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'[EE] DIY Electrocardiograph circuit, selecting an '
2011\01\25@083547 by V G

picon face
Hey all, I'm looking to make this into a quick 1-day project. I found this
website:

website: http://www.eng.utah.edu/~jnguyen/ecg/instructions.html

and this schematic:

schematic: http://www.eng.utah.edu/~jnguyen/ecg/bigsch.gif

for building your own electrocardiograph. It's basically a few opamps hooked
up into your sound card.

1(Q). I don't have *those* specific opamps, as shown on the schematic (LM324
http://www.national.com/mpf/LM/LM324.html#Overview) or (LF353
http://www.national.com/mpf/LF/LF353.html#Overview), but I can go to the
local electronics store to buy some. I looked on Linear Technology's and
Maxim's site for some opamp samples but they all have so many different
parameters with wide ranges that I'm not familiar with. Generally what
parameters and what value ranges should I be looking for in an opamp for
this project when I go to the store? For example: gain, bandwidth, slew
rate, and so on, and what ranges for each?

2. I don't want to be hooking up any part of my body to my computer (I've
had bad experiences with ground loops? in the past. Remember the "magic
smoke" from that HH44780 display?). So before converting the signal to
digital with a microcontroller and optoisolating it, I just want to hook up
a simple LED to flash when the trigger level has passed (when the heart
beats). For this, I'm guessing I'd need to hook up the output of the circuit
to a comparator and set the reference voltage via a comparator, then drive
an LED with the comparator's output. Hopefully, the LED will blink slow
enough for the human eye to see.

2a(Q). Is the comparator method the right way to go about it?

2b(Q). If it is, when I go buy a comparator and the rest of the parts
(hopefully today), are there any special parameters I need to look for in a
comparator?

3(Q). I just realized - I have a laptop which runs on batteries, so it
should be safe to plug into the laptop's microphone input jack and record a
waveform with audacity

2011\01\25@090843 by Carey Fisher

face picon face
On Tue, Jan 25, 2011 at 8:35 AM, V G <spam_OUTx.solarwind.xTakeThisOuTspamgmail.com> wrote:

> Hey all, I'm looking to make this into a quick 1-day project.
>
....

>
> for building your own electrocardiograph. It's basically a few opamps
> hooked
> up into your sound card.
>
>
Take a look at this:
http://blog.makezine.com/archive/2007/03/home_made_electrocardiogr.html

Carey Fisher
Chief Technical Officer
New Communications Solutions, LL

2011\01\25@092032 by V G

picon face
On Tue, Jan 25, 2011 at 9:08 AM, Carey Fisher <.....careyfisherKILLspamspam@spam@ncsradio.com>wrote:

> Take a look at this:
> http://blog.makezine.com/archive/2007/03/home_made_electrocardiogr.html
>

Thanks! But that's just a link pointing to what I posted above. The only
thing new in there was this:

http://plus1plus1plus.org/Resources/EEG-EK

2011\01\25@093037 by Olin Lathrop

face picon face
V G wrote:
> schematic: http://www.eng.utah.edu/~jnguyen/ecg/bigsch.gif

A EKG is is basically a sensitive diff amp with very good common mode
rejection.  The little signal from the heart muscle that makes it out to
your skin is tiny compared to the signals the body picks up from surrounding
electromagnetic emitters, like power cords, radio stations, and lots of
other stuff.

The main difference between the real signal and the noise is that noise is
largely the same over your body.  In other words, it's a common mode signal,
whereas the signal from the heart muscle is differential if you put the
electrodes in the right places.  This means common mode rejection is a very
important criterion of a EKG front end.

I would get a instrumentation amplifier with built-in common mode rejection..
These are not opamps, but look similar.  They are usually diff amps with
specific gains and good common mode rejection.  The circuit you show depends
on the matching of external parts to achieve common mode rejection.  There
is no way you can get separate components matched well enough to achieve the
common mode rejection of a instrumentation amp specifically designed for
this purpose.  Instrumentation amps cost more than opamps with similar
specs, but that only means a few $$ instead of a few tens of cents.  If you
can get samples, it doesn't matter anyway.

I haven't used a instrumentation amp in a while, so haven't had a reason to
check who the players are today.  Analog Devices used to be one of the
leaders.  National, TI, and Linear are good suspects too.

