I am making a DIY ECG sensor using op amps (LM741) and resistors with biasing voltages (5V and -5V). Is it possible to use this DIY sensor output as analog input to the Arduino?
If yes what are the pitfalls I should be careful about.
I am trying to replicate the following circuit.
Negative voltages applied to Arduino inputs.
Is there any way to rectify that?
Was that pun intended?
Sketch your DIY ECG sensor and it will be much easier to give comments and advice.
As mentioned the Arduino is not designed for a negative input, bad things will happen. There are circuits allowing you to offset the input voltage which are common. Another approach is to use a single supply operational amplifier. The LM741 is pretty old and while it does not predate me it's a poor choice for today's circuits. As to old operational amplifiers using a single supply there is the LM358 and many newer operational amplifiers.
The above is an example of how we can apply an AC signal to an Arduino Analog Input. Just work within limits.
Ron
R1 and R2 afford the mentioned offset. Just remember the schematic is for educational purposes and clearly states do not build. You need to place some effort into learning what the circuit does and why it does it. The batteries will result in a split supply of plus and minus 9 volts. Ground not shown is the junction of the two 9 volt batteries. The batteries are series configured.
Ron
Yes. Don't go connecting it to a human body. 
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