IDX-PRO+VDI

[roderico]

I forgot to mention that you also need to measure the resistance of TX and RX, TX 1-2R and RX 70-120R (I don't have the nominal values), so you might need to add e.g. 56R in series to RX...

[roderico]

Sorry I meant Rx, typing mistake.
Will do that tomorrow, i'm done working on it for today.

ok, RX also needs to be in the range of 4.6-4.9kHz or equivalently above your TX frequency, with your current values you have 5.8kHz, so if I'm not mistaken you will need 30-35nF, better if you can measure your RX resonance frequency...

[wallker]

Sorry I meant Rx, typing mistake.
Will do that tomorrow, i'm done working on it for today.

[roderico]

Hi RX should be in the range of 5mV not TX, and it should be connected to pin3 of U1, could you check the connections and upload an image of the oscilloscope as the pin3_u1.png with the null of 5mV (you might need to adjust ch2 scale)?

[wallker]

Hi Roderico,
yes, Ch1 is always Tx in my pics.
R7 is 39Ohm.
I have those documents, and I think I understood the main goal. But the thing is i can't get it to work while Rx is close to null point.
When Rx is in range of 5mV or so, i think i tried everything, changing value of Vr1 (geb pot) and Vr3, tried changing caps on Tx and Rx, slightly displacement of Rx/Tx but still it doesn't work...
It starts to detect only when I significantly shift the value of Rx to some ~2v pp (or ~0.7V RMS).
I'm out of ideas.

[roderico]

For better understanding i uploaded video showing how it behave, it works when is overcoupled or undercoupled, when close to null it doesn't.
Any help appreciated.
https://www.youtube.com/watch?v=vs5C...ature=youtu.be

when it is close to null you can adjust the phase there by a slightly displacement of RX/TX and/or TX/RX wire and of course you need to check the potentiometers, specially disc to hear something...

[roderico]

looking at image pin3_u1.png I guess channel 1 is TX and channel 2 RX, peak-to-peak of TX should be a little greater than 12V e.g. check the value of R7 and what is more important here is that pp of RX is ~ 4div x 500mV/div = 2V when it should be less than 10-20mV, you need to get a better nulling by moving TX and RX coils, there is a pdf somewhere in the forum where it explains step by step how to null and shield a dd coil, but I don't know exactly the link (maybe in the TGSL thread)...

[wallker]

For better understanding i uploaded video showing how it behave, it works when is overcoupled or undercoupled, when close to null it doesn't.
Any help appreciated.

https://www.youtube.com/watch?v=vs5CWr-9yEg&feature=youtu.be

[wallker]

Problem setting up coils

I just can't get correct phase shift between Rx and Tx while the Tx voltage is close to 0v.
Experimented with Tx and Rx cap values, but all i achieve is small difference in phase shift...

It works with poor depth while Tx voltage is almost 0.7V.
I understand that depth will increase when i lower the Tx voltage.
It's built in SMD according to among first schematic with 3 1n4148 diodes.
Running out of ideas.


DD Coil specs:
Tx: 592uH 34x0.6mm wire, currently cap 1uF CH1 of scope
Rx: 34.2mH 260x0.2mm wire, currently cap 22nF
Both unshielded currently, but i think that is not an issue, because it doesn't make to much noise...

I'll attach scope pics while it was working (Tx ~ 700mV).

[Koala]

Can't find phase relation data between TX and RX, for IDX.
I found for TGSL somewhere and it's 20 deg.
What should i aim for IDX?

Not 100% sure but believe the bluemax is around 83 deg and anywhere from 75-85 deg is fine for the concentric

its a long time since I worked on the IDX. I will double check later on



I never bothered measuring it. I use to set the ground balance to the centre and made sure ferrite was rejected around here.

[wallker]

Can't find phase relation data between TX and RX, for IDX.
I found for TGSL somewhere and it's 20 deg.
What should i aim for IDX?

[dbanner]

Thanks. I'll open new thread and will be posting Sprint layout of original bandido through-hole PCB from tesoro design. Maybe helpful to someone.

[Koala]

connected the tx and added or removed turns till it measured 10 kHz
then did the same with the rx coil connect to tx circuit till it measured 10.5 kHz

parameters the same as the TGS as far as I remember


the phase is critical than deepest null. As the discrimination doesn't start at zero and already knocks out small nails.

[Koala]

Koala, can you say which bandido, is it the Bandido 2 or original bandido?
Also can you give details of CC coil you made for it or where info on it can be found.
I've been working on reverse engineering the original bandido. I have layout of original PCB on Sprint file. Just need the coil details to complete the project files.

Bandido II in SMD Board from silverdog and info from here http://md4u.ru/viewtopic.php?f=25&t=2148&start=50

out preforms the IDX on most fields. If you run both machines at 0 discrimination both easy hit a half penny in my lawn at 10". However the discrimination is better. Turn discrimination up on both machines to where iron is mostly discriminated out and the IDX now fails on the coin in my lawn. The true static mode is very useful for determine the shape of targets. Were as the IDX is always winding down.

[dbanner]

I built a 5.75" concentric for my Bandido. Surprised just how deep it was on are hammered coins we have here in the UK. Depth is the same as larger coils up to our pre decimal coppers. Theres only so many corroded copper coins I can collect.


Best of all even coins on edge are within a 3" square making recovery very fast. You do pick up more .22 cases and shotgun pellets.

Koala, can you say which bandido, is it the Bandido 2 or original bandido?
Also can you give details of CC coil you made for it or where info on it can be found.
I've been working on reverse engineering the original bandido. I have layout of original PCB on Sprint file. Just need the coil details to complete the project files.