> 1(Q). I don't have *those* specific opamps, as shown on the schematic
> (LM324 http://www.national.com/mpf/LM/LM324.html#Overview) or (LF353
> http://www.national.com/mpf/LF/LF353.html#Overview), but I can go to
> the local electronics store to buy some.

As I said, you'd get better results with a instrumentation amp instead of
trying to roll your own common mode rejection circuit.

> I looked on Linear
> Technology's and Maxim's site for some opamp samples but they all
> have so many different parameters with wide ranges that I'm not
> familiar with. Generally what parameters and what value ranges should
> I be looking for in an opamp for this project when I go to the store?
> For example: gain, bandwidth, slew rate, and so on, and what ranges
> for each?

The characteristics of EKG signals is that they are low level (a few
millivolts at best), high impedence, slow, and buried in common mode noise
many times stronger than the signal itself.

You don't need much bandwidth.  2 Hz is a fast heart beat, so a few 100 Hz
upper frequency limit will allow all the relevant signal thru.  Any amp you
find will be able to handle that.  Slew rate is not a issue either for the
same reason.

Instrumentation amps come in fixed gains, sometimes selectable via extra
pins.  Overall you probably need a gain of around 1000 to 5000 (I'm guessing
here) between your skin and the A/D.  The instrumentation amp doesn't have
to provide all this.  It's main job is to provide the common mode rejection,
convert the differential signal into single ended, and boost it enough so
that it's well above the noise floor of the remaining circuit.  You can
easily enough add more gain afterwards with ordinary opamps after the
instrumentation amp, so the gain of the instrumentation amp isn't that
critical.  100x sounds good since it's certainly well below what is
ultimately needed (allows real gain selection to be made later), and plenty
good enough to provide a strong signal well above the noise floor for
subsequent stages.  10x is should be good enough too.  Both 100x and 10x are
common instrumentation amp gains, so that shouldn't be a problem.

> 2. I don't want to be hooking up any part of my body to my computer
> (I've had bad experiences with ground loops? in the past. Remember
> the "magic smoke" from that HH44780 display?).

You definitely don't want to have a direct connection between your body and
your computer, or anything else ultimately tied to the power line.  It's not
the magic smoke of the electronic parts you should be worried about, but
releasing the magic smoke from your heart.  Stuff happens.  The probability
may be low, but when the electrodes are tightly coupled to your heart muscle
the consequences can be severe.  Remember that the main difference between a
EKG and a electric chair is what the wires are tied to.

I would run the gizmo off a few batteries, and opto-couple the output to a
serial line on your computer.  Having the gizmo in your pocket also helps
with the common mode rejection, since it will be subjected to much of the
same common mode signals your body is, and they will therefore cancel
without active electronics having to do it.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000

2011\01\25@095322 by RussellMc

face picon face
This is IMMENSELY GOOD ADVICE from Olin.
Ignore it and die, or kill somebody, possibly.

Real world devices go to the utmost care to avoid killing people.

{Quote hidden}

> without active electronics having to do it.

2011\01\25@100016 by V G

picon face
On Tue, Jan 25, 2011 at 9:52 AM, RussellMc <apptechnzspamKILLspamgmail.com> wrote:

> This is IMMENSELY GOOD ADVICE from Olin.
> Ignore it and die, or kill somebody, possibly.
>
> Real world devices go to the utmost care to avoid killing people.


Yes, that was the original intent. I didn't want to hook up anything to
anything higher than 12 volts or so. Everything will be battery powered

2011\01\25@100631 by V G

picon face
@Olin, note: in this circuit (
http://www.eng.utah.edu/~jnguyen/ecg/bigsch.gif), they seem to have made
their own instrumentation amplifier that looks like this
http://www.allaboutcircuits.com/vol_3/chpt_8/10.html

2011\01\25@102555 by Peter

picon face
V G <x.solarwind.x <at> gmail.com> writes:
> On Tue, Jan 25, 2011 at 9:52 AM, RussellMc <apptechnz <at> gmail.com> wrote:
>
> > This is IMMENSELY GOOD ADVICE from Olin.
> > Ignore it and die, or kill somebody, possibly.
> >
> > Real world devices go to the utmost care to avoid killing people.
>
> Yes, that was the original intent. I didn't want to hook up anything to
> anything higher than 12 volts or so. Everything will be battery powered.

