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This is a better solution. There are two solutions: isolated and non-isolated. I recommend the isolated solution because of security.
Use a current transformer to collect the current in the loop, and then convert the current output by the current transformer to a voltage through a resistor, and then simply use a diode to rectify.
If you need precision, use the RMS chip directly.
At this time, you get a Voltage signal, this voltage signal can be compared with the reference voltage through a comparator, and then the output of the comparator is connected to a BJT or NMOS to drive the buzzer
First you need to define
* the current ...instantaneous, true RMS, rectified average, what filtering method
* and define the waveform...frequency, sine, with or without overtones.
* the output signal timing .... referenced to the input signal
But if you want to uild it on your own:
* most probably you want to transform the AC current into a DC voltage signal
* then blank out effects of inrush current, pump start current
* add some hysteresis
* add some protection in case of errors, like huge overcurrent when a short circuit happens.
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