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I want to remotely check if one of my home sockets (which happens to power a heater) is transmitting current or not. I do this as a hobby project, so my main priority is to learn through the process of building it, therefore I don't want to buy 'ready-to-use' devices. Also, this is a heater and I have carpet so, for safety reasons, I would like to not need to peal and connect wires that carry several amps. In particular, my heater is 2000W at 230V, so it will be using ~8.7 amps if I'm not mistaken.

I have been looking at different alternatives. Ideally, I would like to have a socket adaptor that sits between the wall socket and the heater, and the only thing it does is producing 3.3V or so on an external pin when it detects for instance 1 amp going through it. I can then feed that signal to an MCU and do whatever I need. At this point, I'm interested in the step of sensing when there is current flowing through the socket, but I don't need to measure the exact amount of current.

The alternatives I have found (that are safe enough) are:

  • Hall effect sensors This is not ideal, but it's safe as I don't need to manipulate any part transferring a respectable amount of amps.
  • Socket adapter with LED: I could break the LED part and solder a wire to it to use it as an input signal for my MCU.

Am I looking at the right parts? What are other options I could use?

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  • \$\begingroup\$ Can you optically sense when "heater on" LED is on? \$\endgroup\$
    – D Duck
    Commented Mar 18, 2023 at 14:35
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    \$\begingroup\$ What is the purpose of sensing? If you have such an socket adaptor with a lamp/LED, it only tells if the socket adapter has power, it does not know if the heater is even plugged in or if the fuse has blown, and heater has a thermostat so it will also don't always consume current but only when heating. And you don't have to break the LED out, you can just sense the light. But any adapter or wiring between 2kW heater and socket is just extra point of failure that can heat up and burn your carpet if it can't handle current. Typically it is recommended to not use any extension cords. \$\endgroup\$
    – Justme
    Commented Mar 18, 2023 at 14:43
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    \$\begingroup\$ I'd use a current transformer. \$\endgroup\$
    – Andy aka
    Commented Mar 18, 2023 at 14:45
  • \$\begingroup\$ @justme The purpose of sensing is just to display the information somewhere. With regards to the socket with LED, good point, I didn't realise it. That discards that option. It's true as well that any adaptor between the socket and the heater is another point of failure, but given that's not 'home-made', I would expect it to be pretty safe. \$\endgroup\$
    – Martel
    Commented Mar 18, 2023 at 18:49
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    \$\begingroup\$ Yes, that is incorrect; you need to expose one of the current carrying wires and only "sense" that wire to get a reliable interface (just as you would with a current transformer). \$\endgroup\$
    – Andy aka
    Commented Mar 18, 2023 at 19:20

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After reading all the comments, the adapter with LED is discarded. That leaves 2 main options:

  • Current transformer
  • Hall-effect detector

Both devices work by passing a current carrying wire through the hole they expose, thus it's necessary to, somehow, expose only one of the wires that go to the target device (such device will have a single cable with, at least, 2 wires in it: phase an neutral).

Still, out of the 2 options, the hall-effect detector seems safer as the output it generates is a low voltage, which will vary depending on the amount of current going through the sensed wire. The current transformer induces a current on the output, which has a problem: it's necessary to solder a burden resistance in between the outputs to avoid a (theoretical) infinite voltage between them. There are online burden-resistor calculators but again, this is an added difficulty and, if by any chance the burden resistor is damaged or the solder points fail, it can be unsafe as far as I can see.

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