heartbeat monitor design

[Jason Sanders]

I am trying to design a heartbeat monitor for an electronics class. I
had planned to read the heartbeat with a speaker and then display the
output on either a 7-segment display or an oscilloscope. Can anyone
offer suggestions as to how to get started? I am having trouble
finding useful websites. Thanks.

 

[John Woodgate]

I read in sci.electronics.design that Jason Sanders <[email protected]>

I am trying to design a heartbeat monitor for an electronics class. I
had planned to read the heartbeat with a speaker and then display the
output on either a 7-segment display or an oscilloscope. Can anyone
offer suggestions as to how to get started? I am having trouble
finding useful websites. Thanks.

I've tried to do that and found big problems with extraneous acoustic
noise. My test subjects were sheep, not students. The intention was to
detect pregnancy from the lamb's (or preferably lambs') heartbeat.

I adapted an electret microphone to give a better low-frequency response
at the expense of sensitivity by putting 10 pF directly in parallel with
the capsule (tricky!). Then I used a simple op-amp gain stage with a
passive RC filter to limit the bandwidth to about 20 Hz.

But it didn't work well, and I don't know why. Electronic stethoscopes
exist and are surely very little different in design.

 

[Jim Thompson]

I am trying to design a heartbeat monitor for an electronics class. I
had planned to read the heartbeat with a speaker and then display the
output on either a 7-segment display or an oscilloscope. Can anyone
offer suggestions as to how to get started? I am having trouble
finding useful websites. Thanks.

Try "Earpulse.pdf" of the S.E.D/Schematics Page of my website.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

Will you still need me, will you still feed me, when I'm sixty-four?

 

[Charles DH Williams]

I adapted an electret microphone to give a better low-frequency response
at the expense of sensitivity by putting 10 pF directly in parallel with
the capsule (tricky!). Then I used a simple op-amp gain stage with a
passive RC filter to limit the bandwidth to about 20 Hz.

But it didn't work well, and I don't know why. Electronic stethoscopes
exist and are surely very little different in design.

I believe stethoscopes need a frequency response of more like 200Hz.
There is also a bit of art in the design of the in the acoustic
impedance and hence coupling properties of the diaphragm/bell end.

An aquaintance who is a medic once told me that it extremely difficult
to diagnose anything with a 'guessing tube', and his had been broken for
ages, but he could still use it to keep patients quiet for
long enough for him to think about what was wrong with them.

Charles.

 

[GPG]

I am trying to design a heartbeat monitor for an electronics class. I
had planned to read the heartbeat with a speaker and then display the
output on either a 7-segment display or an oscilloscope. Can anyone
offer suggestions as to how to get started? I am having trouble
finding useful websites. Thanks.

http://www.web-ee.com/Schematics/HeMon/HeMon.htm

 

[Product developer]

I am trying to design a heartbeat monitor for an electronics class. I
had planned to read the heartbeat with a speaker and then display the
output on either a 7-segment display or an oscilloscope. Can anyone
offer suggestions as to how to get started? I am having trouble
finding useful websites. Thanks.

Look up "EKG" AND "HEART RATE MONITOR" If you strike out email me. I design them
for a living.

 

[Guy Macon]

I am trying to design a heartbeat monitor for an electronics class. I
had planned to read the heartbeat with a speaker and then display the
output on either a 7-segment display or an oscilloscope. Can anyone
offer suggestions as to how to get started? I am having trouble
finding useful websites. Thanks.

http://openeeg.sourceforge.net
http://openeeg.sourceforge.net/doc/links.html

(I was the Heart Monitor engineer for the ABC Television
game show "The Chair", starring John McEnroe. See
http://www.guymacon.com/ABC/INDEX.HTM for details)

 

[John Woodgate]

I read in sci.electronics.design that Charles DH Williams
[email protected]>) about 'heartbeat monitor design', on Thu, 4 Mar
2004:

I believe stethoscopes need a frequency response of more like 200Hz.
There is also a bit of art in the design of the in the acoustic
impedance and hence coupling properties of the diaphragm/bell end.

Yes, they do, because they are used for listening to other things, such
as lungs, which produce higher-frequency sounds than heartbeats (just
beats - no seagull murmurs!). I started with about 200 Hz bandwidth and
reduced it to improve signal-to-noise ratio.

 

[Bob Stephens]

I read in sci.electronics.design that Charles DH Williams
[email protected]>) about 'heartbeat monitor design', on Thu, 4 Mar
2004:

Yes, they do, because they are used for listening to other things, such
as lungs, which produce higher-frequency sounds than heartbeats (just
beats - no seagull murmurs!). I started with about 200 Hz bandwidth and
reduced it to improve signal-to-noise ratio.

My senior project in Engineering school was a safe cracking robot. We used
a stethoscope with a small microphone in the tubing to monitor the activity
inside a three digit lock. We had to fiddle with the cavity behind the
diaphragm to accentuate the frequencies of interest and damp out the rest,
but after a little trial and error, it worked quite well.

Bob

 

[Guy Macon]

My senior project in Engineering school was a safe cracking robot. We used
a stethoscope with a small microphone in the tubing to monitor the activity
inside a three digit lock. We had to fiddle with the cavity behind the
diaphragm to accentuate the frequencies of interest and damp out the rest,
but after a little trial and error, it worked quite well.

Suuuuuure it was a "senior project"... We believe you. Really we do.

 

[Frank Miles]

I am trying to design a heartbeat monitor for an electronics class. I
had planned to read the heartbeat with a speaker and then display the
output on either a 7-segment display or an oscilloscope. Can anyone
offer suggestions as to how to get started? I am having trouble
finding useful websites. Thanks.

Perhaps you could start by figuring out whether to pick up the pulse
electrically (surface electrodes); by pressure/acoustics (microphone
or pressure transducer); optically (sensing at capillary bed); or some
other method.

Safety should be a primary concern.

-frank
--

 

[John Woodgate]

I read in sci.electronics.design that Bob Stephens <stephensyomamadigita

My senior project in Engineering school was a safe cracking robot. We
used a stethoscope with a small microphone in the tubing to monitor the
activity inside a three digit lock. We had to fiddle with the cavity
behind the diaphragm to accentuate the frequencies of interest and damp
out the rest, but after a little trial and error, it worked quite well.

What sort of microphone was that?

 

[Jan Panteltje]

My senior project in Engineering school was a safe cracking robot. We used
a stethoscope with a small microphone in the tubing to monitor the activity
inside a three digit lock. We had to fiddle with the cavity behind the
diaphragm to accentuate the frequencies of interest and damp out the rest,
but after a little trial and error, it worked quite well.

Bob

I used to do it with my ear against it.
How many of those bots did you sell ;-)?
JP