INA100 isolation amplifier and:

http://ee.cgu.edu.tw/ezfiles/7/1007/img/476/BmeElec99_BiopotentialAmplifier..pdf

In general building circuits from newbie sites is not sucha good idea if other
resources are available, far a number of reasons, two of them being
reproductibility (as in, lack of) and chances of success.

-- Peter

2011\01\25@111137 by Michael Watterson

face picon face
On 25/01/2011 14:52, RussellMc wrote:
> This is IMMENSELY GOOD ADVICE from Olin.
> Ignore it and die, or kill somebody, possibly.
>
> Real world devices go to the utmost care to avoid killing people.
>
>> >  You definitely don't want to have a direct connection between your body and
>> >  your computer, or anything else ultimately tied to the power line.  It's not
>> >  the magic smoke of the electronic parts you should be worried about, but
>> >  releasing the magic smoke from your heart.  Stuff happens.  The probability
>> >  may be low, but when the electrodes are tightly coupled to your heart muscle
>> >  the consequences can be severe.  Remember that the main difference between a
>> >  EKG and a electric chair is what the wires are tied to.
>> >  I would run the gizmo off a few batteries, and opto-couple the output to a
>> >  serial line on your computer.  Having the gizmo in your pocket also helps
>> >  with the common mode rejection, since it will be subjected to much of the
>> >  same common mode signals your body is, and they will therefore cancel
>> >  without active electronics having to do it.

absolutely. One of Olin's top level posts.

Agree 100% you must have at least 400V galvanic isolation and current limited isolated power supply (a battery is simplest method). There is probably some regulation. But that's not a random figure. I used to design 1kV to 2kV isolation on EACH input (analog in, analog out, digital in and Digital out) when even doing just Industrial Controllers for Westinghouse.

Also all regarding instrumentation amps. Don't consider anything else. Analog Devices may have some isolated Instrumentation amps also.

2011\01\25@112630 by enkitec

picon face
On 25-Jan-11 13:06, V G wrote:
> @Olin, note: in this circuit (
> http://www.eng.utah.edu/~jnguyen/ecg/bigsch.gif), they seem to have made
> their own instrumentation amplifier that looks like this
> http://www.allaboutcircuits.com/vol_3/chpt_8/10.html.


    I have designed an EMG using the Analog Devices AD620 instrumentation amplifier feeding a National Instruments ADCS7476 controlled by an ATMEGA128 processor.

    The AD620 are not cheap but has all differential circuits inside.

    Mark Jordan

2011\01\25@114949 by Sean Breheny

face picon face
I want to echo this advice yet again. Unfortunately, the hobbyist site
which was linked here suggested doing this in a non-isolated way (with
the caveat that you have to know what you are doing). I think that is
UTTERLY FOOLISH. Normal power supplies usually have rather large
leakage currents from the AC line to the output. Several milliamps is
common. This could be very dangerous if routed directly across your
chest with a good connection.

DO NOT connect anything to your body unless it is isolated in some way
from the AC power lines.

Sean


On Tue, Jan 25, 2011 at 9:52 AM, RussellMc <.....apptechnzKILLspamspam.....gmail.com> wrote:
{Quote hidden}

>

2011\01\25@123250 by alan.b.pearce

face picon face
> On 25-Jan-11 13:06, V G wrote:
> > @Olin, note: in this circuit (
> > http://www.eng.utah.edu/~jnguyen/ecg/bigsch.gif), they seem to have made
> > their own instrumentation amplifier that looks like this
> > www.allaboutcircuits.com/vol_3/chpt_8/10.html.
>
>
>      I have designed an EMG using the Analog Devices AD620
> instrumentation amplifier feeding a National Instruments ADCS7476
> controlled by an ATMEGA128 processor.
>
>      The AD620 are not cheap but has all differential circuits inside.
>
>      Mark Jordan

I have been involved in heart monitoring as well, I didn't get to design it, but took over some work when a guy left the company. It used three CA3078 op amps for the electrode inputs in an IA configuration, to get enough voltage swing to NBFM modulate an RF signal at ~160MHz IIRC. Worked quite well as far as it went, but it never made it to commercial production unfortunately.
-- Scanned by iCritical.

2011\01\25@125146 by V G

picon face
Sorry for untrimmed message, on phone.

The AD620 seems perfect for this. I just hope I can find it at the
local electronics shop.

