XP deus coil modification

[Henrikras]

No Big deal WM6, you Welcome. But maybee you or someone could help me with this.
I got into the Wall of my knowledge... Can you give me an idea what I should do next.
I'm ready to put the electronic in a box and connect the the RX and TX terminals to a female plug. (Plug would Be nice to easy work)
But what would you do?
1. Try to find a aftermarket coil, another brand and Freq., there could Be tuned to do some test. (Difficult to find with so high mH / R). This only to make some test, how the electronic react.. (Pinpionter / sensitivity / ground balance)
2. Start to make my own small coil and do what I can to get high mH and R, and then finetune by C from results of mH.
My brain says that If I could make or find a search coil with a RX 5.0 mH and a TX 3.0 mH (1/3 of the XP coil) with close to same high R and finetune with outside capacity, there is a chance it could work !
I never seen so high R at any VLF coils I been working at... What the reason to use so high impedance ! Maybee its was the only way to make a multi Freq. search coil, with relay swiching the Capacity, to keep low C (space and size).
Thanks.
Henrik.

[WM6]

It is not so unusual R data of coil.
Some Tesoro Lobo coils are pretty the near to yours:

Lobo 8x15
TX
1.4mH 14E

RX
10.5mH 62E

From my point of view approach under 2. is the best.

Put all electronics in separate box outside of coil (box connected replaceable to upper side of coil), make your own coil(s) by follow measured data - in first line inductance. This way you get unlimited field for coil experiments.

Is all electronic inside Deus, as you post on your photos?

[Tepco]

This is interesting. Now, you already demolished it, can you remove and measure tuning capacitors? And eventually figure out how they are switched at different frequencies. I checked coil data, wire diameter, resistance etc, everything adds up, values are good.


I can just recommend approach #2, making your own coil. Keep inductance and wire size, just recalculate number of turns. Just suppose, coil resistance is critical, intentionally low Q, if you deviate much from original, this can mess up number of things like LC tank impedance, freq. offset etc.



Give me nice idea to add something like this to KROT3 multifrequency detector, hah, 20$ DIY deus...

[WM6]

Hi Henrikras

Are you sure that TX coil data are correct:

L=10.4uH
R=21E
AWG 0.19

L=10.4uH is pretty low value for 21E.
Maybe it is 104uH or 1.04mH?
Or wire is made out of aluminum?

[Skippy]

Oh well, so much for my clever coil ideas. Notice that the coil is very high Q-factor. Even at 4KHz, it calculates as Q=12. That's how they keep the Q high - they make the coil higher in Q than necessary, and possibly reduce it, with added resistors? No matter, you have the coil data, I think you will have to make your own, or else you could get poor performance, or no performance. The L values are not that high, remember, L varies with (turns squared), you probably only need 100 - 200 turns on your coils (very rough estimate), nothing exceptional. It's good that the coil is easy to copy, and it also means the 4 frequencies should all still work, as originally. Getting the L correct should not be too hard - skilled use of Qaoshi's Qoil Qalculator, combined with adding a few extra isolated turns during winding should be all you need, eg. wind 100T +2T +2T if you think 100T is what's needed, then you can make 96,98,100,102,104T.
One idea, if you're fitting the electronics in a new box, is to replace the foil-pouch LiPo cell with a larger capacity better quality one, like a 18650 LiIon cylindrical type.

[Tepco]

Hi Henrikras

Are you sure that TX coil data are correct:

L=10.4uH
R=21E
AWG 0.19

L=10.4uH is pretty low value for 21E.
Maybe it is 104uH or 1.04mH?
Or wire is made out of aluminum?

Values are in mH,not uH

[Henrikras]

Thanks all.. Try here to answer.
WM6 - " Is all electronic inside Deus, as you post on your photos?" YES. I can can upload a new picture soon.
Yes the TX is 10.4 mH... Then everything should Be okay. + / - a little.
Skippy- Good idea with the 18650 cell. But I'm not sure that one them will give longer time. (18650 = 3-3500 ma best ). test needed.

To you all.. Okay making my own small coil is the way I go. Because I didn't damage the XP coil, and still got the cobber wires TX and RX to connect a cable, I could start with a cable at the XP coil, and see the project works. I still got my own 11x13" Deus coil to test how much lose I got.

