Litz Wire Coil

[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.

[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

[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]

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

[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

[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 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]

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

[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.

[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.

[James]

I have another question for the board, where do you folks acquire the coil housings ? I have use tupper ware lids for the top and bottom, but they don't really hold up in service. Thank you for any information. Best to all Jim

[6666]

housings have always been a problem to find one that fits the coil you are using, there are some available from Don, and ebay and George,
or the latest trick is use a 3d printer,
if you fit a skid plate they will last longer

[Altra]

I have another question for the board, where do you folks acquire the coil housings ? I have use tupper ware lids for the top and bottom, but they don't really hold up in service. Thank you for any information. Best to all Jim

James

Here is Don's web page, he sells housings at a reasonable price. The coil I posted above is just for the bench. I may order some 10.5" clam shell housings and adjust everything up to fit.

https://sites.google.com/site/dbcoilshells/home

[James]

Thank you for the info on the coil shells. Best to all Jim

[Sean_Goddard]

I thought this old nugget had been put to bed a LONG time ago. I previously described a way to make a VERY FAST coil using many thin wires wound in opposite directions to make a very low self inductive and capacitive coil. I was getting samples down to 5us with my version. I am intrigued as to why people are still messing with this when a 5us coil is available. If you can get it lower than that then crack on, but I've not seen anyone come close yet