IDX-PRO+VDI

[der_fisherman]

Making a Double "D" search coil.

Also the shielded coils don't want to electrically touch each other.

yes they are insulated from each other

Just noticed that the only part of the coil that is not affected by a charged pen is the cross over points

..and don't forget that the shields may only be connected at ONE point, so the two coil shields must be insulated from each other. I achieve this by fully covering each finished coil with an insulating tape before assembly in the search head. There may be other better ways to do this. Also check that they have not made contact before attaching the permanent wiring. Check the resistance value, it should hopefully be in the meg Ohm range on a Multimeter....

I have never used the thin blankets for a shield, but I will on my next coil attempt, but when I do, I will identify the conductive side. Then I will wind a long piece of un-insulated copper wire on a bed of insulating tape, around the coil, but leaving say a 1 cm gap, as a contact for the shielding blanket foil. Then tightly wind strips of blanket, conductive side towards that copper wire, on top of this, followed by a tight winding of insulating tape again. So insulating tape twice, under and over the shield.

The best insulating tape I find is the ones that "melts" into itself after a few days, "self amalgamating tape"....this excludes air if done correctly which will stop corrosion due to air and water. You will see examples here:-

http://www.detakta.de/en/selfamalgamating-tapes.html

This is a bit thicker and only really needs to be the final layer, not the first one.

Now I am FAR from being an expert in such matters, but the principles should be mostly correct. There are many here far more expert, so you should defer to them in the matter of what components to actually use.....

Before covering, you should roughly shape the coils so as to save putting a lot of stress (spring?) onto your coil and covering when installing in the search head, that typical "D" form. I actually wind mine in the final "D" form on a "D" shaped former, to reduce stresses even more....I learnt from an expert on this blog, dear Don B. his postings are highly recommended reading, all and any of them....

Do remember to identify each connection before removing from your former with direction of winding and the start and ends...."over do" the identification so that even much later you know which is which....do not remove that identification until just before potting....after that its too late anyway!!

Best of luck and regards from

Andy

[golfnut]

Is the coils taped over with pvc tape?

As It may be your 'Charged pen test' effects your coil as it has exposed screen, which is different to commercial complete coil

[Koala]

Also the shielded coils don't want to electrically touch each other.

yes they are insulated from each other

Just noticed that the only part of the coil that is not affected by a charged pen is the cross over points

[Koala]

If your shielding is good. Then what you are describing sound like you have the shield
wire connected to the preamp input and the live wire going to ground?
Double check your connections, they may be reversed.

Only connected at the board side (could this be my problem ?) so can't be the wrong way round.

[Altra]

If your shielding is good. Then what you are describing sound like you have the shield
wire connected to the preamp input and the live wire going to ground?
Double check your connections, they may be reversed.

[Koala]

Use a ohm meter to check if you actually have conductivity around the full radius of the coil winding.

I experimented with space blankets as a shield material. It works very well, but
I found many breaks in the conductivity along the creases or folds. I would cut 1m x 25mm strips
and test them with an ohm meter before using. If you hold the material up to a light you can see the breaks.
The factory must machine fold them while they are still warm. Stretching the plastic and thus
cracking metalized aluminum coating. If anyone knows where to buy this same material in a roll or
non folded it would be handy.

Thanks

I cut avoiding most of the creases.

The spiral tap wire should span any breaks. Did check with ohm and continuity before the tap wire from one end to the other

[Koala]

the space blanket is normally pretty good.

I know you will have a small gap ~4mm - so not totally enclosed.

Also the sheilded coils dont want to electrically touch each other.



The differnces can only really be the

Tx and Rx freq of resonance
phasing
nulling
wiring
screening


Anyone know how the whites cabling is done? S

Yep have a small gap.

Nulling is higher than I would like at 400mv distance and both a iron clad or copper 2p is 37cm

discrimination is excellent ferrite rejection is perfect

Getting frustrated with it at the moment as the coil works really well except for the shield and have been trying for the last couple of days.

tried a different cable as well. First was a USB2 second is a microphone cable

tried two different wires for the tap one tinned copper the just copper.

checked the shield wire goes all the way back to the box

[Altra]

Made a new coil and having trouble shielding it.

Got a space blanket that is conductive on one side. Tried twice failed twice. If I touch the coil with my finger or a plastic pen that I have charged up on the RX side the detector falses if a turn up the discrimination up and touch the RX with iron there is no falsing. Tried wire with space blanket on to and space blanket on wire and also aluminum foil on wire.


Factory coil works with no falsing

Use a ohm meter to check if you actually have conductivity around the full radius of the coil winding.

I experimented with space blankets as a shield material. It works very well, but
I found many breaks in the conductivity along the creases or folds. I would cut 1m x 25mm strips
and test them with an ohm meter before using. If you hold the material up to a light you can see the breaks.
The factory must machine fold them while they are still warm. Stretching the plastic and thus
cracking metalized aluminum coating. If anyone knows where to buy this same material in a roll or
non folded it would be handy.

[golfnut]

the space blanket is normally pretty good.

I know you will have a small gap ~4mm - so not totally enclosed.

Also the sheilded coils dont want to electrically touch each other.



The differnces can only really be the

Tx and Rx freq of resonance
phasing
nulling
wiring
screening


Anyone know how the whites cabling is done? S

[Koala]

Made a new coil and having trouble shielding it.

Got a space blanket that is conductive on one side. Tried twice failed twice. If I touch the coil with my finger or a plastic pen that I have charged up on the RX side the detector falses if a turn up the discrimination up and touch the RX with iron there is no falsing. Tried wire with space blanket on to and space blanket on wire and also aluminum foil on wire.


Factory coil works with no falsing

[Schatztaucher]

ok thanks....i test it today

[Koala]

hi guys,

I hope you can help me ... I have just completed my fourth and fifth board ... and in both smokes away the 1N4001 .... can anyone give me some advice where I can find the error. i have always used the same components. the solder pads are made clean ...

regards

Power connector the wrong way or the diode wrong way. Check your battery pack with a multi meter. I have one here 6X AA that is wire the opposite way so if you put a normal PP3 connector to it the red wire is negative and the black positive.

[Schatztaucher]

hi guys,

I hope you can help me ... I have just completed my fourth and fifth board ... and in both smokes away the 1N4001 .... can anyone give me some advice where I can find the error. i have always used the same components. the solder pads are made clean ...

regards

[Silver Dollar]

I use a wooden stick with the target on it. Holding the same target in my hand
appears to give the same reading. Though sometimes it appears I get more depth
when the target goes next to the coil wire that hangs down next to the coil.

[ampirate]

"this reduces the Range by HALF or MORE"
Yes your hand makes a difference but not that much ?

I had worked on a job project - about 10 years ago for Capacitance Sensors.
You would step on the one Pad with your shoe,
while using your hand with a Screen Touch Sensor (other Pad),
and You being the Capacitor, ...
- it Worked Great - had about a 2-foot Range from the Screen !

I even wrote one of the Patents for it ...