A non-invasive trigger sense based on inductive coupling was chosen after the identification of an inexpensive current sense transformer with a split-core to facilitate non-invasive implementation.

The Sonoff doesn’t use the ESP’s ADC pins, so he’s broken one of them out on a lead to a current transformer which ... ESP port of an Arduino current sensing library. To round off the ...

The value of R cs is obtained by using the ratio of U1’s sensing voltage to the operating current, scaled by the current transformer. Sometimes, however, the IC’s current-sensing input has a ...

The basic circuit is dead simple: a transformer, a full-wave rectifier ... [DiodeGoneWild] chose a simple discrete transistor current-sense circuit. To make it less susceptible to thermal drift ...