Group Design

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Wow!  Designing in a group is strange.  I'm helping with the design of a ve
ntilator and it is a unique experience.  We have people of many skill level
s and talents, many I don't even know.  The design seems to ping pong aroun
d based on the hot button issue of the day.  They already have someone to d
o board level design, but he has a day job, so the work gets done a bit hel
ter skelter.  I mostly try to identify potential bugs.  

Most of the people are in the UK with a couple in the EU.  I'm in the US al
ong with one other person.  

We have semiweekly meetings on zoom or other sites.  There is no strong org
anization.  

I'm surprised as much is getting done as it has been.  The original design  
used an Arduino and once the lack of I/Os became a hindrance we are switchi
ng to an ARM, but nothing remotely like a proper spec was generated and the
 processor initially picked is now out of pins.  The first rev of the main  
board has many issues including the isolation of the heat sink tabs by ther
mal relief connections.  

I literally have no idea how they are ever going to get this thing past any
 sort of approval process.  No one working on the project even seems to und
erstand what is required.  

I guess I'm a bit frustrated by the lack of organization.  I'd like to step
 away, but the person acting as a leader seems to want me in the group.  

There is some work of my own I should do, so maybe I'll stick around to get
 to rev 2 of the board and then step out.  

I guess I'm used to working on my own.  

--  

  Rick C.

  - Get 1,000 miles of free Supercharging
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Re: Group Design
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Sounds like fun, but why a ventilator?  Is the ventilator shortage still
happening and are there more urgent shortages?  I thought there were
already a bunch of ventilator projects.

What is the software going to be like, and is it being taken care of?
This sounds like a good opportunity to write some Ada code.

Re: Group Design
On Tuesday, July 7, 2020 at 10:02:45 PM UTC-4, Paul Rubin wrote:
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Yeah, that was one of my first observations that there are tons of ventilat
or projects.  They nearly all are based on squeezing an Ambu-bag to push ai
r into the patient.  The details of not harming the patient are tricky.  Ve
ntilating a patient while conscious is harder and very few are doing that.  
 They seem to be having problems with the plumbing at the moment, getting a
ll the right valves in the right places to do the right things.  At the mom
ent there is a lot of hardware right at the patient's mouth.  I'm working t
o understand what is needed and what isn't.  

There's a valve called a Ruben valve which allows the patient to be connect
ed to the inspiratory limb (branch from the ventilator) or to the expirator
y limb (the path for exhaling) without a leak to the outside via a straight
 through path.  It's not entirely clear just how the details of this valve  
work.  I have concerns that the valve can be stuck in the inhale position b
y the pressure in the line.  It doesn't seem to have a way to leak out once
 pressurized.  

I'm not sure the software is too hard at the higher levels, but there are i
nterface procedures that have to convert differential pressure to flow rate
 and monitor other marginal sensors.  The O2 sensor is only ~18% accurate.  
 The guy running the project doesn't seem to understand the difference betw
een accuracy, resolution and noise when we were talking about increasing th
e resolution of a reading by averaging many samples.  Not that this was a b
ig deal.  The real issue is I'm not sure improving the resolution of the me
asurement will give him what he wants.  The airflow measurement is very sen
sitive at the low end.  I'm wondering if there is an issue with the flow be
ing more or less laminar at the low end so that it is not going to be an ac
curate reading.  The interesting part is they  verified the home brew flow  
rate sensor by using a commercial flow rate sensor that uses the same techn
ique.  

Whatever.  I'm trying to help without being a drag.  I think sometimes my q
uestions are not what they want to hear.  Maybe I'm too pessimistic.  

The software is C I believe.  I don't think anyone in this crowd is going t
o use Ada.  

--  

  Rick C.

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Re: Group Design
On 08/07/2020 05:36, Rick C wrote:
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It sounds like this group is opportunist (I don't mean that in a bad
way) - they see a potential market for a device, with a short time
frame, and they are trying to get something working as fast as possible
before the window closes.  So they grab the first off-the-shelf "rapid"
development kit they can find - an Arduino - and start banging out code
before they've even figured out what they want to do.

