ECG Circuit Problem

[Johnny101]

Hello everyone, I am using the attached circuit schematic to get ECG signal, Instead of getting ECG signal, the output looks like as in the attached image, the output signal is taken at the node between R2(100k) and R5(100k) after the low pass filter. The PQRS peaks are not comprehendable. The instructable I am following gets a clean ECG. Is there a possibility that the oscilloscope power noise is being coupled. Any Help would be appreciated. here is the link to the instructable I am following:
http://www.instructables.com/id/Electrocardiograph-Heart-Rate-Monitor/

 

[hevans1944]

Ah! And yet another "instructable" bites the unwary novice. Looks to me like you are seeing the power-line radiating into your rig from wiring in the walls and whatever mains wiring that happens to be nearby. My heartbeat is regulated by an implanted device to be about 72 beats per minute, so one pulse every second or so. Your pulses are much faster than that (hence the suspicion this is power-line affecting your circuit), but it could be you are just very excited from getting anything at all out of this "instructable" project. Check your wiring and layout. Use a battery, not a wall-wart, to power it up. Try placing everything inside a metal box connected to your circuit common.

 

[davenn]

and what the hell is that in the top left corner shorting out the battery ??

 

[AnalogKid]

That is a 7805 acting as a rail splitter. If you've ever seen an app note for using a standard positive boost regulator as a power inverter (+5 V in, -5 V out), it's the same trick but without the correct feedback to maintain the pseudo-GND at 50% of total Vout. As the battery discharges, the -5V stays at -5V and the +4V sags.

ak