Rotary switch in place of a pot?
« on: August 28, 2008, 03:34:32 PM »
I know this is probably very basic, and I did search before asking.

I want to use a rotary switch instead of a pot, and I already have the values for the resistors.  My question is....what parts of the rotary switch act as the parts of the pot? If that doesn't make sense....there are three connection points on a pot. Where would you make those same connections on a rotary switch?


Rotary switch in place of a pot?
« Reply #1 on: August 28, 2008, 04:54:03 PM »
Picture the volume pot schematic symbol, a resistor with the top end as input, bottom end grounded, and wiper taken to next stage.

First, make your switch into a resistor. You load up the rotary switch with resistors, each connecting two solder lugs, except the first and last. If you connect those two you don't have a top and bottom to your resistor.

Connect IN to first resistor/first solder lug, connect GND to last resistor/last solder lug. Take Wiper connection from rotary switch center lug/switch contact. This way the wiper is picking the signal off whichever switch position you select, and the voltage division = (sum of the values of the resistors from first resistor to switch position) : (sum of resistor values from switch position to last resistor).
Quote from: PRR
Now, maybe you don't, or shouldn't, grab the ribbon for far-harpsichord, nor the hot condenser for snare-kissing... yet often we do.


Rotary switch in place of a pot?
« Reply #2 on: August 28, 2008, 04:59:21 PM »
I love you!  Thank you so much.  I'm still green, but things are making sense.  I appreciate your response.


Rotary switch in place of a pot?
« Reply #3 on: August 29, 2008, 01:31:34 PM »
Skip wave mentions one way,  but if your schematic shows a the center and one of the end lugs of the pot tied together there's another way to do it.
make the switch go through a full value resistor by connecting one end of each resistor to the switch lugs and all the resistor ends together. as you switch you go from resistor to resistor etc. making a variable resistor of sorts...
If its signal path you've just gone from having 2 or 6 or 12 or so parts in the path to 1.


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