i have this CT current transducer: it outputs 333mV at 5A full scale.
I'm planning to use it in my house/office in order to detect if a load is switched on or off, but i'm worried about how i can protect my arduino pro mini.
The arduino pro mini (based on atmega328p) is running on batteries (2x1.5V) and has some modifications in order to lower the power consumptions (at this time, the arduino itself consumes only 5uA).
Digging around, for my project purpose i've found a lot of solutions but this seems the most pratical:
(The generator and the 33ohm resistor on the left side of the schematic, represents the current sensor)
This is a simple comparator circuit, as you can see from the schematic, the 1.3V power input represents a low power voltage reference based on LM385, that i'm planning to use in order to have a stable reference of my circuit during the battery discharge over time (if you have some alternatives these will be appreciated!)
The treshohold is regulated by hand using a trimmer with the load switched on.
I've not yet tested physically this circuit, but only simulated using this CircuitJS, but i'm not sure about some things:
The aim of the placed diodes is to clamp the voltage if some spikes (that may occour) are injected in the circuit, protecting the arduino pin, i've seen that if i change the AC generator from 50mV to 600v (simulating consistent noise signal spikes) the output signal oscillates between -700mV and 2V...why?
I have some doubts about my circuit...i'm too much worried about my battery consumption that i'm making working bad the circuit? maybe i'm overthinking on that?