On Tuesday, January 25, 2011,  <EraseMEenkitecspam_OUTspamTakeThisOuTgmail.com> wrote:
{Quote hidden}

>

2011\01\25@130735 by N. T.

picon face
RussellMc wrote:
> This is IMMENSELY GOOD ADVICE from Olin.

I think so. It must have taken a lot of his time to compose the message

2011\01\25@131203 by Olin Lathrop

face picon face
V G wrote:
> they seem to have
> made their own instrumentation amplifier that looks like this

There is no special magic to making a diff amp with a fixed known gain
(instrumentation amplifier).  You can certainly make your own.  However, to
get the same kind of common mode rejection ratio in your discrete circuit
that is available in a pre-packaged unit takes part tollerance matching
beyond what you can reasonably achieve.  In other words, you won't be able
to achieve the same common mode reject they can.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000

2011\01\25@142650 by Michael Rigby-Jones

flavicon
face


> -----Original Message-----
> From: piclist-bouncesspamspam_OUTmit.edu [@spam@piclist-bouncesKILLspamspammit.edu] On
Behalf
> Of KILLspamalan.b.pearceKILLspamspamstfc.ac.uk
> Sent: 25 January 2011 17:31
> To: RemoveMEpiclistTakeThisOuTspammit.edu
> Subject: RE: [EE] DIY Electrocardiograph circuit, selecting an opamp
>
> I have been involved in heart monitoring as well, I didn't get to
design
> it, but took over some work when a guy left the company. It used three
> CA3078 op amps for the electrode inputs in an IA configuration, to get
> enough voltage swing to NBFM modulate an RF signal at ~160MHz IIRC

Now that is a fast heart beat!

Mike

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2011\01\25@173607 by RussellMc

face picon face
> The AD620 seems perfect for this. I just hope I can find it at the
> local electronics shop.

This local* electronics shop has it - in stock in a number of packages.
$7 in 1/s.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556125&k=ad620

datasheet:

  http://www.analog.com/static/imported-files/Data_Sheets/AD620.pdf

Also all these mostly local stores have it

   http://www.findchips.com/avail?part=ad620

These seemed to be the cheapest on Findchips.
In stock. Sell in 1s $5.04 for DIP part

    http://www.onlinecomponents.com/analog-devices_ad620anz.html?p=36167273

Ask them some questions

    http://www.onlinecomponents.com/FAQ.aspx

They think they're in Santa Monica - and/or Malaysia




Russell

* Global village

2011\01\25@174119 by V G

picon face
On Tue, Jan 25, 2011 at 5:35 PM, RussellMc <spamBeGoneapptechnzspamBeGonespamgmail.com> wrote:

{Quote hidden}

My local electronics shop had it. And when I say "local", I mean within 500
m of the campus. But they were selling it for $11. I instead went with two
LM324s for $1.40

2011\01\25@174801 by Mark Rages

face picon face
On Tue, Jan 25, 2011 at 4:41 PM, V G <TakeThisOuTx.solarwind.xEraseMEspamspam_OUTgmail.com> wrote:
{Quote hidden}

AD620: 30µV input offset voltage
LM324: 2 mV input offset voltage

How big is the signal you're trying to measure?
-- Mark Rages, Engineer
Midwest Telecine LLC
markragesEraseMEspam.....midwesttelecine.com

2011\01\25@180254 by Olin Lathrop

face picon face
Mark Rages wrote:
> AD620: 30µV input offset voltage
> LM324: 2 mV input offset voltage
>
> How big is the signal you're trying to measure?

That's not the issue since DC offset doesn't matter.  You are looking for a
AC signal and can AC couple the input with a sufficiently long time
constant.

However, take a look at the common mode rejection ratio of the AD620 and
compare that to anything you can even hope to get with some LM324 amps and
discrete parts.  The AD620 has something like 100dB common mode rejection if
I remember right.  That's a voltage factor of 100,000.  That means a 100V
common mode signal won't look like more than 1mV of differential signal (not
that the AD620 can withstand 100V input).


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000

2011\01\25@182506 by Michael Watterson

face picon face
On 25/01/2011 22:48, Mark Rages wrote:
>> >  My local electronics shop had it. And when I say "local", I mean within 500
>> >  m of the campus. But they were selling it for $11. I instead went with two
>> >  LM324s for $1.40.
> AD620: 30µV input offset voltage
> LM324: 2 mV input offset voltage
>
> How big is the signal you're trying to measure?
an LM324 may not work very well compared to AD620. It's a general purpose op-amp.

