Sooo..... not sure if this is the right forum for this question, but here we go.
I looked around and could not find an answer specific to my question.
I would like to build a circuit that monitors the output of an amplifier (speaker output). When a positive DC offset is found (say.. more than .5 seconds), the arduino (or perhaps this is overkill?) would kill the relay.
This amplifier is an old Harman Kardon quad 75+. So.. the amplifiers (4 internally) can be operated in either 4 channel mode (each amp is a simple push/pull) or stereo mode (two amps are bridged for each channel via a switch on the rear).
My theory is as follows:
Take the output of each individual amp and run it through 2 diodes to break out a + and - voltage (relative to ground).
Pass each of the signals through a... 1K (?) resistor and then feed the signal to a 3-5 volt zener (to limit the voltage to arduino-safe levels).
Monitor each of the eight signals with an arduino. I would not care about the level (so ADC is not needed).. only if the signal is persistent more than half a second or so.
I already have whipped up a simple power-on delay circuit that uses a transistor, zener and rc network to provide soft-start for the amplifier. I would prefer to move that to also be controlled by the arduino. Much easier this way - and centralized. I could even provide diagnostic LED's via the PCB this way in case anything went south.
Would the above actually work? Is my reasoning sound? Perhaps this is a much simpler way to do this that I am not thinking about?