Building a battery shelf

Is there a better way to finish out a year than finding an excuse to use the table saw?  Well probably, but anyway...  Today's task was to build a small shelf to hold a few rechargable tool batteries.

There is not much to detail on the process.  I used a scrap piece of 3/4 plywood, cut it to dimensions, routed/sanded the edges, and joined with 3" angle brackets.  I also tie-zipped a power strip to the shelf in order to make easy work of the wiring.  see below for photos...

Repairing the sound on a toy truck

A recent family road trip took us to the Virginia Safari Park in Natural Bridge, VA.  The kids had a great time, and on the way out, we purchased a small toy truck.  Unfortunately, after we were home and unpackaged the toy, the sound would not work.  We ordered the world's smallest batteries on Amazon (LR41s, as who keeps those on hand);  After replacing the batteries, things were still not working properly.

After removing and disassembling the box which appeared to be the sound source, a disconnected wire was found on the piezo speaker.

 

A second or two from a hot soldering iron put the wire back in place, and the sound was functional again.

The last trick was re-assembling the case.  Since the iron was already hot, I just melted the plastic a bit and that seemed to do the trick.

The box was snapped back onto the truck and returned to a very happy 3-year boy.

Creating Backups in AWS Glacier with CrossFTP

Amazon Glacier is a storage service that is priced/optimized for long-term data archival and backup.  At the current time, storage charges are $0.01 per gigabyte per month (eastern region) with a number of minor ancillary charges.  Some basic operations can be performed through the AWS Console, but most require the use of either a specialized FTP client or custom code.  I opted for the quick and easy route, and found CrossFTP after researching a few available options.  They already had a tutorial posted on their blog, and the snapshots below are just my own notes from following that process.

After installing the CrossFTP Pro software, the following steps were used to setup a new site, create a Amazon Vault, and upload a sample file (note that as soon as the file upload completes to Amazon's servers, your charge meter begins to tick).

First, a little house-keeping.  In the CrossFTP Site Manager (menu Sites | Site Manager), create an organizational folder to hold any AWS sites (not required, I just can't stand an unstructured list):

To create the site listing, you will need a two pieces of information in advance:

• Host name for your local glacier sever
• found at http://docs.aws.amazon.com/general/latest/gr/rande.html#glacier_region
• AWS access key and secret
• currently found at https://aws-portal.amazon.com/gp/aws/developer/account/index.html?ie=UTF8&action=access-key
• Based on disclaimers/notices, it appears that Amazon is currently rearranging the access key page, so the link above may move/change in the near future

Press 'Close' to save the site.  It will appear in the CrossFTP site list, and connecting is just a double-click away

Amazon uses the term "Vaults" to refer to the top level directories/folders within your Glacier account, and the only apparent reason for that resides in the brains of marketing personnel; as far as I can tell, they are just directories.  I created a directory called "Backups" by using the "plus folder" icon in CrossFTP
  

To verify the operation worked, I logged into the Amazon console and displayed my list of Glacier vaults in the eastern region.  The new backups folder/Vault was present and accounted for

The last step involved actually putting a file online.  Note that since this is where the primary charging from Glacier originates, you'll want to ensure you upload things you actually care enough to pay for on a monthly basis.  In this case, I selected an old photo, renamed it for illustrative purposes, and uploaded it.

To disconnect from the site in CrossFTP, press the "planetary X" button above.

Next on my radar is to spend some time determining the best file format to use for storage on Glacier.  Since charging occurs by the byte, clearly a compressed format would be desirable, and for the sake of security, some kind of encryption would also be in order.  However, introducing compression and encryption means that the loss of even 1 bit of data could be catastrophic.  Per documentation, Amazon claims an average annual durability of 99.999999999% and performs at-rest encryption using AES-256.  However, for those of us who are truly paranoid, a few more steps are probably in order.  More investigation is needed, but parity archive files via Parchive may be part of the answer.

Upgrading to Windows 8.1

According to the pressers, Windows 8.1 would contain the feature to allow you to boot directly to the desktop (bypassing the tiles screen), which for me, made it worth the cost of admission (its a free upgrade, but lets not discount the value of personal time).  For the time being lets put aside the discussion that the most important feature of the 8.1 release was the inclusion of functionality to bypass the core selling point for the 8.0 release...

I took the option of using the Windows store to install the upgrade, and by and large it went on clean and without any technical hiccups.  There was, however, one absolutely infuriating feature which required linking my existing local account to a "Microsoft account" (ie - hotmail) as part of the install.  Requiring information such as that is fine for free sites/apps, but we were counting on Microsoft to be the "software equivalent of the adult in the room", and just allow us to use our paid software in the manner of our choosing.  Even the much advertised "Start menu" button return is a bit of a kludge (it looks like they spent five minutes building the attached menu UI).  Heading down this path proves again that the cleansing at Redmond is still not complete, and more purging of upper management is required to get this company back on track - they clearly haven't learned the appropriate lessons from the 8.0 fiasco.

In any event, I took the following steps to return my new 8.1 PC "back to normal" and find that without the requirement to boot to the tiles screen, I can now almost pretend that the monstrosity does not exist.

• Disconnecting my local account after the completion of the install
• Control Panel | User Accounts | Make changes to my account in PC settings
• While on the configuration screen, press the DISCONNECT button

• Remove the atrocious new lock screen image
• Again, not sure what they are thinking here, but the new image is horrid.  Back to the 8.0 image...
• Charm Menu | Settings | Change PC Settings | Lock Screen

• Boot directly to the desktop
• On the desktop, right click the task bar and choose Properties
• On the navigation tab, select "When I sign in..."

• Upgrade VMWare Player
• After the 8.1 upgrade, Player 5.0.1 could no longer connect to the network from Virtual Machines
• VMWare | Player | Help |  Software Updates
• As luck would have it, a reboot was not even required for this upgrade. All appears well in Player 6.

After almost a year under my belt in Windows 8 (including betas and such), and honestly really trying to like it and find a way to live with it, I find myself looking forward and hoping that Windows 9 will return to the ways of Windows 7, and back to a fully functional desktop operating system.  This foray into trendy tablet UI features on a desktop has proven a miserable failure, and I find myself ready for the experiment to end.

Netgear WN3000RP Disassembly

After a few years in use, it was time to retire the wireless extender for my network and upgrade to the latest model.  Before decommissioning the device, I disassembled it looking for spare/useful parts.  The case was held together with four torx screws on the exterior, and four more philips head screws holding the PCB onto the case standoffs.

The major chips on the unit are as follows:

• Broadcom 5357 (Intensi-fi® XLR 802.11n Router Solution)
• Winbond W9425G6JB-5 (DDR SDRAM)

The most useful piece turned out to be the power supply and case.  With the size of the unit and convenient location of the standoffs, this remnant will live on in my spare parts bin and may someday be reborn as a new custom device housing for a home-made PCB.

Amazon AWS Useful Links

The following are useful links while working with Amazon AWS services (not in any particular order):

• http://awsnow.info
• A summary of Amazon Services, Costs, Limitations
• http://cloudping.info
• Used to estimate the latency from your browser to each AWS region
• Amazon AWS direct links
• http://aws.amazon.com/architecture/
• http://aws.amazon.com/whitepapers/
• http://aws.amazon.com/solutions/case-studies/
• http://aws.amazon.com/training/self-paced-labs/
• https://aws.amazon.com/marketplace
• http://aws.amazon.com/cloudformation/aws-cloudformation-templates/
• Amazon AWS Calculator  (google: aws simple monthly calculator)
• http://calculator.s3.amazonaws.com/calc5.html
• Presentation: AWS Regions and Availability Zones
• http://bit.ly/aws-arch-prezi
• Miscellaneous Google searches
• spot instance strategies
• https://www.youtube.com/watch?v=WD9N73F3Fao
• cloud formation templates
• aws case studies
• Netflix Ice Project
• Ice communicates with AWS Programmatic Billing Access and maintains knowledge of the following key AWS entity categories: Accounts, Regions, Services (e.g. EC2, S3, EBS), Usage types (e.g. EC2 - m1.xlarge), Cost and Usage Categories.
•  https://github.com/Netflix/ice

Symmetric key encryption in Java using AES

Per Wikipedia, symmetric key encryption is defined as:  Symmetric-key algorithms are a class of algorithms for cryptography that use the same cryptographic keys for both encryption of plaintext and decryption of ciphertext.