2011\01\25@184410 by Mark Rages

face picon face
On Tue, Jan 25, 2011 at 5:03 PM, Olin Lathrop <EraseMEolin_piclistspamembedinc.com> wrote:
> Mark Rages wrote:
>> AD620: 30µV input offset voltage
>> LM324: 2 mV input offset voltage
>>
>> How big is the signal you're trying to measure?
>
> That's not the issue since DC offset doesn't matter.  You are looking for a
> AC signal and can AC couple the input with a sufficiently long time
> constant.

True.


-- Mark Rages, Engineer
Midwest Telecine LLC
RemoveMEmarkragesEraseMEspamEraseMEmidwesttelecine.com

2011\01\25@184935 by RussellMc

face picon face
> > > The AD620 seems perfect for this.

For values of perfect that are as close as you'd get at any reasonable
prices in this application.

LOOK AT THE DATA SHEET

> >   http://www.analog.com/static/imported-files/Data_Sheets/AD620.pdf

Now, look at fig2.

That result is compared to using 3 VERY VERY VERY good separate op amps.

The LM324 is far worse than that.

The LM324 is one of the wonders of "modern" engineering.
It deserves a Nobel prize equivalent.
Value for money it is about unbeatable in appropriate applications.
This is not one of them.
You accept this as an inconvenient truth, put them aside for other
uses (there will be many) and 'bite the bullet' and buy what you need,
OR have endless hours of fun trying "to make a silk purse from a sow's
ear."

Enjoy.

> My local electronics shop had it. And when I say "local", I mean within 500
> m of the campus. But they were selling it for $11. I instead went with two
> LM324s for $1.40.

At $11, a bargain.
Give up coffee and lunch for a week and buy one.
NB remove any tinfoil hats before use.
Note that 12 volts can kill and has killed.

"Who y' gonna kill?"
Ghostb ...

You would be very sad to wake up dead tomorrow.
And possibly sadder if it was somebody else that you killed.

12 Volts can and has killed.

It's unlikely to do so in this case BUT you should try to manage the
range of "unlikely" carefully.

"This morning a promising young medical student was found ..."
"It is believed that he ..."
"Despite numerous warnings, he ... "
"A police spokesperson said that this once again highlights the
dangers of un ..."


Russell

2011\01\25@195209 by IVP

face picon face
> You accept this as an inconvenient truth, put them aside for
> other uses (there will be many) and 'bite the bullet' and buy
> what you need, OR have endless hours of fun trying "to make
> a silk purse from a sow's ear."

This is why I said the other day that generally one shouldn't baulk
at a (reasonable) cost if it's the right part for the job

Unless one doesn't put any sort of value on time spent chasing
rainbows and pulling hair out trying to prove alchemy isn't a crock

Jo

2011\01\26@041451 by Michael Watterson

face picon face
On 25/01/2011 23:48, RussellMc wrote:
> At $11, a bargain.
> Give up coffee and lunch for a week and buy one.
> NB remove any tinfoil hats before use.
> Note that 12 volts can kill and has killed.
>
Agreed.
in this application even an isolated battery back must be current limited form pickup probes.

2011\01\26@080405 by Olin Lathrop

face picon face
RussellMc wrote:
> "This morning a promising young medical student was found ..."
> "It is believed that he ..."
> "Despite numerous warnings, he ... "
> "A police spokesperson said that this once again highlights the
> dangers of un ..."

"But on the bright side, the Darwin Award Committee has ..."


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000

2011\01\26@084059 by V G

picon face
Honest question here. At what point did I say I'm going to directly
hook up electrodes from my computer to my chest hmm?

On Wednesday, January 26, 2011, Olin Lathrop <RemoveMEolin_piclistspam_OUTspamKILLspamembedinc.com> wrote:
{Quote hidden}

>

2011\01\26@091708 by Michael Watterson

face picon face
On 26/01/2011 13:40, V G wrote:
> Honest question here. At what point did I say I'm going to directly
> hook up electrodes from my computer to my chest hmm?
you would not want 12V battery connecting direct to chest electrodes.

your "earth" needs isolated from PC.

Something with electrodes needs total isolation (more than 400v) with known low leakage current and its battery or other power source unable to supply current to the electrodes.

