IDX-PRO+VDI

[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.

[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.

[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?

[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]

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).

[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=vs5C...ature=youtu.be

[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)...

[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...

[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]

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]

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

[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...

[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...

[wallker]

Hi Roderico, thanks for trying to help.
I found the problem, pin8 (balance pin) of u1 was in short with pin2 u1, under the chip side.
This is way it worked when the Rx coil had some higher voltage.
Now i can tweak caps while im close to null, to get better detection and good working disc...
Only thing that concerns me now is Tx amplitude, you said it should go up, and i read somewhere in this thread that it should go up to 16 v pp.
Is it possible that smd is making a problem here? All of my resistors are 1/8w, and Q1 is BC807-40, Q2 is BC817-40 which is ok, i think? Resistance of Tx at coil plug(with cable resistance) is 2 Ohms.
R7 is 39 Ohm also...

[roderico]

I'm glad you found the problem, you might have some other shorts, but also check the output of your voltage regulator, there is also a mod somewhere in this thread that connects the battery directly to R8 instead of the output of the regulator and give more than 16V you could give it a try if you cannot find the problem with your pcb...