I am currently working with a Heart Pulse Sensor
I am using a 0-9v supply voltage which is capped at 5v using a voltage regulator 7805. The 5v powers up the ATmega328P as well as the Heart Pulse Sensor. When measuring the signal from my pulse the voltage ranges between 2.5 to 3.5 v approx, however, the signal has a min voltage of approx -1 to 2.5v. Now since the signal is an analogue signal i am required to use the ADC to convert the values and act upon them. The ATmega328P does not have the differential of negative or positive voltage reference. Therefore, i am forced to do something about it. I was thinking of using a potential divider and a pot to add some DC on to it making a composite signal and letting it rise above zero.
Is it possible to do this using the 5volts supply, or do i need to make this supply voltage from negative to positive... say -9 to 9v?
And what other recommendations can you give to fulfill the requirements regarding the approach?