Re: Current transformer Wire wrapping


"Bordon" <Bordon@xxxxxxx> wrote in message
news:dtOdnV_3LdHoKIDeRVn-qg@xxxxxxxxxxxxx
>
> "Jasen Betts" <jasen-b@xxxxxxxxxxxxxxxxxx> wrote in message
> news:9pqmu2-31b.ln1@xxxxxxxxxxxxxxxxxxxxxx
> > In article <nrydnWy18eXUsIreRVn-ow@xxxxxxxxxx>, Bordon wrote:
> > > Im trying to build a current transformer from a U Bolt.
> > >
> > > I am a novice so be gentle.
> > >
> > > I want to detect 120 volts of current in a household line.
> > >
> > > I wrapped a 1/4 inch u bolt in about 300 wraps of 30 Gage Magnet wire.
> > > I have wrapped about 4 wraps of the house wire as the primary.
> >
> > use more wraps of magnet wire and houuse wire
> >
> > > When I test it I only get about 1/2 volt of power out of the
secondary.
> > >
> > > I want it to light an led or light. I have one led that is about
9volts.
> >
> > most LEDs will work at 2.5V or less
> >
> > > It is my understanding that I should be getting around 12 Volts with
my
> set
> > > up.
> >
> > it depends on the U bolt and how much current the AC mains circuit is
> passing
> >
> > > One question I have is does it matter what the ubolt is made out of.
> > > Everybody talks Iron, but of course I assume that this ubolt is made
out
> of
> > > steel or who knows what, from home hardware. ~ Will this work? (I have
> no
> > > Idea if anything is made out of Iron any more)
> >
> > Iron is better than mild steel (which you probably have) mild steel is
> > better than high tensile, bigger is better.
> >
> > > It also is zinc plated, and then I covered the bare ubolt in Teflon
tape
> to
> > > make the wire stay and in case of shorts. - is this a problem (eg
Zinc)?
> >
> > not really, a bigger problem is that solid metal transformer cores are
> > inefficient, if you can replace your U bolt with a proper transformer
core
> > you'll get better results.
> >
> > > I wrapped it from the threaded part to the other end and stopped just
> before
> > > the other threaded part. and back over the secondary a little because
I
> was
> > > not finished my wrappings. I tried to be neat but of course its not
that
> > > easy. I put one bolt on each threaded bolt and then the plate and then
> > > another bolt to hold it on so it didn't move --o|o---
> >
> > that's about as good as you're likely to get. more turns of magnet wire
> will
> > give more voltage if there's room for them. more turns of house wire
will
> > also help.
> >
> > one way to get more efficiency would be to take a "wall-wart" type
> plugpack
> > powersupply apart, and take a chisel to the transformer secondary
> > (the bit with the thick wires) and remove them, wind a few turns of your
> > house main in their place and take the output from the primary
> > (originally connected to the plug pins) -- something like that could
> > produce upto 100V... using fewer turns of house wire will reduce the
> > voltage...
> >
> > > So far do you see any problems? And possibly why IM getting low
voltage
> on
> > > the Primary. I have tried to test it with a 2 amp drill. The voltage
> ranges
> > > from .5 - .8.volts.
> >
> > Try something that uses more power like a clothes iron, hairdryer, heat
> gun,
> > or electric jug.
> >
> > > thanks.
> >
> > Bye.
> > Jasen
> Thanks Jasen,
>
> Didn't see your post till today because I was away. I have taken apart my
> Ac/Dc adaptor and as you and John suggested cut out the secondary. I used
> pointed wire cutters and just started cutting. I have not wrapped my hot
> line yet, as some other things have got in the way but I hope to try it
out
> in the next day or so. I may also try salvaging the Ubolt with more wraps
> and see what happens. If you are still out there I have one other
question.
> I'm assuming that I should wrap using the (white) neutral(AC) (not to be
> confused with the green ground) wire rather than the (black) hot.
> This is the way I have been doing it anyway.
>
> Thanks.
>
>

If you are doing this as an interesting exercise you might like to visit a
discussion on sci.electronics.design back in April this year titled 'current
transformer winding wire help please'.

You might also like to visit http://www.coilcraft.com/pwrsense.cfm for more
info. They also supply samples if you are interested in a professional
product.

HTH

Gordon

.

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