How to wind teflon wire around a ferrite rod?

[hobbes_lives]

Can anyone tell me how to wind teflon wire around a ferrite rod? I thought about gluing one end to the edge of the rod to hold it in place so I could start winding, but since nothing sticks to teflon, it won't work. The teflon wire is so slippery and does not hold it's form, so I dunno how to go about this. Any suggestions?

[bbsailor]

Can anyone tell me how to wind teflon wire around a ferrite rod? I thought about gluing one end to the edge of the rod to hold it in place so I could start winding, but since nothing sticks to teflon, it won't work. The teflon wire is so slippery and does not hold it's form, so I dunno how to go about this. Any suggestions?

I put rubber grommets over the ends of the ferrite rod to hold the first coil lead and a desoldering wick lead to ground the ferrite. Make it about the same inductance as your coil. Only soft ferrites will work for a PI probe.

bbsailor

[Tinkerer]

Soft Ferrite rods

I put rubber grommets over the ends of the ferrite rod to hold the first coil lead and a desoldering wick lead to ground the ferrite. Make it about the same inductance as your coil. Only soft ferrites will work for a PI probe.

bbsailor

I have a few ferrite rods in my parts box. How do I recognize the soft ones?

Tinkerer

[bbsailor]

I have a few ferrite rods in my parts box. How do I recognize the soft ones?

Tinkerer

Tinkerer,

Check out the following web link.
http://www.intl-magnetics.org/pdfs/SFG-98.pdf

Soft ferrites are not the type used to make rod antennas or the kind used in RF work. Soft ferrites are typically used in switching power supplies.

Soft ferrites focus the magnetic pulse when used in a probe but turn off very fast so as not to hold the magnetic field that would then respond like a target.

Also, do a general web search on "soft ferrite".

bbsailor

[hobbes_lives]

bbsailor,

I'd assume it would be safe to say that soft ferrite would not be detected by a PI, except perhaps at extremely low pulse delay settings? Other types of ferrite would likely be detectable though, I would think. I have not tested this to be true, it's just theoretical.

Also, I found something else that works well to help hold the teflon wire in place; waxed dental floss. I got the idea from the the guy that I buy wire from. He sometimes uses waxed string to tie off the loose end of the wire on the spool. (Other times he uses a rubber band.)

Anyway, I wrapped some of the floss around a rod to hold the ground strap in place, and then did a loop knot around the teflon wire at one end of the rod to hold the first tag end, similar to what you would do while tying a fishing fly. I then wrapped the teflon wire around the rod to form the coil, and finished it of at the other end in a similar manner with the floss. It seemed to work pretty well.

I figure out that the rods I have now are not good for a probe. I do have some good rods on the way, so I guess I'll get to try the technique again when they arrive.

[Tinkerer]

bbsailor,

I'd assume it would be safe to say that soft ferrite would not be detected by a PI, except perhaps at extremely low pulse delay settings? Other types of ferrite would likely be detectable though, I would think. I have not tested this to be true, it's just theoretical.

Also, I found something else that works well to help hold the teflon wire in place; waxed dental floss. I got the idea from the the guy that I buy wire from. He sometimes uses waxed string to tie off the loose end of the wire on the spool. (Other times he uses a rubber band.)

Anyway, I wrapped some of the floss around a rod to hold the ground strap in place, and then did a loop knot around the teflon wire at one end of the rod to hold the first tag end, similar to what you would do while tying a fishing fly. I then wrapped the teflon wire around the rod to form the coil, and finished it of at the other end in a similar manner with the floss. It seemed to work pretty well.

I figure out that the rods I have now are not good for a probe. I do have some good rods on the way, so I guess I'll get to try the technique again when they arrive.

The info I found from soft ferrite manufacturers says that hard ferrites are permanent magnets and soft ones are the ones that do not hold any magnetism.
The soft ones are for high frequency. among others they give as example a TV yoke. I got one of these and it gives a strong response on my IB PI. I expected that because it is highly permeable and therefore will distort the B field from the coil and thus cause a signal.

This does not mean that it can not be used for a probe. What matters is the delay to the first sample. a few turns of wire as a bucking coil on the upper end of the rod might help reduce the delay time. (I have not tried that yet.)

Tinkerer

[bbsailor]

The info I found from soft ferrite manufacturers says that hard ferrites are permanent magnets and soft ones are the ones that do not hold any magnetism.
The soft ones are for high frequency. among others they give as example a TV yoke. I got one of these and it gives a strong response on my IB PI. I expected that because it is highly permeable and therefore will distort the B field from the coil and thus cause a signal.

This does not mean that it can not be used for a probe. What matters is the delay to the first sample. a few turns of wire as a bucking coil on the upper end of the rod might help reduce the delay time. (I have not tried that yet.)

Tinkerer

Tinkerer,

See the 3C80 ferrite rod (2 inches long) on this web link. It works good for making PI probe.

http://www.surplussales.com/Inductor...s/FerRods.html

bbsailor

[hobbes_lives]

See the 3C80 ferrite rod (2 inches long) on this web link. It works good for making PI probe.

I have a dozen of those on the way. I think I read where you had recommended them before.

[Tinkerer]

Soft Ferrite

Tinkerer,

See the 3C80 ferrite rod (2 inches long) on this web link. It works good for making PI probe.

http://www.surplussales.com/Inductor...s/FerRods.html

bbsailor

bbsailor,
thanks for the link. Cool site.

Tinkerer

[bbsailor]

I have a dozen of those on the way. I think I read where you had recommended them before.

hobbes lives

Here are some experiments you can do with your dozen soft ferrite rods that you just ordered.

Epoxy two rods together to make a long rod about 4" long. This will extend the reach a little more than using a single rod.

Try using three rods in trianglar shape and wind the wire around all three.

Try using 7 rods, one in the center and six around that rod to make a fat rod bundle. Wind the wire around all of these rods.

Experiment with adding a ground to the rods by using a desoldering wick as the ground lead. Then try using Scotch 24 mesh as a shield around the coil but do not form a connected loop with this shield. Ground this shield to the desoldering wick rod ground lead.

A single rod gets me about 3" on a US nickel. Two rods glued in series will get you about an extra inch to about 4" on a US nickel.

As a beach hunter, this works well for me. I put the rod into a 0.5" ID plastic water pipe with nipples on both ends. I make my probe about 3 ft long so I can easily get inside the sand hole and find those elusive targets.

Generally you can put more inductance on a probe as the ferrite adds to the inductance value with less wire than on an air core coil. Try winding the probe to about 500 uh and try it with your PI at the lowest delay setting. You can always take off some turns to bring the probe back into the delay range of your PI delay circuit. The extra turns will make the probe a little more sensitive.

bbsailor