From: Thomas Carr (tomcarr_at_e...)
Date: 2000-10-20 17:22:23
Hi Yaniv, Joerg, Rob and everyone,
I'm just emailing some basic questions I have at this stage, as I told
Yaniv, I don't really have time this year to do R&D but am still interested
in the project. As I have said, I have a manufacturing facility in Los
Angeles which makes industrial computers and can do this if it is desired.
My true interest is in the creation of a reasonable EEG, I think the time
has come, and will be happy just to see the product available to all,
regardless of my involvement in the creation. However, design and
manufacture of a product like this is something I have experience at, so
issues are easy for me to see. At this time, I see these issues that raise
questions for me:
1. Investment by Joerg and Rob
I commend the efforts and time dedication of Joerg and Rob and look forward
to this project having postive results for all concerned. As I work with
consultants all the time, it is important for anyone contributing to a
project like this to have comfort with the level of integrity of the
participants, so I would suggest that these issues are important for anyone
doing work, it's an investment of your time, so be specific on these issues
(ie, value your work), don't wait and expect everything will work out to
your satisfaction. Increased communication is the key on this issue.
2. Amplifiers
The amplifiers Joerg is designing don't appear to have any expensive
components, I have accounts with most major electronics distributor and so
can usually obtain parts at a significant savings to radio shack or even the
broad based players like digikey. The parts on the amplifiers will probably
be matched by the pcb 'real-estate' cost, and the assembly another equal
part. I would guesstimate this at about $10+ per amplifier. I think that
Joerg is correct in careful consideration of these amplifiers. Biosystems
amplifier concepts are much more sophisticated than Brainmaster and I can
say that I've worked with sensor interfaces to micro-processors for about a
decade, and this is where systems always fail or perform poorly. It would
be wise to understand that this part of the platform will require the most
testing and fine tuning. If we succeed in a big way here, we will have an
excellent product. But tweaking this can take a lot if time.
3. A/d
Is there a current plan regarding the a/d? biosemi uses a 16 bit, I'm not
sure that an 8 bit won't due, has anyone looked into this? as we are
measuring brainwaves from 1-40hz, it would seem that 8 bit would easily give
us .2 hz resolution, which should be adequate, is my thinking correct? A 16
bit bus may increase costs.
4. channels
as well, how many input channels are we thinking of? brainmaster has 2
channel, but if we create the amplifiers in a modular format, we could have
up to 8 channels pretty easily, I don't know the performance value of this,
but it would seem that more than 2 channels would increase value and
application and a basic system could then be increased easily by adding more
amplifier modules. Typically, then, within the chassis we might put 2
amplifiers on the motherboard and then have headers for adding amplifier
modules.
5.opto-isolation
In the biosemi system, they multiplex the A/D through fiber optics and then
use a pc card to interface the data, this is of course a very expensive way
to go (not in general but within the $ parameters of this project). A key
here is the opto-isolation. Bio-system is using fiber optics, when I asked
Tom Collura, he suggested a "comercial opto-isolator", does anyone have any
imput on this? The idea, as I've dealt with this before but in other
circumstances, is that we have a small potential on the amplifier side for
safety and use the opto-isolators to isolate from the pc side.
6.comm method
It appears you are focused more towards rs232 and 485, rather than a pc card
like the biosystem uses, in which case we can use the parrallel port on a pc
to accept signal data. The maxims 232 (or233) chips are pretty standard, we
can reduce to 3 wire interface if we take it down to 485 using a 75176. If
we use the right micro-processor, we don't have to add a uart, there are
uarts on board, so this saves $, too.
7. 3 parts to software
Does Joerg have a micro-processor in mind and is he writing that software.
Or is Rob writing the PC software and the micro-processor software? Then,
there is the comm software itself, the micro-processor is usually
self-sufficient and the PC is also, the comm process is the link.
Which software is Rob using for the PC? I know comm functions on visual
Basic are pretty straightforward, but you typically have to drop the data
into a database that your user interface then accesses. Visual C++ is
certainly infinitely more capable, but much more complex to write as well
unless you already have some adaptable software. This is absolutely where
the most time investment will take place, and I mean A LOT of time.
8. the pcb
Does Joerg have CAD capability for schematic capture and PCB layout, though
I don't have too much time, this is a very important aspect to a product's
longterm reliability and robustness, as well as maintaining cost
considerations. As stated before, while I don't have the time to do the R&D
this year, I can probably do the board layout work for the project when it
gets to that stage if no one else has capabilities and experience (and after
doing several motherboards, I can say experience is key, probably why Tom
Collura used a pre-made board). So, in this way, I can take the product
from prototype to successful manufacture. I interject now as this is a very
important step, good to have a tentative plan in advance.
9. major components cost estimate
we have to have these components which are pricey: micro-processor($5),
ram($3), rom ($3), 232 ($4), power supply transformer ($8), opto-isolation
(?), a/d($5), pcb ($15), box ($7), LED's and switches ($5), assembly/tech
($30), misc parts ($5-10). If we go with a mpu that has ram and rom
onboard, we may have to get a uart ($5) so the tradeoffs have to be
considered. With 2 amplifiers, the cost is up to about $100. Typically in
manufacturing, you'd figure at least a 2:1 ratio for other costs compared to
COGS, so we're looking at about $300, this all depends on volume, which
won't be large as we are starting from scratch with no resources. So, while
this is much cheaper than $1000 for the 2 channel brainmaster, it's not
$100. Basically, if you remember, Yaniv, this was what I suggested the sale
price would be at the start of this project. I welcome correction in my
estimate. What is the other $200 for? basically overhead, marketing,
distribution and income for those who are investing their valued time- at
this point, these are all theoretical. If you go through distribution, they
mark up, which is figured as a discount off the list price (list price is
$300, they get 40% off = $180 to the wholesaler). Typically, the
manufacturer makes more than the wholesaler, so this would raise the sale
price to $400. Welcome to the world of manufacturing :) As I said, good to
look at this ahead of time, I value everyone and feel they deserve to be
compensated accordingly. And it's good to take a look at these issues before
they become issues :)
even a prototype run of 25 will cost $3-4000 as you have to purchase parts
in quantity and there are engineering start up charges, where is this budget
coming from, which says nothing about promotional costs which will be just
as much just to get started. underestimating it won't change the bottom
line.
best regards, tom carr
tomcarr_at_p...
www.piercingtheveil.com
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