[John Larkin]

On Thu, 03 Mar 2011 07:14:08 -0600, John Fields
wrote:

On Wed, 02 Mar 2011 18:52:53 -0800, John Larkin
wrote:

On Wed, 02 Mar 2011 20:40:27 -0600, John - KD5YI
wrote:

Well, I thought designing a circuit included supplying component values.
No?

I posted topologies. Values can be scaled to the application, but you
need a topology first. If I were actually going to build this, for
money, of course I'd have to define specs and then compute values.
That's just grunt work.

John

---
Being the grunt work that it is, then, one should be able to take a
schematic devoid of component values and then hand it over to a grunt
with the expectation of getting back a working circuit some time
later?

"One" should? I couldn't say. I usually design all of a circuit
myself, but if we brainstorm/whiteboard circuits, we may include
values, or one of the people might go off and finish it. Could be me,
could be somebody else, whoever is responsible or volunteers. We
usually check one anothers' work before we release a board. We have no
techs, so everybody does grunt work.

But all circuit designs start with ideas and topologies. If someone
has never seen a folded cascode, or an opamp's V+ used as a signal
output, or a bootstrapped photodiode, all I may need to do is present
the concept, and then they can run with it.

The laser controller I'm working on now, all the resistors on one
sheet are 100 ohms and all the caps are 0.33u. That reduces the grunt
work considerably. This scheamtic will run about 25 B-size sheets, and
I'll do maybe 18 or so of them, with other people contributing others,
like the FPGA, the ARM, and the PCIe interface. This is a rush job, 7
weeks from start to 1st article, so several people are tossing in
sheets.


One thing about topologies which is misleading is that if the
component values aren't defined, the topology might look fine but the
realization of the circuit will be impossible under economic or
technical constraints.


Sure. A complete electrical/thermal/mechanical design ought to be done
before something goes into production. Lotta grunt work. Newsgroups
are for playing with ideas without consequences.

An example which springs to mind is a circuit which was posted some
time back which looked good, but which on closer inspection you said
needed a choke with an inductance of near 1 henry, as I recall, and a
Q of about 200 somewhere in the audio range.

I went looking for one, just for grins, but found only unobtanium so,
unless I missed something, (got a source?) your guess was wrong and
the topology bogus.

Bogus? Because you can't order some part? Nothing wrong with playing
with a topology if it might work. Whether it's practical or affordable
is part of the downstream analysis. If every idea has to be
immediately and exhaustively analyzed for cost and parts availability
and subtleties, you won't come up with many ideas.

As usual, you're just being bitchy. Why are you so hostile to playing
with ideas? Why do you refuse to do it yourself?

John