Any Website advice using ordinary opamps, non-intrinsic medical standard isolation etc wants to be taken with a pinch of salt.

Googling
   isolated Instrumentation amplifier Analog Devices application note
first 4 hits gives
http://www.analog.com/static/imported-files/tutorials/MT-061.pdf

www.analog.com/static/imported-files/tutorials/MT-071.pdf
first page
ANALOG ISOLATION TECHNIQUES

There are many applications where it is desirable, or even essential, for a sensor to have no direct
("galvanic") electrical connection with the system to which it is supplying data. This might be in
order to avoid the possibility of dangerous voltages or currents from one half of the system doing
damage in the other, or to break an intractable ground loop. Such a system is said to be
"isolated", and the arrangement that passes a signal without galvanic connections is known as an
isolation barrier.

The protection of an isolation barrier works in both directions, and may be needed in either, or
even in both. The obvious application is where a sensor may accidentally encounter high
voltages, and the system it is driving must be protected. Or a sensor may need to be isolated from
accidental high voltages arising downstream, in  order to protect its environment: examples
include the need to prevent the ignition of explosive gases by sparks at sensors and the protection
from electric shock of patients whose ECG, EEG or EMG is being monitored.


http://www.analog.com/en/amplifiers-and-comparators/instrumentation-amplifiers/products/index.html

http://www.analog.com/en/circuits-from-the-lab/CN0067/vc.html

I'm sure ADI has a COMPLETE reliable application note that does exactly what you want. Instead of a random person on Internet who obviously has no clue about ECG, EEG or EMG applications or good designs for low frequency high common mode and isolation.



2011\01\26@102642 by John Coppens

flavicon
face
On Tue, 25 Jan 2011 08:35:31 -0500
V G <RemoveMEx.solarwind.xTakeThisOuTspamspamgmail.com> wrote:

> for building your own electrocardiograph. It's basically a few opamps hooked
> up into your sound card.

Though this definitely isn't a 1-day project anymore, here's some more
info from a source I learned a lot from (HP Journals). The tech isn't
up to date, the security considerations _are_:

http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1981-10.pdf  (page 19...)

Joh

2011\01\26@105401 by RussellMc

face picon face
> Honest question here. At what point did I say I'm going to directly
> hook up electrodes from my computer to my chest hmm?

Youngster, alive keeping,
Till wisdom, attained in the fullness of time has been,
Much knowledge-aforehand of past paths,
Cognisance needs.

At the pass, off, heading,
Guessing second and waning dire, oft repeated,
all too too little, alas, probably is.

Try we valiant,
Strive we ever,
More care we him for than he for he does thus far.
Hope we for fine outcome
Mourn we if short falls he
Win yet perhaps may we
Breaths hold we do not.

hmm!

           Rod

2011\01\26@111735 by N. T.

picon face
V G wrote:
> 2. I don't want to be hooking up any part of my body to my computer (I've
> had bad experiences with ground loops? in the past. Remember the "magic
> smoke" from that HH44780 display?). So before converting the signal to
> digital with a microcontroller and optoisolating it, I just want to hook up
> a simple LED to flash when the trigger level has passed (when the heart
> beats).

I remember a couple of years ago was the link
http://www.thisisant.com/news/stories/spectecs-minisdio-anttrade-card-enables-smartphones-and-pdas

In demonstration form, the SDA-320 allows a miniSDIO card
slot-equipped Motorola Q phone to wirelessly collect and analyse data
from sports performance and health monitoring sensors such as heart
rate straps and speed/distance activity monitors.

I think, it would not hurt to look through the solution. Also,
probably the technology can be of some interest to the thread "[EE]
Asking for pointers about NFC Near Field Communications"

ANT™ is a proven protocol and silicon solution for ultra-low power
practical wireless networking applications.  Designed for 2.4 GHz
operation, ANT is perfectly suited for any kind of low data rate
sensor network topologies in personal area networks (PANs) and
practical wireless sensor networks (WSN).

2011\01\26@120325 by alan.b.pearce

face picon face
> Though this definitely isn't a 1-day project anymore, here's some more
> info from a source I learned a lot from (HP Journals). The tech isn't
> up to date, the security considerations _are_:
>
> http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1981-10.pdf  (page 19...)

Agreed. Also look at the following issues: -

1974 issue 04 for some stuff on mathematically dealing with the waveforms, which should interest solarwind as he is a medical student.

