IDX-PRO+VDI

[zoomix]

Hi,

I placed a white 950's original coil that works well. My PCb silverdog does not contain the potentiometer VR3 (phase adjustment?)
Sensitivity P5 is 100k then edouardo pcb indicates 10k
the diode D2 is removed
There is short-circuit strap on top

Edouardo explain having improved sensitivity with these changes

Page 10 post 232 234

R7-39 ohms, R43-1K8, R24-1M ohm R25-47, P5-10K.

I note with maximum sensitivity and max threshold I have no chatters. Are these changes are recommended to improve the sensibility and phase ajust with the scop?

Does anyone made the change with an original coil?

thank you very much

[Koala]

Space blanket does shield from near charges but falses as soon as it touched anything except dry sand.

When u do this is the sheilded coil in a shell?

No it's not in a shell

Two layer of PVC tape Then a thick MDF board then a wooden stool about 18" of the ground

Torching the bottom of the stool legs is enough to cause it to false. Even touching the headphone lead and that's insulated from the metal housing. The coil cable the same worse the nearer the coil you are


Tried more insulation between the coils and between the coil and the MDF board tried resting a empty wire spool on the RX and touching that no difference.

Removed the space blanket and placed the same coil on a piece of card covered with graphite from a battery and a tap wire just taped to it and the same coil that was unusable is fine

Same falsing with three coils and space blanket only have two left (damaged the RX winding removing the space blanket) but both work on the graphite and card.


Tried two types of PVC tape so either my space blanket is the fault or something wrong with my exicution. I have not read of any way to properly test the shield in the real world but the problem of falsing looks identical to the wet grass videos I have seen.

[Koala]

Hi,

I placed a white 950's original coil that works well. My PCb silverdog does not contain the potentiometer VR3 (phase adjustment?)
Sensitivity P5 is 100k then edouardo pcb indicates 10k
the diode D2 is removed
There is short-circuit strap on top

Edouardo explain having improved sensitivity with these changes

Page 10 post 232 234

R7-39 ohms, R43-1K8, R24-1M ohm R25-47, P5-10K.

I note with maximum sensitivity and max threshold I have no chatters. Are these changes are recommended to improve the sensibility and phase ajust with the scop?

Does anyone made the change with an original coil?

thank you very much

The Whites 950 is know to be a excellent coil for this project probably the best all round factory coil

The older Classic 6B coils also work but the phase is different so you have to increase the value of ground balance POT

I also use the 8" 6B concentric which is very stable and deep for its size. But because of its small cone of detection you can only move forward half it's diameter per sweep.

[golfnut]

I have not had them so lively that the headphone lead falses..


I have my idx in a hammond ally case.



I make the pcb edge connect to the metal box. So lots of chassis and cable sheilds at 0V





The return of the phones cannot touch the case due to the way the rails are organised ( +/-4V ) from a 12v battery and 8v reg with op amp splitter. So the batt -Ve is -4V wrt to chassis ( local 0V )

I use a glass fiber plate to hold the phone jack.


I use thin coax on the GEB pot as one side is 0v and keep pot leads short.

I use 3x4.2V LiPos in series

[paku]

i need ask about my idx board when i turn PP mod i cant detect metal but when in Disc mod my idx is working
what it that problem

[golfnut]

A build error.

[zoomix]

Hello

My IDX is assembled with the PCB silverdog whitout VR3, d2 etc.

My original loop coil is 950 ^. there are only four wire. For information, Pin 3 of the connector is not used.

I replaced 470R by 47r and 2M2 by1MB for sensitivity.
Sensitivity, treshold, pinpoint is OK

My problem is that discrimination does not work! Aluminum and steel are directly discriminated. there is no control on pot discir ..

I checked everything. I think in the first time to control phase with the oscilloscope.

I controlled the frequency with PicoScope directly on TX and I 6.58khz! it is already very good.

Could you tell me where to measure the phase shift TX and RX and wath phase shift? 90° ?

Is it on the outputs of NE5534 pin6 RX and TX pin 7?

To correct the phase is that I can put the VR3 pot with 1k8?

Thnak you for your work

[golfnut]

Get a clean bit of steel or iron, not rusy or plated. Not a loop or ring.

