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PICList Thread
'Heart pulse'
2000\05\13@230815 by Soon Lee

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Hi everyone

is there any circuit that i can use to measure, detect, heart pulse?

thanks

2000\05\13@235056 by Tim Hamel

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I saw an interesting circuit in one of these Circuits Encyclopedias. It
consisted of an IR detector/transmitter pair set an angle. Human skin
reflects IR and the presence (or not) of blood enhances it to some degree. I
think it's the pressure causing the skin to move closer to the IR LEDs.
Anyways, as the skin's reflectivity changes, so does the output.
Unfortunately, I don't have a schematic. The circuit I saw was fairly simple;
IR Emitter/Detector rigged up using a NPN transistor as an amp.

Regards,

Tim Hamel

In a message dated 5/13/00 8:08:46 PM Pacific Daylight Time,
spam_OUTpslnTakeThisOuTspamCYBERWAY.COM.SG writes:

> Hi everyone
>
>  is there any circuit that i can use to measure, detect, heart pulse?
>
>  thanks
>

2000\05\14@094305 by Alan B Pearce

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>I saw an interesting circuit in one of these Circuits Encyclopedias. It
>consisted of an IR detector/transmitter pair set an angle. Human skin
>reflects IR and the presence (or not) of blood enhances it to some degree. I
>think it's the pressure causing the skin to move closer to the IR LEDs.

is this not what they do with the clip they put on a finger? I understood they
shone the IR through the finger, and the blood was opaque enough that it
modulated the light beam as the heart pumped.

2000\05\14@130735 by Reginald Neale

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<x-flowed>>Hi everyone
>
>is there any circuit that i can use to measure, detect, heart pulse?
>
>thanks

  There was a thread on this topic two or three years ago.
  Might be in the archives.
  You could search for "plethysmograph" :-)

  Reg Neale

</x-flowed>

2000\05\14@150008 by Patrick J

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I saw a VERY cool way to measure the hearbeat.
When the heart beats, your weight change a little.
Very very little, but it is detectable (I saw the curves live on TV)
The person just steps up on the scale and as well as
measuring their weight you measure the pulse !

A more common way is to send, usually red, light through
one fingertip and detect light variations and get the pulse that way.

Or it should be possible to use a microphone and 'listen' to the
heart and detect the heartbeat/pulse


>€mne: Heart pulse
>Hi everyone
>is there any circuit that i can use to measure, detect, heart pulse?

2000\05\14@160824 by Peter L. Peres

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Hi,

there used to be projects using a IR or even red LED and a photoresistor
or phototransistor as detector, followed by a AC amplifier with bandpass
(0.2-8Hz or so). The sensor was designed to clip on an ear lobe or on a
fingertip (pinky) while closing off external light. I remember one I tried
using a wooden clothes clip painted black with the spring weakened (ouch
!) and holes drilled in jaws for the LED and phototransistor. I also
remember the paint coming off and not noticing until I was told to wash my
ears ;-) This one was used through an amp (no microprocessor) to listen to
the heartbeat. It should be easy to feed the signal to a PIC. The LED
needs to be run fairly bright. A 'superbright' red LED will certainly
help.

Peter

2000\05\14@174151 by Brent Brown

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I think they work on the intensity of the light being modulated by
the blood as it passes through the finger. I saw one of these just
recently on TV, probably on "ER", and it used visible red light
(looked like that nice pinky-red colour that you get from some
really super-bright LEDs). The persons finger tip was lit up like
rudolfs nose! Main advantage I guess is that you get a visible
indication that the equipment is in fact working, before deciding to
throw the patient away.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile: 025 334 069
eMail:  .....brent.brownKILLspamspam@spam@clear.net.nz

2000\05\14@230539 by Soon Lee

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Hi everyone

must the detector be of any special type??

regards

----- Original Message -----
From: Brent Brown <brent.brownspamKILLspamCLEAR.NET.NZ>
To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Sent: Monday, May 15, 2000 5:39 AM
Subject: Re: Heart pulse


{Quote hidden}

2000\05\15@013401 by Mark Willis

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To be picky a little here - I'd think your weight doesn't change there.
Your body probably moves a little though, in response to the pressure
change when your heart beats - and that's what they measure;  your
inertia's effected by the pulse, and oscillates <G>  Interesting info!

Same effect as if you drop a hammer in an airplane - You can NOT use the
oscillation of measured weight as an antigravity drive AFAIK, you CAN
measure the change to tell that the hammer's been dropped, though...