1976 issue 10 on arterial blood non-invasive oxygen level measurements.

1977 issue 09 - battery Powered ECG Monitor for Emergency and Operating Room Environments

1972 issue 04 - An Effective ECG Telemetry System - this came out while the company I was with was developing their system, and has a lot of info on dealing with the various muscle artefacts that you get on the signal, especially when the person being monitored is moving around. It was this article I was looking for and found the others as well.

There are others as well, that cover medical monitoring.
-- Scanned by iCritical.

2011\01\26@121249 by Denny Esterline

picon face
While I COMPLETELY agree on the importance of not connecting mains
voltage to your chest, there's at least one other way to safely do
this without the opto isolation:

Hook it to a laptop that is _not plugged into mains_.

-Denn

2011\01\26@123408 by V G

picon face
On Wed, Jan 26, 2011 at 12:12 PM, Denny Esterline <EraseMEdesterlinespamspamspamBeGonegmail.com>wrote:

> While I COMPLETELY agree on the importance of not connecting mains
> voltage to your chest, there's at least one other way to safely do
> this without the opto isolation:
>
> Hook it to a laptop that is _not plugged into mains_.
>

That's what I'm doing right now

2011\01\26@124305 by alan.b.pearce

face picon face
> While I COMPLETELY agree on the importance of not connecting mains
> voltage to your chest, there's at least one other way to safely do
> this without the opto isolation:
>
> Hook it to a laptop that is _not plugged into mains_.

Yes he has already said that is what he intends to do, while running on batteries only.
-- Scanned by iCritical.

2011\01\26@130157 by Michael Watterson

face picon face
On 26/01/2011 17:12, Denny Esterline wrote:
> While I COMPLETELY agree on the importance of not connecting mains
> voltage to your chest, there's at least one other way to safely do
> this without the opto isolation:
>
> Hook it to a laptop that is _not plugged into mains_.
>
> -Denny
And if the laptop develops any kind of fault?

Not safe.

Laptops have enough voltage/power to kill.

What about any other connections to laptop also

2011\01\26@131534 by Olin Lathrop

face picon face
V G wrote:
>> Hook it to a laptop that is _not plugged into mains_.
>
> That's what I'm doing right now.

I wouldn't do that.  It's too easy to forget to unplug the laptop, or not
notice it's plugged in.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000

2011\01\26@132004 by Yigit Turgut

picon face
TI's INA1XX series is the best candidate for your requirements, trust me. (

2011\01\26@132559 by John Coppens

flavicon
face
On Wed, 26 Jan 2011 18:00:48 +0000
Michael Watterson <RemoveMEmikeKILLspamspamradioway.org> wrote:

> Laptops have enough voltage/power to kill.

And... not mentioned before, I believe. If you do such a circuit in
real life, it won't be long till someone applies electro-shock to the
patient. If the computer isn't properly separated, it'll be fried.
Laptop or not.

Joh

2011\01\26@132637 by V G

picon face
On Wed, Jan 26, 2011 at 1:20 PM, Yigit Turgut <y.turgutSTOPspamspamspam_OUTgmail.com> wrote:

> TI's INA1XX series is the best candidate for your requirements, trust me.
> (:
>
>
What company makes these? And why do you say that

2011\01\26@144508 by IVP

face picon face
> "A police spokesperson said that ...

..... 'e wuz a accident waitin' to 'appe

2011\01\26@144625 by Olin Lathrop

face picon face
V G wrote:
>> TI's INA1XX series is the best candidate for your requirements,
>> trust me. (:
>
> What company makes these?

"TI" stands for Texas Instruments.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000

2011\01\26@145206 by V G

picon face
On Wed, Jan 26, 2011 at 2:47 PM, Olin Lathrop <spamBeGoneolin_piclistSTOPspamspamEraseMEembedinc.com>wrote:

> V G wrote:
> >> TI's INA1XX series is the best candidate for your requirements,
> >> trust me. (:
> >
> > What company makes these?
>
> "TI" stands for Texas Instruments.
>

Oh wow, I completely did not see that at all, for some reason. Probably the
glare from the sun. Thanks

2011\01\26@145739 by Spehro Pefhany

picon face
At 02:47 PM 26/01/2011, you wrote:
>V G wrote:
> >> TI's INA1XX series is the best candidate for your requirements,
> >> trust me. (:
> >
> > What company makes these?
>
>"TI" stands for Texas Instruments.

