Eric Blade

I know, way past Christmas, but hey at least it’s still January.  Just wanted to share what great Geek Christmas presents look like.

The part on the left is a gps module from sparkfun.  I have been wanting to experiment with some gps stuff for robotics, and just to try something like geocaching, so I am really looking forward to having time to start playing with it.  The other thing that looks like a can of tuna fish is a 40m Ham Radio Receiver kit.  I really can’t wait to play with that.  I have had my Ham license for over a year now, and have somehow managed to not buy any radio gear.  This will be my first receiver.

I have been a real slug about posting updates.  It’s not that I am not doing anything, it’s that I am doing too many things.   The other weekend, I was getting in some quality shop puttering, and was really frustrated with my previous attempts to Re-Saw wood into thinner stock.  I had been attempting the method where you align your rip fence to take into account the drift of your particular bandsaw blade etc.  Well it never worked for crap for me.  The strips were never even close to uniform, and was always a struggle.  I did a little searching on the web, and found that others equally frustrated with that method had much better luck with a Re-Saw jig that works by having basically a single vertical surface on which to guide the board as opposed to an entire fence.  This way, you can manually adjust the angle of feed as you are re-sawing.  I created the below jig out of scraps and parts I had in the shop in about 30 minutes.

Well, I skipped the whole part that I am pouring a concrete sidewalk on the side of my house.  I had originally planned on this being a quick, knock it out in one day kind of a project, but the fates consipired against me.  That and forgetting things like baseball games etc.  Anyway I digress. (Wow, can’t believe the spell checker fell for that one.)

Steps to the side door.  Actually building the stairs was pretty easy, which confused me based on some comments a friend of mine had initially made.  Then I finally understood.  My stairs were easy, because I have NO design restrictions on where the stairs end.  I had a 30″ drop from the deck to the concrete sidewalk I had poured, so I just divided the by 7, which gave me four steps, then rounded it up to have all the same rise (7 1/2″).  Then just used the framing square trick to cut the stringers.  I had to pause for a minute to take into account the first step thickness.  I can see how tricky it would be when restricted by the linear dimension of where the stairs can start and end.

Here are some pic’s of the stairs and me in action.

Ok, I am a fan of the who, but I also feel guilty.  I seriously considered back dating some posts just because it has been so long since I have posted anything.  Well, as I often like to say, if you don’t stand for something, you will fall for anything.  ie, you gotta have values and stick to them.  So, there will be NO backdating of posts on this site.  If I am a slug, then so be it, I am a slug.  Now to supplant my Guilty feelings, expect a few more recent posts.

So I was exploring the Lair a few months back, and came across an HP Jornada 620 that I forgot I had acquired.  I am pretty sure it was a donation to my geekiness by a friend.  Anyway I was thinking “wouldn’t it be cool to run Linux on something like this.  A quick search of the net and I came up with Jlime the Jornada Linux Mobility Environment.

My first step after reading through the FAQ was to locate an appropriate CF card to install the boot loader and file system on.  I know I have a couple of CF cards floating around, but somehow they eluded capture.  Thank goodness for Wal-Mart.  A quick trip and a lightening of my wallet by about $20 and I was back in the lair with a 4GB CF card.

Going through the installation, it was all pretty straight forward.  The CF card needed to be formatted with 3 partitions.  One FAT partition to hold the boot loader and config, one ext2 partition to hold the Linux File System, and a swap partition.  I am really impressed with how well the Ubuntu drivers on my workstation handle my USB card reader.  I didn’t have any issues with that step, and I soon had it completed, and all of the necessary files in place.  The next step was simple.  Put the CF card in, navigate through WinGoo CE and kick off the bootloader from the card.  Slight mis-start as my config pointed to /dev/sda whereas the jornada was seeing it as /dev/hda.  Quick modification to the config file, and wazzam.  My heart started racing as I saw the system drop into a classic linux boot screen, and then.

hda:  lost interrupt

hda:  lost interrupt

over and over again.   My first thought was the CF card was not compatible.  So over the next few weeks, I begged, borrowed and bought a couple of different CF cards to try.  But it was not to be so easy.  Same results ;(

I tried not to think thoughts of utter despair, but it was not to be.  All I could think of, was my Jornada has a bad CF card slot.  I went to ebay and started looking at the Jornada’s thinking of picking up another.  Then I remembered my recent posting and personal committment to re-use.  That was the whole reason I dug out this thing in the first place.  So, I did what I normally don’t do.

