I am trying to build a level shifting circuit for my project in order to make sure that the input will be appropriate for a 0-3.3V ADC.
I am using two 9V batteries connected in series so my thought is that I have to shift the incoming signal by around 1.6V in order to be in range for ADC.
I have tried two ways to create a voltage reference using 4 1n5818 diodes in series that gave me a reference of around 1.8V and a LM317l voltage regulator giving me around 1.66V.
The problem in my schematic is that the when I connect the reference circuitry to the opamp, it doesn't work as expected. I am not sure what I am doing wrong here.