From: yaniv_vi (yaniv_vi_at_yahoo.com)
Date: 2001-12-18 12:25:17
hi
you have some sense in your reply , to see what is bein used in other
machines , and by this decide .
it's a point needs to be checked .
also the other point , that we are not pretty sure about it , that we
need to check , is can we get this device out without fda and for
what purpose (personal , clinical ) ?
assuiming that personal use don't reuire fda , still if want to make
it avail to professionals , we need fda clearance , and that's one
big question .especially because of testing . it might be expensive .
on hint i got on this issue is that if you can prove ! that you
design is safe , testing won't be needed . i seen in some book
describing medical standard , but i don't remeber what standard , and
the book is somewhere in a library in india .
about what you said on layout , yeh your probably right , but don't
you think prototype or everyboard would need safety testing ?
that's the biggest question .
but still about isolation , assuming we can isolate with something
that people can know without a doubt it's isolated , with very little
or none addup to cost , and small working time (hopefully , but i
must admit , it's not my working time - at the moment i don't have
this option , so maybe it's not so small ) , and on the other side
looking at benefits - no testing , assured safety ?
and i really believe that we can find a isolation methods that takes
little money , little design time , and you can know it's safe !
we just have to think a bit !!!
and about ad-dc .
i don't understand something .
assumoing you use rechargable batteries , and charge them in an
external device , i don't see any problem , and why people won't use
them , if we explain that this kind of setting makes the machine
safer ? i believe , but maybe i'm wrong that most people wouldn't
mind this little hassle so much that they would pay $1000-$4000 for
compatible machine from other company .
sincerly yaniv
p.s. if you're going to buy all the parts for your design , can you
post price list ? if possible for 20-50 qty ? it could be helpfull to
estimate mfr price in usa .
--- In buildcheapeeg_at_yahoogroups.com, Doug Sutherland <wearable_at_earthlink.net> wrote:
> Hi Yaniv,
>
> > everybody says that the optocouplers are in compliance to
> > the iec601 standard for medical safety. <snip>
> > if badly designed ( for example bad layout ) it could not
> > be really isolated. does bad assembly can affect this?
>
> I think it would have to be a really big mistake in layout
> to be not isolated. Same goes for assembly.
>
> > what are the ways to verify the total design is safe from
> > this point (high voltage from pc)?
>
> I have no idea what the regulations are, but the sensors
> mag article I referred to said that manufacturers of bio
> amplifiers, especially EEG and ECG, provide up to 10^12
> ohms isolation.
>
> http://www.sensorsmag.com/articles/0199/iso0199/main.shtml
>
> I don't think we can achieve that with opto-couplers, but
> then I don't know that it's really necessary either. I am
> personally comfortable with using simple opto-couplers on
> my body, but then I'm not planning on asking anyone else
> to do the same. Here's what I would like to know: what
> kind of opto-couplers are inside brainmaster, waverider,
> procomp, etc? I wish I still had my commerical brainmaster
> (I sold it) or I would take a look.
>
> > what are the costs asociated?
>
> It seems that the isolators that provide 10^12 ohms of
> isolation are expensive, like $100. But then the simple
> phototransistor method or IR would achieve the same for
> a lot less money. The other issue is AC/DC ... I wonder
> if there are regulations on these adapters. Does that
> TMA0505S DC/DC converted provide safety if something
> goes wrong with an AC/DC adapter?
>
> > are they are needed for each device going out to market?
> > or not, just for the prototype?
>
> Good question. Again, it would be interesting to look
> inside some commercial units and see what's in there.
> I think brainmaster always runs on batteries, even when
> plugged into AC, but I'm not sure how they did that.
>
> > please assume, like i myself doing here, that this
> > safety issue should be 100% for each device on market!
> > this is a very very critical point, we don't want
> > somebdoy to die !!!
>
> Someone mentioned that nobody has ever been electrocuted
> by an EEG, arguing that opto-isolation was not needed,
> but I don't think electrocution is the only threat.
> According to that sensors mag article "A normally harmless
> 60 Hz current can cause cardiac arrest under certain
> circumstances". It seems to me that the only way to
> guarantee protection is to run on DC (batteries) all
> the time. But that implies built-in charging to be a
> viable solution. People won't want to swap batteries.
> I know that brainmaster is usable while plugged into
> AC and charging, the question is: what safety measures
> are there to prevent injury if something were to go
> wrong with the AC/DC adapter?
>
> -- Doug
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:35 BST