Question for Win Hill

[John Larkin]

IMHO, if you aren't doing electronics by the age of 10, you probably
aren't going to do it very well, unless you are very bright indeed,
including practically. By the time you graduate, you have 12 years
experience to catch up!

Agreed, but maybe 12 isn't too late. It's like tennis, skiing,
driving, languages, music: if you wait till you're almost grown up,
you're unlikely to be really good at it.

John

 

[BFoelsch]

I read in sci.electronics.design that John Larkin <[email protected]>


Yes. In many cases, think 'boot camp'.


... as a reaction to the 'boot camp'...


Yes, it went much too far.

In UK, and in theory, we have a liaison programme between practising
engineers and schools, to enlighten the students. It works in a few
cases, but my impression is that it very largely doesn't work. I think
many teachers find it too challenging; 'Can we do some PIC projects like
the engineer lady told us about?'

IMHO, if you aren't doing electronics by the age of 10, you probably
aren't going to do it very well, unless you are very bright indeed,
including practically. By the time you graduate, you have 12 years
experience to catch up!
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Playing devil's advocate for a minute, the nature of engineering has
changeddramatically since WWII, and I'm not talking tubes vs. semiconductors
or PCs (well, not directly, anyway.)

When I went through school, in a somewhat different line of engineering, the
principles were all known, the equations were pretty well known, but there
were almost no tools available to do the math!! As a result of this, the
engineering "art" was largely one of estimating answers, because finding
the"correct" answer was either impossible or impractical. A lot of what you
did was based on tabulated data or historical info, based on what usually
worked, or something that somebody put together and measured.

A whole generation of what I will call "Radio Engineers" grew up, who could
use tables to slap together a resonant circuit, figure out its Q, make
allowances for external effects and move on to the next problem. There was
really no "engineering" involved, just patching together bits and pieces of
what had been done before. These people absolutely, positively had the
"hands on" experience that seems to be missing today, but I am ill at ease
to call them engineers. Think about how much of the consumer electronics
stuff of the 1950's worked "by accident," changing lead dress would throw it
into oscillation, etc. Hell, think about all the truly rotten test equipment
of the 1950's. This stuff was largely designed by the aforementioned "radio
engineers." All experience and intuition, no real analysis or synthesis.

Today we are at the opposite end, largely due to the fact that simulation
lets us instantaneously perform calculations that were impossible years ago.
The student doesn't develop a sense for component values and functions
because exact calculations are painless and instantaneous, no estimates or
guesstimates are necessary. It's hard to force one's self to learn a hard or
inaccurate way when the exact way is at you fingertip, and that is where we
are today; hands-on is the hard inaccurate way, simulation is the (arguably)
exact way.

Think about the chatter here a while back about the "decade boxes' being
offered by another poster. A perfect tool for gaining experience, a lousy
way to do engineering.

It's an uphill battle to push engineering schools or students back into
"hands-on," but, as another poster said, if you aren't into it by the age of
10 you probably never will be.

 

[John Woodgate]

I read in sci.electronics.design that BFoelsch <[email protected]

Today we are at the opposite end, largely due to the fact that
simulation lets us instantaneously perform calculations that were
impossible years ago.

Yes, quite so. I was getting frustrated earlier to day over the delay in
plotting some graphics, until I realised I was asking my PC assistant to
do 4 x 4 x 4 x 100 x 100 evaluations of an eight-term expression. For
four different plots. Luckily, I could reduce the 100 x 100 to 50 x 50
without unacceptable loss of resolution.

 

[Kevin Aylward]

Agreed, but maybe 12 isn't too late. It's like tennis, skiing,
driving, languages, music: if you wait till you're almost grown up,
you're unlikely to be really good at it.

Well, speaking from the point of view of starting both guitar and
electronics at 11, there is no correlation whatsoever in technically
competency in music and success in music. Fortunately, one can be as
ugly as desired to get work as an analogue designer, in fact it helps.

Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[John Woodgate]

I read in sci.electronics.design that Jim Thompson

But I've had not one fail driving speakers.

Because most loudspeakers have much higher impedance than the nominal
value at frequencies where the impedance is significantly reactive. But
there are a few 'amp killer' loudspeakers out there that have impedances
like 1.0 + j3.0 ohms over a critical (usually low-frequency) range.

