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Which sensor or transducer should be used for picking up human heartbeats?

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thisistausif

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hello,

which sensor or transducer should be used for pickingup signals of human heart beat
 

DMan

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heartbeat sensor wiki

There are 2 methods that I know of:
1. By light-with IR LED and IR photodiode/photoresistor/phototransistor
2. ECG-electrocardiogram

First method is using the fact that tissue has different light transmisive or light reflective properties. It's done by either puting LED on one side of thin tissue and sensor on the other (transmisive) or by watching reflectiion of the skin(reflective). Usually it's placed on an fingertip or earlobe.

The second method is used more and it's gathering signal by the means of wearing a belt that has 2 electrodes one on left side of the heart second on the right. The electrodes measure small voltage difference between the electrodes and get the signal in ECG shape.
 

kender

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heartbeat sensor wikipedia

DMan said:
1. By light-with IR LED and IR photodiode/photoresistor/phototransistor

First method is using the fact that tissue has different light transmisive or light reflective properties. It's done by either puting LED on one side of thin tissue and sensor on the other (transmisive) or by watching reflectiion of the skin(reflective). Usually it's placed on an fingertip or earlobe.

Also, there's a similar device called "Pulse Oximeter" https://en.wikipedia.org/wiki/Pulse_oximeter.
 

DMan

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project msp430f413

Both methods of IR heartrate measuring rely on the fact that you get a voltage variation on the receving side of the sensor(photodiode/phototransistor/photoresistor). You just have to amplify that AC signal and get the frequency of the variating signal. This frequency is equal to heart frequncy.

**broken link removed** you can get a simple PIC heartrate monitor project.

Added after 8 minutes:

kender said:
Also, there's a similar device called "Pulse Oximeter" https://en.wikipedia.org/wiki/Pulse_oximeter.

Thanks for the wiki link of oximeter kender. Oximetry is a lot more complicated than just plain heartrate sensor becouse you have to do FFT to get the spectrum of the signal. Amazing what can be retreived by simple pair of IR reciver/transmiter.
 
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thisistausif

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what does 1140 mean in heartbeat

does the IR method is efficeient ..

Added after 19 seconds:


does the IR method is efficeient ..and hows its accuracy
 

DMan

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heartbeat detector infrared

Yes it's accurate. It would't be used in medical aplications if it was not accurate. It's used practically in every hospital to monitor patients heartrate and blood oxidation level.

But for sport aplications when the pesorn is moving a lot it's not so good as ECG method.
 

kender

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heartbeat ir sensor

DMan said:
But for sport aplications when the pesorn is moving a lot it [pule oximetry] is not so good as ECG method.
DMan,
Thanks for bringing it up! Why is pulse oximetry not so good for an actively moving patient? I always thought that - on contrary - ECG would be a worse method for an active patient, because contracting muscle will be generating electric noise that interferes with heart's signals.
 

thisistausif

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ir heart beat sensing

i hve got something on IR sensor , will it be correct and working with fine accuracy..

is there any chance of error in this ckt ,

please comment on this ckt

how would be the arrangment of IR devices on the hand
 

bobcat1

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ir reflective sensor oximeter

HI


This is a compliceted circuit - search google you will find circuit less compliceted to build

Also you can eliminate some part of it who is not needed (whether you need only analog signal who can be sampled by a micro controller you can eliminate the digital part
and use some modern electronic design approach to make the circuit less compliceted


All the best

Bobi
 

thisistausif

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best sensor to measure ecg,heart beat

how should we develop reference voltages for ADC, as that should be stable.
 

RegUser_2

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hartbeat senseo ir

The problem with the optical methods which rely on modulation of the light absorbtion due to change of it's optical path when it passes through an pulsating artery lie with the much stronger absorption in the rest of the tissue, so small variation in the tissue absorption due to motion (aka motion artefacts) easily twarf the pulsatile signal due to hearth beat.

And the bad news is, the signal bandwidth of motion artefact noises overlaps with the signal bandwidth of pulsatile signal, so standart ways of filtering aren't applicable.

The EKG also suffers from similar problems but it is much easier to reliably detect the QRS complex, and there is free developed software to do real time QRS detection on the web.

Also Texas Instrument provides application notes and code on how to built pulse oximeter and ECG using their MSP430F413 microcontrollers.
 

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pulse oximetry artefacts cable

kender said:
DMan,
Thanks for bringing it up! Why is pulse oximetry not so good for an actively moving patient? I always thought that - on contrary - ECG would be a worse method for an active patient, because contracting muscle will be generating electric noise that interferes with heart's signals.

Sorry for the delayed answer. My comment on pulse oximetry and it's application in sport was based on my experimentation. I had a lot of problems with the light commig from the side of the earlobe or finger. So to reduce this disturbance you would have to enclose the earlobe/finger fully or be still or move slowly so that the period of the AC voltage caused by the movement would not be a problem.

The other thing that you should take in account is users comfort. When using ECG the measuring belt fits tightly and causes no discomfort to the user, while pulse oximetry needs a cable connection and it's a lot harder to make it fit tightly and secure. I can't imagine a sprinter with a sensor on his finger or earlobe while sprinting.

ECG has no problems with the signals from the other muscles since the electrodes are enough apart to take the differential voltage from each side of the heart muscle, while other muscles in abdominal area are not big enough to affect the measuremnt.
 

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photoresistor optical sensor pulse

If some wants to learn in debt about various pulse oximetry solutions, h/she shout brouse the patent databases.

There is a HUGE amount of valuable information about diferent ways to deal with motion artefacts.

The leader in this field is the US company Massimo, whch implements adaptive filtering and smart three wavelenght algorithm to estimate the motion contribution separately from the total measurement.
 

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microcontroller based heartbeat monitor wikipedia

thisistausif said:
how would be the arrangment of IR devices on the hand

Usually transmisive method od IR heartrate measuring is done witha clip that goes on **broken link removed** or earlobe. The circuit in the link of one of my previous posts uses this method.

When using IR reflective method (like in the case of the circuit you have attached) it can be worn basicly on the whole body: **broken link removed** **broken link removed** etc.
 

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heart beat sensor

Atached here are Texas Instrument application notes and code to built simple pulse oximeter and ECG
 

thisistausif

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wikipedia heartbeat sensor

what if the device is to be used for animals, i mean to check heartrate of animals and not humans
 

RegUser_2

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light modulation used heart beat sensor

thisistausif said:
what if the device is to be used for animals, i mean to check heartrate of animals and not humans

Most mamals are blessed with big ears, and the ears are known to contain a lot of arterioles, what makes an optical clip reasonably easy to implement :D

Besides somewhere on the net I saw an article about doing pulse oximetry on a lab rat. The leg clip construcion was described in great detail, also the problems with dealing with motion artefacts.
 

thisistausif

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heart beat sensor electrode

thats a god idea, so this device will work on almost all animals..
 

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