Current Sensor

Could I put some type of current sensor around the outside of an insulated wire ( for example, around the outside of a wire hooking up to a 60W ceiling light in your house) that would tell whether or not there is any current flowing? I know there is a magnetic field around the wire when current flows, an I could create a sensor with that in mind.

My concerns are:
A) How the 60Hz AC frequency of the wire would change the way I would need to make a the current sensor (which I have been thinking about like it is DC).
B) Would the (roughly) .25mm - .5mm insulation on the 12 or 14 gauge wire become a barrier?

Hello.

If you do a search for something like “clamp meter”, you’ll get a lot of results for meters that can measure current without having to put the meter in the circuit.

If you are looking for a sensor you can build into a project, I’d look for hall effect sensors. I haven’t tried this, so I can’t recommend a particular part, but you should be able to use them to detect the current in a nearby wire.

- Jan

To measure AC current without making an electrical connection, you can thread the current carrying wire through a small toroidal coil. It forms a transformer with a single turn primary and outputs a millivolt-range signal proportional to the current flowing in the wire. Sensitivity is fractions of an AC ampere. You can wind your own, but Coilcraft is one manufacturer of such sensors and they give out free samples!

coilcraft.com/pwrsense.cfm

I’ve done this before but I cannot remember what current sensor I used. Once you’ve got the current transducer, it will output an AC signal that corresponds to the AC voltage. This will need to be stepped down and converted to DC in order for your microcontroller to recognize the signal.