IDX-PRO+VDI

[golfnut]

" have a range of 30 cm to a coin"

This is good sensitivity - it may indicate that your Tx freq and your Rx freq are too close - they injection lock when co channel and phase pull each other and the unit is incredible as air test but very twitchy and not usable on soil.

Alter the Rx cap by 1nF or so - you will find the U1 signal output reduce, the noise should reduce, and the sense to air coin go to ~25cm this is more usable and in line with others Ive seen. S

[golfnut]

Hi Barry, the 0.24mm is ideal for the Tx and Rx on this.

The main things a builder needs is a cheap scope or a pc scope. This enables the builder to adjust the phasing of the Rx wrt the Tx signal. It appears the Rx signal needs to be 180deg out of phase wrt to Tx signal for these to function correctly.


As for air test, this is only useful to assess if..

1) You can reject ferrite
2) You can reject clean small iron

then having got this far you should be able to ...

3) Accept aluminum, gold, bronze, nickel, silver alloys, silver


IN uk Soil - From hunting this year with my IDX at 12kHz Tx

Small hammered silver coins in the <1gram range dont come out below 5-6"
small roman AE4 dont come out below 5-6"

medium copper eg 18th century farthing dont come out below 7"

full unclipped groat would be ok to 8"

victorian penny, thick ring or D buckle good to 9"

medium ball pein HHead, large shoe 12"
All Approx

Some finds mostly roman and medieval from the summer while crops off, all being catalogued through my finds liason officer. (I would have doubled this with a deus!) but I enjoy the fight with the simple machine!!

[hoadlies]

Hi Barry, the 0.24mm is ideal for the Tx and Rx on this.

The main things a builder needs is a cheap scope or a pc scope. This enables the builder to adjust the phasing of the Rx wrt the Tx signal. It appears the Rx signal needs to be 180deg out of phase wrt to Tx signal for these to function correctly.


As for air test, this is only useful to assess if..

1) You can reject ferrite
2) You can reject clean small iron

then having got this far you should be able to ...

3) Accept aluminum, gold, bronze, nickel, silver alloys, silver


IN uk Soil - From hunting this year with my IDX at 12kHz Tx

Small hammered silver coins in the <1gram range dont come out below 5-6"
small roman AE4 dont come out below 5-6"

medium copper eg 18th century farthing dont come out below 7"

full unclipped groat would be ok to 8"

victorian penny, thick ring or D buckle good to 9"

medium ball pein HHead, large shoe 12"
All Approx

Some finds mostly roman and medieval from the summer while crops off, all being catalogued through my finds liason officer. (I would have doubled this with a deus!) but I enjoy the fight with the simple machine!!

[ATTACH]27845[/ATTACH]

THANKS ,,G/NUT ,, Especially as I bought a roll of 0.24 ,I did however dismanlte a couple old Oil-Cooled 12v ignition-coils & the primary winding is 0.68 & it comes off easilly as it was imersed in oil !!!.Thought this may have been OK for the TX winding..

But I will be most happy to use the New roll of 0.24mm ..

WOW that a great collection of artifacts & old coins ..
In Australia we are too young a country to have any really old artifacts as you have in the UK ..

I do have an old but little used Scope ,But I will need some help to get it doing the job as I only used it on Audio etc I also have a signal-gen

NOT sure if this older type will do the Job????


Thanks for your Help ,,BARRY

[Koala]

" have a range of 30 cm to a coin"

This is good sensitivity - it may indicate that your Tx freq and your Rx freq are too close - they injection lock when co channel and phase pull each other and the unit is incredible as air test but very twitchy and not usable on soil.

Alter the Rx cap by 1nF or so - you will find the U1 signal output reduce, the noise should reduce, and the sense to air coin go to ~25cm this is more usable and in line with others Ive seen. S

I found this out the hard way. 27DD gave just under 40 worked very well with air testing. Not much use over real soil. Chattering and false signals all the time. Does work very well over dry powdery sand.

[sinclairuser]

I do have an old but little used Scope ,But I will need some help to get it doing the job as I only used it on Audio etc I also have a signal-gen [ATTACH]27846[/ATTACH]

NOT sure if this older type will do the Job????


Thanks for your Help ,,BARRY

that should be fine barry, a scope is better than no scope.

[ricalbertvig]

Greetings coils who sells ready-idx? ... anyone has any information of anyone selling?

[Valters]

Hi,

I twist pot wires, i think it little helped, but MD is still unstable ( notably when touch GB pot) and PP mode is weak.

I made 27.5 DD coil, but only yesterday i buy a Peak Tech 2010 multimeter and measured coils:
TX- 0.665 mH 1.5oms (0.2 wire x 260turns+parallel 1uF)
RX- 45.2mH 103.2oms (0.6wire x 34turns+parallel 47nF)
I think, that i will made a now RX, because my target is get 34mH(+/-10%).


When I turn on MD with out coil I don`t get beep. If I turn off MD, connect coil, turn on MD, then I get a beep.

When I balancing coils, I attached one of test wire not in U1 pin 3, but on RX wire, which goes to U1 pin3, I think its not a problem.
If I use multimeter in AC 200mA range, I got 0.06 (about 2sec.) and then it go down (0.05, 0.04, 0.03,... 0.00 mV). If I turn multimeter on AC 2V range, then min what I get is 0.009-0.010 V. It is multimetr problem? DCV is 3.95V.

[ossamaussama]

ok
are you sure (TX- 0.665 mH 1.5oms (0.2 wire x 260turns+parallel 1uF)
RX- 45.2mH 103.2oms (0.6wire x 34turns+parallel 47nF)

RX should be 260 tuns with 27-30 nf you have to try

replace GB pot may it is defective

you need scope ,computer scope software is good

Zelscope pc software is the best for me

idx frequency:6.5---6.7khz

[ossamaussama]

scope.zip

sound card scope

[hoadlies]

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

HI DON thats a great bit of info-mate I thankyou for Sharing ..

CHEERS AUSSIE-BARRY..

[ossamaussama]

HI DON thats a great bit of info-mate I thankyou for Sharing ..

CHEERS AUSSIE-BARRY..

i tune my idx using sound card scope in computer test frequency in u1 pin 6 there is alot of harmonic but i chose 6.5k hertz i tune it by capacitors until i get the maximum voltage then i move the two coils for null result 25-27 cm for coin iron reject

is my way correct?

[hoadlies]

I'm thinking of a simple and frugal analogue divider (tangent of the target angle) and after some signal conditioning connect it to a dial instrument.
It would not make much sense if a digital VDI unit uses less than 10mA.

HI DAVOR & ALL ,,I like your Analog meter Idea YES analog rules at times a visual needle is an instant Aid to the Eye ..
A ELCHEAPO detector I have MD3006 YES I know Chinese but it has a centred needle goed left & right indication ..

But any meter [milliamp] would be A-OK..
LIKE a VU meter in stereo's [Older units etc]Also very Cheap to Buy & no programming involved as with digital units..

KEEP AT IT MATE,,,,,,,,,,,BARRY..

[ossamaussama]

i think analog VDI CAN can be designed but problem is that IDX is fast motion machine

[paku]

hi can any one explain what is goin on this board have 100k but not connected

[Thomas]

It would go on the bottom side and it is connected.