Or, in this case,  Burr-Brown. ;-)

eg.  http://focus.ti.com/lit/ds/symlink/ina103.pdf

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
KILLspamspeffspamBeGonespaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

2011\01\26@170635 by N. T.

picon face
Yigit Turgut wrote:
> TI's INA1XX series is the best candidate for your requirements, trust me. (:

Trust No 1, I'd say regarding 1X

2011\01\26@181536 by V G

picon face
On Wed, Jan 26, 2011 at 5:06 PM, N. T. <EraseMEntypesemispamEraseMEgmail.com> wrote:

> Trust No 1, I'd say regarding 1XX
>

Is that "Trust no one, as in nobody", or "Trust number 1"?

And so you wouldn't recommend TI INS1xx

2011\01\26@185726 by RussellMc

face picon face
>>> Hook it to a laptop that is _not plugged into mains_.

>> That's what I'm doing right now.

Carefully note that "not plugged into the main" does NOT mean - "It
uses an isolated wall wart or waddever power supply in the lead and
feeds low voltage so I'm OK to  plug it in and, urk ..."

Carefully.

12 Volts applied to the chest  can kill, and has.

Many power supplies have capacitors from mains leads to ground. O/C
ISOLATED output is half mains supply. Youcan get a nasty "tickle" from
such.

Various tables etc show fatal results for chest currents of 50 mA up.
You could argue that having even say 10kohm in each input lead would
be "safe enough" (12/10k = 1.2 mA).
I'd avoid arguing that. Dead is dead.

Carried to it's illogical conclusion you could limit mains current the
same way. Get it wrong and you may never know.


Russel

2011\01\26@195434 by V G

picon face
On Wed, Jan 26, 2011 at 6:56 PM, RussellMc <@spam@apptechnz@spam@spamspam_OUTgmail.com> wrote:

{Quote hidden}

I'm not taking chances. The laptop is NOT connected to ANYTHING that's
touching any wall. It's on a little island table by itself, running purely
off of batteries. I'm powering everything else off of 2 Li-ion or the 5 V
supply from the laptop's USB port

2011\01\27@001746 by Mohit (Lists)

picon face
V G wrote:
>>
>> "TI" stands for Texas Instruments.
This is rather late in the thread...
Every year or so TI brings out a medical applications guide, where they present their solutions for common medical applications. Have a look at this if you've not finalised the components of your design. They also have a great samples policy and ship free through FedEx.

Hope this helps,
Mohit.
http://www.BioZen.co.in

2011\01\27@011400 by N. T.

picon face
V G wrote:
>
> Is that "Trust no one, as in nobody", or "Trust number 1"?
>
> And so you wouldn't recommend TI INS1xx?
> --

It was a joke :-)
Regarding TI INS1xx, - I don't know. The Op Amp is sort of two decades
old. Just google with "precision instrumentation amplifier" and figure
out on your own whether the industry gave birth to the Op Amp that
fits better your needs

2011\01\27@034300 by Yigit Turgut

picon face
You are correct! it's almost ancient design but I had designed and built an
EEG (which requires much better signal quality than an ECG) w/16+channels
and had very promising results. I was just having fun then but that specific
design is now went commercial and used in a couple of local clinic here in
Istanbul. I am still working on this very problem (detection of  electric
fields very small in magnitude and low in frequency) as my MSc thesis and
there is progress, if someone is interested in drop me an email if I like
your name I will reply (:

Btw, you can go with TLC272 as well, a cheaper yet stable alternative for
INA series.Even they are completely different purpose products, both have
very close responses in this specific application.

Hope this helps!

On Thu, Jan 27, 2011 at 8:14 AM, N. T. <spamBeGonentypesemispamKILLspamgmail.com> wrote:

{Quote hidden}

>

2011\01\27@044419 by alan.b.pearce

face picon face
> > >> TI's INA1XX series is the best candidate for your requirements,
> > >> trust me. (:
> > >
> > > What company makes these?
> >
> > "TI" stands for Texas Instruments.
> >
>
> Oh wow, I completely did not see that at all, for some reason. Probably the
> glare from the sun. Thanks!

Yup, there is reputed to be a lot of sun in Texas ... ;))
-- Scanned by iCritical.

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