I have made a USB webcam from an old laptop camera, a 5 V/3.3 V DC power supply powered by USB, and an old USB cord. When I looked at similar setups, however, I found they tended to have one or two diodes in them, and I cannot figure out why. I have a rather basic knowledge of diodes, as far as I know, they are used to prevent current from running in the wrong direction (for example. if a battery were put in the wrong way), but that does not explain why some of these tutorials use 2 diodes.
On to the actual question: I am using a small DC power supply intended for breadboards to convert from the 5 volts of the USB to the 3.3 V my camera requires. Is there any reason I would need to include a diode in my circuit?