|At a current of about 0.5 Amps, the voltage is
sufficient to start turning on the green LED indicator light. The schottky
diode in the circuit prevents reverse biasing the LED and the resistor limits the
peak current. There is sufficient resistance in the current transformer
winding, so even at a 40 Amps of AC current, the LED will not be driven with
excessive current. Since the current transformer offers exceptional voltage
isolation, the LED can be located some distance from the transformer, using
inexpensive low voltage insulated wire.
If you wish, you can wrap more than one turn of wire around the
core of the transformer to detect even lower AC current. With one wire, the
LED glows nicely with 0.5 Amps. With two turns, the LED should glow with 0.25
Amps. With four turns, the LED should turn on with only 0.125 Amps of AC
current, which corresponds to only 15 watts of 120vac power.