My IB

[Gervm]

Here is inside view of really devise

[Geo]

Congratulation.
Good work

[Gervm]

Thank you

[Esteban]

Very nice. Go ahead!

[detectoman]

my congratulations gervm, thanks very much, for post, for my these is very dificultous jaja, i love little circuits, mua mua, these is pretty built

[Patrick]

P1 really consist of 2 resistors connected sequentially - they tune phase. One does it roughly anoter does it smoothly or you can use one good many turns resistor as shown in circuit. R5 - 470kom. At the table it can "find" coin at 25-40 santimeters. It depends of diametre of coin and quality of unit and its head. Working requency is 8 kHz.

Thanks Gervm.
I have other issues :
What use for R27 ?
Why R22/C10 and R26/C15 ?
There not overlap between C17/C18 and C31/C32 ?

[Gervm]

R27 was only in first unit for tuning threshold. You may delete R27 and connect this input of comparator to virtual earth. So did I.

[Gervm]

These capasitors are for filtering power surply. Indeed the number of filtering capasitors more than you see on circuit espesially ceramic but it is not principial...

[dfbowers]

IB detector

Hello, Gervm.

Very nice. The circuit has many similarities to Volksturm Sm but looks like you have added a nice feature to adjust phasing.

I have built Volkstrum Sm and it too is a very sensitive, but has fixed discrimination and does not appear to cancel ground to well, unless phasing is adjusted, but then it operates in the all metal mode.

With your design, how do you deal with ground cancelation? Do you use a "figure 8" coil or some other geometry that cancels ground?

Thanks.
Don

[mesy64]

hi dear
please give info about coils
best wish

[detectoman]

esta chido el aparato verm, se ve que le metiste mucha buena ciencia, muy acertada la eleccion de componentes

hello verm, sems is cool the aparatus, look what you put in these very much science, my congratulations, too very good components
what whit estabilitym what whit alkaline soils? what whit grass? thanks in advance

[Gervm]

I use omega or 4B-coil. The detector does not see grass. During tuning the "fase" I reject ground soil effects. It has fixed discrimination. I use two search heads. The first tuned on all metals and the second one tuned with discrimination and does not see ferros metals. TX coil has diameter 39 sm and consist of 71 wings of 0,4mm wire (~ 6,8mH), RX coil has 140 wings of 0,23mm wire (~11,5mH). The diamiter of RX coil is about 20sm. TX and RX coils have shields maden from aluminium foil. Both have gaps in shields. I advise to experiment with correlation of diameters of TX and RX coils.

[dfbowers]

Gervm
Thank you for your response.

When using your Omega coil with phase set for not seeing ferrous metals, does the detector respond to ground as well?

Don

[detectoman]

thanks gervm, those details of omega are very important for me, best whises

[dfbowers]

Volksturm Sm + GEB

I added a GEB mod to Volkstrum Sm. www.md4u.ru I also kluged in the mod to the PCB. Works nicely! This is single channel only though (all metal) but very sensitive and stable. Good project for $20.00 in parts!!!

I know that other have added a GEB mod, but this one allows for a full 180 degrees of phase adjustment with near unity gain on the TL061 stage.

Coils are as follows:
Tx 75T .25mm wire - 2709mH (untuned square wave)
Rx 105T .25mm wire - 5128mH ( Tuned & shielded)
dd = 25cm diameter - used basically the same former as Tarsos.

Results:
U.S. Dime - 25cm
Gold band - 35cm

Thanks KT315 for good design!