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I need a current detector that outputs a logic signal (1 or 0). I DON'T need to measure current.

  • Detected current: AC.
  • Voltage: 220V.
  • Load power: ~1kW.

FOR EXAMPLE: I need a current detector that will give out + 5V at a current greater than 0.15A, if the current is less than 0.15A, then the output is 0V (adjust the threshold with a trimmer resistor).

I think that an optocoupler and some kind of transformer current sensor (for example ZMCT103) could be used for this. It is advisable not to use additional power from the LED side (which is located in the optocoupler).

Do you have any thoughts and solutions?

Rohit Gupta
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Mia
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  • Why do you want to use an optocoupler? A transformer can already provide safety isolation. – The Photon Apr 16 '23 at 14:36
  • @ThePhoton Nobody canceled power surges. And if you look at the [SCT-013-000](https://www.elecrow.com/download/SCT013-000_datasheet.pdf) datasheet , you can find a built-in TVS diode there. I need to signal the presence of a certain level of current to a microcontroller 24/7 that will be connected to the computer via usb. It's better to have extra security than not to have it. Paranoia:D (joke). – Mia Apr 16 '23 at 14:51
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    What would an optocoupler do for power surges? Maybe share your proposed circuit to make it more clear? – The Photon Apr 16 '23 at 15:02
  • @ThePhoton The optocoupler could have failed instead of the microcontroller. – Mia Apr 16 '23 at 15:35
  • @ThePhoton https://i.postimg.cc/rsRwPYwr/image.png I'm a beginner, so don't be scared. Most likely this is not a working scheme, but just a presentation of an idea. – Mia Apr 16 '23 at 16:14
  • AFAIK the opto is not required and not helpful. Something like the TVS (you might want to choose your own in addition to the one built in to your transformer) will provide the protection you need without failing when used, probably at lower cost. – The Photon Apr 16 '23 at 17:16
  • Optocouplers have a very specific purpose: To carry signals that might have DC components across an isolation barrier. There are generally better and cheaper solutions for the other functions that you see people using them for. – The Photon Apr 16 '23 at 17:19
  • @ThePhoton I want to use ZMCT103 or make CT (Current Transformer) by myself. According to the datasheet [ZMCT103](https://5nrorwxhmqqijik.leadongcdn.com/ZMCT103C+specification-aidirBqoKomRilSjpimnokp.pdf) does not contain TVS. The [SCT-013-000](https://www.elecrow.com/download/SCT013-000_datasheet.pdf) has TVS but I'm not going to use it as it's not compact. I have included SCT-013-000 as an example only. – Mia Apr 16 '23 at 18:09
  • Like I said it wouldn't be wrong to choose your own TVS based on the limits of your load. But an opto will just add cost, and require replacement if it is driven to failure. It's not meant to be used like a fuse. – The Photon Apr 17 '23 at 00:35
  • @ThePhoton Great. After all, replacing an optocoupler is more expensive than replacing a microcontroller or repairing a usb on a motherboard.:) – Mia Apr 17 '23 at 12:54
  • What is the required resolution in time? – Jens Apr 17 '23 at 23:51
  • @Jens Time doesn't matter – Mia Apr 18 '23 at 09:36
  • If the solution has size constraints you may consider to use a hall sensor chip like ACS724 to replace a current transformer. A comparator behind it is needed here as well. – Jens Apr 18 '23 at 12:27
  • @Jens My main requirement is non-interference with existing wiring. My opinion: in the supply line of my house there should be as few unnecessary elements as possible, because every extra unit is a potential point of failure. In other words, as a solution to the problem of measuring current in a household network, everything that is installed in the wiring gap disappears - both branded and home-made. Traditional shunts are clear why (to everything else they are also fire hazardous), but meters based on Hall sensors (like the popular ACS7xx) are also not suitable. – Mia Apr 19 '23 at 07:13

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You know, they make ready-made products that do that. No need to reinvent the wheel. They are used to turn on the blower next to a circular saw to suck out the dust.

https://www.amazon.com/Current-Sensing-Normally-Adjustable-SZC23-NO-AL-CH/dp/B07P87TG8F

https://www.walmart.com/c/kp/current-sensor-switch

Davide Andrea
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    This solution takes up a lot of space. I need a compact solution. That's why, I began to look for small transformer current sensors. But thanks for answering my question. You prompted me to further search for the query "Current Sensing Switch". – Mia Apr 16 '23 at 14:18