What do you mean about 90 degree directional shifts? Thanks.

When current flows through a wire, the magnetic field spins around the axis of the wire. Winding turns ON the wire that is carrying the large current does not cut any of the magnetic lines. It lays in parallel to the magnetic lines. Putting a magnetic loop around the wire will allow the magnetic lines to induce magnetic flux in the core, and THEN you can wind a coil on the core, parallel with the current conductor, and it will use the magnetism to create a voltage. Without a magnetic core, you have to lay your pickup coil along the length of the wire to pick up any energy.

With a toroid, the magnetic lines go into the core and induce magnetism which you can pick up with a similar coil wound around the core.

You can either use a magnetic conductor to deal with the 90 degree angles or place (my) winding differently. What you tried is to get the magnetic lines to come out of the toroid through the hole, and they are much more interested in the magnetic permeability of the core.

 

The use of a powder core in toroid winding is because they are unique in the sense they give us a way to speed the design...i.e. they have a built in air gap however the idea of cutting them is not really feasible. The core mfgs list both permability and Millihenrys per 1000 turns. A tape toroidal core would be better suited but again if you are cutting not highly recommended for what I think you are trying to accomplish...just my two cents Jon

 

The use of a powder core in toroid winding is because they are unique in the sense they give us a way to speed the design...i.e. they have a built in air gap however the idea of cutting them is not really feasible. The core mfgs list both permability and Millihenrys per 1000 turns. A tape toroidal core would be better suited but again if you are cutting not highly recommended for what I think you are trying to accomplish...just my two cents Jon

A toroid only has an air gap if you order one that has.

Dust cores are usually soft enough that you can cut them with a Dremmel cutting disk - but the slot will probably end up wider than you wanted.

A trick I use for winding more than just a few turns on a toroid, is estimate the length of winding wire (add a bit for safety margin) feed the wire through and let the core drop so its weight finds the middle of the wire while you hold the ends.

Winding half the wire one way then the other half the other way is much easier than trying to do it all in one go - you can tape a weight to the end you're not winding to keep it pulled straight and avoid tangles and kinks.

 

another way is to wind the wire on a narrow strip of cardboard and pass that through the core, unwinding from the cardboard and onto the toroid.

 

another way is to wind the wire on a narrow strip of cardboard and pass that through the core, unwinding from the cardboard and onto the toroid.

Also known as weaving not winding!
Max.

 

another way is to wind the wire on a narrow strip of cardboard and pass that through the core, unwinding from the cardboard and onto the toroid.

Depending of the diameter of the toroid you could implement something like the "navette" used for "crochet" (both French expressions).

 

Depending of the diameter of the toroid you could implement something like the "navette" used for "crochet" (both French expressions).

The clever bit is putting a lot of wire into the smaller toroids.

A long thin bobbin made from stout plastic card - possibly trimmed from an old phone card if it isn't too brittle.

 

You guys do realize the OP was last heard from 6 months ago, right?

 

You guys do realize the OP was last heard from 6 months ago, right?

A new poster (#22) , so maybe he didn't catch it.
Max.

 

You guys do realize the OP was last heard from 6 months ago, right?

Maybe still winding...?

 

The way I c it, u r pushing urself in2 a corner really. Go thru all the previous posts..they mean what they say. The central beauty about the hole issue about a torroid (No pun intended here(;-0) is the amount of time trouble n effort taken to conceal all electromagnetic radiation and concentrate them on the winding's only so that the waste losses and the consequential losses&heat dissipation is bought dwn2the lowest. Nw clearly u seem2b looking4something thats really not there @all2start with in the 1st place rt? Be Judicious spin some winding wire on2some iron rod or so. or do take a tube choke apart. its pretty much the same (U may have to reduce the turns 7increase the gauge 4 lo voltage however) Happy building ok...Bye

 

May I remind you that the original poster has not been logged in since last December.
He is probably not watching now.

Oops. wayneh beat me to it.

 

The way I c it, u r pushing urself in2 a corner really. Go thru all the previous posts..they mean what they say. The central beauty about the hole issue about a torroid (No pun intended here(;-0) is the amount of time trouble n effort taken to conceal all electromagnetic radiation and concentrate them on the winding's only so that the waste losses and the consequential losses&heat dissipation is bought dwn2the lowest. Nw clearly u seem2b looking4something thats really not there @all2start with in the 1st place rt? Be Judicious spin some winding wire on2some iron rod or so. or do take a tube choke apart. its pretty much the same (U may have to reduce the turns 7increase the gauge 4 lo voltage however) Happy building ok...Bye

I guess if er t torroid (bter toroid) mul 4 u so3ti. Maybe soon.

But hole or whole? Txtin' s gud.all mst) no bo de ndrstnd a jck.

 

Don't you hate 'SMS' language (that's one right there) in forum posting, I generally ignore these type of posts.
Max.

 

I just skimmed through that, and no, I am not gonna read that.

prashanth 58 can´t you see that everyone here uses plain old legible english? Using http://forum.allaboutcircuits.com/member.php?u=73742text speak makes your post really hard to read, and most of members will not even bother to read such posts.

 

Don't worry too much. I pulled a similar stupid a few weeks ago when I tried to wrap 100 turns around a wire and use that to measure current in the wire. Dummy! That shape of coil doesn't cut across any lines of the magnetic force. You have to remind your self to think about the 90 degree directional shifts between current and magnetism.

Should'a used a torriod.

 

Should'a used a torriod.

For quick & dirty current transformers, some people wind on one half of those clamp on EMI ferrites - the best ones come in a snug nylon case that clips together, I salvage any I find on stuff I'm scrapping.