For some products, that's fine.  For something medical related, it is
not.  They appear (from your description) to be missing a fundamental
understanding of the task, and haven't got in experts to cover that
base.  And without paperwork covering everything from research, design
calculations, specifications (hardware and software), reviews, project
management, issue tracking, personnel qualifications, development,
testing, certification, production qualification, and a dozen other
topics, there is no way they can get any kind of approval.

I would guess that the group is used to small systems for small
customers who are happy with a demonstration that shows the device
works.  That's great for many things, and gives people solutions that
work when a serious high-level development process would be orders of
magnitude too expensive.

But making things that are relevant to life and death is a different
world entirely.  Some people think that the current Covid situation is
so desperate that /anything/ is better than nothing, so throwing
together a cheap and simple ventilator is helpful - that is very far
from true.

So I hope you get paid up-front, and keep your distance from the group -
be an external consultant, but don't take responsibility for anything
other than your reviews.

(And the choice of language for the software is the least of their
concerns!)

Re: Group Design
On Wednesday, July 8, 2020 at 3:31:55 AM UTC-4, David Brown wrote:
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Pay???  This is open source, volunteer labor.  They have a few companies donating fabrication services.  A sheet metal shop fabricated a few chassis.  I think they may even have a Chinese assembly house donating some board assembly work.  

I started on a different project which was doing a very similar thing and I questioned the need for yet another project.  In the end the guy leading that effort bailed and the group decided to merge with this project that was further along.  

I think I feel awkward because I don't have a defined roll.  It is hard for me to tell if/when my comments are welcome and when they are kibitzing.  

--  

  Rick C.

  -- Get 1,000 miles of free Supercharging
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Re: Group Design
On 2020-07-08 Rick C wrote in comp.arch.embedded:
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That is the good part of designing with a group. You can have many more talents
and skills than can be combined in a single person. For a medical product like
this you need medical, software, hardware, mechanical and lots more skills. Not
something that can be found in one person very often.

<snip, some project frustrations etc.>

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This is very worrying. As David already explained, documentation and approval
is a very large part of medical device development. There is this famous
Boeing quote about the weight of the paperwork required for a plane. I think
you can extend this to medical devices as well.

Did they at least have a look at some standards that apply to ventilators to
check what will be required? I would start off with IEC 60601-1, IEC 62304
and ISO 80601-2-12, make sure you use the latest versions. But there will be
more.

And this should have been done before the first schematic was drawn or line
of code was written. Some standards put requirements on the development
process and you can not comply with those if you start your certification
efforts after the development is completed.


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If there has indeed been done nothing on the certification side, my feeling
would be to step away as well.


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Yes, than all is in your own hands. ;-)

But the advantage of a team is that you can concentrate on what you are good
at and let others do what they are good at. And if the team is diverse and
skilled enough (and properly led) the end result will be better that that of
a single developer.

And I think a lot of medical device stuff can not be done by a single
person. There are many cases where you need an (expert) reviewer in the
process. Reviewing your own work is less than optimal. ;-)


--  
Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail)

It seems that more and more mathematicians are using a new, high level
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Re: Group Design
On Wednesday, July 8, 2020 at 8:14:05 AM UTC-4, Stef wrote:
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a ventilator and it is a unique experience.  We have people of many skill l
evels and talents, many I don't even know.
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alents
 like
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s. Not
 any sort of approval process.  No one working on the project even seems to
 understand what is required.  
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oval
ink
 to
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4
 be
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ne
step away, but the person acting as a leader seems to want me in the group.
  
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 get to rev 2 of the board and then step out.  
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ng
ood
d
 of
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It seems the UK has an abbreviated set of requirements for response to COVI
D-19 and that is what they are mostly working with.  I forget the name of i
t.  

They do get advice from time to time from professionals in the field.  My m
ain concern is a direction they are currently going in where more and more  
valves, pressure relief, etc. is being added to the tubing right at the pat
ient.  I'm not sure how it all will be held in place.  That and how they pl
an to get this through the approval process.  

