XP deus coil modification

[Skippy]

It would be good if you could post some good photos of both sides of the electronics board. Even though they are covered in silicone, we can probably work out some details of the circuit, and maybe identify test-points, things that would be useful to you when adjusting your coil.

[Henrikras]

Sorry Skippy. The board is allready in the new box and it did take some time to install it properly. I do hope to find the output from the preamp just by trying spot after spot. My plan was to compair with the Big coil, thats why I gave this big coil some effort to get working.
If something fail and I must take the board out.. Some new macrophoto will be taken.
hope you understand.
Henrik.

[Skippy]

That's disappointing news, you really are going to need to use that circuit-board a lot in order to set up / test your search-coil. Even if you have to look at the raw coil output on a 'scope you still need to connect up TX & RX. And maybe finding the digital switching signal that ultimately drives the coil would be handy, for triggering your 'scope, for example.

[Henrikras]

Thats not good news Skippy..
And this is the part where my knowledge must give up. Im so glad that you would help with this.
First picture one side is done.. But you need back side allso. I look into that soon.
Thanks Henrik.

Edit - reverse side FOTO.

Now I wouldn't close it before you say GO... and If some part need better FOTO, Maybee with less silicone, just say it, and I would try to do that.

[Funfinder]

Thx for the pix!

If you open a W-Lan (WiFi)-USB-stick it looks pretty similar.
Even the voltage-level is nearly or directly the same.


Its always good keeping the option to open the box whenever you want or if its needed,
but you must create a waterproof housing if it isn't already waterproof.
Especially the region where the cable comes out is important for this task,
also the location where this cable vanishes into the coil.


Henrikras, if you have already now good working experience creating a small XP-Deus coil
it could be a good idea for you to keep this project open and you use this created coil
as a sample for further modifications of such kind.

It could be other people now are interested and you can help them to create their own
XP-Deus mini-coil or perhaps you are interested in creating more such coils for other ones.

First now we are interested in real search-results and perhaps you can finetune and improve
the performance of this new coil. Good luck!

[Skippy]

Thanks for the pics.
I suspect that most of the IC's will have uninformative markings on them, which makes reverse engineering a pain. But the SO-8 packaged device on the non-relay side of the board, at the coil-connection end would be worth identifying. I think that is probably the RX pre-amp. Could you remove the silicone, and read off a part number for us?
It seems like the test points may be the I - shaped solder-coated pads. If these were cleared of silicone that could be helpful.
I was expecting more test/ probing points, to be honest. After all, it is a complex board, and I thought there would be programming port pins (jtag etc).
It would be interesting to see what others think the circuit consists of. I think the amplified signal is synchronously demodulated at 0 and 90 degrees (so ther should be DC voltages to measure) and these two signals go to an ADC, likely 24-bit, via a multiplexer (analogue switch).

[Henrikras]

Thanks Funfinder and Skippy..
Sorry If I'm not answer all. If any important got lost, please remind me.

Picture shows this area I must remove more silicone and take some new pictures ! Did I get this correctly Skippy ?
You say I should make some scope measureing ! Can you more specifike point out what and where ! Or is not now but when the small coil is ready to finetune / adjust.
Silicone off and new pictures later this evening.
Henrik

[Skippy]

Yes, the SO-8 is probably a pre-amp, but...it could be a dual amplifier, forming a two-stage amp. If there are demodulators, then there are two DC voltages that can be measured with A DVM. Measure them relative to the RX coil negative, I think it's likely to use a 0V / +1V5 / +3.0V supply, with the +1V5 acting as a ground. To see if a point is a demod signal, you would need a ferrite rod, and some non-ferrous items, a high conductor copper/silver coin, and a low conductor - an airgun pellet? Small cupronickel coin like the Norway/Sweden 10 ore from 1970's 80's.? Bring the ferrite rod end-on up to the coil, maybe to 20cm, and the 'zero degrees' demod signal will change, but not the 90 degrees. The non-iron targets will change both 0 and 90 sigals, the low conductor mainly the 90 degrees,the silver coin mainly the 0 degrees, in the opposite polarity/direction to what the ferrite rod does. This demod stuff is just useful but interesting. You should be able to get a good enough null by simply observing the amplified coil signal, but the DC signals (if they can be found) may make it easier.