 Mark

Patrick J wrote:
{Quote hidden}

--
I re-ship for small US & overseas businesses, world-wide.
(For private individuals at cost; ask.)

2000\05\15@045255 by Patrick J

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Well by definition your weight DO change, but your mass doesn't.
SImple test: Stand on a scale and raise your arms fast as you look at
the scale, it will indicate your wight increases. That is what it measures,
not your mass, which is constant.
I was impressed when I saw it on TV, very cool but prolly not easy to duplicate ;)

You need a very sensitive scale that can detect the total weight and also
handle the small delta weight measurments. Also some digital filtering
to get the pulse from the signal.... DSP ?



> To be picky a little here - I'd think your weight doesn't change there.
> Your body probably moves a little though, in response to the pressure
> change when your heart beats - and that's what they measure;  your
> inertia's effected by the pulse, and oscillates <G>  Interesting info!
>
> Same effect as if you drop a hammer in an airplane - You can NOT use the
> oscillation of measured weight as an antigravity drive AFAIK, you CAN
> measure the change to tell that the hammer's been dropped, though...
>   Mark

2000\05\15@051802 by Mike Witherden

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Well :  weight = mass * acceleration so you are measuring a change in weight as your (constant ) mass is oscillating thus acceleration is varying.

MikeW

>>> mwillisspamspam_OUTFOXINTERNET.NET 05/15/00 07:33AM >>>
To be picky a little here - I'd think your weight doesn't change there.
Your body probably moves a little though, in response to the pressure
change when your heart beats - and that's what they measure;  your
inertia's effected by the pulse, and oscillates <G>  Interesting info!

Same effect as if you drop a hammer in an airplane - You can NOT use the
oscillation of measured weight as an antigravity drive AFAIK, you CAN
measure the change to tell that the hammer's been dropped, though...

 Mark

2000\05\15@083937 by Fansler, David

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I am not how sure this applicable this would be to a human - but there was
an article in Scientific American in the spring of 1996 where they were
measuring the heart beat of a roach.  They attached a small magnet to the
back of the roach.  The roach was in small jar that was covered with a
plastic wrap.  On top of the plastic wrap was a Hall Effect sensor that was
amplified and displayed on an oscilloscope.  The beating of the heart would
expand the shell of the roach making the magnet change it's distance in
relationship to the Hall Effect sensor - thus changing the output of the
sensor.  

An interesting side point was they startled the roach once and the heart
stopped beating for a period of time.  Their explanation was that the
nervous system of the roach is so simple that it does not have the capacity
to deal with making the heart beat and the "flight" syndrome of being
scared.  True multitasking of computing power!

David V. Fansler
Network Administrator
TriPath Imaging, Inc. (Formerly AutoCyte, Inc)
336-222-9707 Ext. 261
@spam@dfanslerKILLspamspamautocyte.com <KILLspamdfanslerKILLspamspamautocyte.com>
Now Showing! http://www.dv-fansler.com <http://www.dv-fansler.com/>  
Updated March 31,2000
Ann's Cancer, David's Observatory, Disney World


               {Original Message removed}

2000\05\15@084557 by paulb

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Mark Willis wrote:

> To be picky a little here - I'd think your weight doesn't change
> there.  Your body probably moves a little though, in response to the
> pressure change when your heart beats - and that's what they measure;

 This measurement is referred to as ballistocardiography.  I'm sure you
can follow the derivation.

 Electrical measurement is called electrocardiography.

 Measuring the expansion of tissues such as the finger or earlobe is
called pulse plethysmography.

 A rather alliterative form of plethysmography is used for another
application but the topic might be a little delicate on this list...
This was *supposed* to be demonstrated to us during our course, but for
some reason that particular demonstration didn't work out properly.
--
 Cheers,
       Paul B.

2000\05\15@090913 by Alan B Pearce

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>This was *supposed* to be demonstrated to us during our course,...

Hmm, this does leave the imagination wide open to suggestion as to what the
course was.

2000\05\16@172534 by Jeffrey D Spears

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Yes--I saw this article. It was in Scientific American, probably 97 or
98 sometime. It used a pretty fancy linear hall effect device and an
amplifier. The magnet they used was a chip of very strong magnet
(Neobydium?)


On Mon, 15 May 2000, Fansler, David wrote:

{Quote hidden}

>                 {Original Message removed}

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