I had a friend who worked on medical devices for a while before getting out
.  He said they required that you "prove" your design will not hurt the pat
ient in any way.  Hard to do with a ventilator.  

I don't mind working on the team.  It's seeing them go in odd directions th
at bugs me.  This thing will probably cost hundreds of dollars in the final
 BOM without anything like profit or overhead added in.  People were arguin
g against adding $0.10 for more pins on a processor.  Then later they decid
ed to not only go with the larger pin count, but bump from an 8 bit AVR to  
an ARM CM4F adding several dollars.  That sort of inconsistency drives me n
uts.  "Every dollar counts!"  Yes it does, so you need to justify the cost  
*rationally*.  

--  

  Rick C.

  -+ Get 1,000 miles of free Supercharging
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Re: Group Design
On 2020-07-08 Rick C wrote in comp.arch.embedded:
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[...]

[Is there a way you could limit your line length to a more usenet friendly
number?]

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How long will this last? If you look at the new cases curves, the UK is well
over the initial peak. https://www.nytimes.com/ has nice graphs of world
cases on the front page.

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Sounds like they are moving to more and more features instead of sticking to a
simple emergency use device. Feature creep is not uncommon when getting advise
from several medical professionals. ;-)


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That is not entirely true, it is more a risk/benefit analysis. Otherwise you
could not even get a scalpel approved, it will always hurt the patient.

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Does every dollar count in this case? If this is for solving short term
ventilator shortages, should development speed not count more than dollars?

--  
Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail)

A national debt, if it is not excessive, will be to us a national blessing.
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Re: Group Design
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I think the UK competition is over:
https://www.gov.uk/government/news/ventilator-challenge-hailed-a-success-as-uk-production-finishes

Demand from the rest of the world is a different, unclear, question...

Theo

Re: Group Design
On Wednesday, July 8, 2020 at 1:00:04 PM UTC-4, Stef wrote:
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of a ventilator and it is a unique experience.  We have people of many skil
l levels and talents, many I don't even know.
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y

Not without copying messages to some other editor and then pasting back int
o Google groups.  I know there is a spec for this, but I've switched newsre
aders several times over the years and I'm just tired of trying to find too
ls that last the test of time.  So I've settled for ease of use over strict
 adherence to the spec.  

Why is your newsreader intolerant of longer line length?  


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COVID-19 and that is what they are mostly working with.  I forget the name  
of it.  
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ell

As was the case for much of the US... until they started to open things up  
again.  My crystal ball is not working so well these days.  Seems it needs  
a lubricant that is also used in making protective gear and is in short sup
ply.  


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My main concern is a direction they are currently going in where more and m
ore valves, pressure relief, etc. is being added to the tubing right at the
 patient.  I'm not sure how it all will be held in place.  That and how the
y plan to get this through the approval process.  
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 to a
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dvise

Don't know about "more and more" or "feature creep".  They are responding t
o the issue that virtually every other piece of gear is doing the same limi
ted job of ventilating an unconscious patient because it is easier.  Kenned
y promoted the space race to the moon "not because it is easy, but because  
it is hard".  So why not take on the harder task of being not just more use
ful, but safer.  I don't recall all the terms, but when the patient is only
 assisted in breathing there is less risk of harm from use of the machine.  
 So this is not just a less often implemented feature, it is an important f
eature.  

In particular, it was in a conversation with a medical professional that th
is need was pointed out.  


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 out.  He said they required that you "prove" your design will not hurt the
 patient in any way.  Hard to do with a ventilator.  
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you

That is a bogus comparison.  So nothing to discuss there.  


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s that bugs me.  This thing will probably cost hundreds of dollars in the f
inal BOM without anything like profit or overhead added in.  People were ar
guing against adding $0.10 for more pins on a processor.  Then later they d
ecided to not only go with the larger pin count, but bump from an 8 bit AVR
 to an ARM CM4F adding several dollars.  That sort of inconsistency drives  
me nuts.  "Every dollar counts!"  Yes it does, so you need to justify the c
ost *rationally*.  
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s?

