first selfmade coil

[Levin]

Hello
Im buliding a voodo metall detector. I want to build the coil myself. The coil I want build ist the in georges book used 9“ diameter concendic coil. But I´d never build a so complicated coil myself. Please could some eplain me how I do this.
thanks Levin

[MartinB]

Lots of information on the forum, but read this document several times. You will find it useful.

[MartinB]

Some more good information in these two documents

[MartinB]

Follow this link for essential information to help you design your coil. I would suggest that you start experimenting with a mono coil. You don't need to make a housing at this stage. Just tape your coil to a stiff piece of card or plastic which you can glue of tape to a wooden dowel or a piece of plastic pipe if you wish. Test your coil away from sources of EMI such as the TV and other electrical appliances and large metallic objects. Outside in the garden is probably best. Building a coil can be frustrating and time consuming unless you are lucky and get it right first time. Once you have perfected a mono coil, you can then move on to more involved designs. Good luck. Coil Calculator - Geotech Forums (geotech1.com)

[Levin]

Thank you very mutch for helping!

[MartinB]

You will need a LCR test meter to measure the inductance of your coils. There are lots of them out there, but it all depends on how much you wish to spend. The LCR T4 M328 Multi Component LCR Tester with Graphical Interface is inexpensive and will serve you well. You can always upgrade later.

[MartinB]

Almost forgot, you will also need and oscilloscope.

[Levin]

hello
thanks for helping, but it would be very nice if you can me say how i can build exactly the in georges book used '9“ diameter concendic coil'. I want to use these coil to test my detector electronic and how you surely know, the voodo detector is a hybrid detector between, PI and VLF. I a beginner, but how is a mono coil with a vlf detector supposed to work. If the acceptance , that a vlf detector doesn't work with a mono coil False, it would be very nice if somebody could tell me that. the second cause, why I want build these coil is, because the coil is in the book with these detector tested and the most oscilloscope graphs are made with this coil.
thanks Levin; sorry for my bad english

[Qiaozhi]

hello
thanks for helping, but it would be very nice if you can me say how i can build exactly the in georges book used '9“ diameter concendic coil'. I want to use these coil to test my detector electronic and how you surely know, the voodo detector is a hybrid detector between, PI and VLF. I a beginner, but how is a mono coil with a vlf detector supposed to work. If the acceptance , that a vlf detector doesn't work with a mono coil False, it would be very nice if somebody could tell me that. the second cause, why I want build these coil is, because the coil is in the book with these detector tested and the most oscilloscope graphs are made with this coil.
thanks Levin; sorry for my bad english

The 9" diameter coil in the book is a Troy coil
If you want to build one like it, then please look at the attached documents. With the assistance of the Coil Calculator you should be able to figure it out. If not, then I suggest you buy a ready-made commercial coil.

[Levin]

thank you for the dokuments they are great

[Levin]

Hello
I calculated a coil, but i don´t know if it will work. It would very nice if somebody could control my calculations.
the tx(+bx) coil have a inductance of 1.18 mH and is wound with 0.3 mm wire.
the rx coil is wound with 0.2 wire and have a inductance of 6.96 mH

In the end I have a few questions:
do I need any capicators in this coil, if yes, where they are needed?
could you null a coil, by connecting an AC voltage source to tx, measuring the voltage applied to rx, and then continuing to wind bx until no voltage is applied to rx?

thanks Levin

[Levin]

sorry correct , not control

[Levin]

if noboby want correcty my calculations its would be so nice, id you could see my if I need any capicators
thanks alevin

[Carl-NC]

Offhand, it looks reasonable. I might add 1 or 2 extra BX turns just to be safe, then peel them off if not needed. Yes, you can wind the BX coil while watching the RX signal.
If this coil is for Voodoo, then the RX coil needs a cap. The book explains what value. You can put it in the coil or in the circuit.

[Levin]

thank you
itś right so?