Hi there, I started with Arduino and electronics recently.
I have a pretty basic question about wiring a soft pot with 3 pins.
I understand that the 2 side pins are power & GND, and that the middle one is connected to the A0 pin on the board for reading the voltage.
But looking at the diagram on my training book (comes with Sparkfun RedBoard) I saw that the middle pin also connected to GND through a 10KΩ resistor. My question is why?
Thank you for the help 
The vast majority of us do not have a copy of that training book.
Unless you provide us with the diagram (and it's accompanying information) you are limiting your possible sources of reliable information to the small percentage who do have access to that book.
Don
A pot is basically two resistors in series.
The middle pin (wiper) of the pot is the tap between the two resistors.
You can continiously vary the ratio between the two resistors.
Good if you want a variable signal or voltage.
But sometimes a circuit needs a single variable resistor.
Then you can use one side pin and the wiper, and ignore the other side pin.
The other outer pin (which is basically the other/unused resistor) is usually shorted to the wiper,
because a (dirty/old) wiper can loose contact during turning.
The circuit might not like an intermittend "no resistor connected".
If the pot is used as single adjustable resistor, then you can't ofcourse connect the pot to 5volt AND ground.
Turning the single resistor to zero ohm would otherwise short the 5volt rail to ground.
Leo..
floresta:
The vast majority of us do not have a copy of that training book.Unless you provide us with the diagram (and it's accompanying information) you are limiting your possible sources of reliable information to the small percentage who do have access to that book.
Don
Thanks for the comment,
Here's a diagram from the book, Please ignore the part about the RGB LED, as I understand it well.
the only thing I don't understand here is why the 10K resistor connects the middle pin of the soft pot to GND.
A resistor from wiper to ground changes a lin pot into a log pot.
Read this.
Leo..
Wawa:
A resistor from wiper to ground changes a lin pot into a log pot.
Read this.
Leo..
... and scroll down to the section on "Tapering".
Don
Cohn_Gal:
. . . Here's a diagram from the book . . .
The perpetrator of that particular diagram should be imprisoned, but I was able to find more information on-line.
Experiment 10: Reading a Soft Potentiometer
Don
Just realised, after seeing the full picture, that we're talking about a touch-style potentiometer.
The resistor is needed, because the 'wiper' of the pot is normally not connected to the track of the pot.
That results in a 'floating pin' when the pot is not used (random values).
10k is rather low for a 10k? pot. That would also change it into a log pot.
Leo..
