Multi-zone music triggering

Projects General Guidance
1

I have a homebuilt multi-zone music system in my house that I want to improve.
Currently, the audio sources and all amplifiers are always on and when I want audio in a zone, I just turn the physical volume knob in the zone to anything but zero.
Physically, the output of the amplifier goes to the volume knob and the output of the volume knob goes to the speakers.
I know that there are several scenario's to improve this, but I'm looking for the following solution:

  • when the volume knob is turned from 0 -> non-0: Arduino should detect to turn on the involved amplifier
  • when the volume knob is turned from non-0 -> 0: Arduino should detect to turn off the involved amplifier

My idea to Arduino detect the changes for

  • measure the resistance between signal and the mass running between the amplifier and the volume knob; when the resistance is lower than infinity, turn on the amplifier
  • measure the current in wires running between the amplifier and the volume knob; when there is no current, turn off the amplifier

Measuring the current seems to be possible using a device like TA12-100.
Measuring the resistance seems to be more difficult to avoid too much current flowing to the Arduino.

What do you think about this approach and can you please advice on the circuits to be used?

Thanks!

2

Replace the pot inside the volume knob to one of those which also contains an on/off switch at the zero position. Wire that switch to control the amplifier (check current ratings, you may need to use a relay). No Arduino required!

3

@PaulRB

yes, that would be the easy solution, except for the fact that the volume knob comes as-is. I should have include that in my original post: http://artsound.be/en/multiroom/volume-controllers (scroll to TNS-VOLST volume controller).
Furthermore, the installation is already finished some years ago and I did not provide an extra line between the volume controller and the location of the amplifiers.

5

Delta_G:
OK, but for your Arduino solution you would have to run those wires anyway. So why complicate the installation with the Arduino?

No, I want to use the existing wires going from the amplifier to the volume controller that carry the amplified audio signal (which is an AC signal). Obviously, those wires are already there. The Arduino would be located in the central place where all the amplifiers are located.
The volume controllers are stereo controllers and thus 4 wires run from the amplifier to the controller: 2 ground wires and 2 signal wires.

6

Those TA12-100 sensors are intended for measuring current in mains AC circuits. They may also be suitable for amplified audio signals, but I think it would be wise to buy just one to begin with, and do some testing.

Not sure about your resistance measuring approach.

As these signals are not as dangerous as ac mains, you may be able to simply take a feed off the wire to an Arduino analog pin. But the signal must first be rectified and the voltage reduced to a safe level and put through a low pass filter of some kind. This is beyond my knowledge of analog electronics, so maybe do some Googling.

7

Is it a 70V system, or do you just send speaker level to all the locations? What is the pot in the wall?

8

MikeLittle:
Is it a 70V system, or do you just send speaker level to all the locations? What is the pot in the wall?

The amplifiers are all in a central location together with the music sources. From there it is speaker level to the volume controls in each room. The volume controls are these: http://artsound.be/en/multiroom/volume-controllers (scroll to TNS-VOLST volume controller)