All About Circuits

All About Circuits - Blogs http://forum.allaboutcircuits.com/blog.php A discussion forum for electronics and circuits en Tue, 13 May 2008 17:37:31 GMT vBulletin 60 http://forum.allaboutcircuits.com/images/misc/rss.jpg All About Circuits - Blogs http://forum.allaboutcircuits.com/blog.php <![CDATA[Passive Pi Filter and Millman's Theorem]]> http://forum.allaboutcircuits.com/blog.php?b=60 Fri, 09 May 2008 22:06:38 GMT Here is a derivation using Millman's Theorem of the transfer function for a passive Pi-Filter that I put together several years ago.

As always your comments and suggestions are welcome.

hgmjr

Attached Files

Pi_network_Transfer_function_RevA.pdf (137.5 KB, 26 views)

]]> hgmjr http://forum.allaboutcircuits.com/blog.php?b=60 <![CDATA[Second-order Sallen-Key Bandpass Active Filter and Millman's]]> http://forum.allaboutcircuits.com/blog.php?b=57 Wed, 07 May 2008 01:55:54 GMT Recently in the forum a member questioned if there was a member that could provide the derivation of the transfer function for a Second-order... Recently in the forum a member questioned if there was a member that could provide the derivation of the transfer function for a Second-order Sallen-Key bandpass Active filter. I took on the challenge and the attached document is the results of my efforts. The answer I was able to obtain using Millman's Theorem agrees with the answer that appears in this example on the web at link.

All comments and suggestions are welcome.

hgmjr

Attached Files

sallen-key_REV_C.pdf (105.5 KB, 30 views)

]]> hgmjr http://forum.allaboutcircuits.com/blog.php?b=57 Useful Matlab Links http://forum.allaboutcircuits.com/blog.php?b=56 Wed, 07 May 2008 00:26:53 GMT (I originally posted this on the forums). Matlab is a proprietary numerical computing environment developed by the Mathworks which allows for matrix... (I originally posted this on the forums).

Matlab is a proprietary numerical computing environment developed by the Mathworks which allows for matrix manipulation and mathematical analysis across a wide range of engineering and scientific disciplines. Through out my time using Matlab I have come across a wide range of site and tutorials that have helped me learn to use Matlab and get the most out of it.

The following is the first set of links that I have complied for the users here at AAC. The information covered in this section is the Mathworks website, general Matlab tutorials, tips and tricks for using Matlab, debugging in Matlab, and some Matlab FAQs. Note that some websites contain common information, but this is intended to be catch all:

The Mathworks Website:

Mathworks Homepage

Matlab Functions List - this is the same function listing that is part of the Matlab help

MatlabCentral - Matlab User Community, including the file exchange and link exchange

Matlab Tutorials:

Introduction to Matlab

Getting Started with Matlab

Helpful Information for Using Matlab

Matlab Tutorials from MatlabCentral

Matlab Tutorial from the University of New Hampshire

Matlab Special Characters

Matlab Commonly Asked Questions from MIT

3-day Matlab Tutorial from MIT

Matlab on Athena at MIT

Matlab Basics Tutorials

Plotting Tutorials for Matlab

Matlab Tips and Tricks:

Matlab Tips and Tricks

Matlab Array Manipulation Tips and Tricks

Exploiting the comma seperated list - article from the Mathworks

Matlab Tips and Previews

Matlab Visualisation Tips

Matlab Programming Tips - PDF article from the Mathworks

Matlab Debugging:

Debugging Matlab m-files

Debugging in Matlab

Guidelines for Debugging in Matlab

Matlab FAQs:

Matlab FAQ from the University of Florida

Matlab FAQ from Stanford

Hope this is useful for some of you. Any comments and corrections of broken links are welcome.

Dave ]]> Dave http://forum.allaboutcircuits.com/blog.php?b=56 <![CDATA[Unbalanced Bridge Circuit and Millman's Theorem]]> http://forum.allaboutcircuits.com/blog.php?b=54 Sat, 03 May 2008 01:30:56 GMT Attached is a solution of the unbalanced bridge circuit example present in the allaboutcircuits.com located at the link... Attached is a solution of the unbalanced bridge circuit example present in the allaboutcircuits.com located at the link http://www.allaboutcircuits.com/vol_1/chpt_10/3.html

The solution found in the AAC e-book has been solved using mesh analysis. I took on the challenge to solve the problem using Millman's Theorem.