Reactive loads may cause second breakdown but also result in
considerably increased heating of the output devices. Second breakdown
problems can be investigated by Peter Baxandall's protection circuit
evaluation test, described in IEC/EN/BS EN 60268-3.

 

[Harry Dellamano]

The mosfet model I'm often concerned the most about is the thermal
model; that's what determines whether the part will blow up. I haven't
had a lot of luck reconciling the transient thermal resistance curves
on the datasheets with real life, so we test them ourselves, either by
measuring Tj versus time, or just by pushing them to destruction and
backing off by some margin for the real design.

Some of my amps digitize everything - heatsink temp, power rails,
Vout, Iout - and simulate junction temps in real time, shutting down
when Tj get scairy. For that you need a practical time-domain thermal
model of the real-world, heatsunk mosfet.

I wish people would publish thermal models that were similar in detail
to the electrical ones.

John

Hey John
Check out this thermal model on page 4.
http://www.infineon.com/cmc_upload/documents/010/2562/SPW20N60CFDv1.pdf
Now that's what i'm talking about!

Harry

 

[John Woodgate]

I read in sci.electronics.design that Kevin Aylward
ueyonder.co.uk>) about 'Question for Win Hill/ Athlon64', on Sat, 1 Jan
2005:

Well, speaking from the point of view of starting both guitar and
electronics at 11, there is no correlation whatsoever in technically
competency in music and success in music.

So much the worse for music. But there are a lot of 'three-chord'
electronics designs out there, too.

Fortunately, one can be as
ugly as desired to get work as an analogue designer, in fact it helps.

Your face is your fortune? (;-)

 

[Guy Macon]

(Why are you crossposting text maeesages to
alt.binaries.schematics.electronic?)

A whole generation of what I will call "Radio Engineers" grew up, who could
use tables to slap together a resonant circuit, figure out its Q, make
allowances for external effects and move on to the next problem. There was
really no "engineering" involved, just patching together bits and pieces of
what had been done before. These people absolutely, positively had the
"hands on" experience that seems to be missing today, but I am ill at ease
to call them engineers. Think about how much of the consumer electronics
stuff of the 1950's worked "by accident," changing lead dress would throw it
into oscillation, etc. Hell, think about all the truly rotten test equipment
of the 1950's. This stuff was largely designed by the aforementioned "radio
engineers." All experience and intuition, no real analysis or synthesis.

Today we are at the opposite end, largely due to the fact that simulation
lets us instantaneously perform calculations that were impossible years ago.
The student doesn't develop a sense for component values and functions
because exact calculations are painless and instantaneous, no estimates or
guesstimates are necessary. It's hard to force one's self to learn a hard or
inaccurate way when the exact way is at you fingertip, and that is where we
are today; hands-on is the hard inaccurate way, simulation is the (arguably)
exact way.

To my way of thinking, having one of each kind of engineer is an
ideal solution.

Think about the chatter here a while back about the "decade boxes' being
offered by another poster. A perfect tool for gaining experience, a lousy
way to do engineering.

I disagree. For example, I recently had to deal with a marketing
department that wanted to have a series of meetings about product
color, pacaging - and the brightness of the front-panel LEDs.
Whether we like it or not, letting them see different brightnesses
is just as much a part of engineering as giving them proposed
box designs is part of graphics design.

I rather suspect that any attempt to use simulation to decide
how much current to send through those LEDs would have failed.

 

[John Larkin]

Well, speaking from the point of view of starting both guitar and
electronics at 11, there is no correlation whatsoever in technically
competency in music and success in music. Fortunately, one can be as
ugly as desired to get work as an analogue designer, in fact it helps.

Exactly. Lots of universities have excellent music schools, and their
professors are no doubt technically competant to perform music and to
analyze it. But how many university music professors ever write great
music?

John

 

[John Larkin]

But I've had not one fail driving speakers.

...Jim Thompson

Audio amps, by the nature of the signal, have a huge amount of
headroom.

John

 

[John Larkin]

Hey John
Check out this thermal model on page 4.
http://www.infineon.com/cmc_upload/documents/010/2562/SPW20N60CFDv1.pdf
Now that's what i'm talking about!

Harry

Beautiful. I wish more people would do this.


Oh, you can spice things like this...

thermal == electrical


1 K/w == 1 ohm

1 w == 1 amp

1 k == 1 v

1 sec == 1 sec

1 gram aluminum == 1 farad

which is accurate to something like 5%.

