16 April 2004

Material Science and Electronics, Part 2

Mark Streitman

I recently had a simple physics problem that I needed to solve.  I was working with a heavy string in an environment where the temperature was changing.  I needed to know how much the string length changed over the temperature change.  So the first thing was to go to the Handbook for Chemistry and Physics and get the delta change in length for the material.  I don't own a copy, and I didn't want to spend the money for the on-line version. I know I should, but I'm cheap.  So I went to the library and looked at their copy.  But first I needed to identify the material.  The package says polycord,  OK, polyester.  Guess what, no polyester in the HC&P.  So, I decide to look on the web.

What I found dwarfs the handbook for material properties.  MatWeb, Your Source for Materials Information is a web site that all the professionals use.  I did a search for polyester and wow, I got back many pages of information. It turns out there are 2,328 different products that are some kind of polyester.  Type "steel" and you get back 4,470 materials.  In other words, they have real info on the real materials that are being used in the world today. 

Yes, a lot of the polyester or steel values are going to be similar, but if you need an exact value for a material you're working with, it will pay for you to find out the exact value for one you have.   Of course since the site is free, pay is just an expression! 

For each material they have the chemical composition, physical, mechanical, electrical and thermal properties.
If you ever need any material information, add this site to the top of you bookmark list.

In my last column I talked about beginner electronics resources and I'm continuing from that point. If you want a magazine that caters to the amateur and hobbiest you might want to look at Nuts and Volts   magazine.  It has articles on robotics, interfacing and other small electronics projects that are really interesting.

There are other electronic company sites that I found useful.  National Semiconductor is not as well
known to the public as, say, Intel or AMD, but they have been around for years and make a lot of different chips.
Their web site has a lot of basic information about their chips and something they call  Analog University.
It has all kinds of seminars, presentations and design software to teach electronics and create all kinds of projects. Of course it's all free.  If you do a Google search you can find other electronics companies that will have even more free stuff.

Ok, suppose you have gone through some of the training or you already have some electronics knowledge and you want to design and build a circuit.   There are a number of free software packages to design and test circuits. From the GNU folks there are 3 (free) packages gEDA-gaf - Tools for electronic circuit design. This  is a total electronics design and test system for UNIX/LINUX only. Electric is really designed to make your own chips.  It can be used to design circuits, but I found it difficult to use. PCB is a circuit design layout program. I haven't used it , but it looks like a pain to use, too. However since they are free there is no harm in trying them.

The program I like best and have used is Eagle Lite .   This is a complete design and PCB board creation package.  It's a for-profit company but they have a limited version of their software called Eagle Lite.   Eagle Lite has the limitation of creating up to a 4 in x 4 in board and it can only be 2 layers (copper circuits).  For me this is no problem.   They have a large and reasonably up-to-date library of electronic components.   I have created a board design that I had prototyped by a board manufacturer.  The program is free for nonprofit users.  If you do make a profit, it's only $50 for the software.  If you really need it, they have a more expensive program that remove the limitations. But unless you're building a motherboard type of project, you don't need it.

In the next column I'll continue from here and tell you how I designed some professional PCB boards for not much money.

Free is good.


Mark Streitman is the president of the New Jersey chapter of the SAS. You can reach him at president@njsas.org