AC current detection (not measurement)

Started by lukash, March 11, 2016, 09:23:58 AM

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lukash

#15
April 14, 2016, 03:33:34 PM
Not 100% sure so I measured again .. now it's 100% sure 1X probe with 1X compensation .. but it's very similar, I think the "problem" yesterday was that I shifted channel 3 to the bottom part of the screen so the measurements on top would not cover it (see where the little arrow with 3 is on the left - that's middle/zero of channel 3).

Here are some more pics from today..

1. No load


2. Extension cable w/ 60W bulb - about 1/2 inch away from the inductor


3. Extension cable w/ 60W bulb - very close to inductor


I also ordered some 10mH and 47mH inductors with a lot of windings, the publications said it might provide better distance, this has to be quite close. INA now has gain of about ~910 .. maybe I can even raise that .. some fine tuning will be needed  :)

What I'm trying to achieve now is to map that AC signal of 20mV - 150mV approximately to DC 0-3.3V so we can read it with analog input of moteino .. ideas for something easy? It'd be perfect if it was possible to do with just on op-amp (the remaining one of the quad MCP6004), we'd just have that opamp and that's it.

mikebar

#17
July 17, 2019, 04:35:37 PM
Hi Lukash, did you go any further with this project ? Have you connected it to an ADC? If so, could you share the schematics?
Thank you very much.

lukash

#18
July 17, 2019, 05:27:51 PM
Hey Mike,

unfortunately life happened and I was not able to finalize this as far as I'd like. I hope I can add "yet".

I have made it to revision 0.3 :D Made a prototype board, got a few pieces from OSH park, assembled the prototype and it seemed to be working except one caveat I did not manage to debug due to lack of time (and skill I think too, lol).

The caveat being once AC current triggers the second opamp (output high) and it (sometimes) keeps the output high even after the AC current from the coil is gone - not quite sure why, to be honest I don't exactly remember that much anymore.

I have found the schematics + the board (Eagle .sch and .brd files) + BOM I made at the time and shared it on my Google Drive here: https://drive.google.com/drive/folders/0B_Qu9F7qJpuHNVlERmVCNGdpRnM

If you'd spot the bug and/or improved the design I'd really appreciate if you let me know, either here or [email protected], also feel free to write me if you have questions, I'll answer what I'll be able to remember. I'd love if this could be finalized as I still do plan to use it in the future in my woodworking shop to turn on dust collection automatically.

Have fun!

mikebar

#19
July 20, 2019, 08:59:30 AM
Thank you for sharing it.
I'll give it a try to see what's going.
What I'm trying to do is a "sensor" able to feel the 50Hz (or 60Hz) from a powered solenoid valve.
Of course, I cannot touch the wiring of the solenoid and not even use a Clamp type Current Transformer (CT).
So, the only option left is to catch the AC "noise" from the solenoid when it is powered.
If you have any idea, it will be really appreciated.
Thank you.
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