IDX-PRO+VDI

[karakus]

vdı hex

helo holyuser no achtung minen hex tenks [email protected]

[karakus]

helo holyuser writes of achtung minen code Thank you karakus_70@hot...

[dfbowers]

I'm looking for some data on winding a DD coil for IDX. I basically have the specs on wire size, resonant frequencies, tuning caps, inductances, etc. for concentric.

What I am looking for is addition information from others on how the series resistors are used, particularly the 51 OHM resistor in series with the RX coil. It is suggested in the following post that other resistors are used as a voltage divider to aid in the nulling process. These resistors do not appear in any schematics that I have.

http://www.geotech1.com/forums/showthread.php?t=17949

Thanks!
Don

[Altra]

Hi Don,

The series resistor is to fine adjust the RX phase. It also raises the Q of the coil. Nothing to do with nulling. Which is mechanical. White's did put a high mega ohm resistor between the TX and RX windings which I never understood. I guessed it was for static dissipation? Maybe nulling.

Make your windings matching the inductance then add a resistor in series with the RX to equal the original total of 111 ohms.

regards

[dfbowers]

IDX MOD

I finished the IDX kit from Silverdog, minus the VDI module as I do not plan on using it.

Everything works fine, but I was looking for more. With the stock 9.5 coil from my XLT, I could only detect rings and coins to about 25cm. Then I realized that the offset on pins 1 & 14 of U3 was a mV or 2 below ground potential. The signal just has too far to go to trigger the inputs on U4!

I am using the LM324 from the supplied parts from silverdog instead of an LF347. In looking at the specs for the LF347 is can have an offset as high as 5mV!!. With no way to adjust the offset of quad op-amps, I just implemented the same fix as I used with the TGSL. It allows you to adjust the reference voltage slightly negative so the LM393 can trigger earlier. This brings the detection range to 40CM for coins and rings,, the ragged edge of the detection range for the stock 9.5 concentric coil.

This may be a band-aid fix and may be a symptom of another problem, but I'm not sure what. I just figured out a fix..

Don

[Mullihaka]

Hi dfbowers,

What's the target in nulling the coils for this detector: certain phase shift at some point or just minimun voltage at RX input?

I have the PCB fully populated but haven't started the coil winding yet.

All hints appreciated.

[dfbowers]

Hi dfbowers,

What's the target in nulling the coils for this detector: certain phase shift at some point or just minimun voltage at RX input?

I have the PCB fully populated but haven't started the coil winding yet.

All hints appreciated.

I am just getting ready to wind a pair of DD coils so I have not gotten that far yet. I just attached a factory 9.5" coil to test the assembled circuit board. It does not appear as though the factory coil has a deep null. I will have to take note on how it is nulled but I did see that the RX signal is shifted by about 90 degrees from the TX signal.

Don

[joop]

With no way to adjust the offset of quad op-amps, I just implemented the same fix as I used with the TGSL.

Interesting stuff. Can you please point me to the fix for the TGSL, I have just finished building it.

Thanks!

[6666]

Hi Don
you say the stock 9.5 coil from your XLT works good with this project
are there any numbers or markings on the coil so it can be identified ?
thanks

[dfbowers]

Hi Don
you say the stock 9.5 coil from your XLT works good with this project
are there any numbers or markings on the coil so it can be identified ?
thanks

I have an older Whites Spectrum XLT. The part number on the coil is 624-0329. Plus any of the 6.59 KHz coils listed for the XLT on this pages should work:

Also works on 6000XL, QXT, IDX, ID CLIII and 5900
http://whiteselectronics.com/index.p...rticle&id=1811

[6666]

Thanks Don thats very good information to have for this project
cheers

[dfbowers]

Interesting stuff. Can you please point me to the fix for the TGSL, I have just finished building it.

Thanks!

This just allows you to adjust sensitivity as crazy as you want.


http://www.geotech1.com/forums/showt...864#post112864

[joop]

Thanks Don!

[6666]

Ok here is todays dopey question
I just got a nice new shiny laser printer
and I want to try this hot iron transfer method to make a pcb
so i thought I would try the Idx pro , pcb for first try.

But is there a plain black and white pcb ?

Looking through this thread there are a few lay files
I have a lay file viewer, but in it the pcb's show up as a black background and green tracks
with all the components, and I cannot seem to be able to just get
the tracks to show, so i can print just the tracks
So whats the trick ? I hang my head in shame.
thanks
6666

[kliner]

Just ask it to print then you"ll see that the tracks are black and you can select/deselect other layers for printing on the left, you want C1 or C2 (copper layers)