I welcome any comments or questions concerning the analysis.

hgmjr

Attached Files

wheatstone&millmans.pdf (405.4 KB, 38 views)

]]> hgmjr http://forum.allaboutcircuits.com/blog.php?b=54 <![CDATA[Simple Start with Millman's]]> http://forum.allaboutcircuits.com/blog.php?b=21 Sat, 26 Apr 2008 20:26:11 GMT It has always been my contention that in order for a circuit analysis tool to be of any value to me, it must be scalable. This means it needs to...

It has always been my contention that in order for a circuit analysis tool to be of any value to me, it must be scalable. This means it needs to solve the simpliest problem as well as the most complex problem by using the same repeatable algorithm.

My experience has been that Millman's Theorem meets this criteria fully.

For example, take a simple problem such as a resistive divider (see figure insert above). Those familar with the simple resistive divider circuit will recognize that the expression below is used to calculate the attenuation of input voltage $V_I$ expressed as $V_O$ .

$\frac{V_{O}}{V_{I}}\ =\ \Large\frac{R2}{R1+R2}$

To show the Millman's at work you simply apply Millman's to the two resistor divider circuit.

$V_{O}\ =\ \Large\frac{\frac{V_I}{R1}}{\frac{1}{R1} + \frac{1}{R2}}$

Next, multiply the numerator and the denominator of the expression on the right of the equal sign by the least common denominator factor R1*R2 .

$V_{O}\ =\ \Large\frac{\frac{V_I}{R1}}{\frac{1}{R1}+ \frac{1}{R2}}\ * \ \Large\frac{R1*R2}{R1*R2}$

$V_{O}\ =\ \Large\frac{\frac{V_I*R1*R2}{R1}}{\frac{R1*R2}{R1} +\frac{R1*R2}{R2}}$

$V_{O}\ =\ \Large\frac{V_I*R2}{R2+R1}$

Divide both sides of the expression by $\ \normalsize V_{I}\$ and rearrange the denominator and you end up with the familiar expression that is identical to the one that is associated with a standard two resistor divider.

$\frac{V_{O}}{V_I}\ =\ \Large\frac{R2}{R1+R2}$

This example illustrates that Millman's Theorem can be used to solve uncomplicated circuits. ]]> hgmjr http://forum.allaboutcircuits.com/blog.php?b=21 reference:Einstein http://forum.allaboutcircuits.com/blog.php?b=51 Sat, 26 Apr 2008 16:40:55 GMT If you consider all blogs and the string's of
intelligence that may exist.Then consider
the number transistor's in a super micro-proceessor. (answer) ______ give details
of the question,hint genesis of electronic
need. I am exploring, I am no Einstein. I do not have the perfect question for the answer.I am sure the best question is on this blog.Try me for hints, beleive me you
are using a form of this now. ]]> loosewire http://forum.allaboutcircuits.com/blog.php?b=51 PLL Frequency Synthesizer http://forum.allaboutcircuits.com/blog.php?b=50 Sat, 26 Apr 2008 11:24:27 GMT [IMG]http://forum.allaboutcircuits.com/D:/My%20Document/plls[/IMG] ]]> amr_col http://forum.allaboutcircuits.com/blog.php?b=50 Introduction, and Paint as CAD http://forum.allaboutcircuits.com/blog.php?b=49 Sat, 26 Apr 2008 09:49:22 GMT At this time I've been on this forum for about a month, and have made myself known. I've been drawing like crazy for the forums, submitted a new section for the eBook (ESD), and made a fair pest myself everywhere around here.

The picture to the left was a joke for my mom, I wanted to show her my latest martial arts acquisition. She took it pretty much as expected, didn't find any humor in it at all. The picture is still pretty accurate, minus the black eye (guys fighting for their black belt test don't hold back). I am currently a blue belt in a Southern Kung Fu style, and have currently dropped out for lack of time.

I am a practicing FreeMason, and have been a lead tech for Collins Radio in Richardson, TX, which is now gone. It was originally part of Rockwell International, and then sold to Alcatel in 1990, and shut down in 2001. I am currently a gold wire bonder for Raytheon, I operate the machines I used to repair and maintain, a definite downturn.

