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August 03, 2010

Engineer This! (Part II)

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Learn from a mentor In an earlier post ("Engineer This!") that I published almost exactly one year ago, I challenged engineers world-wide to solve some fundamental issues regarding energy - I think everyone is still working on those (my fusion powered electric car hasn’t been delivered yet...).  However, the other day I was talking with a very wise man I met from Egypt.  It is not often you find such wisdom in an individual and so I wanted to absorb as much of this as possible... we were talking about how we influence one another and how our little actions effect so many.  He said something so profound it stopped me in my tracks.  He said, "You can know exactly how many seeds are in an apple, but you will never know how many apples are in a seed".

Nikola Tesla or Thomas Edison would never know how their great inventions would affect so many lives.  Simply removing those two individual’s contributions from history would almost immediately lead to the death of half of our population followed by many more dying from diseases.  It is not to say that those technologies would never have been invented, it simply states how wide spread those technologies have become and how much humanity depends on them.  But this post is less about great inventions and more about how we as engineers touch others through our work and also how we can help the next generation of engineers become even greater.
 
When I was a young designer I had a mentor.  His name was Jorge and he had worked for Control Data Corporation along side greats such as Seymour Cray (father of the vector super computer and the founder of Cray Corporation).  I was very fortunate to have had him as a mentor.  He challenged me daily and always continued to push my abilities as an engineer.  He would assign me design challenges even if he had already completed the design just to see what I would come up with - on occasion, I would surprise him.  I left that job in 1984 to join National Semiconductor and also had a string of mentors during the development of my career - and to this day continue to have mentors to help guide my decision processes.

So what is this all about? We’ll here’s another call to action for all of you out there... and I’m pretty confident these can be accomplished long before my fusion powered electric car reaches my garage!
1. Become an Engineering Mentor - Young minds are fertile ground and combined with the enthusiasm of these new designers they will learn what ever you have to offer.  Many companies have formal mentoring programs and they will help you find a suitable candidate. In my career I have mentored three young engineers (2 post graduates and 1 undergraduate) and it has been one of the most rewarding things I have ever done.
2. Find a Mentor - I am a true believer that you can never know too much or have too many skills as an engineer (or as a human being). Much of what I have learned about Engineering and business has come from older, more experienced engineers and businessmen and I owe much of my personal success to them.  Finding a mentor is less difficult since there are always those inside an engineering lab that know the "old man" or a "guru" of something.  Usually they will be more than happy to teach you what they know.
3. Share your Knowledge - Join a professional organization such as the IEEE and attend meetings.  There you can share your ideas or discuss possible ways to solve a problem.  In many cases you will help someone else solve something by sharing your expertise.  There are committees and teams you can join to set standards or work on larger issues which can be extremely rewarding.

Whatever you chose to do realize that, as my wise friend had stated, "From the apple seed many new apples will be created."  Your action will start in motion the future of many new engineers to what extents you may never know.  In addition, I personally feel if you want to learn a subject, you should teach it - that forces you to learn it better than your students (or Mentee).  So either way you may learn something new or even something about yourself in the process.  Till next time...

May 27, 2010

Where Did I Go Wrong? Funny Mistakes in Electrical Engineering

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Train wreck at Montparnasse in 1895 This week I thought I’d diverge a bit from the Energy Efficiency theme and share some funny engineering experiences I’ve had over the years. I’ve been a practicing engineer for over 30 years and have been involved reviewing projects and circuit designs a good part of that period.  I’ve collected a list of several of my favorite oversights (the names have been withheld to protect the guilty).  Hope you enjoy these as I did when I found them!

Isolate Yourself
One of the funniest (and probably most embarrassing) "faux pas" I’ve seen was the attempt to provide high voltage isolation for a power supply.  In a design review I had recommended a 0.100" clearance between the primary and secondary side.  About two months later the engineer called me and was concerned about something in the design that was causing them to fail their HV isolation test.  He emailed me the layout and in about 10 seconds it became apparent what had happened.  The designer passed my recommendation to the layout technician who instructed their auto-router to provide the 0.100" clearance between the primary and secondary side... the auto-router did just that - funny how machines do exactly what you tell them.  The software provided exactly 0.100" clearance between the PCB lands on the primary and secondary sides of the transformer but left the default clearance of 0.010" on all the others.  It takes about 70kV to jump 1" in dry air... it would only take around 700V to get across the barrier the auto-router provided thus the failing board.  Luckily, it was an easy fix and the board passed without issue... the moral of the story? Don’t think your auto-router knows more than you do...

Stability Is Your Friend
One day I get a call from an aerospace engineer that was concerned that a batch of voltage regulators were not working properly in their circuit.  The design had been working fine for years, but lately they were experiencing failures due to an apparent oscillation in the output voltage of our regulator... this was a very "mission critical" military application that was using a linear voltage regulator to provide a clean voltage in a projectile.  I asked the engineer to describe the design.  He went on to describe the input power stage and the large heat-sink mounted on the side of the projectile where the regulator was mounted.  The regulator’s leads were then wired to the PCB where they provided the regulated voltage - about 16 inches away.  The first question I asked was where the output capacitor was located - it was on the PCB 16 inches from the regulator!  I choked for a moment realizing that it was amazing these things were working at all - real kudos to the National Semiconductor engineer that designed the regulator.  Effectively what the aerospace engineer had done was place parasitic inductors (the wire) in series with the capacitor shifting the stability point of the regulator right to the edge... most of them worked at the temperature where these "projectiles" were deployed... the new batch of regulators had higher gains and thus were oscillating.  I gently told the guy on the phone the bad news and referred him to the data sheet where it clearly stated how close the output cap had to be to the regulator to guarantee stability.  This raised the next question, "if they are working now, will they continue to work?" The answer was - maybe.  It depends on so many factors including process aging, temperature, the type of wire used and gauge.  The engineer on the phone suddenly inhaled, thanked me for my help and hung up... I assume that the problem was resolved. I didn’t sleep well for about a year after that.

The Linear Boost Converter - Not!
OK, this one really made me think... where did we go wrong in writing the data sheet.  I received this email from an "engineer" that was wondering why his circuit was not working properly.  I replied and asked for that section of the schematic so I could review the design.  Within the hour an email with an attachment showed up.  I opened the PDF and had to stare for a minute... this could not be right.  They were using a linear regulator where the input voltage was lower than the programmed (resistor divider value) output voltage.  They were supplying 5V to the regulator and expecting 12V at the output!  This is fine for one of our boost simple switchers, but not going to work for a linear regulator.  OK, now I wondered how I was going to respond to this... so I sent a copy of the data sheet pointing out the "drop-out" voltage or loss component of the regulator along with a boost power supply application note and introduced this person to the world of switching regulators.  I doubt that would happen today since integrated switching regulators are so common and most likely taught in university programs.

Disclaimer
Any similarities to the above problems are coincidental and not intended to make you feel bad if you made the same mistake... we’ve all made mistakes - the real question is "did you learn from them?"  Engineering history is filled with stories of failures or bad decisions ("let’s use the most reactive chemical in the world to float a dirigible" kind of thing).  But the main thing is that we learn and improve our skills as engineers - I certainly have tried and continue to do so every day.  Hope you enjoyed these tails from the past.  Till next time...