From: Jim Meissner (jpmeissner_at_mindspring.com)
Date: 2001-12-21 01:13:55
Dear yaniv:
> hey jim
> so you worked in emc / emi testin and design ?
> why didn't you said so before :)
I have also done the testing to get a ECG machine into the Hospital for a Doctor I was working for. The 10 micro amp requirement comes from the fact that there might be an electrode inside the heart during surgery. The actual safety for the EEG is much less stringent, but they have chosen to address the worst case scenario. The actual 10 micro amp measurement is quite simple, and if you buy a triple shielded medical grade transformer it is notdifficult to meet.
If you use battery power only and do not have an on board charger, you are home free. The danger would be if someone used a cheap wall wart transformer to recharge the batteries while they were hooked up to their head. I would want the customer to take the batteries out and put them into an external charger. An opto isolator would meet the 10 micro amp spec easily. A realistic breakdown voltage would be the peak of the 240 volt AC line.
If you go the direction of the Hal-4 and sell a kit, the customer is responsible, but I would want to have done my best to insure safety. Again, battery operation without charger and a good opto isolator would be my suggestion.
Someone on this list suggested a discrete LED and Photodiode mounted far enough apart and coupled by a light guide could meet the 5000 volt breakdown and leakage spec. Very inexpensive.
Juergen P. (Jim) Meissner
Check out my Website at www.MeissnerResearch.com
Read about the benefits of the Brain State Synchronizer sounds for improving your life and health.
----- Original Message -----
From: yaniv_vi
To: buildcheapeeg_at_yahoogroups.com
Sent: Thursday, December 20, 2001 8:11 AM
Subject: [buildcheapeeg] Re: modularEEG input stage prototype ... Some Ideas :
hey jim
so you worked in emc / emi testin and design ?
why didn't you said so before :)
maybe you can help with cheap ways to pass emi testing for our device
(because again were volunters ) , and with cheap ways to pass the
leakage current tests ?
how much would they cost ?
are there ways to design the machine in such a way that such tests
ewon't be needed at , and just by deign you can say , the machine
is o.k. from this perspectives ?
does this kinds of tests needed to be done just for prototype or for
each device (taking in acount that if they don't stand in these
requirement might hurt a person ) ?
thanks
yaniv
--- In buildcheapeeg_at_yahoogroups.com, "Jim Meissner" <jpmeissner_at_mindspring.com> wrote:
> Dear Sade:
>
> My background is analog. How can I help? I have designed
equipment to measure 10 tera ohm (that is 13 zeros) resistors
accurately. That makes this EEG requirement seem like Childs play.
>
> I am in the process of redrawing the schematics of the Brain Wave
Monitor that I built some years ago. I will post them on my website
for anyone who might be interested.
>
> I have done quite a bit of mil spec EMI and EMC testing and
design. Spent weeks at a time working in screen rooms designing
filters.
>
> I might be able to help with your UV sensor project. I have done
some work with super high sensitivity photo detectors to look at the
human aura.
>
> I worked as a consultant for over 30 years and just recently
retired. I would be happy to pass on what I learned.
>
> Juergen P. (Jim) Meissner
> Check out my Website at www.MeissnerResearch.com
> Read about the benefits of the Brain State Synchronizer sounds for
improving your life and health.
> ----- Original Message -----
> From: sademade
> To: buildcheapeeg_at_yahoogroups.com
> Sent: Thursday, December 20, 2001 1:08 AM
> Subject: [buildcheapeeg] Re: modularEEG input stage prototype ...
Some Ideas :
>
>
> 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.
>
>
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:35 BST