Electronic Design

Bob's Mailbox


I love you!  (Do not get your hopes up, I am 50, overweight...and male).  I was beginning to think I was the only engineer left in the world who still thought there was merit in bread-boards, or common sense designs for that matter.

I am fighting a losing battle against the invasion of simulated labs (plastic labs as a friend put it).  Recently, the administration at the engineering school where I teach was talked into replacing our logic design laboratory (undergraduate) with a network of workstations.

I have been trying to convince everybody that such an action was a huge mistake, and that the only people who should have (limited) access to such tools were experienced designers who could instinctively know when they were being fed rubbish.  But I have been sadly outgunned by those (almost all) around me.  The main argument against me and my position has always been: "that is how INDUSTRY does it."

My contention that such machines are a hindrance to learning and should be banned from a learning environment was always received with total disbelief, because "those are the tools REAL ENGINEERS use to improve their productivity."

I also got absolutely nowhere when pointing out that those engineers who do derive advantages from such tools are people who learned their trade without these machines.  They use them to supplement their knowledge and abilities rather than replace them.

It gives me immense pleasure to see that someone else (with maybe a limited knowledge of the real world, not an academic type like myself) seems to be fighting the same battle.  I might not win the war, but I shall not be alone in my abject defeat.

What can we do?  These people will not read (at least not seriously) such "sour grapes" prose as yours.  After all, they know that is how INDUSTRY does it.  I sometimes get the feeling technology is shooting itself in the foot.  By using technology to replace thinking, we are freezing it at the state the software engineers used to design their wares.  And I sense that, a generation or so from now, when everyone else has forgotten how a transistor works, and the computers start to die off, nobody will be left to fix them or design new ones.

Are we seeing the last technical generation?  Will the computer simulations do to creativity what the calculator has already done to mental arithmetic? I fear it might, and I am at a loss on how to stop it.  Taking a hammer to the darned things will only divert more funds to fixing and protecting them.  Maybe a more direct plea from people such as yourself to university planners would help, since it is not "politically correct" to criticize computers within our walls.  People were less defensive of their religion during the Spanish inquisition than they are of their computers these days.  Anything you can do would be greatly appreciated.

Georges-Emile' April, Professor of Electrical Engineering Ecole Polytechnique de Montreal, Montreal P.Q, Canada

I hear you!  I agree.-RAP

Dear Bob:

I enjoyed your article "What's All This Spicey Stuff, Anyhow? (Part III)" in the October 10, 1991 issue.  Unfortunately, the main idea of the article expressed with a Russian proverb "Trust, but verify" was somewhat turned upside down for me, because Proverai no doverai means exactly the opposite: "Verify, but trust."  The reason for this confusion is that you misplaced two words.  This proverb should read Doverai no proverai.  Being a recent newcomer from Russia to the U.S., I couldn't help but notice this little mistake.

Mike Korkin, Development engineer Fischer Imaging Corp. Denver, Colo.

I sorry.  Thanks for the correction.-RAP

Dear Bob:

Gee, I wish we had more sensible people like you.  One of my young engineers came to me with the plaintive cry that his SCR R/C snubber circuit was oscillating!

He had set up the circuit in Tutsim, or something of the sort, and kept juggling component values in an effort to "stabilize" it.  He had not even examined what he was doing far enough to realize he had a passive circuit oscillating.  The problem, of course, was the default step size on the canned program.

Keith H. Sueker, PE, Engineering manager Robicon Corp. Pittsburgh, Pa.

Exactly my point!-RAP

Dear Mr. Pease:

I have read your article in the October 10, 1991 issue, "What's All This Spicey Stuff, Anyhow? (Part III)", and I find that I agree with most of what you say.

The current debate on the extent to which universities should rely on simulation in the teaching of electronics has an interesting historical parallel.  Twenty years ago, many universities replaced their electrical machine labs with analog (and later digital) simulations.  The "old school" regarded this as a backward step in the education of practical electrical engineers.

There is one part of your article on which I would appreciate some further elaboration:  the paragraph on metastability.  Since this is a statistical phenomenon, a deterministic circuit simulation is not going to give much directly usable information, even if there were no artifacts due to numerical problems.

However, the probabilistic model for the metastable behavior of a latch is simple, and has been thoroughly tested over a number of years.  The circuit design problem is finding the parameters to use in the statistical model, and then to optimize the circuit with respect to its metastable operation.  Here, the use of Spice can help.  (Many papers have been published on this topic, not all from universities.)  Obviously, the only model in which you can have full confidence is the breadboard.  But CAD can help, in my opinion.  Any comments?

Martin J.P. Bolton, Inmos Ltd. Bristol, England

Spice can develop the facts you need to study metastability, but can't do it directly.-RAP

Dear Bob:

Thank you for writing all those great articles.  I save all of them and share your views of this linear world.

Would you believe that straingauge power supplies are now extinct?  I sure wish I could still buy one, but have been unable to find a single vendor that still sells them.  I think we need to raise a hue and cry about this.  I have always considered them one of the true basic building blocks and are about as close to batteries as you can get.  Too many power supplies today have high capacitance between windings and they transfer line noise right into the circuit we are trying to clean up.  Once in a while, we can find a simple foil shield between windings.  But almost no one will tell us about it, much less give any specs on the strays.

When you specifically buy an isolation transformer, the single shield seems to be added by the vendor as an afterthought, and there are no specs.  And to add insult to injury, it is arbitrarily grounded at the case and/or returned to the third wire on the line cord.

I am convinced that nobody makes decent power transformers anymore.  Any bench supply should have carefully isolated windings with adequate shielding from the power line.  A little care in that area would save us hours later on when the noise hunt begins.

In the meantime, I'm going to be watching for old strain-gauge supplies in the junk stores.  There should be a lot of them out there, unwanted and unused.  Maybe it's about time to rediscover what they can do.

Neil Iverson, Boeing Co. Seattle, Wash.

Can anybody recommend where to buy good, well-isolated supplies; or a good transformer so you can make them?-RAP

Dear Sir:

Please keep up the good work.  I have read trade publications for ten years now and have never regularly read a columnist.  But now I read your column.

The pictures and handwritten captions are great.  I have also never written a letter to a columnist, which means I'm enthused about yours.

I want more of the black magic of analog engineering.  Things like why amplifiers oscillate, and why oscillators amplify.  I'd also like to see more of your circuit breadboards.  I teach "communications" here; we build (my students and myself) RF amps, VCOs, mixers, etc., on breadboards.  I want to see how you do it.

Send a copy of this letter to your publisher and ask for a raise.

David D. Draper, Electronic Technology Dept., Utah Valley Community College Orem, Utah

I'll hire your kids a lot quicker than guys who can only drive a simulator.-RAP


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