Electronic – Rotary Cam Switch wiring help

If you wire all three switches to give a single analog output, you require 0.1% resolution. Since common precision resistors are 1%, and ADCs typically have a couple of counts of uncertaintly, I don't think this technique is practical.

However, if you wire each switch independently to an ADC input, with resistors selected to give evenly spaced voltages, it would be much easier to get reliable readings, and would even work with 5% resistors.

You could use three ADC inputs, or a single ADC with analog switches to read the input switches one at a time.

You can get a reed relay, such as this one, with contacts rated at 200 VDC @ 500 mA, and a nominal coil voltage of 5v. The datasheet is here.

The advantage of a relay over a transistor solution is it would provide total isolation. Also the easiest way of integrating into your current system, just wire the relay contacts across your switch contacts.

Since you are switching a fairly low current, you might want to use a relay with two Form A contacts and wire them in parallel. This relay is identical to the one above except it is DPST (and costs about twice as much).