A peice of ferrite


A copper coin

Silver item

aluminium item




Ferrite should not ( require to adjust GEB pot for this )

With the Disc pot set to zero
Iron
Ally
copper
silver

should sound


If your initial phases are all good, then you should have enough throw to at least reject aluminium.


With the IDX you are not really moving the Disc phase with the Disc, rather it is preset with phase shifters Rs and Cs - So it is a bit more critical to get this right .

When I got more time I will post some pics of phase but I gotta go out.

[Koala]

Hello

My IDX is assembled with the PCB silverdog whitout VR3, d2 etc.

My original loop coil is 950 ^. there are only four wire. For information, Pin 3 of the connector is not used.

I replaced 470R by 47r and 2M2 by1MB for sensitivity.
Sensitivity, treshold, pinpoint is OK

My problem is that discrimination does not work! Aluminum and steel are directly discriminated. there is no control on pot discir ..

I checked everything. I think in the first time to control phase with the oscilloscope.

I controlled the frequency with PicoScope directly on TX and I 6.58khz! it is already very good.

Could you tell me where to measure the phase shift TX and RX and wath phase shift? 90° ?

Is it on the outputs of NE5534 pin6 RX and TX pin 7?

To correct the phase is that I can put the VR3 pot with 1k8?

Thnak you for your work

Golfnut made an excellent schematic with the test points interactive showing the scope trace. http://www.geotech1.com/forums/showt...658#post181658

[Koala]

Shield

Found another way not to make a shield.

Bought some micropore tape from Asda and wrapped two layers. Covered in graphite spray (lock lub from Maplins) and tested for continuity . Then two layers of PVC.

Coil has gone backwards. Now the coil chatters all the time from power on.


Removed everything from the coil and place back on the graphite coated card back to a working coil chatters gone



Think it might have something to do with the distance of the coil to shield my winding are sealed with resin the outer edge thickness is not consistent.

[Silver Dollar]

Hmm Keep going with this and you might help me out. I can't get my coils to stop chattering mainly.
The original Bandito Brown works great and the Deep Search is low amplitude but my own chatter
endlessly. I have one layer of E tape and a 1" wide metal screen then E tape again.

Factory coils generally have graphite paint on the shell which is some distance away from the coils.
I wonder if this is why some people have no problems and some have continuous problems?

[golfnut]

I have had repetitive motor boating b b b b b b b b b b b sometimes with a NEL Hunter.

But not random chatter, Do you have a video clip of your chatter?

Or a scope trace. Is it 8Hz?

[Koala]

I have had repetitive motor boating b b b b b b b b b b b sometimes with a NEL Hunter.

But not random chatter, Do you have a video clip of your chatter?

Or a scope trace. Is it 8Hz?

Sorry stripped the shield off and don't have a video.

Does not sound the same. It was random spitting like swinging over large iron just kept going. Did try a coin over it and worked fine but hard to hear through the chatter.

Thought the coil was dead but a hour or so removing the shield and it was back to normal

Pretty sure I sill have my spare TX and RX covered in a space blanket so could do a video of the touch sensitivity if you want.

[Schatztaucher]

Hello

My IDX is assembled with the PCB silverdog whitout VR3, d2 etc.

My original loop coil is 950 ^. there are only four wire. For information, Pin 3 of the connector is not used.

I replaced 470R by 47r and 2M2 by1MB for sensitivity.
Sensitivity, treshold, pinpoint is OK

My problem is that discrimination does not work! Aluminum and steel are directly discriminated. there is no control on pot discir ..

I checked everything. I think in the first time to control phase with the oscilloscope.

I controlled the frequency with PicoScope directly on TX and I 6.58khz! it is already very good.

Could you tell me where to measure the phase shift TX and RX and wath phase shift? 90° ?

Is it on the outputs of NE5534 pin6 RX and TX pin 7?

To correct the phase is that I can put the VR3 pot with 1k8?

Thnak you for your work

HI at all!

zoomix, when you have buy the PCB? I got the same problem with one of silverdogs lasts PCB....perhabs a mistake on the board? i got a second new board...i will make some pics. perhabs the gurus can see something on it....

regards

[golfnut]

Silver dollar makes a good point..

With metallised foils we have these very close

With graphite it is a ways off the coil


This may be a significant difference