!

Solar Powered Robot Bugs!

The finished product

My new Hakko FX-888 soldering station

This is not a project in which I spent much time designing or planning things myself, but I had a lot of fun with it, and it let me try out my brand new Hakko soldering station. It simply entails the assembly of the Photopopper Photovore robot kit from Solarbotics.com . What is a Photopopper Photovore? It’s basically a small solar powered robot, which uses Infrared and tactile sensors to simultaneously move towards sources of light and avoid obstacles. It also bears resemblance to an insect, especially a stinkbug. This kit really interests me, because the “behaviour” of the robot is caused through hardwired circuitry alone, and no microcontrollers or code are needed. The description included by Solarbotics says it is based on something called MillerEngine technology which (in all honesty) means nothing to me. Regardless, the circuit isn’t overly difficult to follow, and one need not know what a MillerEngine is to appreciate it.

The Photopopper Photovore circuit

Since I am only a hobbyist, my assessment may not be correct, but hopefully I’m not too far off the mark. Essentially what happens is that the solar cell charges the large 4.7mF capacitor (C1), and then when the voltage in the capacitor is high enough, the voltage trigger on one of the sides engages.The determination of which voltage trigger is engaged is determined by the IR and tactile sensors, where the tactile sensors take priority over the IR sensors to ensure obstacle avoidance in addition to the light seeking behaviour. The voltage trigger then trips the corresponding transistor which applies a current across the motor on that side until the voltage  drops enough to disengage the voltage trigger. The small capacitors (C2 and C3) are responsible for determining the length and frequency of the motor activity by affecting the voltage at the voltage triggers, and the diodes simply make sure the current moves in the correct direction. The trimpot makes it possible to tune the robot to favor one side over the other, or to balance it so that it moves directly towards sources of light.

Before going further, I feel like it would be a good idea to make it clear that this project was very enjoyable even though I encountered several issues while working on it. I wouldn’t want to discourage anyone from taking it on simply because I like to complain about things.

The components all laid out (I apologize for the blurriness)

The assembly instructions were good, and I really can’t complain too much in that regard. To start, you are shown a parts list, so you can be sure you have all the necessary components before proceeding. The most interesting part in this kit is probably the PCB, which is cut and formed to make this robot recognizable as an insect. In addition, there is  a large capacitor, trimpot, solar cell, and a pair each of diodes, voltage triggers, transistors, capacitors, motors, IR sensors, and the components to make each antenna (the tactile sensors).

The underside with the voltage triggers, diodes, transistors, capacitors and trimpot installed

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The first components to be installed are the voltage triggers, trimpot, and diodes, followed by the transistors and small capacitors. After this, the IR sensors are added. The installation of all these components was fairly straight forward, and was easily accomplished with the new soldering iron.

The motor mounts with motors soldered on

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The next component to go on was the large storage capacitor, which had to have its leads bent 90 degrees so that it could lie flat against the PCB. The motor mounts were also fairly easy to attach, using a combination of folding tabs and plenty of solder. Once attached, the motors themselves simply clipped into place.

The support wire: Murphy’s Law finally shows up.

Next, it was necessary to install the support wire to ensure the photopopper’s legs would reach the ground. Unfortunately this is where my problems began, since I failed to make sure the wire was short enough before I began soldering it on. While it is technically possible to fix this by twisting it to increase tension, I found the spring of the PCB itself was stronger than the wire and I had to constantly re-tighten it. Eventually metal fatigue occurred, and the poor wire broke. Luckily I had a paperclip of a similar gauge (seen in the picture to the left) which seemed to be much stronger, and was capable of withstanding the flex of the PCB. After this, some of the heat-shrink tubing was applied to the motor shafts to make the tires/feet, and the paperclip was given a small twist to make sure they reached the ground.

The solar panel is now attached

Attaching the solar cell was fairly easy, though wire strippers were needed to prepare the twisted red and black wire before it could be soldered to the right places. A piece of double sided sticky tape was then used to hold it into place. This was the next source of problems, because I mounted the solar panel before making sure each of the motors was working, and ruined it when I removed the panel to resolder one of the wires to the board. Luckily I had a replacement available, and I tested the conductivity of the adhesive before use to make sure it would not short anything. To best way to test each motor is to place the robot in direct sunlight or under an incandescent lightbulb, and then use something to short the square and circle pads on each side of the robot’s head (where the antennae will later be installed). From experience I recommend this step is performed before the solar panel is mounted. It is now a good idea to tune to robot, before the antenna are installed. To achieve this, the robot should be put near a source of light, and then the trimpot should be adjusted to make sure it moves towards that source, and doesn’t veer to either side. after this is achieved it is best to not to fiddle with it, as troubleshooting antennae and IR sensor balance at the same time was unnecessarily difficult.

The structure of the tactile sensors

With the antennae installed

The idea behind the tactile sensors is that when they collide with something it causes the spring to bend and connect with the central pin. This shorts the circuit and bypasses the IR sensor to make sure the robot moves away from obstacles. This step was especially troublesome, since the heat shrink tubing didn’t contract enough, and the spring would not fit without significant forcing. Through a combination of slightly untwisting the spring to increase its diameter, forcing the tubing through with a screwdriver, and applying excessive force (enough to bend the pin), the spring was eventually moved into place. The antennae were then ready to be soldered on, with the wire from the spring connecting with one pad, and the base of the pin onto the other pad. Because the pins were bent from the previous step, a fair amount of adjustment had to be performed to ensure the short only occurred when the sensors were triggered. The antennae alone took at least as long as the rest of the assembly combined.