It's not about rushing to the finish line for sure.  None of the goals are  
clearly stated.  That's my point.  

We meet using video tools and Zoom seems to work the best.  I have various  
latency and bandwidth issues and was not able to participate yesterday.  Th
at's really frustrating, especially when everyone is missing an important p
oint.  Today we had a one on one to test Google Meet and compare to Zoom (G
oogle was a second runner).  So I had a chance to make clear what is and is
 not a problem in the plumbing.  Understanding what I was saying he agreed  
so the plumbing next to the patient is less cumbersome now.  

Maybe more 1 on 1s will help.  

--  

  Rick C.

  +- Get 1,000 miles of free Supercharging
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Re: Group Design
On 2020-07-08 Rick C wrote in comp.arch.embedded:
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Slrn may be a bit ancient, but so is usenet. ;-)
Slrn can handle long lines, but after quoting it does not wrap them anymore,
so I need to shift the screen to view the entire line. Luckily the editor for
replying does still wrap those. But hey, it's a minor inconvenience, just
asking.

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So the aim is to create a new type of ventilator, not to cope with immediate
shortages? This is very big task indeed. This sort of thing usually takes
years of development and and clinical testing. They have certainly gone for
"not easy, but hard".

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I don't agree. ;-)
The scalpel example is a bit extreme of course. But for every medical  
device there wil be a risk/benefit analysis. There are medical devices
that do some harm to a patient, but as long as the benefits outweigh
the harm it may still be a good thing to use those devices.

A ventilator is never good for your lungs, so it will do some damage,
the aim is to keep the damage as minimal as possible and as short term
as possible.

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Well, get that point across and try to get the goals clear before
proceeding.

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Good luck.

--  
Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail)

root rot

Re: Group Design
On Wednesday, July 8, 2020 at 5:35:53 PM UTC-4, Stef wrote:
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gn of a ventilator and it is a unique experience.  We have people of many s
kill levels and talents, many I don't even know.
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ndly
 into Google groups.  I know there is a spec for this, but I've switched ne
wsreaders several times over the years and I'm just tired of trying to find
 tools that last the test of time.  So I've settled for ease of use over st
rict adherence to the spec.  
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re,
 for
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I wish Google was amenable to requests regarding their software.  As far as
 I can tell they ignore any feedback and happily ignore rules for newsgroup
s as if they invented them.  I think it was Al Gore who invented the Intern
et, no?  So we can blame him perhaps for giving Google a license to drive o
n the cyber-highway.  

Thanks for understanding.  


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to COVID-19 and that is what they are mostly working with.  I forget the na
me of it.  
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s well
ld
 up again.  My crystal ball is not working so well these days.  Seems it ne
eds a lubricant that is also used in making protective gear and is in short
 supply.  
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.  My main concern is a direction they are currently going in where more an
d more valves, pressure relief, etc. is being added to the tubing right at  
the patient.  I'm not sure how it all will be held in place.  That and how  
they plan to get this through the approval process.  
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ing to a
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g advise
ng to the issue that virtually every other piece of gear is doing the same  
limited job of ventilating an unconscious patient because it is easier.  Ke
nnedy promoted the space race to the moon "not because it is easy, but beca
use it is hard".  So why not take on the harder task of being not just more
 useful, but safer.  I don't recall all the terms, but when the patient is  
only assisted in breathing there is less risk of harm from use of the machi
ne.  So this is not just a less often implemented feature, it is an importa
nt feature.  
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t this need was pointed out.  
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ate
or

I would not say "a new type".  This is what commercial vents do.  But being
 the hard part, most of the quick turn projects leave it out.  I expect it  
will be the hardest to get approvals for too.  


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ing out.  He said they required that you "prove" your design will not hurt  
the patient in any way.  Hard to do with a ventilator.  
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se you
.

