From: sademade (sademade_at_yahoo.com)
Date: 2001-12-20 06:08:54
I do not know what an earth happened to my first post, all text
disappeared, and just a quote was posted ...
Well, I just wanted to say that would like to see those who do not
contribute to the hw or sw design, to contribute $ donations to
Joerg for making pcb prototypes at pcbpool.de which is an excellent
and lowest priced service on earth, at least, that I know of, second
comes Advanced Circuits in US, who have offer for 2 layer boards
for $33 each, have used the latter, and gotten very good results,
5 day service, pcpbool has 15 days, but, they have really good
prices, and even better they are on 4-layer pricing, one can have
4 layer board of nice size for $99 there, which is really killer prize
as well. And their small series, from 10 and up, are even better
deals, which should be used for the list to let more people build
protos, and get ahead with software/hw design progression, so that
not just few people would have to carry the weight of 200 lurkers
and nodoers, but that others could also start contributing, or
take a hike ... I know this idea of using pcbpool was there before,
but it is always a good one, and should be done, not just talked
about.
I have used BBrown ADS1211 4 diff channel A/D part in some projects,
and would think that such part would allow using just single stage
of the INA114's, and make the analog section much smaller, and
perhaps boost the noise-performance, provided someone better than
me routed the guardings/shieldings, though, I would like to learn
more of how to route high-quality low-noise analog microvoltage
input stages. I used ADS1211 in interfacing to pressure sensors
and RTD's that provide very low voltage when driven with precision
constant current generators, and it just is superior to many other
A/D parts. I am sure that combining it with something like INA114
and good routing techniques could somehow boost the analog section
yet, and not cost much more to speak off.
Then, would consider optical isolation layer right after the
ADS1211, and operate it trough the optosisolated SPI port
signals, taking total 2 isolator packages to accomplish, if
using some nice doubles and quads that are out there these days,
smt, go to very small space.
After that, would throw in possibly either some small risc
flash microcontroller with hw multiplier, or, consider
some of the nicer versions of the TI flash DSP's, combined
with a USB controller chip from some company FTDI, who provide
a good way to solve the driver problems, and then approach
the host PC Program with VB and encapsulated C++ made
VB controls, GUI with VB quickly, graphics with VB quickly, and
then, suitable USB access control access the USB driver, to
get the data in fast, and the math portions could be produced
with Matlab with the C++ code generator that generates C++
from Matlab.
This way, one set of people could write GUI with VB, one set
of people could write the Math code with Matlab and Matcom
or whatever there are these days, and one set of people could
learn to encapsulate the Matlab generated C code to the VC++
made VB controls, and one set of people could spend their time
and effort accessing the USB or creating the USB control to
interface with the FTDI chip/driver.
But, that is just how I would approach it, even though, I am
poor writing any PC code, I am sure that I could participate
in some of the areas though not being the best choice for
any particularly, but perhaps able to contribute something
to some of these, at least the embedded side, schematics
drawing, board designing ( minus being bad analog in shielding/
guarding, which other people would have to help me to become
better with ).
Let me know, if anyone sees any potential in these thoughts.
And, in any case, the lurkers, either please throw in plans
for the software design / break-up top down / modularisation /
tools / etc, or donate $ to Joerg for parts and protos, or
help me to learn analog guarding and shielding, so that I
could attempt a version of the amps+A/D converter the way
I saw it above, not necessarily viable, but would like to attempt
it, as I'd have also other uses for the low-noise microvolt level
amplifier, such as amplifying UV-photodiodes, etc.
Appreciate, Sade R. M.
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:35 BST