Converting analog controls to digital?

[VA2FSQ]

Hi,
I was wondering if I could get some advice on converting a device that has an analog potentiometer (1K) and a multi-position switch (4 positions) to digital operation.
I know you can purchase "digital potentiometers" of 32/64/128/256/1024 resolution as well as electronic switch IC's. 
I was thinking that this would be a good start towards learning about microcontrollers to control these devices.
Is there anything I need to know or any complications in using these devices?
I know that the circuit in question runs off 12 V so the switch or potentiometer should support at least this level of voltage.

Thanks for any advice.

[TANAKASAN]

You might have a problem using a digital pot at 12 volts. Most of these devices have a 5v supply and the maximum voltage on any of the three pot terminals is about supply + 0.25v.

Tanakasan

[WB6BYU]

We would have to know a lot more about how the pot is used in the circuit.

You can use an encoder to pass UP/DOWN information to a microprocessor (or a
simple counter) and drive an D/A converter to vary the output voltage accordingly,
if you just need a varying DC output.  Just because the circuit runs on 12V doesn't
mean that is the voltage across the pot, however, and as Tanakasan says getting
anything above +5V will take some work (possibly driving an op amp to multiply the
output x3 or x4, for example.)

If the pot is used to vary an audio output, such as a volume control, then it may
require a different approach to varying the level.

So the first step is to determine what the voltages are across the pot, and whether
they are DC, audio, RF, etc.  Based on that you can think about what would make
a good replacement.

[N4KD]

It looks like there are two questions, "Can I convert analog devices to digital in an existing circuit?", and "How can I interface analog components to a micro-controller?". I think the answer to the first question is no, and actually a switch is about as digital as it gets, anyway.

To accomplish what's asked for in the second question, you would need to connect each of the four positions of the multi-position switch to a discrete input on the micro-controller and read the pot voltage with an A/D converter, connected to more inputs on the microcontroller.

If you need to create discrete outputs, you may need to drive transistors or relays to get the voltage/current level desired. Analog outputs are created with a D/A converter and, as said earlier, you may need to drive an op-amp to get the desired voltage.

I'm not completely sure I understand the question, so if I not on topic, let me know.

[KH2BR]

You could start your digital project with a rotary encoder . Search for rotary encoder volume control.
I'm sure you will find what your looking for.
KH2BR

[WD4HXG]

Yes you can substitute a digital pot for a carbon pot.
Yes you can substitute digital switches for mechanical
switches.

You need to pay attention to protecting the digital
parts from higher voltages you may encounter in
analog circuits.

You may also want to look at the Arduino micro-
controller experimenters board. It uses a versatile
micro and the programming language is pretty simple.
It is "C" like but does not have the rigid structure.
That has pluses and minuses but all in all it seems to
works well for my needs. I paid around $25.00 for
the Arduino board. The wall wart was another $10.00.

There are accessory boards for the Arduino that provide
LCD displays that use a three wire serial comm port
to display ASCII characters (alpha/numeric). The
boards are failrly cheap. The LCD display board was
about $17.00 two years ago including the backlit
LCD display.

I had the LCD display connected to the Arduino and
displaying simple text within an hour after connecting
the display to the Arduino with a homemade jumper cable.

The big aggravation with using digital controls is
keeping the digital racket out of demodulated signals.
This is particularly painful in tube gear with the high
impedance signal paths.

But the hobby is about learning, experimenting and
having fun. So have at it and you may be surprised
at the way your tube rig winds up looking or even
how cool that Kenwood Tuner looks with digital displays.

73

Chuck WD4HXG