homemade coil

[Unregistered]

Has someone ever build a homemade coil for a production MD?
My ACE250, for example, has a little 6,5x9 coil, and a larger one will be to test.
But my first dilemma is: how is the wiring is in the four-wire socket?
and: is any circuitry in the coil or winding only?

I think a homemade larger coil can be a nice alternative to buy a new one that costs almost as a new metaldetector.
Has anyone some experience on this?

[Richard Greswell]

home made coils.

You can make coils at home. It is easy and straight forwards provided you are keen. Vlf coils have two coils inside the plate that means 4 wires. O.K. ? 1-2-3-4 and a 5th that would be a shield. This shield should not cover the entire loop. It should almost. It can be made of thin al. foil.
Some coils have three wires in but really they are four because two are joined. in other words the two coils are conected in series and three cables are presented to the electronic board.
The number of turns and diameters and wire diameter really is not that critical; normaly for 9 inch diameter coils the coils are of about 80 turns each on .3 mill wire. What is critical is that the coils should be conected to the machine and presented and located in such a way that you can silent the signal just about, maybe leave a threshold sound on them. This is arcieved by moving one of the coils into the other. The these coils should be "poted" in exact place with liquid poliester . They should become rigid. This is the way you make any coil you want. THere are infinete sizes and position but hey should always be balanced so that the signal be just silenced. You can also silence a set of coils by sticking into one of them a condencer to increase the capacitance. A good capacitance meter can be useful to obtain equal coil capacitances.... With this info you can become a profesional coil maker. I became one. Making coils bigger has never been that a good idea. What you can experiment with is to make a same size one but much better and much more responsive. Don´t be afraid of making them heavy. TO make good coils these should use a rather thick wiring which makes them heavy all right and the windings must be very compact and potted with resin. If they dont´t have resin then detection becomes poor.In the internet there are charts of coils with resistance values, capacitance, turns, positions etc..etc.. look for them to help your self
Cheers Richard.

[Unregistered]

Richard, i thank you for your nice answer.
Surely the homemade coils need some tests to be done.
I want to start, and the first thing is reach some insulated copper wire bobbin.

Many tanks again and i will make you know any progress.