This is my first post on this StackExchange after years of lurking, so please be gentle!
I would like to be able to enable an output (for example an LED) based upon an AC voltage from a split-core non-contact sensor like the following: https://www.mcielectronics.cl/website_MCI/static/documents/Datasheet_SCT013.pdf
I want to detect when three to seven 50W incandescent bulbs (racing circuit start lights) connected to the AC supply are switched on and then off.
From my reading of that datasheet, the SCT013-005 and its voltage output siblings, all induce an AC voltage in proportion to the current flowing through the wire around which it is clamped (0-1V).
I would like to enable an output (for example a MOSFET in the below diagram) if the current flow in the clamped cable is above a certain (adjustable) level.
Since the amplitude of the signal voltage is so low, I thought to use an Op Amp with part of the feedback loop (R5) being adjustable with a potentiometer trimmer, however since I haven't worked with either AC signals or OpAmps before, I wanted to check my design was sane.
(It works in the circuit simulator, but I don't think that guarantees anything!)
D3 and R7 represent the hypothetical load. In reality, this would be the input of an optocoupler inside a piece of proprietary hardware.
I expect that the smallest load I will detect will be 2x 50W incandescent bulbs, with no other load on the mains supply cable, giving a mains current of 0.23A = (100W / 230V).
This should induce a voltage of 0.046V = (0.23A / 5A). Picking round numbers, if I aim for a max gain of 100x then using a potentiometer (R5) with a maximum of 10k and an R3 resistor of 100 Ohms should give a gain of (1 + 10k / 100) = 101x gain, giving an output from the OpAmp of around 4.3V (or whatever the amp can drive, I don't expect I need a rail-to-rail part here), more than sufficient to drive the gate on a BSS138 or similar MOSFET.
In use, the operator would adjust the gain using the R5 potentiometer until switching the start lights on just enables the output.
A few more questions, should all that be sane:
Are there any caveats I should be aware of before I try building this?
Do I even need the diode D2?
Is it reasonable / correct to tie one leg of the AC signal to Ground?