3 feet depth metal detector

		Quote:			Posted by belief
	Hi all  Is there anybody to know that how calculate the  Formula of making coil ?  Thanks .  Iman Boroumand.

YES!

If it is a tubular coil you need to measure length and diameter and number of turns (I tell you this one first, so the next one makes sense,) the formula is: radius (R) squared X number of turns (T) squared divided by 9 X radius (R) plus 10 X coil length (L):  [R x R] x [T x T] / [9 x R] + [10 x L]

That formula is for single layer coils, for multiple layers you need the average diameter thus the average radius. Always in inches, for this formula.

The measurements MUST be in inches, for this formula... I have NEVER seen a metric formula.

OK for scramble wound or flat pancake coil: the average diameter has to be found, also. To find the average radius.... for radius = R; turns = T and length = L: add the inside diameter to the outside diameter and divide by 4.... this gives average radius only. So the same formula applies, below:

   [R X R] X [T X T] / [9 X R] + [10 X L]

- but you MUST use inches.

If you have a coil with thick insulation, so it is 1/8 inch, thick, per turn, then a coil 12 inches outside, with 24 turns (24 x 0.125 = 3 inches on both sides) is 6 inches inside so the average diameter is 6 + 12 / 4 or 4.5 inches average radius.  Plug that into the formula:

   [4.5 x 4.5] x [24 x 24] / 9 x 4.5 and length, in this case = zero because it is flat.... the answer is 288 uHenries.

So, if you want a coil for a pulse inductance detector that needs to be 16 ohms at the frequency of operation, you have to find the needed inductance: for 10 kHz ; 16/ 2pi / frequency in mHz so -

   16 / .01 / 6.283 = 254.65 uHy           2pi = 6.283

The coil, above, is uHy x F x 2pi = 18.095 ohms

I hope you can understand this jumbled presentation, but finding coil values is really simple, but you really need a meter to measure small inductances. An LC bridge is really simple. With a 10 kHz bridge, you can measure down to about 150 uHy, with good accuracy, but for capacitors you need a higher frequency than 10 kHz because you can only measure to about 0.01 ufd, accurately. 100kHz would be good to nearly 10pf and maybe 300pf.

A simple LC bridge is and audible device so for higher frequencies, you need some diodes and a sensitive meter. Plus a couple different frequencies to use.

These formulae do NOT apply to square loops.  I would guess, if you take the square loop total dimension (measure around outside and measure around inside, average these and then use pi) and divide by 3.1415 (this is pi,) you would get approximate diameter, as if it were round. Also, for a tube, holding the turns, you can use the tube diameter for the coil length, in the formula..... that is, if it is 0.75 inch inside diameter, use no more than 0.75 inch for the length L. Of course if you only have 10 turns, do not use the full 0.75 inch.

Either guess at it or measure it.

goldigger


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That was some funny answers   Yeah, the axe or hatchet was good inventions.

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Dear eugene52
I am delighted this forum interesting.
Will not for years and I am participating in more than a forum, and I worked hard to search for a dive into the depths to one meter or two but to no avail .. got plans for the funds is more than one source, but not everyone .. encouraged by it,  I can not find the schema Alkwylat and so dear .. I'm in a spiral and confusion .. Can you help me in building this device a good scheme, tested, and up to this depth and you have my full appreciation of your help.

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Dear Eugene52 ... I am very interested in building a device that connects to a depth of at least two meters
Of course I want it to the land  and very accurate.. and provide whith -screen to measure the depth, if possible...im searching of larg cash in the ground not coins...thats why ineed something spesial..for this thing..im confused by snifer 71 and delta or 2box...ineed your advice....pls.
            I have suffered a lot and I'm looking forwerd to see it soon .. have my full appreciation and respect

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		Quote:			Posted by bajes2008
	Dear Eugene52 ... I am very interested in building a device that connects to a depth of at least two meters Of course I want it to the land  and very accurate.. and provide whith -screen to measure the depth, if possible...im searching of larg cash in the ground not coins...thats why ineed something spesial..for this thing..im confused by snifer 71 and delta or 2box...ineed your advice....pls.             I have suffered a lot and I'm looking forwerd to see it soon .. have my full appreciation and respect

Hello Bajes2008 . Our 3 different PI projects that we have on our forum are very close in design all have around the same Maximum depth depending on the size of search coil you decide to build . The frequencies of the Delta and the DBP are slightly different but NONE of our projects have a LCD readout YET ,  just a analog panel meter battery check and signal strength . There is no depth read out or Target ID on our PI projects !!
Right now I am working on finishing the 3 projects for Final Zip packages . For the fancy options you will need to build a DSP or PIC and or Atmel controlled PI circuit , we do not have that on this Forum right now . If you are searching for a "large cache target" then 2 meters is amost possible with our projects ..... The LCD Delta Pulse is on a foreign language forum . There are some Russian Pic microcontroller-PI projects also on foreign language forums and last there are some atmel PI cicuits on a German Detektor forum . Other Thunting.com moderators or PI builders here on this forum may have better answers than I do , so stay on our forum keep checking back , and sorry to hear of your suffering due to waiting for answers . Please be patient !! I have been very busy this last week working on this forum , trying to answer questions and make the "TECH TALK" area better .

Regards........Eugene

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