 The following is a public service announcement for solderless breadboard users. When wiring your circuit on a breadboard, take note of the lines indicating each power bus. If these lines are separated, then so are the conductors inside your breadboard. You'll need to bridge the gap with jumpers in order to use a single supply across the board. A simple fact that can easily escape the human mind when it's troubleshooting something more complex, like say an electronic circuit and or code. And if you're muttering to yourself why do they do this, consider the fact that split rails can be helpful when using multiple voltages across the same breadboard.