Abishek Speaks

Current or Voltage characterestic curves of transistors were introduced to me as early as my twelfth standard. There were other curves, heat transfer et al, that were taught in physics text books for a major part of school. But, in school we just used to laugh our heads off when the teacher displayed a graph and explained something. I don't remember even one graph that made sense at that time. The trend was similar all through engineering classes. The plots/graphs made no particular sens, at least because we never chose to make any sense out of it.

One primary reason for this, I would say, is the way some of us did our lab work in school. When we had to obtain a characterestic curve, the text book told us what they looked like. More often, we plotted a curve, picked the points and fitted the observation!! I hope my physics teacher is not reading this. Some time in engineering, we used some part of this technique to get satisfactory graphs! Even otherwise, this is way easier than doing that experiment correct enough to get believable curves.

Last week, I had to obtain an estimate of the current flowing through a pMOS device for a particular lab work. For the calculations part, we used a simple model. This model needed me to identify the region of operation of the device. The trouble started here. I was trying various references to figure out a way to do this. My teacher suggested that I use the Vds - Ids characterestics for a pMOS transistor. Of course, I set up the simulation and got the curves and located the region of operation to be saturation due to pinch off.

So, why am I writing all this? That was the first time I used a characterestic curve of any kind known to me! Maybe, I should get back to all those physics and engineering text books and redo the stuff to see if the curves have other significant points missed in ignorance!!

Interestingly, I could have done the same with some theoretical reasoning also. The current equation uses a voltage which is the minimum of three possible values - triode, velocity saturated or saturation due to pinch off. The plots suggest the same too. Now, I know why I will remember the characterestic curves of devices I use.

Current Mood: thoughtful

Remastering a distro is not any unheard of topic today. And especially remastering Knoppix with all that brillian step-to-step documentation, it is just about having some interest and time to try one. Last week I just had the right mix of things and I got the first remastered version. The idea was to cut down on the multimedia and the jazzy kewl apps and add some electronics stuff from opensource, some computation tools like octave, numeric-python and all that. Well, came around well I should say. Only wouldn't fit a CD yet. I remember reading this in one of the early linux for you magazines about how the remastering quickly becomes a balancing act?! I still have some act left for the week ahead. I wonder if there is something left to be stripped at all! Anyways, If it ain't getting smaller, I just might choose a bigger disc. Do they call these DVDs?

Current Mood: hopeful

There are a couple of tools that you can use to connect from linux to a mobile phone over a bluetooth conection. Some of them that I tried include gammu, gnome-bluetooth. I was trying to install gnome-phone-manager. Of course, I did an apt-get to install gammu. I installed gnome-bluetooth from ubuntu repository. Wouldn't debian maintain that? I am using sid after all!!

Most of these tools are not as simple to use as the nokia phone manager. Part of the reason is certainly the fact that I got used to the PC Suite well before other linux based tools. Nevertheless, I wanted to transfer some backgrounds on to my phone and these tools wont help me right away!


So, I decided to get my hands wet using these primary tools - hcitool, obexftp. Good ones and did the job! Here is what I did and the results.


abishek@ingeneur:~$ hcitool scan
Scanning ...
        00:15:DE:11:6B:74       Ingeneur' nokia

That is my phone alright.

abishek@ingeneur:~$ obexftp -b 00:15:DE:11:6B:74 --put  splash.png
Browsing 00:15:DE:11:6B:74 ...
Channel: 10
Connecting...
done
Sending "mac_osx_linux_splash.png"...|done
Disconnecting...done

That was the simple bg pic from my debian that I wanted on my phone. Getting files as simple as that too.

Interesting, right?

Current Mood: geeky

Yes. This is the first topic from the series I spoke about in my earlier post. Atom model. I learned about atom models like Rutherford and Bohr models as early as my High School (10+2). But, it was in Chemistry. The "but" is because I was never all that brilliant as far as chemistry was concerned. My chemistry teacher still remembers the way I used to conjure up new compounds to balance my equations!!!

Ok. So, if I learnt it then why am I writing it here. In 10+2 I never got the subjects the way I got them in undergrad college. This is one major reason why I never kind of understood the atom models even to the requisite detail. In undergrad college, this was not the topic that fetched your score, so I could comfortable keep out of it. Yesterday, I thought I will just give it a try and see what the models had to say. What I saw was revelation to me!!

Here is what I understood. The Rutherford model was based on classical mechanics. That is there is a positively charged nucleus and there are as many negatively charged electronics outside the nucleus as to keep the entire setup electrically neutral. These electrons revolved around the nucleus. The entire setup is analogous of the planets and the sun in our solar system. This I remember from my 10+2.

But, there is something from classical electromagnetics that disrupts this setup. Classical Electromagnetics suggests that an accelerated charge must radiate energy. And if it were oscillating in the frequence 'f', then it would radiate energy in the same frequency. The electron is a negative charge revolving(oscillating) around the nucleus in a particular frequency. Then it would radiate energy in the same frequency. That atoms radiate energy in discrete ferquencies are confirmed by the spectral line studies.

So, if an electron radiated energy, then it would lose the radiated energy from its kinetic energy. This implies that the electron slows down. Then by classical mechanics, the electron's radii around the nucleus would have to reduce. If this continued, the electron would eventually collide into the nucleus. This is not true as atoms continue to exist over time!! Moreover, if the radius reduced, the frequency would vary and thereby the energy spectrum would be spread out. This is also not the case. The spectral lines are rather sharp and well defined.

Here the Bohr model comes to the rescue. This model suggests that the electrons revolve around the nucleus in discrete states called the stationary states. In these states, they do not radiate energy and hence do not lose energy. They radiate enegry whenever they transit from one stationary state to another and the amount of energy is proportional to the difference in energy levels between the states. And the stationary state is defined such that the angular momentum of the electron in this state is quantized.

Refer http://en.wikipedia.org/wiki/Bohr_atom.

Current Mood: nerdy

For quite sometime now, I was wondering what I should be putting up here! I ve been getting crazy ideas of posts and one of them you saw here earlier. But, last week, I was getting back to my electronics text books trying to get back to electronics days of college. I am getting back to college shortly!

This thought has given me some stuff to fill this journal! No, no ramblings about college. I think I ll post all those things I am learning now, that I ought to have learnt in undergrad college. Yes, and it is a shameful lot of electronics!

I ll try to make this a series. So If you want to follow or comment, you may gladly do so. I am by no means an authority in this subject! I am merely posting what I am learning. And if you find it stupid or incorrect, take the time to inform me!

I am using these books first

Integrated Electronics - Jacob Millman & Christos Halkias

and Electonic Circuits - Donald L.Schilling and Charles Belove. Well, I do not know if these are the best, but, these are what I have now!

Current Mood: nerdy

Entish


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