Voodoo Main Discussion

[ivconic]

No - we may just be talking at cross purposes, so I'm reserving judgement until I see the actual schematic. No conspiracy theory here.

It was a joke.
But than again...
Ron ask him is he fancy buying a genuine brick, since he disregards me totally!
Reason i am pushing this is because modern brick is not the same "beast" as ancient Roman one.
Last time i checked; Romans missed to occupy Pennsylvania... they busted half way there...
Damn stupid Nero!

[dfbowers]

It was a joke.
But than again...
Ron ask him is he fancy buying a genuine brick, since he disregards me totally!
Reason i am pushing this is because modern brick is not the same "beast" as ancient Roman one.
Last time i checked; Romans missed to occupy Pennsylvania... they busted half way there...
Damn stupid Nero!

Brick is the worst I could come up with to simulate ground. I have 40 some bricks in the basement and I just create an artificial ground. I hate bringing dirt in the house ��

[ivconic]

Brick is the worst I could come up with to simulate ground. I have 40 some bricks in the basement and I just create an artificial ground. I hate bringing dirt in the house ��

Than what you done is total success!
It should perform good on my local soils/sites too.
Precious coins are not deep, but are heavily masked by pieces of such bricks and pottery, scattered all over the place.

[dfbowers]

Here is what I have been playing around with. I can disc iron or non ferrous depending on where the sample it taken. The ground signal seems to have no overall effect. Since that original PI audio is left uncorrupted.. no double beep. All that is needed is to look at meter deflection. I can disc through two layers of brick and which is probably a stronger ground signal than my actual ground. It?s still on a breadboard but I can move my coil off the bench to a bed of bricks to test. If nothing else it had been a fun experiment!

Found my first mistake.. add a 10n cap across the coil.

[Orbit]

Scheme I can't put because it will be a commercial detector the project was given a well-known companies ... But I can send it to you a snapshot of how the detector works!

[waltr]

It was a joke.
But than again...
Ron ask him is he fancy buying a genuine brick, since he disregards me totally!
Reason i am pushing this is because modern brick is not the same "beast" as ancient Roman one.
Last time i checked; Romans missed to occupy Pennsylvania... they busted half way there...
Damn stupid Nero!

Brick is the worst I could come up with to simulate ground. I have 40 some bricks in the basement and I just create an artificial ground. I hate bringing dirt in the house 🙄

The 'modern' bricks used in my house are not bad. However, at some old farms I detect I have found bricks that that are detectable if no GB is in detector. This was my reason to add GB to my HammerHead. Seems many Early Pennsylvania bricks were made with iron rich clay, which we do have. Iron rich soils, and iron mines, are very common out where Don lives (about 2 hours west of me).

Just received my Voodoo book. Now to read up.

[dfbowers]

The 'modern' bricks used in my house are not bad. However, at some old farms I detect I have found bricks that that are detectable if no GB is in detector. This was my reason to add GB to my HammerHead. Seems many Early Pennsylvania bricks were made with iron rich clay, which we do have. Iron rich soils, and iron mines, are very common out where Don lives (about 2 hours west of me).

Just received my Voodoo book. Now to read up.

lThe ground here around Middletown/ Harrisburg can cause a problem with PI detectors without a GB. The Baracuda for instance needs to be run a a reduced threshold because it screams. Ideally they should all have a GB. I will get started on the VooDoo next . The ground will tell if that will work too!

[ivconic]

The 'modern' bricks used in my house are not bad. However, at some old farms I detect I have found bricks that that are detectable if no GB is in detector. This was my reason to add GB to my HammerHead. Seems many Early Pennsylvania bricks were made with iron rich clay, which we do have. Iron rich soils, and iron mines, are very common out where Don lives (about 2 hours west of me).

Just received my Voodoo book. Now to read up.

That explains why Don picked those bricks to use in his workshop.
That's even better, justifying that he made indeed success.
...
I am keeping few genuine bricks in my workshop too.
Since those are large and heavy; i gave one to stone cutter to cut me small cubical pieces, various sizes, to serve for testing purposes.
Those are dating from IV century. Have magnetic features. All the detectors reacts on those.
It's the large amount of ferroxide particles in such clay. They didn't have advance methods to purify clay in those times.
So it is perfect mimic for hard soil in workshop.

[Qiaozhi]

Here is what I have been playing around with. I can disc iron or non ferrous depending on where the sample it taken. The ground signal seems to have no overall effect. Since that original PI audio is left uncorrupted.. no double beep. All that is needed is to look at meter deflection. I can disc through two layers of brick and which is probably a stronger ground signal than my actual ground. It?s still on a breadboard but I can move my coil off the bench to a bed of bricks to test. If nothing else it had been a fun experiment!

If I understand your schematic (and correct me if I'm wrong) the audio is only driven from the PI channel, but the signal prior to the SAT circuit is sent to a differentiator located on an add-on board. The DISC channel is also single-differentiated, and the output is wire-ORed so that the meter only responds to non-ferrous targets. This is analogous to the signals in pane 2 of Table 7-4 on page 81. If the lower connection on the meter was connected to 0V, I presume it would swing right for non-ferrous, and left for ferrous? The only problem would be non-ferrous targets would first swing to the right followed by a swing to the left. Ferrous targets would do the reverse. So I suppose that's why you've connected the meter to -5V?

This means that the detector will beep for all targets, and reliance is on the meter to indicate the target type. Have you tried using the meter signal to disable the audio for ferrous targets?

I have experimented with a single-differentiating topology on a previous version, but separation of targets was poor. In my test garden (which is littered with ferrous trash) it was impossible to identify the location of the buried coins.

I would be interested in what you discover when you take the detector outside.
Good work by the way.

[Qiaozhi]

Scheme I can't put because it will be a commercial detector the project was given a well-known companies ... But I can send it to you a snapshot of how the detector works!

Yes please. That would be interesting.

[Qiaozhi]

If the lower connection on the meter was connected to 0V, I presume it would swing right for non-ferrous, and left for ferrous? The only problem would be non-ferrous targets would first swing to the right followed by a swing to the left. Ferrous targets would do the reverse. So I suppose that's why you've connected the meter to -5V?

Thinking about that some more ... I've probably got that wrong. With the meter connected to 0V the non-ferrous would swing right and then left, but the ferrous targets should do nothing. This is (of course) assuming the meter was adjusted so that the needle is in the middle.

Maybe you could simply trigger the audio from the meter circuit.

[dbanner]

With a level shift and some nand gates/Schmitt trigger perhaps, Along with an audio chopper. Or a big bright LED for underwater.

[6666]

Scheme I can't put because it will be a commercial detector the project was given a well-known companies ... But I can send it to you a snapshot of how the detector works!

Does it have a patent number ? thanks.

[6666]

Here is what I have been playing around with. I can disc iron or non ferrous depending on where the sample it taken. The ground signal seems to have no overall effect. Since that original PI audio is left uncorrupted.. no double beep. All that is needed is to look at meter deflection. I can disc through two layers of brick and which is probably a stronger ground signal than my actual ground. It?s still on a breadboard but I can move my coil off the bench to a bed of bricks to test. If nothing else it had been a fun experiment!

Great work Don, with your conc coils how much tail do you leave between the TX end and bucking coil, so you can make a nulling loop ?

[dfbowers]

Great work Don, with your conc coils how much tail do you leave between the TX end and bucking coil, so you can make a nulling loop ?

Yes, exactly. I used the area under the clevis tabs to make the fine tuning loop. Then several pours of potting compound until I got it close. It was a whole new challenge working around the open center coil! It's much easier with a solid center.