I am trying to follow an Audrino tutorial with my kid and I am confused by the role of the diode in this circuit.
In particular, I have the following questions:
- It looks like the circuit will work without the diode. The purpose seems to be to allow the current flow from the pin9 power source, but why do we need that?
- Does current flow from pin 9 through the emitter to the ground?
- More generally, when someone says “the current” is in this direction, do they mean that is the + => – direction, or the flow of the electrons?