Litz Wire Coil

[James]

I tuned my 25 cm coil, now it is 303uh , 1.6 ohms. I also posted pic's of both of the PI units I do the test with.

[6666]

This is what I came up with to test this style of winding and it seems worth while.

15 turns 24 awg speaker wire on a 18cm core. It's wired(stacked) like post #38 by 6666. The top layer finish(outside) is connected to the bottom layer start(inside). Cable is RG-58 and the coil shielding is GC graphite spray. It worked very well on the tdi at 10uS sample delay. Tommorow I will scope the pre amp. Next I want to try some 18 awg.

333uH 2.0ohm with cable

Well done thanks for the pictures, glad it worked for you, the 18awg will get the R down.

[Altra]

This is what I came up with to test this style of winding and it seems worth while.

15 turns 24 awg speaker wire on a 18cm core. It's wired(stacked) like post #38 by 6666. The top layer finish(outside) is connected to the bottom layer start(inside). Cable is RG-58 and the coil shielding is GC graphite spray. It worked very well on the tdi at 10uS sample delay. Tommorow I will scope the pre amp. Next I want to try some 18 awg.

333uH 2.0ohm with cable

[James]

I must of push the wrong button, I use the Surf PI-1 and Overton-Moreland PI in the book. The circuits seems to perform the same. I triggered the scope on the receive and the second pulse is the delay pulse. I use the MG chemical electrostatic spray to coat the construction paper. I attach the ground lead to the paper with very sticky tape. I have the coil shields on the top and bottom. Best to all Jim

[Altra]

Hi James, which PI circuit are you using? Is the narrow pulse in the last photo the delay or sample period?

I built a nice speaker wire coil yesterday. Waiting for shielding to dry and will post photos tomorrow.

[James]

I did the test on the basket weave coil, I have added a electrostatic shield, I sprayed the coating on a couple of pieces of construction paper, top and bottom. The first picture tis the noise on the trailing edge of the detection pulse, the second picture of the coil with the shield, the third picture is the is the detection pulse with the timing pulse. Here is where I have a question, is the timing pulse in the correct spot ,in relation to the detect pulse. Thank you all. Best to all Jim

[James]

I checked the input and output of the NE5534 op-amp for ringing. I used the spiral wire speaker wire, basket weave, and the 2 hoop coils. I have a good lab scope (50 MHZ), dual trace. I could not find a problem. I now wonder is 390 ohms the optimum value? I did see some noise on the trailing end as the op-amp output went down to zero volts. the noise was very,small Well that concludes my test. Best to all Jim

[6666]

I finished winding my 1st spiral coil, it is 25.4 cm in diameter , 362uh, and 1.65 ohms. I will test it on the bench this week. Best to all Jim

looks good, what was the glue ?

[James]

!ST spiral coil

I finished winding my 1st spiral coil, it is 25.4 cm in diameter , 362uh, and 1.65 ohms. I will test it on the bench this week. Best to all Jim

[green]

If you want faster coil most important is to use good quality wire - teflon silver plated stranded wire, and then see what arrangement works best. but is not cheap. And most important, setting up the detector correctly for the targets you seek.

You are correct but the lead wire has probably 2 or 3 times the capacitance the coil I'm using so I don't think using different wire to wind the coil would make much difference. First delay 6usec, if wanting to sample at a shorter delay a different wire would. Might have to decrease inductance also.

[ionut_mtb]

No. When I started making coils I had a large spool of awg28 solid magnet wire I wanted to use if I could. Tried a bundle coil first, wanted to make something faster. Tried to wind a flat spiral without success. Flat basket looked about the same, flat spiral wrapped around tooth picks. That worked so that is what I've been using. Didn't think the 3DSS coil would be any faster(lead wires have more capacitance than the coil I was using) so I didn't try one, plus I would have to make a form. The flat basket requires a reusable form. Thinking about making a larger IB coil so thought I would try a flat spiral again after reading your reply. Worked good but it did take longer than 10 minutes wrapping the awg28 solid wire, my vision not the best.

If you want faster coil most important is to use good quality wire - teflon silver plated stranded wire, and then see what arrangement works best. but is not cheap. And most important, setting up the detector correctly for the targets you seek.

[green]

Thanks Green! Did you tried 3dss coil from chance pi thread?

No. When I started making coils I had a large spool of awg28 solid magnet wire I wanted to use if I could. Tried a bundle coil first, wanted to make something faster. Tried to wind a flat spiral without success. Flat basket looked about the same, flat spiral wrapped around tooth picks. That worked so that is what I've been using. Didn't think the 3DSS coil would be any faster(lead wires have more capacitance than the coil I was using) so I didn't try one, plus I would have to make a form. The flat basket requires a reusable form. Thinking about making a larger IB coil so thought I would try a flat spiral again after reading your reply. Worked good but it did take longer than 10 minutes wrapping the awg28 solid wire, my vision not the best.

[ionut_mtb]

Tried with double sided tape. Compared with flat basket I've been winding, no lead wires. Shielded top and bottom with graphite paint, 2mm craft foam spacer top and bottom. Flat basket slightly better, probably no difference with added lead wires.

James, Haven't tried with speaker wire, I would try with the 2 wires vertical, minimum radial width.

Thanks Green! Did you tried 3dss coil from chance pi thread?

[Chiv]

just reading this about speaker wire, I built a mono 40cm in dia with a half second winding on top of the first to use up the right length of cable to get my 350uh for my barra build. whell ended up with a real heavy coil (no need for the jim after swinging in around) but very fast response. ended up been 296uh at the coil and time I added my 2m of lead it come to 454uh, the good old air test with plenty of emi every where I'm getting 85cm on pliers and 35cm on 9crt ring. but its real heavy so was looking at building a litz coil to make a lighter one. one thing wether it the heaver wire or just the way it worked out , but the damping resister was a real low one(230ohms) compared to my mono bunch wrap 385uh using (670ohms). the other thing is that not much stuck to the pvc insulation while winding the coil hold for a bit then it let go after a few days, end up with glue gun to hold it together and then sandwich it together in 20lts bucket lids

[6666]

short the ends

Just to be clear on this
when I said short the ends, if you use figure 8 speaker wire cable
you will have two parallel wires from one end to the other
at each end of the cable twist the two wires together
so you will have a separate join at both ends of the cable,
this makes the coil one thick wire.

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