My BBS is a dinosaur, I'm going to close down the existing phone line and put it on my voice line with hours soon. A BBS is a computer connected to a modem that will answer the phone, think pre-internet. It will allow file swaps, local email, and (if I had the section working) online games. I've had this one up since 1994, but it wasn't my first. If you want to check it out you can call it using hyperterm (a windows telecom package) at (972)276-6721, its name is the Mars Den BBS. I still occasionally use a Commodore 128, and have quite a few programs available for it and other old machines available.

I am a fair technical artist (read that as I can't draw people for squat). I've come up with a tool to draw schematics using MS Paint. I use Paint for the simple reason is that it is on most computers out there, even some that aren't M/S operating systems. Since some of the computers I use are very restricted on installing software this works for me.

I am offering the package as public domain, if you can use it feel free, make changes. It is a work in progress for me, I've just added FETs (and labeled them on the symbol sheet to keep them straight). As I come up with new stuff I'll update it here and put a date time stamp on the upload, American style (MM/DD/YYYY TIME). All I really ask is don't claim the idea as your own.

I'll also post projects as I complete them here, as well as in the forums.

See ya around.

PaintCAD Upload 04/28/2008 9:14AM

Attached Files

PaintCAD.zip (348.5 KB, 57 views)

]]> Bill_Marsden http://forum.allaboutcircuits.com/blog.php?b=49 Rework Curcuit Boards http://forum.allaboutcircuits.com/blog.php?b=48 Sat, 26 Apr 2008 06:00:39 GMT I Am Starting A Conversation About Reworking Printed Curcuit Boards. There Is A Global Market Already In Place And Expensive Tooling Involved. This... I Am Starting A Conversation About
Reworking Printed Curcuit Boards.
There Is A Global Market Already In
Place And Expensive Tooling Involved.
This Market Will Be Shipped Overseas
If More Is Not Done To Keep It Local.
While Some People Can Compet,with
Math And Science,others Should Be Aware That Reworking Curcuit's May
Become A Career. This Application May
Be More Popular That I Realiize.that Is Why Bring The Word (rework) Before The Member's For Comment's.member's That Log On During Business Hour's Are More Likely To Know About This Subject.it More Likely That Nite Researcher's Need Hand's On Experience.
I Am Hoping That Your Member's Can Contribute More On This Subject And Have Question's Thank's Again. Wake Up
Member's(reply) ]]> loosewire http://forum.allaboutcircuits.com/blog.php?b=48 Useful Websites for Electronics http://forum.allaboutcircuits.com/blog.php?b=44 Wed, 23 Apr 2008 09:40:04 GMT A couple of years back we started a thread asking for suggestions for useful websites that members have come across that have helped in all aspects... A couple of years back we started a thread asking for suggestions for useful websites that members have come across that have helped in all aspects of electronics, from information, learning, software etc.

The original thread is one of the most viewed threads here at AAC: Useful Websites for Electronics

A forum member, web, decided to clean up the old thread and categorise the websites by area; thus Useful Websites for Electronics ver.2 was created.

We ask for members to suggest websites they have found useful, however stipulate several conditions on appropriate suggestion of websites (see here). Please note:

Suggestion and discussion of websites and books must adhere to the All About Circuits Forum Rules, Code of Conduct and Terms and Conditions of Usage. As a result:

Suggestion of websites and books should have relevance to the field of electronics. Off-topic discussion of websites and books should be made in the Off-Topic Forum.
All About Circuits does not support any form of commercial advertisment or promotion; therefore suggestion of websites must not advertise any product or service, and suggestion of books must not be a stand alone advertisement. This is in accordance with item 8 of the forum rules.
Suggestion of softwares or website services must not impose limitations other than basic and fair feature suppression as interpretted by the Moderator team. An example of basic and fair feature suppression would be a restriction on numbers of components in EDA software, but time restrictions are not permitted in any circumstances.
No website or software recommended should have any adverse affect on another forum users computer without exception; this includes, but is not restricted to, malware, phishing attempts etc.
To suggest a website that provides free access to information and resources for electrical engineering and electronics should be made in the Useful Websites for Electronics Thread.

All websites suggested in all threads will be vetted by the Moderator team. In all instances the Moderator team reserves the right to remove or edit and web-based content without reason.

We hope this will continue to be a useful resource for the members here at AAC.

