I'm using Circuit Wizard to simulate a circuit and I'm trying to understand how to wire a potentiometer.
While trying to learn how current flows through the pot, I found that it works in both directions as it's just a variable resistor. But when drawing a schematic, which is the RIGHT way that current should flow through the component?
See the following two schematics:
I have the following questions:
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Is current supposed to flow in the direction of the arrow or away from it?
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Is it unusual to wire a potentiometer what appears to be reverse as I've done here?
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Is there any problem with not using the third lead in this circuit?
Best Answer
It's good to keep track of which way a pot is wired. All the schematic symbols for pots that I have created have that information as part of the symbol.
For pots that are not 'B' (linear) taper, such as audio volume controls, it's not only good, it's necessary, because the resistance change for a given angle rotation is much different at one end compared to the other. The consequence would be that the volume is very high over most of the rotation and then suddenly drops as the pot is rotated mostly CW, with reasonable volume levels being very hard to set.
It's intuitive (to me anyway) that clockwise rotation of the shaft should increase the brightness in this case, so you would want to connect the pot so that happens. (You should also add a series resistor so that the maximum current is limited and does not damage the LED and/or pot).
In fact, it's functional either way, and with a linear pot, not much different.
And, as others have suggested, it's typical to connect the "open" end of the pot to the wiper, which slightly reduces the wiper noise and has other beneficial effects.
As far as current flow, the simulator diagrams show conventional current, which flows from + to -, so in the direction of the arrows. Electrons flow the opposite direction but you don't need to worry about that in most situations.