Thread: Suggested Resistor values for 3.3V resistor ladder?
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Unread 02-27-2011, 10:36 PM
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Suggested Resistor values for 3.3V resistor ladder?
Hi Gang,

I'm building an external controller for our driver station based on the EStop CCI. I want to use a couple of 6 position rotary switches for the analog inputs on the CCI and wire a resistor ladder for voltage dividing. Normally, for 5V I'd use something line multiple 20K ohm resistors that would give me roughly 1V per stage. At 3.3V, I think that the number should be roughly 13K ohms/stage. Am I doing that math right? My concern is that I don't want to exceed the 100ma max current on the CCI.

Maybe I've been working on software too long to remember my basic physics. But, I have to admit that I'm getting confused dealing with voltage drops across the resistor ladder given that I want to minimize the current to keep it well below the 100ma. A quick clarification of the math would be greatly appreciated.

TIA,

Mike