Anduino ECG - do I need an amplifier?

Using Arduino Project Guidance
1

Hi guys,
I'm looking to make a simple ECG based on Arduino, but I'm not really sure, do I need some sort of an amplifier chip between arduino and the leads? or can I just connect the leads to the arduino's inout pint?

Thanks.

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ECG based on Arduino

what do u actually wish to do? plot the ECG or count the heart rate?

3

I want to plot the whole ECG and transfer it via bluetooth to a smartphone, that would analyze it and draw the waveform on screen.

4

Artem85:
the whole ECG

I'm not a doctor and I don't know what that means. Do you?

All I know from having and seeing ECG readings is that it involves having multiple electrodes stuck in multiple paces which seem to need a lot of care to find, and the set of places that have sensors attached do not always seem to be the same. Then some sort of analysis is done to compare and consolidate the readings from all of these sensors to determine various health indicators. It's not just a glorified voltmeter.

5

Well, yes, there are multiple electrodes ( for a holter monitor, usually 3-7 ) stuck to a patient... in this case, I want Arduino get reading from this electrodes and pass it over to a bluetooth module, which will pass then to a smartphone.

So the question is - should leads from this electrodes go to Arduino's input pins, or should there be something in between, like an amplifier or something?

Thanks. :slight_smile:

6

So the question is

Rather than beating yourself to death trying to figure out if it works with your sensor / arduino, why don't you just hook the two together and get some sense as to what kind of signals your sensor generates?

7

I just ordered and will receive them in a few days. So I thought maybe someone already has experience is this field and knows how it should be done. :slight_smile:

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So I thought maybe someone already has experience is this field and knows how it should be done.

Probably true. But, since you haven't mention what brand/type/model sensors you are trying to get a signal from, anyone that has used them can't answer your questions.

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I do believe it's just a standard ECG wire with a standard disposable electrode. Isn't it? :~

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I do believe it's just a standard ECG wire with a standard disposable electrode. Isn't it?

I'm sure that there is a datasheet that goes with the picture. I'm also sure that the datasheet contains a lot more information. I'm also sure that the datasheet will tell you whether you need an amplifier, or not.

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Storage and transport environment: -5~+40?
Operating temperature: 0~+40?
Humidity
Operating/Storage/Transportation 0% to 80% non condensing Altitude
Hyperbaric Pressure 86kPa?106kPa
Biocompatibility: All patient contact materials are latex free and have been tested

Lead wires
Low profile, insert molded snap or pinch connectors offer patient comfort and secure attachment to snap electrodes. The snap termination’s ergonomic, teardrop design reduces tangling at the patient end connector. Grabber and mini clip terminations have dual sided metal contacts to provide the connection.

All data that it has. I do believe it's just a screened off wire, nothing more.

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You want to look for data for the device that the manufacturer has packaged. Otherwise, just buy the thing that that package is supposed to connect to.

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http://www.eetimes.com/design/medical-design/4213140/Techniques-for-accurate-ECG-signal-processing has some useful information. The amplitude appears to be about 40mV 2mV peak to peak, so you will need an amplifier with a gain of 50 or 100 1000 or 2000 on each channel to get good readings.

Be very careful of connecting anything to the human body, especially near the heart. I recommend that you power the Arduino and associated electronics from a battery, and do not connect the Arduino to a PC or to anything else while using it as an ECG.

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I think u may need an amplifier as well as a filter for accurate readings. The electrode readings would rather be weak and needs some modifications.after that u may able to input it onto an ADC

15

Thanks for the tips! :slight_smile: Any ideas what kind of amplifier and filters would be better?

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Found such circuit, based on LM358N , what do you think?

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Artem85:
Thanks for the tips! :slight_smile: Any ideas what kind of amplifier and filters would be better?

What voltage are you trying to record, and within what frequency range?

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An Electrocardiogram Amplifier does a very specific job and has been studied a LOT. Start with Google "Electrocardiogram Amplifier"

Read some of the work that has already been done, such as:

"http://www.rle.mit.edu/acbs/publications/journal_papers/micropower_ekg_amp.pdf

...it's not a good subject to start from Zero Base on.

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what kind of amplifier and filters would be better?

you may need an instrumentation amplifier stage to ensure low voltage signal is amplified providing minimum attenuation to actual signal.
heart rate is usually upto around 200 bps-250 max right? so any thing above the frequency could be removed
for signal amplification you may employ a high gain stage using opamps (i assume you observe the waveform on a CRO to get an idea of the range of amplification needed) regards

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Thanks for the input guys. From what I learned so far, guess AD620 chip would be the best, what do you think? :slight_smile: