Long story short, I'm trying to use a photodiode to detect and measure sunlight. I followed the instructions given on the link below, but for some reason the serial monitor just keeps reading 0.00 volts indefinitely. I used that exact code and circuitry and even swapped out several different resistors to try and get new results. Everything ended up the same. Any idea what I am doing wrong?
Post your code your wiring and your results. Your problem has nothing to do with the serial monitor.
Presumably there is something wrong with your hardware, either a design fault or a faulty component.
Can you prove beyond any possible doubt that you have the same components connected in the same way shown in that article, and all the components are the right way round etc?