How to Question/Potentiometer

[overdrive]

When substituting a fixed resistor (where one end is attached to a transistor & the other end is grounded) with an external potentiometer, which of the three lugs are used?

#3 to transistor with #1 going to ground? OR

#3 to transistor with #2 (wiper) going to ground? OR

some other configuration (e.g. where the wiper is also attached to #1 & both are grounded?)

Thanks for your input. I still find potentiometer wiring confusing at times.

[Jazz P Bass]

Think ot a potentiometer as a hair comb.
The overall resistance is fixed.
The different "teeth" have progressively higher resistance from left to right. That is the wiper.
If you connect one end of the comb to the wiper you now have a 2 element variable resistor.
You will have to verify which lead is the top & which is the bottom to get the pot to behave the way you want it to.
ie: CW more resistance CCW less R.
That's all there is to it.

[Enzo]

My comb faces less and less resistance every time I use it.


Visualize what is happening inside the control. You have a resistor stretched between the two end terminals. Then the wiper - center - terminal - connects at some point along that resistance. So if wiper is 2, and the ends 1 and 3, as we turn the control one way, the resistance between 1 and 2 gets larger and larger, while at the same time resistance between 2 and 3 gets smaller and smaller. SO you need to decide if you want clockwise to be increasing or decreasing resistance for your application.

In the case of the control making a single resistor variable, then you pick the two terminals to use, leaving a free end one. You can conect that free one to the wiper if you like, it won;t affect the resistance between the wiper and other end.