Dave ]]> Dave http://forum.allaboutcircuits.com/blog.php?b=44 <![CDATA[A Technician's View]]> http://forum.allaboutcircuits.com/blog.php?b=42 Fri, 18 Apr 2008 18:57:04 GMT I mentioned that I had a disagreement with an news article that reported that people associated Apple with innovation and IBM for something like... I mentioned that I had a disagreement with an news article that reported that people associated Apple with innovation and IBM for something like reliability.

Having delivered opinions on Apple, I start in on IBM.

I do realize that the GMR head on hard drives has been an absolutely essential development in hard drive technology. But IBM has a poor record of technical developments - at least from what I have seen.

If you read "When Computers Went to Sea", one of the devices mentioned is the IBM disk file that went aboard the USS Wasp. Storage technology of the day was by dancer arm tape deck.

Searching for records on a reel of tape was very slow. An aircraft carrier may have over 100 contacts - aircraft and surface units - to keep track of. The computers used were limited to 32K of memory. It took two to three of them to run the NTDS (naval tactical data system) software and have a bit of storage for each track on the system. The track buffer was pretty limited, so something more than a tape deck was in order.

Enter IBM and the 1311 (militarized) disk file. It held two removable packs with 10 platters each. The read/write heads operated in pairs to cover both disk surfaces. Latency was not too bad, and the beast used a high speed interface - 250K words/sec. The computers clocked at 1 MHz, but the clock got divided into 4 phases, so execution time was from 4 uS to 48uS depending on the instruction.

While stationed at Dam Neck, Several significant thing s happened to me. First, I really irritated our E-9 chief. This was not smart. But we had received a sympathy card from his last division before he arrived, and he was just bad news.

Secondly, we got the IBM1311 off the Wasp. In a somewhat discarded (we used another word) state. One disk pack was missing and the other had been dropped. It still worked, but the four lower heads were a blur as they ran up and down the bend in the lower platters.

So we had this marvel of technology and the chief gave it to me, with dire warnings about what would happen if I didn't get it running.

This was model XN-1, serial number 1, by the way. Real bleeding edge stuff for 1968 when they built it. It used IC's, but not standard ones. They were not DIP shaped, had crimped on metal covers, and were made by IBM - don't bother looking for substitutes.

The logic planes were hinged to swing out for access. The IC's were in sockets which made contact with copper foil in multiple layers under the top surface. The contact pins also led out the rear of the board and could be used for wire wrap.

This was handy, as the original foil was mostly unused by the time we got the 1311. Included was a handy cutter that fit around a contact pin. When run in to where the cutter bottomed out on the pin, it left the contact mechanically held in place, but electrically isolated. If you worked on one, you got lots of OJT in wire wrap.

Even more clever was how the 1311 moved the heads. They were all in a frame so they went in and out together. The frame was pushed by hydraulic oil - at 90 PSI. There was also a rack and pinion gear on the frame. The rack moved with the frame, and the pinion gear stopped it.

Actually, it was an arm with a steel tooth that stopped it. The arm, also hydraulically controlled, dropped into the pinion gear to stop it turning, and somewhat hopefully leaving the heads on the right track.

On a big move, the arm could skip over the tops of the gear teeth and let the frame go all the way forward. This made a horrible mess. a the hydraulic piston seal could blow out, dumping oil all over.

The crowning glory was the power supply. It was the first switcher. IBM called it time regulated, but it was the prototype SMPS.

Sigh, if only FET's had been available. Instead, they used SCR's. The transformer had a center tap to ground on the primary side. Two SCR's alternated dumping charge from a pair of capacitors through each half of the primary. The charge on the capacitors was controlled by another pair of SCR's.

The whole mess actually used more SCR's to deliver charge from the secondary windings to the LC filters. The time each was gated on controlled the output voltage, which was where IBM came up with the time regulated descriptor.

The main frequency was 20 KHz. The control circuitry was located on several PCB's. These used conventional discreet parts, but IBM potted a tough black rubber on top to make the components invisible and unreachable. The control circuit was a black box on the schematics.

The power supply was not reliable. Every now and again, an SCR died. It always went short to the gate, and always took out one of two control boards. We referred to them as either the $1100 board, or the $1600 board.

We never did find the source of these failures, although I found out a lot about intermittent problems and overbearing chief petty officers. It took a whole year, but I got rid of the 1311 and got the chief reassigned to software only. It only cost me one article 15 charge and some extra duty.

