I wanted to use a transistor to switch a circuit that has its own power source (a battery).
It appears you could do something similar if you had two battery power sources, but in simulators, it doesn't seem to be the same for an Arduino connected to the USB port's ground.
This seems to work as best as I can tell. The attempt is to simulate a battery powered Arduino switching the transistor with an output pin.
This doesn't seem to work but I don't know why. The intent is to simulate connecting the negative terminal of the battery to the Arduino ground. In the simulator I have that shows current flow, this is a no-go.
Is this just generally a bad idea? Should I use a relay instead? Or an optocoupler?