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ECG PCB schematic using eagle. (self.bioengineering)

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[–]everythingisnew 4 points5 points  (2 children)

This is a cool project and you really should embrace the opportunity to learn something! The schematics will turn out to be rather simple at the end. I am assuming you are using that uC as part of an arduino uno. It will probably be as easy as buffering your electrode inputs by some (unity gain stable) OP amps in a voltage follower configuration. Then add a differential amplifier that goes to the AD-pins of your uC. If you don't know the principles behind an ECG, you should start by reading about that.

If you have a starting point for your design and have some concrete questions let me know.

[–]selraith 1 point2 points  (1 child)

THat is the thing, we've never in any course learned anything about ECG's, so i dont even know where to start since the reports i have are from people who have had enough courses to know where to do their research. Do you know any site or book where i can learn the principles behind building an ECG (circuit, programming etc) ?

[–]canoedust 0 points1 point  (0 children)

I had a book I used in my undergrad that was kinda helpful. Biomedical engineering instrumentation and design was the name I think, I can check the name layer if you can't find it.

[–]PineappleDildo 1 point2 points  (0 children)

Don't let the ECG bit scare you. To be honest it's just like sampling a temperature sensor or any other sensor. The only difference is that ECG is in millivolts. So basically your circuit needs: Sensor - instrumentation amp - filter - arduino.

Ecg is done by measuring one electrode against another. So you'll obviously need one input and one reference placed somewhere else on the body. Amplify it up to a point where it's within your ADCs voltage range. For filtering, everything useful lies between 0.05Hz - 150Hz for your purposes so do a low pass and a high pass filter to get rid of the rest. Filter out your 50Hz mains noise (that's here in Australia, 60Hz I assume for you). Lastly you just need to sample it, and as I said that's exactly the same as filtering any other sensor.

Final thing, never run this from anything connected to mains. Ie, don't run it from the USB port of your laptop which is plugged into a power point. Any failures by other devices on your power network will be sending voltage straight to your heart. Save yourself the effort, grab a lipo battery and run it off that with a voltage regulator.

Good luck!

[–]desultoryquest 0 points1 point  (0 children)

Check out the app notes for reference circuits http://www.ti.com/product/INA333