As with most things, everything you need to know about AES in Java can be found on Google, but scattered across a number of partial code snippets.  Below is a my attempt to consolidate that information into a single example application (JDK7) which takes a sentence and runs it back and forth through the encryption process.  In reality, you would be best served by not using "password" as a password, avoiding sequential byte sequences as your keys and/or initialization vectors, and removing passwords from your code. :)

   
 package chris;  
   
 import java.io.FileInputStream;  
 import java.security.Key;  
 import java.security.KeyStore;  
 import javax.crypto.Cipher;  
 import javax.crypto.spec.IvParameterSpec;  
 import javax.crypto.spec.SecretKeySpec;  
   
 /**  
  * JAVA AES EXAMPLE APPLICATION  
  *   
  * java cipher documentation:  
  * http://docs.oracle.com/javase/7/docs/technotes/guides/security/SunProviders.html#SunJSSEProvider  
  * http://docs.oracle.com/javase/7/docs/technotes/guides/security/StandardNames.html#impl  
  *   
  * @author Chris  
  */  
 public class Application  
 {  
      public void aes(boolean useHardcodedKey) throws Exception  
      {  
           System.out.println("---- AES EXAMPLE ----");  
   
           System.out.println("original string: " + CLEARTEXT);  
           System.out.println("original length: " + CLEARTEXT.length());  
   
           // SELECT ALGORITHM  
             
           String algorithm = "AES/CBC/PKCS5Padding";  
                        // or "AES/CBC/ISO10126PADDING";  
             
           SecretKeySpec secretKey = null;  
             
           if(useHardcodedKey)  
           {  
                secretKey = new SecretKeySpec(RAW_KEY, "AES");  
           }  
           else  
           {  
                FileInputStream in = new FileInputStream(AES_KEYSTORE);  
                KeyStore keystore = KeyStore.getInstance("JCEKS");  
                keystore.load(in, PASSWORD);  
                Key key = keystore.getKey("mykey", PASSWORD);  
                secretKey = new SecretKeySpec(key.getEncoded(), "AES");  
           }  
             
           // INITIALIZATION VECTOR  
          
           byte[] ivBytes = new byte[]  
                     {0x00, 0x01, 0x02, 0x03,0x04, 0x05, 0x06, 0x07,   
                      0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F};  
          
           IvParameterSpec ivSpec = new IvParameterSpec(ivBytes);  
   
           // ENCRYPT  
          
           Cipher cipherENCRYPT = Cipher.getInstance(algorithm);  
           cipherENCRYPT.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);  
           byte[] crypted = cipherENCRYPT.doFinal(CLEARTEXT.getBytes());  
   
           // DECRYPT  
          
           Cipher cipherDECRYPT = Cipher.getInstance(algorithm);  
           cipherDECRYPT.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);  
           byte[] decrypted = cipherDECRYPT.doFinal(crypted);  
          
           // VERIFY  
          
           String compare = new String(decrypted, "UTF8");  
           System.out.println("decrypted string: " + compare);  
           System.out.println("decrypted length: " + compare.length());  
      }  
        
      public static void main(String[] args)  
      {  
           Application app = new Application();  
             
           try  
           {  
                app.aes(true);  
           }  
           catch(Exception e)  
           {  
                e.printStackTrace();  
           }  
      }  
        
      private static final String CLEARTEXT = "Here is a proprietary sentence to protect.";  
        
      // HARD-CODED AES SECRET KEY  
        
      private static final byte[] RAW_KEY = new byte[]  
                {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,  
                 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F};  
   
      // KEYTOOL commands for generating an AES keystore  
      //  
      // keytool -genseckey -alias mykey -keyalg AES -keysize 128   
      //     -storepass password -storetype JCEKS -keystore aes.jks  
      // keytool -list -v -keystore keystore.jks -storetype JCEKS  
   
      private static final String AES_KEYSTORE = "c:\\temp\\aes.jks";  
      private static final char[] PASSWORD = "password".toCharArray();  
 }  
   

Thanks to codeformatter for providing the easy-to-use code formatting tool for use with blogger.

