Read Multiple Inputs on Single ADC Pin

[rWAVE]

For those who are input pin constrained (i.e. 08M), here is another simple and clever way to read multiple switches and a potentiometer on a single ADC pin.

The April 22, 2010 issue of EDN Magazine (page 71) or HERE (if you don't have the magazine) shows how to do it. I have used something similar with great success; just be sure to have an ample "guard band" around each input device for reliable operation, as all inputs map into the dynamic range of the ADC.

Note: There is an error on the supplied schematic. See it?
Hint: The supplied equations and spreadsheet analyze both a voltage divider AND parallel resistors!

Richard

 

[fernando_g]

Is the error that the dot that connects the pot's cursor to the two switches is not shown ???

Analog "multiplexing" techniques have been shown previously, most notable to encode a 3X4 pushbutton Matrix.