Tech Talk

We had a small tutorial session on preliminary ASIC design flow using synopsys and cadence tools. I was handling the tool demo while my guide introduced the concepts. We used VNC for demoing the tools, since I had set the entire thing on my work station.

One of the professors attending the session wanted to record the setup. I suggested vnc2swf to record the session, since we were not so keen on the voices. We only want to record “what menu, what choice and after what”! Anyways, as usual after a few technical glitches we managed to record the entire session in four SWF files. Interestingly, the combined file size was about 40-45MB. I guess lack of audio did the trick.

There is an internal wiki site where some of these recordings get hosted. We decided to host the files on that wiki, so that others can get to use it also. The problem started exactly here. How do you convert SWF to a flash movie like what they have on youtube? There are a bunch of proprietary solutions on google. I am the only guy who uses VNC for these things and I certainly don’t want to afford a converter!

There is a pyvnc2swf project that is hosted along side vnc2swf. Little did I realize that this project did exactly what I wanted. Power of using python? I was woken up by this forum via google. There is a simple edit.py that does the conversion. The command itself is
$ edit.py -o file.flv file.swf

And mplayer played the flash video fine, so I guess the web flash players would do the same too.

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I was helping a friend of mine construct a simple robot to plot some characters written in a text file or just follow a random scribble updated-live between the robot and the paint tool used. We were only at very higher levels of abstraction because how-on-earth-will-you-get-the-actions-done-in-paint is certainly an unanswered question.

But doing this excercise just gave me another point that I never seemed to use all this time. It is nothing we have not known so far. Components of a vector along the axes of interest. One of the things I am interested in doing includes assembling a robot that would move about like one of us in a workshop floor. Only I want to do this without all that complex research done all over the world. Ridiculous, isn’t it? (By the way, I meant my thought is ridiculous and not the research work done!)

One of the problems I faced in my project work was passing on the control information to the robot over a wireless link. I had not thought about/read research papers on how to do this in an efficient manner. I was trying to send the entire bit sequences to keep the motor rolling! But there seems to be better ways.

Suppose I generate a constrainted box in my application and map it to the space that my robot will move about in. Then all I need to send over the link is just some binary representation of the component angle. Since I mapped the space onto my application, I can hardwire all the other constants such that any binary sequence read in will cause the motors to move such that the robot itself moves in that angle.

Now the question remains, how-will-i-hardwire-computation on a pcb?? I don’t plan to by FPGA kits!! Let me see. Maybe there will be an easier way out to do this too. Or probably an easier way to do the entire thing. How much easier can easier get without doing any research??

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.

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!

If you had the access to the Electronics for You magazine and you are trying to construct a simple robot, then I recommend you try the June 2006 issue. It contains an interesting article — Remote-Controlled Land Rover—A DIY Robotic Project. This article explains a simple land rover construction. It also has the entire electronics assembly explained along with the PCB layout diagrams. This couls help you start sith something moving at the earliest. You can always add to it, right?

After a year, I will be back with my solder iron. I am planning to test and find out the power and torque ratings of the stepper motors that I have. I have managed a good driver circuit form the net. I ll see if it can help move about 2-3 kgs with two motors. I should check out on Servos also. I will push that for the next weekend because, I ll first need to hunt for some cheap servo motor stuff. I am planning to implement a ATMEL microcontroller based circuit to start with. That way I will get some time to choose a decent PC or tablet like mobilis. Heard about PC 104? I did very recently. Wonder what they cost like.

I hope to be posting my experiment results here real soon.

Last post on New Age Ideas is now kinda making me feel dumb. How could I have forgotten Bluetooth and think of WLan?? I have also managed a bunch of developerWorks links for some high level design ideas. You can find some of them in the robotics tag here.

Ok. Last week I was browsing through this Wi Fi for home networks, their setup et al. Interesting and holds a promise for completing my project. All I will need to do is set up a wifi network between my bot and my desktop and bingo, I can even internet enable my bot. Wow. But I wonder what it costs like in India!??! I have just started researching the costs and will have a budget early next week.

Next step would be plan the set up and then complete the n/w code for the bot. Its pretty incomplete too. This time around, I am sticking to Linux. For the project work, we were wasting time with Windows. Its too heavy for a bot, that too a controlled one. Windows was trying to get more intelligent than my code and blowed the whole idea. But then, I did not know even this much Linux during project days!

Ok, that calls for laying out a project development strategy and tools acquisition strategy. I almost have to start from scratch. I only have the four wheels and the frame and one old mother board. I wonder if that board can go alive??? Also, I need to figure out how to get a PC on a battery!? Stupid, right?

Heard of Mobilis? Its a tablet PC from some Indian Co. Costs something like 10 grands. I ll probably get its specs and start from there. That way, I won’t have to worry about the supply details. What says you?