John

 

[John Woodgate]

I read in sci.electronics.design that Guy Macon <_see.web.page_@_www.guy

I rather suspect that any attempt to use simulation to decide how much
current to send through those LEDs would have failed.

We need a Spice model of the corporate marketroid. Any offers?

 

[John Woodgate]

I read in sci.electronics.design that John Larkin <[email protected]>

Audio amps, by the nature of the signal, have a huge amount of
headroom.

If second breakdown is possible, the fact that the signal spends a lot
of time 10 or more dB below peak level is irrelevant. It only needs to
hit peak level for a few ms, and BANG!

For thermal overstress caused by a reactive load, the low duty cycle IS
relevant, but remember that the heat sinks are also designed with that
duty cycle in mind!

 

[John Woodgate]

I read in sci.electronics.design that John Larkin <[email protected]>

Beautiful. I wish more people would do this.


Oh, you can spice things like this...

thermal == electrical


1 K/w == 1 ohm

Or in proper SI symbols (too bad about the ohm!):

1 K/W == 1 ohm

1 w == 1 amp

1 W == 1 A

1 k == 1 v

1K == 1 V

1 sec == 1 sec

1 s == 1 s

1 gram aluminum == 1 farad

1 gm Al == 1 F

 

[Guy Macon]

We need a Spice model of the corporate marketroid. Any offers?

That would be less work than trying to convince the "simulation
can do anything, prototypes are obsolete" crowd that the are wrong.

Maybe if we *simulated* them we could figure out how to convince them...

 

[Ken Smith]

We need a Spice model of the corporate marketroid. Any offers?

We could get the most of the characteristics with a model including a
Dilbert cell and a nop-amp. The noise characteristics would be tricky to
model.

 

[John Woodgate]

I read in sci.electronics.design that Ken Smith

We could get the most of the characteristics with a model including a
Dilbert cell and a nop-amp. The noise characteristics would be tricky
to model.

Oh, very good! I love 'Dilbert cell'.

 

[BFoelsch]

(Why are you crossposting text maeesages to
alt.binaries.schematics.electronic?)

Dunno. Just hit "Reply to group" without looking. I'll behave next
time......

To my way of thinking, having one of each kind of engineer is an
ideal solution.

Or one engineer who has both experience and theoretical knowledge.

I disagree. For example, I recently had to deal with a marketing
department that wanted to have a series of meetings about product
color, pacaging - and the brightness of the front-panel LEDs.
Whether we like it or not, letting them see different brightnesses
is just as much a part of engineering as giving them proposed
box designs is part of graphics design.

I rather suspect that any attempt to use simulation to decide
how much current to send through those LEDs would have failed.

You are of course correct, but had the marketing department specified the
desired light output you would certainly have been able to calculate the
required circuit parameters.

Again, my original post took the position of devil's advocate. A successful
engineer must possess both theoretical and practical knowledge. I was just
commenting on my observation that, in the case of many EE curricula, the
pendulum has swung over 50 years from the "too little theory" side to the
current "too little practice" side.

 

[Jim Thompson]

Agreed, but maybe 12 isn't too late. It's like tennis, skiing,
driving, languages, music: if you wait till you're almost grown up,
you're unlikely to be really good at it.

John

I don't know about that. I built a lot of toob stuff from around age
10 to age 15, from kits and schematics, but I really didn't have a
clue as to why it worked... I just needed a good amplifier to play my
classical music records.

I was all set to go to college and study architecture.

Then, in 1956, my father became a Raytheon wholesaler, with stock
including CK7xx devices.

I was hooked. In barely two years I could design and build
rudimentary circuits.

So off I went to MIT to study EE instead of architecture ;-)

At MIT I lucked into a technician's job working for Professors Woodson
and Jackson (and Professor-and-head-of-EE-department-to-be Jim
Melcher) in Building 20, which is where I really got the hands-on
experience.

...Jim Thompson

 

[Al Borowski]

I think the concept has been, all along, is that engineers learn
theory in school and practise on the job. That actually makes sense,
because the theory is what sticks with you all your life, as the
technology keeps changing.

What many schools miss is the fact that
concurrent hands-on work greatly enhances the understanding of the
theory. If the theory is just equations and stuff, without physical
insight, it's soon forgotten.

I think you've hit the nail on the head.

Al