The trade off issues for a ventilator are well known, not something to be n
egotiated.  So there is no point in comparing to scalpels.  The rules are t
he rules and it will be hard to get approvals.  I'm sure it costs lots of m
oney, not unlike FCC approval.  I believe the plan is to find a manufacturi
ng partner to turn this design over to who will bear the brunt of approvals
.  

This is not impossible, but I think that should be one of the early steps s
o they have some input to the process, guiding what comes out at the end ra
ther than simply having to redesign it all over again potentially.  


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ions that bugs me.  This thing will probably cost hundreds of dollars in th
e final BOM without anything like profit or overhead added in.  People were
 arguing against adding $0.10 for more pins on a processor.  Then later the
y decided to not only go with the larger pin count, but bump from an 8 bit  
AVR to an ARM CM4F adding several dollars.  That sort of inconsistency driv
es me nuts.  "Every dollar counts!"  Yes it does, so you need to justify th
e cost *rationally*.  
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m
lars?
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are clearly stated.  That's my point.  
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I have provided my input and the project moves forward.  The rev 1 of the m
ain board is full of issues mostly because the guy doing it is donating his
 time while continuing to work full time.  There was no design review I ass
ume because there was no one to conduct it with but also I think because no
 one recognizes the need.  "It's just an Arduino" plus some interfacing cir
cuitry.  

The design includes window comparators for alarm settings.  I found that ac
cording to the labels and the polarity of the outputs the alarms will be gu
aranteed to be on all the time.  Fortunately the prototype uses pots for th
e set points so the max can be set to the min value and vice versa.  

I'm also concerned about the board layout.  The board is not at all dense b
ut there are several parts that need copper area for heat sinking.  They ar
e using a linear regulator to drop 12+ volts to 5V and 3.3V.  The back ligh

C!!!  There is a motor controller that has to handle several amps of curren
t.  Both of these parts had thermal breaks on the thermal pads on the rev 1
 board.  So virtually no heat sinking.  


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ous latency and bandwidth issues and was not able to participate yesterday.
  That's really frustrating, especially when everyone is missing an importa
nt point.  Today we had a one on one to test Google Meet and compare to Zoo
m (Google was a second runner).  So I had a chance to make clear what is an
d is not a problem in the plumbing.  Understanding what I was saying he agr
eed so the plumbing next to the patient is less cumbersome now.  
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Thanks.

No small part of the problem is I don't have a defined roll.  Someone is do
ing the electronic design part time and I get to figure out what is wrong o
nce in a while.  Not enjoyable really.  

--  

  Rick C.

  ++ Get 1,000 miles of free Supercharging
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Re: Group Design
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Frankly this project sounds like amateur hour.  If US FDA approval works
the way it's been explained to me, there is no chance of the device ever
getting it.  Other countries' mileage may vary.

There are other devices that they could build that would be much less
dangerous (therefore easier to get approval for), but that fill a need.
For example, polysomnography machines for sleep studies, or other
diagnostic equipment.  Compared to a vent, they are pretty safe, since
they only measure your body functions (heart and breathing rate, etc.)
rather than being an invasive intervention.  But having more of them
available could help people with underdiagnosed conditions like sleep
apnea.


Re: Group Design
On 2020-07-08 Rick C wrote in comp.arch.embedded:
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[...]
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I don't think you got mu point here. I just commented on your (friends)
statement '"prove" your design will not hurt the patient in any way'. That
is simply not true. There is always a risk/benefit and as long as the
benefits outweigh the risks, some risk may be deemed acceptable. This
presentation highlights how important risk/benefit is in the new MDR (EU
medical deviceregulation).
https://www.bsigroup.com/meddev/LocalFiles/en-US/roadshow-resources-2017-fall/bsi-mdr-risk-and-clinical-requirements.pdf

And this goes for all medical devices, from complex (like ventilators or
MRI scanners) to simple. The scalpel being an example of the latter, not
a comparison to the ventilator.

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I'm not familiar with FCC, but if it's anything like EU CE marking to get
(non medical) electronic devices approved for sale, you might be in for a
shock when it comes to electronic medical devices, especially those that
include software.


