December 2005 - Posts

• My Last Post

  Yesterday I posted about almost burning my house down because of a li-po battery and my ignorance. In the post I captured the emotion I felt at the time by using the words OH FUCK. The thought of a fire in my family's home with my daughter and my immediate family brought nightmares to mind. So I posted about it and how to avoid such situations. But I got this response: "Does this really belong on the main weblogs.asp.net page? Please use some discretion, especially if you choose to put profanity into your post." To this I have no retort.The first thing that came to mind was "wow, what a pussy..". I've been posting here since 2003 when this blog was given to me and before it was part of the asp.net website. I would love to focus on .Net in all of my posts but do you really need to read another post about web 2.0 and AJAX? Do you really need another "Top 10 Best Programming Practices" by Joe Nobody? Do we really need to go over the stuff that is written in plain english in the .Net documentation just one more time? This response also begs the question - Do I need to edit my own thoughts because someone may get offended? So on the train this morning I got to thinking.. (Dangerous I know, but I can't help it.).. I realized how much of this is bullshit. I'm one of a million blogs spouting off into the void about myself and all of this material is bound to be sent to the bit bucket and never read again. At first I was going to setup a blog at my own website but I have decided that I refuse to be part of this circle-jerk any longer. The greatest in computing don't sit on the top of the mountain and preach about how to program, they DO. They take action. Donald Knuth doesn't even use email! One of the greatest minds in computing and somehow he manages to not even use email, let alone have a blog or podcast. Linus Torvald, a man that changes the world of computing more each day doesn't even have a website! If they can do without well I think I can too. Now I will crawl back into the low place that I came from, to hang out with foul mouthed geniuses, the scourge of internet society, and the wreckers of all that is good. Have a good one. PS. Don't take this as "I'm going home and I'm taking my ball with me!", instead take this as "I need to be more focused in what I do". Posted Dec 28 2005, 09:50 AM by shedao with 4 comment(s)

• Lithium-Poly Batteries and Safety

  Over my X-mas break I attempted to put together a remote control plane (1.5 MB image) I intend on using as my first UAV. My first order of business was to get my electronics hooked up correctly and working on the bench and then proceed to the assemble the fuselageand mount it. This is how the "incident" began. I was working with a friend and we hooked an 10A electronic speed controller (ESC) to the battery, then to the reciever. The engine channel would not respond so I hooked up a servo to another channel and it worked. I repeated with 3 other channels hooking servos to them and they responded. But the engine would not turn. Then I gave it full power and I see smoke. I kill the power. The smoke is coming from the ESC heat shrink wrap and also from the connection to the battery. I stop everything and while trying to get the battery unplugged I notice the wires are hot as shit! It's melting the wires! I still have it connected to the ESC and receiver and I'm trying to get it unhooked as fast as possible knowing the warnings about this type of battery. The battery starts to balloon immediately and I think OH FUCK it's going to explode. Images of the house burning down are very real now. So my friend gets it disconnected with a little pain (hot melting wires remember) then drops it to the floor and moves quickly. I toss a hard hat on it to try and contain whatever might happen. After about 5 minutes of waiting we decide to delicately remove it outside where it can cause the least amount of damage. The next day I took this picture and did some research. I found a few videos online showing exploding li-po batteries. I find that I was not nearly as careful enough. Take a look at this forum post to show the needed safety precautions when deailing with this type of battery. From now on I will treat it like nitro and keep an eye out for safety concerns. Upon my research I realized that a few things may have happened to cause this: Discharge rate was too high - ESC might have been on the fritz. I doubt this. Voltage dropped below 3.0 volts per cell and made the battery unstable. I dropped the pack that day and did not inspect it. A dropped li-po pack can become unstable by shorting out internally. So what I plan to do is start fresh with a new brushless engine (The one I'm using was an old can motor brushed 370 from another kit), a new brushless speed controller with programmable low voltage setting, and a nice battery with built in over-discharge detectionand temp guage. I will charge them outside and leave them in a "bunker" made out of a flower pot and lid. Many people sware against li-pos because of the fire hazard. Many swear by them and claim they are safe with the right precautions. I say this - anytime you store energy you have a potential hazard. Treat them with respect and you will be ok. Treat them with a lack of respect and you may end up homeless. Posted Dec 27 2005, 05:14 PM by shedao with 1 comment(s)

• NIST Dictionary of Algorithms and Data Structures

  My friend Jesse pointed out that the US National Instititute of Standards and Technology has a great dictionary of algorithms and data structures. Some of these I have never even heard of. I am pretty amazed at the sheer size of this dictionary. For instance I've heard of Soundex, but I've never heard of a Jaro-Winkler. I'll put this nice addition in my toolbox. It may come in useful. Posted Dec 14 2005, 09:57 AM by shedao with 2 comment(s)

• A Month of "Free Time" and my IPod

  Everyday I take the commuter train into work. I've been doing this since October to get to my job in downtown Washington DC. The commute is 1.5 hours each way. After doing a bit of math I realized that next year at this same rate I will spend 32.5 days on the train! Over a month! That's a lot of time spent doing nothing. So I read. But you can only read so much so I bought a new IPod video and have been watching Battlestar Galatica, Lost, ripped movies, etc. This thing has really been a "sanity saver". It makes the time go by nicely, even when squished in a seat by two large ladies that could've played as starting linemen for the '84 Redskins. I'm completely sold on the format, I have never watched this much TV in a long long time. I like the whole TV-to-go plans hollywierd is coming up with. Keep it coming. Posted Dec 12 2005, 02:26 PM by shedao with 1 comment(s)

• Euler Angles vs Tait-Bryan angles..?

  So in my study of using Euler Angles to represent rotations in euclidean space I came across the following quote that you can find all over the place: "To add to the confusion, flight and aerospace engineers, when using yaw, pitch, roll (also called heading, attitude, bank) to refer to rotations about the x, y, z axes, respectively, often call these the Euler angles. These x-''y''-''z'' angles are properly known as the Tait-Bryan angles,.." Wikipedia on Euler angles: "Euler angles are the classical way of representing rotations in 3-dimensional Euclidean space, named after Leonhard Euler." Wikipedia on Tait-Bryan angles: "In geometry, Tait-Bryan angles are three angles used to describe a general rotation in three-dimensional Euclidean space by three successive rotations, once about the x-axis, once about the y-axis, and once about the z-axis." So can someone knowlegable in the subject please explain the difference to me? Is it the abstraction? Is this a case of semantics or am I just a large ape that needs to stick to beating a stick? [Edited:] Ok, so my understanding is that the difference is this - after each rotation using Tait-Bryan the axis will be redefined, the coordinate system relying on the object itself. Whereas when applying Euler angles the axis will not move. In other words the object defines the coordinate system. Posted Dec 05 2005, 10:51 AM by shedao with 1 comment(s)