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How can I improve this ECG Circuit?

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Brown22

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Hello, I'm trying to build ECG circuit for my school project. I'm using opamp INA128 and LM741 in my circuit. however, this circuit is not working. Can somebody explain how can I improve this circuit. Here is the schematic of my circuit.

ECGfrit.png
 
One improvement would be to throw away the ancient 741 and replace it with a more modern opamp having a very low input offset ;). When you say "not working", what exactly is wrong?
 
Thanks for the reply. I'm very new at this electronic stuff. What I mean by "not working" is that the output show only distorted signal. No pulse is detected. I used the arduino to read and show the value using Serial oscilloscope.
 
The 741 opamp was designed 47 years ago to use only a +15V and -15V power supply.
Your 78xx voltage regulator has no part number showing its output voltage, it is wired wrong and it is missing important i9nput and output capacitors shown on its datasheet.

In Google Images look at the thousands of ECG circuits that feed a DC reference voltage and a signal to the patient's right leg that cancels interference.
The input probes should be connected with shielded audio cables.


 
You have the output from the regulator going to ground.:confused:

The regulator probably is a TL7805 which gives the Gnd as output, which works
-5V for Vee and +5 comes out of the UNO from the 2nd battery.
This uses the +5V LDO as a -5V reg..

But the old 741 cannot handle inputs or outputs within 2,5V of the supply rail, so much better choices are avail now.

Since the 741 has low headroom, It would make more sense to change the Op Amp with a Comparator with an input RC LPF filter and 5V open collector output and 10K pullup with analog input on +/9V for Vcc,Vee.


AC hum can interfere, so rather than simply stick on a ground electrode, they usually buffer the average of the 2 electrodes back to the leg as a "virtual" ground for better immunity.

Of course good 0.1uF//10uF caps near the chips , and shielded electrode cables give better noise immunity.


Show some pictures. pls of layout and scope.
 
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