Building an alternate nozzle for a Karcher K5.540 Power Washer

It seems like a rather odd thing to do, but in order to support a recent project, I needed to find a way to replace the gianourmous spray gun attachment which ships with the Karcher K5.540 with something a bit smaller.  The resulting sprayer nozzle looks like this when assembled:

The Karcher units are a little tricky as they use a proprietary fitting on their hoses.  Luckily, RJ Bowers carries a part (black piece above) which connects the high pressure hose via a quick connecter and terminates in a common M22 thread.

The four magic pieces used to assemble the sprayer gun replacement are as follows:

• RJ Bowers: Karcher 4.470-041.0 (4470-0410)
• General Pump M22 Male to 1/4" NPT Male Adapter (D10021)
• Brass Sleeve-Lock Socket, 1/4" NPTF Female, 1/4" Coupling (6537K73)
• Briggs & Stratton 6193 Quick Connect Spray Tips (6193)

The B&S quick connect spray tips come with a variety of angles:

• Black - low pressure tip
• White - 40 degree
• Green - 25 degree
• Yellow - 15 degree (seen in the above picture)
• Red - 0 degree

The red tip is fairly useless unless you are planning to write your name in concrete.  The next most powerful is the yellow tip at 15 degrees.  The resulting spray is not quite as intense as from the original spray head (perhaps the nozzle output hole is too large), but is still respectable and has a much smaller profile.  In short, its perfect for the prototype system I'm working on.

I initially had some concerns about back pressure from the new head, but based on the results, I do not think it will be a problem.

Enabling Amazon AWS Billing Alerts

To eliminate billing surprises at the end of the month, an Amazon account can enable billing alerts which will monitor usage and send notifications when threshold limits are exceeded.  This is done through the "Account Activity" page for the user.

Log into the AWS Console, navigate to the Account Activity page, and click "Enable Now".

The site will take a minute to process your request, and then alert you when the task is completed.

After alerts are enabled, on the same Account Activity page there will be a link to "Set your first billing alarm".

After clicking the link, a dialog will pop up; Press "Create Alarm" from here.

Fill out the form below; specifically, enter the email addresses where notification should be sent, as well as the US dollar amount which is your threshold.

After clicking "Create Alarm" on the dialog box, the alarm is created and enabled.

Disassembly of a Karcher 3.379 Power Washer

This weekend's fun consisted of breaking down an old electric power washer;  I have need of the high pressure water pump for a new project.

The breakdown went much quicker than anticipated.  The soap feed bottle just pops out, and the handle came off after removing two slotted screws at the base.

After the handle was off, the black accessory case on the back slid off (towards handle) with a few taps from a rubber mallet.

Then a T-15 screwdriver was used to remove about a half-dozen screws holding the two sides of the outer shell together.

With the case off, the water pump lifted out easily (nothing holding it in place except for the plastic casing being snug all around).

With the pump out, there was an elbow held in place with a "shim key" which was used to get the outfeed connector outside of the yellow plastic case.

Finally the hand wand attachment was disassembled in order to see how the outfeed water supply works.  As it turns out, just a few plastic moldings and springs holds the entire works together.

I'm not entirely sure what I was expecting when I started the disassembly, but I'm fairly sure I was expecting something a little more complex than a water pump held together with about $5 worth of injection molded plastic.  In any event, I now have a much better understanding of power washers, and even have a salvageable high-pressure water pump to be re-used in another project.