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Like has been said multiple times. You should start (preparation for) the
approval process before/during the design, not after.

And any idea who this manufacturing partner will be? It will need to be
a partner already familiar with medical devices, preferrably with
ventilators. And you have to come with something they could not have
done themselves.

[...]
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One hand, these problems are only minor and can be solved by any capable
electronics engineer. On the other this sort of thing would get me worrying
about the skills of the team. But if their skills are in medical and
regulations, an electronics engineer would be a good supplement to the team.


--  
Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail)

The whole earth is in jail and we're plotting this incredible jailbreak.
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Re: Group Design
On 07/08/20 23:20, Rick C wrote:

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parts that need copper area for heat sinking.  They are using a linear  
regulator to drop 12+ volts

to 5V and 3.3V.  The back lights for the LCDs draw 300 mA!  So the 5V  
regulator gets quite warm,



You should be concerned. The whole thing about safety critical kit is
that it should be conservatively designed, with all parts running well
within their ratings. If the hw bod is happy with a regulator running
at 70c, he must be clueless. Sorry, but it needs to be said.

If you care about your professional career and any litigation
issues, you should either have enough influence on the project
direction to stop design errors like that, or just walk away from it...

Chris

Re: Group Design
On Thursday, August 6, 2020 at 7:01:55 PM UTC-4, Chris wrote:
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se but there are several
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It was a prototype board before I came on board.  I am involved in the desi
gn review of the next rev and I will be pushing for a design review of the  
layout as well.  Not sure how well that will be received.  

The project leader has indicated numerous times that he wants to get the bo
ard rolling in spite of us not having good requirements.  He brought someon
e on board to help with that, but this is very different from what I am acc
ustomed to.  My experience with requirements analysis was on DOD projects a
nd it had lots of formalities with each requirement being linked to a test.
  

We just had a meeting today with the guy who has written a systems level re
quirements document.  He has indicated that he will be breaking requirement
s down further for the software, but not for the hardware.  I asked why and
 time was cited, not enough time to do that.  What???  

I don't have any specific duties at the moment.  I might participate in a d
esign review of the schematic and layout, but I won't be doing any further  
design work.  

I just think it is crazy to try to push this design to completion without k
nowing what it is supposed to do in detail.  There seems to be an obsession
 with turning the machine off even though it has battery backup which would
 be depleted in an hour if left connected or in a couple of months if not.  
 There is an alarm for when the machine is unplugged and running off batter
y.  So what should turning the machine off do exactly?  I can't get an answ
er, but we need to complete the board design.  

Yeah, we are nearing the end of this road.  

--  

  Rick C.

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Re: Group Design
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It's ok, a group of Afghan schoolgirls is on top of it and seems to be
doing a more serious job:

https://www.reuters.com/article/us-health-coronavirus-afghanistan-ventil/afghan-all-girls-robotics-team-designs-low-cost-ventilator-to-treat-coronavirus-patients-idUSKCN24L0WO

Re: Group Design
On 2020-08-06 19:01, Chris wrote:
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Hmm, interesting.  Most linear regulators I'm familiar with are rated to  
125 C junction temperature, and some higher.  What safety or regulatory  
issues have you run into that were caused by running some part 55C below  
its rated temperature?

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Group Design
On Thursday, August 6, 2020 at 9:50:24 PM UTC-4, Phil Hobbs wrote:
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ll  
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near  
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o the 5V  
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That was the case temp via an IR gun.  So the die was hotter.  I would not  
approve a design with a part running so hot.  I believe the failure rate go
es up quite quickly with temp.  The real point is this is because the layou
t was not correct using thermal breaks around the thermal pad!!!  Easy enou


Did you not read the original post about this?  

--  

  Rick C.

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Re: Group Design
On 2020-08-06 22:12, Rick C wrote:
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I've designed a fair bit of stuff to work in ambients higher than that,  
from remote satcom stuff to downhole instruments running at 175C.

The amateur vent stuff is all March 2020 at this point, so I'm  
interested in the broader context.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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