I was looking for a way to detect a line-in device transmitting audio. I got the idea to use ADC for this from this question: How to detect line level audio signal?
I already have a 4-channel ADC (the ADS1015) on my board which uses only one channel to read from a resistor network. So, I still have three available, but is this a good idea?
What should I expect line-level audio to be, worst case? Less than 5V, 10mA?
From what I understand from the datasheet, the ADS1015 is tolerant of analog voltages up to 5.5V, 10mA continuous/ 100mA momentary. But it seems not to be able to handle negative voltages:
Although the ADS1013/4/5 can read bipolar differential signals, they cannot accept negative voltages on either input. It may be helpful to think of the ADS1013/4/5 positive input as noninverting, and of the negative as inverting.
Now, I don't fully understand this. Will negative voltages damage the circuit? Or can't they be measured? In the latter case, for detection purposes, I guess it's ok to measure positive voltages only? In the first case, can we filter out the negative voltages?
I have a three channel passive summing box. Can I simply hook it up to the ADC from there (see schematic)? Or should I add filters, safety, and/or, ...?
- The programmable gain is currently set to "2/3".
- I read the values from a Python script, so I can be "smart" with the detection, for example filter out fluke spikes.
- Any tips to make it robust (prevent false positives) and somewhat idiot proof (the Line-In is on my car's dashboard, who knows what stuff people plug in when i'm not looking)?