Driving a Trapezoidal Lead Screw

With the motor shield assembled and stepper motors in hand, I ordered a number of mechanical parts and waited almost 2-3 weeks for everything to arrive. Some of the key parts in use are as follows:

• Roton 10x2 RH trapezoidal lead screw [purchased here]
• Roton 10x2 RH flange nut [purchased here]
• 10mm base mounted bearing [purchased here]
• Stepper motor 200 steps/rev 12v [purchased here]
• NEMA17 Stepper motor mount [purchased here]
• Aluminum Flex Shaft Coupler 5mm - 10mm [purchased here]
• 8mm Linear Rail Shaft Guides x 4 [purchased here]
• 8mm Linear Bearing Platform x 2 [purchased here]
• 8mm miniature drive shafts [purchased here]
• Impact resistant polycarbonate, 90 degree [purchased here]

It took an afternoon to cut/measure/assemble all of the parts.  Unfortunately I was thinking a bit too much in 2 dimensions when I ordered the parts, and did not account for the height differences that would come into play during final assembly.  In order to place the stepper motor and mated bearing at the correct locations, I cut down some scrap pieces of 2x4 lumber I had remaining from a different project -- a bit of a sloppy hack, but it worked fine.  The final assembly is shown below:

To drive the motor, the following code was uploaded to the Arduino board:

To my great surprise, everything worked as expected the first time the system was powered up.  The unit was a little noisier than expected, but I think that may be due to a slight misalignment of the flange nut and its associated vibrations.  In the future I'll try to track down a washer to install between the flange nut and plastic angle to reduce vibration and help compensate for the noise (building something a little more exact that a hunk of 2x4 wouldn't hurt either).

Next up will be to determine what to use for limit switches so that the unit can travel from end-to-end (and not just travel back-and-forth in a coded fixed length) - either a physical switch or a Hall-effect sensor are the likely final candidate.  I'll also need to determine some better wire quick connects to easily connect/disconnect the electronics.

Driving 12V Stepper Motors

With a motor shield fully assembled (see earlier post), it was time to connect up 2 x 12V stepper motors (purchased here) and see if the soldering job was all goodness.

The motor wires were connected in the order [RED, YELLOW, GREEN, GREY]. I guessed a bit on  the location of pin one for each of the terminal blocks.  Here is the final layout:

I drove the Arduino via USB (+5V), and the motors off of a separate lab power supply (+12V):

For the code, I kept the first scenario fairly simple;  Sample code from the vendor was borrowed and modified to alternate the motors, driving them both forward and reverse.  The code is below:

For this build, the impossible happened: everything worked the first time.  The next steps will involve figuring out some kind of drive mechanism to make the steppers do something productive (well, more productive then rotating two blue painters tape flags).  Since I have degrees in EE not ME, I'll need to spend a bit more time deciphering the right lingo for google queries (actuators, drive screws, linear bearings, etc., etc.)

Assembling an Adafruit Motor Shield for Arduino

I guess my first clue should have been in the name "Adafruit Motor Shield Kit", but somehow my eyes rolled right over the last word.

The motor shield arrived as a PCB, 3 ICs, and a handful of passive components, meaning it was time to break out the soldering iron.  The kit assembled without too much trouble, with full assembly instructions online.  The online instructions appear to be for an earlier edition of the board, but it wasn't too hard to decipher the differences.

The only part of the directions that were unclear was a statement that "the four 'middle' pins of the L293D motor driver chips are tied to a large heat sink and thus may end up getting 'bridged' with solder as shown in the second image."  I wasn't sure if that meant you were supposed to bridge the pins, or it was just something that just may happen.  A little digging on the forums revealed that the pins in question are all GND, so it doesn't really matter whether they get bridged or not.

BEFORE

AFTER

I thought about showing you the outstanding soldering job on the back of the board, but decided instead to blame the camera for taking a poor picture, which has no relation to the high-quality soldering which actually occurred on this assembly.  I also installed a set of stacking headers in the extra provided through-holes, and cut them short on the back as they will not be used for stacking; since I've never worked with motors before, I'm guessing I'll have need of the convenient headers for debugging.

Next up will be the connection of the stepper motors and a sample sketch to get them moving, after of course reading the manual.