IDX-PRO+VDI

[yo4hfu]

Hello Geotech!

I finished IDX Pro and the results are very good for my first VLF IB detector.
For air test the 1E coin is detected at 45-47cm and 34cm at ground test with better sound for high power option (TX oscillator have full power supply from 14V battery pack). I need to make more tests in clean soil.
RX front end was replaced with LT1115 and the sensitivity increased with some centimeters. GB/DISC Filters use LF347. Voltages for operational amplifiers are filtered with 100nF + 10uF smd tantalum.
Null voltage is 500mVpp measured after RX preamplifier (U1-pin 6) and TX voltage 15,7Vpp for normal mode. Voltage across TX coil was 25,5Vpp for high power mode. For shield i use aluminum foil from RG-6 coaxial cable.
Coil type: DD 27cm
TX coil=0,62mH + 973nF; 6,5KHz
RX coil=35,5mH + 27nFll5,6nF; 4,68KHz
Now i don't remember exactly phase shift angle but is not very critical. I chose coil position for minimum rx voltage and the discrimination was ok.
The machine is stable and iron discrimination is good, only some audio cracks from rusty iron.
Also i have VDI box with PIC16F690, the indication is useful for visual discrimination .

Next device is KID FM 1 Pinpointer, good sensitivity and discrimination capability with PIC12F629.

[Koala]

Dear eduardo1979,
data do not match with the math. Are the data for wire gauge or diameter?
If the diameter of the wire: TX-0.7mm = 872uH (0,872mH)
RX-015mm = 67,46mH

If the cross section of wire: TX-0.7mm = 0.9736..mH
RX-015mm = 89.086...mH

Here's the link and check out: http://www.technick.net/public/code/...uctance_circle

Its for a DD shape coil

Its the data I use to build my coil. Works perfect. Ground balance and discrimination where they should be. Used the DD shape in the TGSL thread

[Mustac]

TX wire from 0.70 to 35 laps - 0.587 mH - within 1 mF capacitor
RX wire from 0.15 to 270 laps - 35.6 mH - 0033 mF condenser inside

Dear eduardo1979,
data do not match with the math. Are the data for wire gauge or diameter?
If the diameter of the wire: TX-0.7mm = 872uH (0,872mH)
RX-015mm = 67,46mH

If the cross section of wire: TX-0.7mm = 0.9736..mH
RX-015mm = 89.086...mH

Here's the link and check out: http://www.technick.net/public/code/...uctance_circle

[ossamaussama]

I have question

Can I build large coil for idx 50 cm *50 cm
With the same inductance needed
I can slow done idx by use 100 uf instead of 1 uf because for large coil detector should be slow


my perpose is to get 1.7 depth with discamanation and ground rejection

I have pi metal detector with depth 2.5 m but iron ground is problem really
Also pi is not sensitive to gold


Deep hunter use large Dd coil any ideas?

[CDI]

IDX is never quiet in iron infested ground.

suprised your Bandido uMax 2 was no good. Never had one myself but most highly regarded in trashy sites maybe you just got a bad one

I didn't said bandido was bad, it was great machine, extreme lightweight. Problems with him started when IC TLC2262 burned for some weird reason. I never found in local shops that ic to replace, cause that i put several replacement, but sens was much less with those other ic's. From 35 cm to 25. That's so much less distance. Also, on ebay is hard to find umax2, and more harder in good condition.

[Koala]

IDX is never quiet in iron infested ground.

suprised your Bandido uMax 2 was no good. Never had one myself but most highly regarded in trashy sites maybe you just got a bad one

[CDI]

I run most of the time with 0 discrimination. Shallow loud targets I turn the discrimination up 45 degrees and swing over the target while lifting the coil large iron will have a sharp cut off to the sound and a good target will fade out.


Small silver on its edge has a 50% increase in depth between 0 discrimination and enough to quieten a large nail.




Funny how good your ears became to the different sounds. Out last Sunday and not had many good finds swing the coil over a target and thought that sounds like a deep copper coin and it was. An hour or so later I thought that sounds like a shallow copper coin and it was. Only two decent sounding targets and my only two decent finds even though I came back with a bag of scrap.

In my hunting area(30 km around Viminacium, also there is legend about lost golden roman chariots), ground is very infested with iron, and im thinking to sell my classic and try with some other md with higher frequency, atm i have tgsl which works pretty good, totaly reject big and small iron, hot rocks and ferrite rods, without sound cracks, complete quiet. Coil nulled to 0.02v.