[Henrikras]

Okay Skippy - I try hard to follow you and think I understand 80%.. + / - .
All this degrees / phase change I know it happens, and I know that the TX is a stable sinus and the RX is zerro (Nuul)...without a signal. Is it then when a coin, ferrit rod, iron, silver, Kobber, is passing the coil, then I must watch how many degress the RX signal at the scope prope 2 moves when this object passing the coil ??? Like Prope 1 at TX and prope 2 at the RX after the Preamp ?
And you say, that Maybee I can find a DC changing somewhere around the Preamp, instead of the phase change with the scope ?

Any idea to another thread there Maybee got some illustration with some of this scope pictures. ?

Next... I did remove some more silicone. New pictures.
But I think we got some new stuf to think about... I you watch one the pictures where you can see the TX terminals... The TX - (minus) is Very strange.. It look like the Board got a third connection, like a sandwich board.. I saw it when the light was behind at one picture.
One more thing there is Strange ! The TX - (cold side) and the RX - (cold side) got same connecting !!!!! Okay Maybee the relays has something to say, because this TX - is going to the area with the relays... But If TX- and RX - is connected, will that Be posible to work ???

All comments are Welcome.
Henrik

[Skippy]

Good. The pre-amp is based on the ADA4841-2 dual opamp:
http://www.analog.com/en/all-operati...s/product.html
So now you have two outputs, pins 1 and 7 to look at, pin 1 has a solder-pad to probe on. You also know the power supply + and - now, pins 4 and 8 of the opamp, the (virtual?) ground is the RX coil -ve. You should be able to work out what other supplies are used, maybe the TX coil has one end to +3V ? have a poke around. See what is on the other test pads, like the two next to the big PIC24 chip. Maybe you can find square waves at the coil frequency.

[Henrikras]

Hi again... I did some work at the coil project this evening.
Okay... The V+ is 3.3 Volt and 1.65 volt at the preamp. The TX is cold.. Nothing to measured.
The Nuul (rx hot side) is 18-20 mv.. Did a video link http://www.youtube.com/watch?v=kEUaEDlTT0k&sns=em
I was in 11 khz GMPower prg. with disc. at 4.9 (my settings from today)
I can't figure out this phase change / iron-coke-low and high conducted objects !!!
I can see a action at the scope, but still its difficult to get into my brain what to look after!
please some advice.
The Nuul (I think 18-20 mv) was easy to get better (lower) with a small ferrite in the front of the searchcoil.
Remember all todays work was still with the 11x13" Stock coil..
I think ist time now to Wind the small coil, and start to work with that... What would you say.!
Henrik

[golfnut]

I watched the vid,

You think this isnt correct? What should it do? I saw no reaction from ferrite - this is good, yes.

Iron tone was uniquie to iron. Is this what a deus normally does> S

[Henrikras]

Yes Golfnut... The iron tone is a low buzz. ( 200 hz. ) This program got 3 tones, Iron 200hz (lower that the disc. setting), low conducted (562hz), and high conducted (644hz). We allso got ID at the display from 00-99. Those test objects I was useing, had; Iron 02-03,
coke 22-23, low conducted coin 52-54 -and last high conducted coin 92.
Henrik

[Skippy]

Is that null 18mV RMS ? Or peak-to-peak? Either way, it looks high, but that is probably because the battery and PCB are no longer in the middle of the coil.At least you know the supplies now. The LiPo battery is regulated to 3.3V, and this is halved with a virtual ground generator to make 1.65V, which acts as the analog ground. I'm unable to view the video, I hope I haven't missed anything important. You should aim to get your coil nulled to less than 5V RMS, 1mV should be possible at one frequency.
Did you look at the pre-amp output? Pin 1 for the first stage.
Sure, if you have the wire, start making the RX coil.
Don't worry about finding the demod signals for now, you have found enough useful signals to start.

[Henrikras]

Hi . (From my iPhone out.)
The battery is 3.9 volt. ( the 3.3 and 1.65 ) is at the ic preamp
Pin 1 is the same signal just higher.
the 18 mv is pp.