The finished Photopopper with curled antennae

After a fair amount of testing, I found that the antennae worked best when curled around, otherwise they would often spring past an obstacle, and fail to provide continued avoidance behaviour.

The last issue with this kit is that the solar panel it uses works extremely well in direct sunlight, but for us Canadians direct sunlight is in short supply this time of year. The alternative is to use an incandescent light bulb (florescent and halogen bulbs wont work), but these days incandescent lightbulbs are not so common. Luckily I was able to find an old desk lamp and incandescent bulb to use for testing and tuning. The video below shows some of this testing, in which the robot turns around to face the light source, then moves forward a short distance. This process slowly repeats itself. Obstacle avoidance is harder to fine tune, as the antennae often get stuck in the shorted position if mishandled. The problem of antennae springing past obstacles and not providing persistent avoidance still exists after they have been curled, though it’s less common.

Despite the issues encountered, this kit was very fun, and it was a great way to test out a new soldering iron. That being said; from start to finish it took much longer than the 2 hours they estimate in the instruction manual, and I can only imagine how difficult it would be with a cheap “fire starter” stick iron.

Posted by Everett in Electronics, Kits, Robotics, 0 comments
Arduino Project: HTML to LCD

Arduino Project: HTML to LCD

The original source code for this project can be found Here.

WHAT YOU NEED:

  1. Arduino (I use the UNO, but I think the older revisions should also work)
  2. An Ethernet Shield
  3. 16×2 Basic Character LCD (There are many more colour options than just white on black)
  4. An Ethernet cable (I just used an old one lying around)
  5. A Breadboard  or some other means to connect the LCD to the Arduino and one 2.2 kΩ resistor

WHAT IT DOES:

This project combines the above to turn the Arduino into web server which is hooked up to the LCD. It produces a simple HTML web page, from which the user may see what text is currently displayed on the LCD, and provides them the opportunity to change the text using simple input forms. The hardware side of this project is fairly simple, and there were no physical hacks or modifications that needed to be made. The real challenge to this project were working within the limitations of the Arduino as a computing device.

SETUP AND OPERATION:

As we can see, the Ethernet shield is plugged into the Arduino, and is hooked up to the breadboard and LCD according to the scheme outlined in the comments of the source code. This one is completely set up and running, since there is already some text displayed on the LCD. The Arduino’s digital pins 4, 10, 11, 12 and 13 are left free since they are utilized by the shield. All the remaining pins are used by the LCD, so unfortunately this means all of the digital IO pins are used which restricts future additions to this project . The Arduino is also being powered over the USB cable, since this allows me to use the serial monitor to debug, and also because the Wiznet chip and voltage regulator get very hot when my 9V wall adapter is used. I have read that this may be because the shield draws a fair amount of current, and the linear voltage regulator reduces the voltage in accordance with the equation       P = I*ΔV. The power is proportional to the current draw, and it is dissipated by the voltage regulator in the form of heat.

With those notes aside, we can connect to the web page by typing in the local network IP address of the Arduino, which I have set up to be fixed using my router’s DHCP reservation functionality. The Arduino did not automatically receive an IP address when the Ethernet cable was first plugged in, so it was necessary to manually add the it to the router’s client list using the mac address on the underside of the shield.

On the web page served by the Arduino it tells us what is currently displayed by the LCD, and it provides us with two boxes to enter more text, one for each row. Each row is limited by the HTML code to 16 characters which provides instant feedback about the limitations of our setup to the user.

Typing in a couple of new lines and clicking the submit button causes the page to refresh and update with what we just entered! In a related issue, due to the RAM limitations of the Arduino and the way symbols are encoded for a URL (a % sign followed by two Hex digits), symbols initially use three times as many bytes as normal alpha-numeric characters. Therefore, if a user were to enter nothing but symbols in each field, the Arduino would crash due to memory issues. To solve this problem I added some code to limit the length of the raw text accepted, but this means that if a user enters too many symbols, the second line will be truncated. In fact, if nothing but symbols are entered into both lines, the second line will be truncated to nothing. It is an unsatisfactory solution, but it’s not an issue if the user uses symbols responsibly.

 Putting these issues aside and returning to our example, we can see that the the web page is now displaying what we entered earlier, and that the LCD also reflects the changes made on the web page.

While my Arduino is only hooked up to my local area network, it is possible to release it into the wild world of the Internet, though there is some risk (which I lack the expertise to properly assess) to doing so on your home network. There are some instructions for implementing this at http://sheepdogguides.com/arduino/art5serv.htm involving changing the settings on your home router and utilizing DynDNS to get a readable and static domain name.

The most difficult aspect of this whole project was without a doubt managing the heavy use of strings within the Arduino’s small amount of  RAM. Lots of work went into preventing any major or obvious memory leaks, but I am not entirely sure that I have gotten them all. To ration the memory effectively, I also utilized the ability of the Arduino to store constants in flash memory for the strings of HTML code that are sent to the client’s browser. This means I have at most only a single line of HTML stored in RAM at any time.

That wraps up my first post and first major Arduino project that involved some real coding and which was more than just random experimentation and tinkering. There is still some work that could be done debugging, and I intend to work on some extreme and border conditions to see if there are any bugs remaining that will cause it to crash or do some other bad thing.

(what fun is it if you don’t try to break it?)

As a reminder, the source code for this project can be found Here.

Posted by Everett in Arduino, Electronics, 36 comments