[Koala]

I run most of the time with 0 discrimination. Shallow loud targets I turn the discrimination up 45 degrees and swing over the target while lifting the coil large iron will have a sharp cut off to the sound and a good target will fade out.


Small silver on its edge has a 50% increase in depth between 0 discrimination and enough to quieten a large nail.




Funny how good your ears became to the different sounds. Out last Sunday and not had many good finds swing the coil over a target and thought that sounds like a deep copper coin and it was. An hour or so later I thought that sounds like a shallow copper coin and it was. Only two decent sounding targets and my only two decent finds even though I came back with a bag of scrap.

[CDI]

Should reject ferrite rod. Sounds like the RX capacitor need adjusting. Your discrimination will be out. Probably the main problem with the hot rocks


But the Classic/IDX are not the best at rejecting coke/hot rocks. On fields where they are a problem I adjust the ground balance away from true ground towards the hot rock just enough so it gives an iron tone. Its a compromise as there will be a small loss in depth. If you don't want to hear the iron tone you can turn the discrimination up but with even more loss in depth especially to small target on there edge.

That's true, i need to set my disc pot to 12h to reject bigger nails, also foil and bottlecaps cant be rejected, but gives sharpness and louder sound on them, in 99% of my hunting i know if is in the ground coin or foil. Air test is a bit impresive, 1 euro coin detectable at 40 cm with loud sound, 42 - 43 with week sound. My coil is homemade 27 cm, Bulgarian dd shell. Before Classic 3, i had Tesoro Bandido uMax 2 (original one, from USA), i maked terrible mistake when i sold that bandido.

[Koala]

I had that coil for Fisher CZ, my friend tryied to adapt for my Classic 3. It's worked, very deep, but cant reject hot rock, old roman brick and ferrite rod is not well rejected.

Should reject ferrite rod. Sounds like the RX capacitor need adjusting. Your discrimination will be out. Probably the main problem with the hot rocks


But the Classic/IDX are not the best at rejecting coke/hot rocks. On fields where they are a problem I adjust the ground balance away from true ground towards the hot rock just enough so it gives an iron tone. Its a compromise as there will be a small loss in depth. If you don't want to hear the iron tone you can turn the discrimination up but with even more loss in depth especially to small target on there edge.

[CDI]

No idea. Not heard of anyone trying.

Detech don't make a coil that is a straight plug in and go. Whether one can be hacked and made to work with correct ground balance and discrimination is anyone's guess.

Golfnut did modify a NEL Hunter to work but don't remember if the details have been posted

Also a 27cm Quicksilver coil for Fisher CZ can be made to work very well but again I don't think the mods have been posted.

I had that coil for Fisher CZ, my friend tryied to adapt for my Classic 3. It's worked, very deep, but cant reject hot rock, old roman brick and ferrite rod is not well rejected.

[Koala]

Does anyone know if Ultimate Detech 13 coil can be compatible with idx?

No idea. Not heard of anyone trying.

Detech don't make a coil that is a straight plug in and go. Whether one can be hacked and made to work with correct ground balance and discrimination is anyone's guess.

Golfnut did modify a NEL Hunter to work but don't remember if the details have been posted

Also a 27cm Quicksilver coil for Fisher CZ can be made to work very well but again I don't think the mods have been posted.

[CDI]

Does anyone know if Ultimate Detech 13 coil can be compatible with idx?

[Koala]

I have been using my IDX for a couple of years and very pleased with it.

Not sure if I have a slight error or if it needs a slight tweak to improve it.

If I turn the threshold down about 10 degrees the sound in disc mode is much sharper and last for a longer distance before it starts to distort but PinPoint mode obviously does not work unless I turn it back up. Which is what I am doing at the moment.

Can someone confirm this with their detector it only really noticeable on tiny targets like a silver sixpence on its edge. If you pass it in font of the coil as if testing for maximum depth. Now try it with the threshold turned on mine with the threshold where it should be the sound starts good then changes to a grunt towards maximum depth. With it turn down the the sound just fades. Both have the same depth but with it turned down the last few percent are still dig targets gut not with the threshold at its proper setting


Also is there a way to quieten the very loudest sounds without loosing the faint ones. On field with a lot of plough shear my ears are buzzing at the end of the day LOL

[CDI]

Nothing should get hot or even warm. Not much to go on. Make sure everything is place the right way round.No shorts and the voltages are correct. Post some nice photos would help.

also check the voltage pin 1 and 7 of U5 should be just under 3V

Seems the all voltages are ok, checked twice. In my pcb, i reversed collector and base pins, cause on board is shown like ECB pinout, like i write before, that's very first version of idx from page 1. Today i will post pictures.