I asked for help.  I went to the JLime forums, registered, got my account info confirmed in the email, and then carefully crafted my plead for help all the time expecting no reply or a “you got a bad Jornada reply”

Instead, I got a quick reply to the effect of “Oh yeah, that’s a known problem with the 620, just use Rafa’s Kernel”  A couple more detailed exchanges of information later and Voila!!

The moral of this story is a simple and humbling one.  Don’t be afraid to ask for help.  In can save you a lot of time, frustration and money.  And you might even learn something.

Really need a catchier name, but for now we’ll just go with that.  A number of people have asked what my Lab/Lair/Man Cave looks like (ok, one person asked).

So here I present a short tour of (/ominous music on)  The Lair (/ominous music off)

This image is kind of blurry, but you sort of get an idea of the space.  Work bench is to the left.  The glowing blue neon is from the Linux workstation I have on my bench.
Here is a shot of the workbench.

And finally, here for the first time seen by public eyes, is The Chair of Eternal Contemplation (or at least until dinner time).

After a brief pause for resource re-allocation, plans for world conquest are continuing.  Here we see a crack research team working on a prototype killer robot.

This is a first revision prototype code named Fi-Fi.  The following image shows some detail of the primary motivator substructure and power core.

“Shape your tools or you will be shaped by them!”

http://www.youtube.com/watch?v=MOTw_PkK_SU

(This is a back dated Post of the first entry in my new notebook)

Moleskine is a type of notebook supposedly used by a lot of famous artists.   Specifically, the current manufacturer’s claim it as “the legendary notebook used by European artists and thinkers for the past two centuries, from Van Gogh to Picasso, from Ernest Hemingway to Bruce Chatwin.”  I had started looking for a new notebook, since my current one was on it’s last page.  I wandered over to the bookstore for lunch today, and I saw this one, loved the way it looked, as well as it’s size and format.  I like engineering style notebooks with the graph style paper. (squared according to the moleskine vendor.)

When I got home tonight, I decided it was time to mow the grass.   Well of course I needed to tinker with the mower a bit before I could mow.  I checked the oil, checked the gas, and filled the tire that only seems to hold air for about a day.   As I was working on it, I started thinking about Zen and the Art of Motorcycle Maintenance.

I had read this book many years ago, and found it interesting and inspiring.  About 6 months ago or so, I saw it on CD at the library.  I have a 46 mile commute each way, so I have a pretty big appetite for books on CD, so I picked it up.  Well having it read to me, and being the second time through was very enlightening.  I really think I ‘get it’ on a level I didn’t really understand before.

A man truly grows in any of those moments in his life when he is attempting to achieve quality.  In my mind at least, the achievement of quality is just the striving for perfect order within the universe.  ie Natural order.   This opens up a whole can of philosophical worms that ends up leading me into the whole Teilhard de Chardin / Frank Tippler Omega Point idea.

But, the grass still needs to be cut.

This has been done a million times on a million different web sites, but as a robot geek I am obliged to post it on my site.  Hobby servos like the ones you use in model airplanes are very easy to control from most micro controllers.

The servo’s are made to only rotate slightly less than 180 degrees in each direction.  A fairly simple modification allows the servos to rotate a full 360 degrees continuously.

The actual modification is going to vary slightly depending on the particular servo in question.  There are two modifications that need to be made.    The first modification is to circumvent potentiometer that provides feedback to tell the servo it’s current position.  This part will vary the most. In this particular servo the feedback pot is in the lower right corner of the following picture.

The cog is on the pot, and connects with the gear on the left when assembled.  In this servo all that is needed is to remove the cog that connects the pot and the gear.

Then center the potentiometer.  If you want to be exact, you can throw an ohm meter on it and make sure your resistance on both legs is equal.  Many servos wont be the easy, and you will have to actually remove the entire pot.  In that case there is usually enough room to solder two resistors of equal value in place so that the resistance is the same on both legs.

The other modification is to remove the mechanical stop that prevents the servo from physically rotating.  Usually you can identify this quite easily.  In the picture below, there is a small tab on the shaft of the gear.

This is a pretty crappy picture as I have the tab on the shadow side, but I think you can make it out.  The tab needs to be removed.  You can usually do this with a utility knife.  I like to use a nice sharp chisel.

Then you just put the whole thing back together and your all set.  There are tons of links of how to do this, so if your actually interested, and this doesn’t provide enough info, just google servo mod.