IDX-PRO+VDI

[dfbowers]

Thanks for reply Don. Main difference between DD and concetric is that in DD right phase shift is 90 degree and concentric has 180 degree, i now it because i saw orginal bluemax pluged in to osciloscop.
Could You please show me scheme with values of all parts your Colpitts oscilator?
Right resonance freq. should be 4900 or 4600Hz?
Regards
Rafal

Rafal, I made my observation of phase shift for concentric by doing exactly what you have done. I was using a Blue Max 600 coil and observed a 90 degree phase shift. I will double check my results sometime today.

Also, others have posted 4900 Hz for RX, but in doing the calculations, 33nF & 36mH in parallel resonates at 4620 Hz so that was my target. That gave me the correct adjustment range for the GB and DISC.

Don

[reiv]

for TGSL, Eldorado etc..., this thread concern IDX.

[hugo]

it seemed that for the DD phase shift should be 20 °, unless it is only for TGSL. you can confirm my words thank you.

Hi ashefr10,

You're right, 20° (0°+20°) for DD coil and 200° (180°+20°) for concentric coil.

[ashefr10]

it seemed that for the DD phase shift should be 20 °, unless it is only for TGSL. you can confirm my words thank you.

[reiv]

I have successfully built 2 DD coils for IDX so far. I can tell you what I did and maybe the same can be applied to a concentric.
If you can achieve 6.5 kHz with the TX windings then you are 1/2 way there.

For the RX section, tune the LC resonance to 4.9KHz (I tuned mine to 4.6kHz) . There are many ways to to it. I tuned mine by building a simple Colpitts oscillator and adjusted the windings on the Rx coil.
Now while nulling, your RX coil should give a 90 degree phase lag from the TX signal, an INCREASE in RX amplitude for ferrous and a phase shift to the RIGHT for non ferrous.
With my DD coil, things are not EXACTLY as described above but still functions correctly.

Again, here is the coil data:TX tank circuit
Resonance frequency 6590 Hz max
Capacitance 1uF min, 1.2 uF max (3 caps in parallel)
Inductance 540 uH nominal
Resistance 1.6 ohm max
RX tank circuit
Resonance freq. 4900 Hz max
Capacitance 30 nF min, 36 uF max (3 caps in parallel)
Inductance 36 mH nominal
Resistance 70 ohm min, 120 ohm max
Hope this helps..
Don

Thanks for reply Don. Main difference between DD and concetric is that in DD right phase shift is 90 degree and concentric has 180 degree, i now it because i saw orginal bluemax pluged in to osciloscop.
Could You please show me scheme with values of all parts your Colpitts oscilator?
Right resonance freq. should be 4900 or 4600Hz?
Regards
Rafal

[Firebox]

Thanks for the info @eduardo! then my 1N4148 Diode is in the right way

@eduardo, is it possible to give the IDX Pro an Iron Discrimintator like tesoro one? The Disc on IDX works well, but sometimes on Iron trash field the idx is very fidgety. So the user means the detector runs with too much sensitivity ...

regards

Firebox

[eduardo1979]

Hi DAVOR,

i have my kit from silverdog. It has a Schematic printed on PCB, but i belive the position of the zener diode is wrong, it must show in the other way...

So what position is right?

regards

Firebox

If you are using a 1N4148 diode, the position marked on the PCB is correct. If you're using a 2V7 Zener diode, diode position has to be invested.

[Firebox]

Check the diode in comparator circuitry - it is supposed to be a zener

Hi DAVOR,

i have my kit from silverdog. It has a Schematic printed on PCB, but i belive the position of the zener diode is wrong, it must show in the other way...

So what position is right?

regards

Firebox

[Davor]

The discriminator does not close properly.....

Check the diode in comparator circuitry - it is supposed to be a zener

[dfbowers]

I have successfully built 2 DD coils for IDX so far. I can tell you what I did and maybe the same can be applied to a concentric.
If you can achieve 6.5 kHz with the TX windings then you are 1/2 way there.

For the RX section, tune the LC resonance to 4.9KHz (I tuned mine to 4.6kHz) . There are many ways to to it. I tuned mine by building a simple Colpitts oscillator and adjusted the windings on the Rx coil.
Now while nulling, your RX coil should give a 90 degree phase lag from the TX signal, an INCREASE in RX amplitude for ferrous and a phase shift to the RIGHT for non ferrous.
With my DD coil, things are not EXACTLY as described above but still functions correctly.

Again, here is the coil data:TX tank circuit
Resonance frequency 6590 Hz max
Capacitance 1uF min, 1.2 uF max (3 caps in parallel)
Inductance 540 uH nominal
Resistance 1.6 ohm max
RX tank circuit
Resonance freq. 4900 Hz max
Capacitance 30 nF min, 36 uF max (3 caps in parallel)
Inductance 36 mH nominal
Resistance 70 ohm min, 120 ohm max
Hope this helps..
Don

[Firebox]

is there a possibility to close the discriminator something better? or is it possibility to install a silencer in the circuit of the idx, so that the iron scratches will be hidden?
On an iron trash field IDX is my very restless. The discriminator does not close properly.....

[ashefr10]

hello, are what someone could do a tutorial full of pro idx as was done for the golden sword or bandido. thank you

[reiv]

Ivconic
I have one question to you if you don`t mind about coil tunning on IDX or Whites classic family. How to chose correct capacity to Rx coil? You have wrote on 2 page of this subject like this:

"RX cap can be critical to tune up closely.
Generally it is close to 0.033 (33nF). But if you put just 33nF that will not do.
Better put 22nF + .... in parallel , close to 33nF..
Be patient and give it chance, try to tune it as closest as possible.
Once tuned - hell of detector !
Deepest from all hand made presented here on Geotech forums.. no competition at all!"

but i don`t understand this. I have build completely IDX with concentric coil but i think I was wrong on tunning coil, soe i want build another one coil. I was tunning it like this: First I connect Tx and correction to PCB and match numbers of winding correction with 1uF cap to get 6.5kHz, then i match numbers of turns in correction coil to see if it will be zeroing. Rx coil was winds witch winding data and 33nF cap connect. Rechecked frequency of Tx and must to add cappacity (1uF+39nF) to get 6.5kHz, after that i`m starting to zeroin with proper phase shift 180degres for concetric and watch to Vpp on 6pin NE5534, ok I saw that I can`t get about 150mV only higher soe I had to add cap to Rx +4.7n+1.5n. And finally i get Tx with 1uF+39nF cap and Rx with 33nF+4.7nF+1.5nF cap.
Is this method is ok? I think that in Rx cappacity is to much, but i want to reasure.
If it is wrong please tell me anybody step by step how to proper tuning coil in this machine.

Regards
Rafal

[Ropcsika]

I changed U3 to lmc6484 to lf347n. It so sensible. I changed the r25 too a trimmer. So I can adjust for more sensibility. A hungarian "20 forint" http://www.hamispenzek.hu/hamis_fempenzek_forint/20%20Forint%201994%20hamis%20hamisitvany.jpg comes from 40-45 cm. :-) Waohhhhh! It is fantastic... But! The of-key sign frequenter. I set up down the sensibility.

Very, very good..

[szucs_g]

I changed U3 to lmc6484 to lf347n. It so sensible. I changed the r25 too a trimmer. So I can adjust for more sensibility. A hungarian "20 forint" http://www.hamispenzek.hu/hamis_fempenzek_forint/20%20Forint%201994%20hamis%20hamisitvany.jpg comes from 40-45 cm. :-) Waohhhhh! It is fantastic... But! The of-key sign frequenter. I set up down the sensibility.