Mains Current Sensor Idea

Yes basically you have the right idea. A transformer feeding a rectifier and loaded with a resistor will indicate the current nicely.

Don't forget the load the output side. If you don't you get a high voltage on it and perhaps may destroy it.

I have used a 120V to 6.3V transformer as a current transformer. The

A hall sensor over a PCB trace.

How accurate?

An optocoupler. Two optocouplers for the increased dynamic range.

Isn't 10ma too small for the Hall sensor?

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Perhaps. I thought he was talking about the secondary current in the current transformer. I guess the OP could make a coil with multiple windings on the PCB so the Hall sensor sees a higher field strength.

the

Notice: Now slightly "Off Topic"

Is it just me, or does anyone else squirm when they hear the words "Mains" as referred to electric service?

To me, this is never very clear whether someone means the voltage, or the conductors themselves - and in either case, is it at the service entrance to the building (or other), or the wall outlet, power cord, or power terminals of the device in question.?? Or all of the above?

Seems very loosey-goosey terminology to me. Though, generally, I guess I know what is meant - at least in the way of "don't touch it or you might get electrocuted". But generally, not much beyond that.

Does NEC use this terminology? I know a lot of other terms used in NEC, but I'll have to review my copy to see if there actually is a recognized & accepted definition for "Mains".

Not to mention, why is "Mains" plural?

small toroidal power transformers work well, too. I used one in a test rig, to generate 0-10A in a shorted loop (which incidentally passed thru a CT, to test that part of a circuit) from a 16Vac source supplying not very many mA. I stuck a suitable loop thru the centre of the toroid, then experimented with which windings I needed to drive from 16Vac to get the max current I wanted, then chopped off all the other windings.

the OP can do the same thing in reverse. the advantage of using a small toroid is they are easily available from hobby shops, whereas CTs generally are not.

Cheers Terry

Terry Given wrote: (snip)

Have you checked, lately, for how many different current transformers are available from Digikey? The variety has multiplied in the last year or two.

yeah, they have a reasonable selection. I wanted one RIGHT NOW, and I got it.

I use dgikey a lot - mostly from a design-in perspective, rather than actually purchasing components, which I prefer to do from Farnell (quicker and I dont have to fill in any stupid "what is this for" crap). that being said, I buy from digikey and mouser where necessary. such as, for example, LEM DCCTs :)

Cheers Terry

What's that? More export controls BS? Talk about shooting yourself in the foot..

Best regards, Spehro Pefhany

I think its akin to the "will all terrorists please report to the security counter for immediate arrest" announcements at airports.

just another irritating layer of hoops for us furrners to jump thru. I always write the same thing: intended for use in a SMPS, by me.

hao3 jiu3 mei2 jian4

Cheers Terry

Well, if they keep up the stupidity, a French company is going to be making a whole stack of Euros. The US product is half the price, (and half as good, but good enough), but the Frenchies don't try to dictate what happens with it once it's sold by them (or by us, or by our customer).

Shenme?

Motivational management term of the day:

"We're facing insurmountable opportunities".

Best regards, Spehro Pefhany

long time no "see" (come across, etc).

Ive been in china & oz for the last 5 weeks. I was going to PCIM in the middle of the China trip, but had a problem at the factory in dongguan, so went there and caught some disgusting virus instead. luckily the problem turned out to be with an IC :( but we've worked around it without even needing a PCB re-spin :)

still, I got to practice my putonghua some more, learned some great swear words, and a bit of arabic, too (from my Iraqi mate who lives in zhangmutou). If I guess what people are saying, I can make it look like I speak fluently, but I can now have slow conversations with the aid of my pocket dictionary. another 3 weeks in China and I will hardly need the dictionary at all.

Good to know. Last time I needed a bunch I got them direct from Toroid Corporation of Maryland, but that's a while back.

Ed

Two wires? ;-)

Cheers! Rich