Beyond the 1311 disk file, I should only have to mention the 5150 to have people recall what a botch IBM can make of something. ]]> beenthere http://forum.allaboutcircuits.com/blog.php?b=42 <![CDATA[World's Biggest Knife Show]]> http://forum.allaboutcircuits.com/blog.php?b=37 Sun, 13 Apr 2008 17:27:59 GMT I went to the 33rd annual OKCA Knife Show yesterday.

Once upon a time they billed themselves as "The largest knife show West of the Mississippi." The epithet is still accurate, but is now insufficient. "Largest knife show in America" would also be accurate, but insufficient.

According to the April '08 Knewsletter, the OKCA Knife Show now rightfully claims to be the largest event like this in the world.

It certainly was an exciting show.

I'm always amazed by the variety I see at knife shows. Not simply the variety of knives, enough in itself to astound. But in the variety of people, of types of exhibitors and exhibits, and of ways to appreciate knives. Old men in fine three-piece suits chat pleasantly with young mohawk & black bedecked lads about ideal edge geometries for culinary use while standing in front of a collection of pocket knives. A museum-quality display of Remington's Larry Duke illustrations stands as backdrop to a banker asking advice from a young housewife regarding collectable swords. Long time custom makers, new custom makers, factory representatives, collectors, purveyors, booksellers, and miscellaneous vendors all cater pleasantly to a crowd of more than 2,000 enthusiasts.

Despite having been there all day, and having stayed for the Club Social afterward, I feel I was barely there for an hour.

The OKCA doesn't just put on a big knife show, they put on a good knife show.

This really has me jazzed to dig out my induction heating experiments and try once again to make some differentially austenitized blades! Unfortunately, my wife will kill me if I drag out that box from storage prior to finishing our remodel...:rolleyes: ]]> thingmaker3 http://forum.allaboutcircuits.com/blog.php?b=37 File corruption...again! http://forum.allaboutcircuits.com/blog.php?b=36 Sat, 12 Apr 2008 14:32:56 GMT Today I've had a little reminder on how Windows preserves the files inside a drive intact. Once more, I had my pen drive corrupted, and as a result just lost three datasheets.

Now I recall why I lost those datasheets. It was because I've read the same on the other day. When I tried to remove my pen, Windows couldn't remove it. My pen was not even reading or writing. To solve the problem, I've closed explorer.exe and reactivated it again (that's what I do when that happens). Worked like a charm. But today, when zipping a folder containing one of the affected files, I came to the conclusion that I had one of files corrupted. So I ran checkdisk (in DOS), and bang, the three PDF files I've been reading that day, all corrupted.

That makes me wonder. how those files got corrupted in the first place? They were PDFs and I opened them with Acrobat Reader. It was a reading operation! Fortunately the lost files are replaceable. But next time...who knows!?

Yup, no wonder Windows is known to corrupt files in the most spectacular ways. ]]> cumesoftware http://forum.allaboutcircuits.com/blog.php?b=36 The PCB is finished! http://forum.allaboutcircuits.com/blog.php?b=35 Thu, 10 Apr 2008 13:41:41 GMT Finally I made it. It took days, but now it is completed. The PCB for the "Quatour" project is finished and now I can dedicate to other projects.

Since I was so busy with this project, I had no time to post to the AAC forums in the past few days. I had to keep all other projects suspended, including the fireplace model.

After checking and double checking, I can say that the PCB is finished and should have no problems. The routing and grounding is not the best, but I made sure that the tracks were thick enough to have the lowest resistance possible. They sure withstand the current by a large margin. ]]> cumesoftware http://forum.allaboutcircuits.com/blog.php?b=35 <![CDATA[Linear Regulator and Millman's]]> http://forum.allaboutcircuits.com/blog.php?b=32 Sun, 06 Apr 2008 19:37:12 GMT The attachment in this post is the derivation of the equation for calculating the output voltage of a 3-terminal adjustable linear voltage regulator... The attachment in this post is the derivation of the equation for calculating the output voltage of a 3-terminal adjustable linear voltage regulator using Millman's Theorem.

All comments or questions regarding the writeup are welcomed.

hgmjr

Attached Files

LINEAR REG and MILLMANS.pdf (31.1 KB, 141 views)

]]> hgmjr http://forum.allaboutcircuits.com/blog.php?b=32