[sdiy] rotary switches in general

[Roy J. Tellason]

On Tuesday 10 August 2004 06:16 pm, Tim Parkhurst wrote:

> One alternative that I've seen used by others is to take a pot, hook it up
> as a voltage divider and run the voltage into a simple (2, 3 or 4 bit) A/D
> converter. The output of the A/D can then control an analog
> switch/multiplexer, transistors, or even relays. You'll need to add some
> indicator LEDs to provide user feedback, but this is relatively easy. A
> very simple "A/D" solution would be to use the LM3914 bar graph chip (10
> outputs = approx 3.5 bit resolution).

Now *that* is kinda nifty!  :-)

> This gives you the option of "bar" or "dot" modes,

I guess the "dot" mode would be more useful in this context,  mostly?

> and the outputs can be easily grouped together if you need fewer than 10
> positions. Given the cost of quality rotary switches, the A/D setup should
> be cost competitive, plus you now have a voltage controlled switch!

<...>

> There are some other examples of how to run +/-10V signal through a 4051,
> but I can't find them right now. It can be done however, and I'll dig them
> up if you really need it.

I'd be a little curious about this since the usual max power supply on those 
is 15V,  and +/-10V would appear to need a wider range,  unless I'm 
misunderstanding something here?