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I need a quick fix for a small problem. I need to detect current flow in a 240v 5-15A circuit.

Extremely simple please. No power supplies, computer inputs & etc, just a detector to light a common or garden type LED. Perhaps using a Yhdc non invasive current detector, [Hall effect torrodial?] or equivalent. Current flow above leakage would be good.

Thanking you in anticipation


0 Votes


July 24, 2019 15:20

Hi Lan,
You can use an inductance coil to measure ac current flow and there are kits or ready-made units. Another way is by using a Hall detector. For example, clamp meters use Hall's detector to measure current in an ac circuit. You could use a microcontroller with a threshold to turn on turn off .

0 Votes

October 24, 2019 08:33

@robnevada Will try. Thenkyew for your input, much appreciated. Cheers ian

July 24, 2019 15:21

Hi Ian, I think your proposal is good, see if you can find the spec for the 'burden' resistor on the secondary to give an output voltage across it greater than the LED + dropper resistor requirements to give a suitable brightness at 5 and 15A primary.
I did a search on "current transformer load indicator" and others have done this with a diode + resistor + LED in series across the burden resistor, or used a bridge rectifier followed by the LED and resistor. This will obviously cut off at some lower limit of the primary current flow, but that is what you require, so just check it works at 5A.
Some search results did not have a burden resistor but this is bad for a current transformer as the voltage can go high without this!

October 22, 2019 12:33

@Boss Thenkyew. Will try. Much appreciated. Cheers Ian

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