The Litz wire thing...

[GT Blocker]

Hey All;

I found a nice explanation of Litz wire while searching for Litz core coax (no, I haven't found any). Anyway I thought I would post it for those who are curious:

QUOTE:

"If the strands are insulated (Litz wire) and frequency is increased, eventually we reach a point where the conductor resistance increases and we are much worse off than we would be with braided or stranded wire. The upper limit point is generally around 1 MHz for Litz wire.
From Radio Engineering by Terman:



In reality, the real advantage of Litz wire is NOT reduced resistance per unit length for a given diameter. The advantage is less slope in resistance with frequency and reduced eddy current when the conductor is in a multi-layer coil or transformer. The individual strands are like laminations in a transformer core, and below a certain frequency they greatly reduce eddy currents by decreasing the "short circuit" path distance for magnetic flux induced currents that are not in the normal current flow direction."

END QUOTE

I found this explanation interesting and thought I should pass it on.

GTB

[sido]

Interesting reading.....

Was about to start a new thread about this Litz wire topic.... Have managed to wire up me own litz wire type (38 strand) mono coil....First attempt though, but suprizing results.

I used recycled copper wire from Microwave oven fan motors and seams to work well. Do not know the guage size of wire but it is insulated and thin. Used my side boundary fence to support each individual strands, then twisted the whole bunch for a 38 strand Litz type of cable, if thats what its called.

Managed to reach a Inductance of 160uH, 6 inch round coil....mis-calculated the overall initial required length....A bit short of my intended target of 300uH, but achieved a Coil Resistance of 0.3 Ohm or there abouts.
It is possible i may have not soldered all the individual strands, so my Inductance reading could be better though.

The average person can make there own as i have attempted first time round. Have photo's of the process if people are interested for me to post to experiment for yourself.

Cheers Sid

[6666]

Have photo's of the process if people are interested for me to post to experiment for yourself.

Viewers could be interested in your photo's.

[sido]

Viewers could be interested in your photo's.

?? is Could be interested, but seems otherwise.
Anyway, i have no idea what real Litz wire looks like as i have never had any or a disected M.L Coil to compare.
Below is what i made into a 38 strand twisted wire. Not sure if it could be called Litz wire though??

Cheers Sid

[Davor]

If each wire is enamelled, in a somewhat broader definition this is a Litz. In a bit more narrow view, a Litz should be a braid that would interleave the wires, not just twist. For our purposes the most important feature is a cross section of each wire, as it is responsible for eddy current generation, so braided or twisted comes just about the same.

[sido]

If each wire is enamelled, in a somewhat broader definition this is a Litz. In a bit more narrow view, a Litz should be a braid that would interleave the wires, not just twist. For our purposes the most important feature is a cross section of each wire, as it is responsible for eddy current generation, so braided or twisted comes just about the same.

Hi Davor, each wire is enamelled.
The original wire is from 2 desected Microwave oven fan motors, see pic below.

Supprised at how low Coil Resistance i am getting for a 6 inch, 160uh coil.

BTW, Microwave ovens have that lovely large Capacitor inside them. Have desected one and removed the intercapacitive Mylar sheilding material. If anyone is thinking of doing the same, wear surgical gloves as the oil filled Capacitor is very messy and smelly, but the Mylar material can be stripped, cleaned and possibly used for shielding our coils. Have meters of this material from one capacitor to work with once cleaned of oil contaminants.

Microwaves also have a large fast switching heavy duty diode that may be used in PI detectors.

All this information above is in experimental stage, but so far i like domestic Microwaves, other than heating food.....and the good part is they are given out free. So if you see one lying out in the street gutter, consider the material available to us experimenters of Metal Detectors. Another positive, sell the rest as scrap metal (large mains copper wire transformer) and make another 5 dollars or so for your effort

I like the outcome of the homemade Litz copper wire so far. It is time consuming to make. Wish i had only made it a bit longer for a Inductance of 300uH to compare with standard copper enamell coil to see if its worth all the trouble to make it.

Cheers Sid

[sido]

Hi 6666, I will post the rest of the copper wire i made in detailed photos for others and yourself to experiment with and hopefully make a functional coil with it and the mylar i stripped from the Capacitor and see what results can be obtained, apart from generic coil building principles that most people use otherwise.

Can see this turning into a really fast low sampling coil

Cheers Sid

[multieagle]

Interesting. Look forward to more info. I've seen the odd microwave kicking around, but never thought about recycling parts to metal detectors.

[Carl-NC]

Sounds like a potential business, converting microwave ovens into metal detectors.

[GT Blocker]

Sooo... Litz wire coax,

My search for Litz wire cored coax is over. It has to be easier to build the crap than to find it.

I have a few questions before I order some Litz for a Litz cored coax build.

Question 1: What size seems reasonable for the inner core?
Question 2: Is Litz wire needed for the outer braid as well? I suspect that it is.

I'm going to try threading mono fishing line through the center of a core conductor Litz wire (to prevent collapse of the core later). The hope is that the mono fishing line prevents distortion of the Litz cross-section profile under pressure. After covering that with heat shrink (the afore mentioned pressure), the assembly will be pulled through an outer layer of Litz and again covered in heat shrink. Dual cores in the case of dual coils, of course.

Whether or not teflon wrapping between layers would help is another question to ponder (or test).

Your thoughts, all?

GTB

[Davor]

Tinned braid should work fairly close to litz regarding eddy currents, and if you seek just a little you'll fing RG58 with tinned core.

[GT Blocker]

Thanks for the reply, Davor,

I still want to go for a pure Litz solution for my app. A 'small' difference is only relevant to the scale of the desired result. And tinned braid will then leave me with a 'fairly close to Litz' cable result. That is not my goal.

That said, NO tinned woven wire is going to preform as well as individually insulated woven strands in the sub-8uSec sample zone. Re-read the precise deffinition of Litz wire in my start to this thread. If tinned wire was 'close enough' no one would need Litz wire to start with, in radio nor anywhere else for that matter.

Just my thoughts...

GTB

[Davor]

Yes, I think I understand. You must see what the best of the best can do before you can settle for something less superior. Most probably I'd do the same.

[multieagle]

Found this for sale on eBay. Would it be of any use for metal detector coil? It is Xizi Litz wire ( compared to Kerrigan-Lewis brand Litz wire). 175/46 Type II, 175 strands of individually insulated AWG #46 (0,04 mm) wires. Double layer nylon for the outside insulation. Outer di 0.094 mm. Insulation voltage 500V.

Brand K-L Xizi
Type 160/46 175/46
Coil diameter (D) 3.5” 3.5”
Coil length (L) 1.5” 1.5”

D/L 2.33 2.33 ( the best D/L should be 2.46 )
Turns 49 49
inductance (uH) 301 300

Q factor ( 460–1500 KHz )

505 KHz 525 555
605 KHz 594 632
705 KHz 652 696
805 KHz 702 751
905 KHz 731 786
1005 KHz 748 804
1105 KHz 855 838
1205 KHz 760 820
1305 KHz 755 814
1405 KHz 741 799
1505 KHz 720 784

[Skippy]

This UK wire supplier has a decent range of silk-covered Litz wire in stock. They also state they can custom manufacture it to your requirements. They also sell multi-strand enamelled wire, non-Litz I assume. http://www.wires.co.uk/acatalog/litzwire.html and http://www.wires.co.uk/acatalog/st_wire.html