I got one Questions ! There is no wire to the Shielding coming out to the board !! I can see that the ground at the board is connected to the cold side of the TX.. Is this a good idea, be the shield connecting at the Coil cable ? I think I saw this Once before. !

Did I forget something please ask again.

Henrik

[Henrikras]

Some more pictures...

[golfnut]

Hi - a few questions/observations for you..


Was this one working OK?


If yes, i would scope the Tx drive and the Rx amplitude and phase so you have a reference to aim for.


Also
Consider the screen options and connection point for your modified version..





The suggestion in discussion is that the relays are switching caps in for various frequencies - what I find hard to believe is, these relays take about 200mW - so say in lowest freq - all caps in - both relays ON thats almost 1/2Watt - this doesnt add up to me.

Could someone confirm if audible click occurs on freq change?


I suppose the relays could be latching type with small magnets in - so pulse to toggle state - no keep alive current required??



The other thing that is odd, the published frequencies and freq shifts available does not sound like LC tuned Tx (as too precise published numbers) - I suspect the Tx wave is derived in SW and passed out to the drive electronics to coil.

Can we get image of reverse side pls.

Solvent will make the silicone expand and go weak for peeling.

S

[Skippy]

It's a good idea to try the existing coil with the circuit-board & battery remote.....but: don't forget the coil was nulled with those items close/inside the search -coil. If you remove them, the induction balance may be upset. The long extra wires may also pick up interference, I suggest making a twisted pair for TX and the same for RX, or even use screened twisted pair cable.
I think you (we) are going to have to work out some point on the circuit-board where coil output can be monitored, eg. pre-amp output, maybe even the two demodulated X and R DC signals. These would be useful for nulling your new coil.
Edit: the relays are almost guaranteed to be latching types (internal permanent magnets) - the Axicom datasheets should be easy to find.
The precise freqs are software/DSP derived, for certain, but the coil is still LC tuned to the correct frequency, within a few percent, anyway.
I don't recall reading what the capacity of the standard LiPo cell is, but I know that early coils had lower capacity than later production ones, maybe as much as 50% more on newer models. This could be simply a bigger cell squeezed in, or 'technological development' of LiPo cells. I recall a fugure of about 1000mAh, you can work it out, the cell will have a type number that is related to it's physical size, eg. a 263441 cell is 2.6mm thick by 34mm by 41mm

[golfnut]

They do latch.. You get all of the benefits of almost zero signal loss - no Q degradation /loss and no current consumption post latch.

There is a requirement to reverse the drive direction to latch and to reset

[WM6]

.....but: don't forget the coil was nulled with those items close/inside the search -coil. If you remove them, the induction balance may be upset. The long extra wires may also pick up interference, I suggest making a twisted pair for TX and the same for RX, or even use screened twisted pair cable.

Agree. As I understand, his idea is (mine too), only to put DEUS board outside coil housing instead inside. Without any coil cable or very short. Probably board box fixed to coil housing using some adequate connector only. Or very short cable only for direct connection.

[Tepco]

Relays are latching type, Axicom IM41, looking at this board picture, my best guess is, actually only TX is resonant, need to be, driven from 3.6V battery, probably series resonance, then Rx is non resonant. Making DIY coil for this seems to be relatively easy assuming some form of software implemented electronic coil balance is not used. Reducing coil diameter by half and recalculating no. of turns, total wire length, and resistance will be only some, roughly, 20% lower, I don't think this is fairly significant. Will be nice to see some scope measurements, or macro mode photos of cleaned board.

[Henrikras]

Thanks guys...
I can see that I got a lot to learn.. Still new in this Remember. I will try as good I can to follow you.
Picture reverse side of the board is uploaded, see down. Sorry can't remove all the silicone.
It think would Be difficult with a short coil cable.. 1. Big mechanis influence at a small 5x8 coil. 2. Difficult to work at with scope and finetune close to the coil.
I can allso hear the relay's swiching, changing Freq.
When I did the LC test to find resonans... First with a 6.8 NF and then a 15 NF, I noticed that the peak was lower that I'm used to working with some other VLF coils.. I was using a 2.2 Kohm in this test. I dont know what you call it, but it seem to me that the L is wide...!
Yes the coil was working nice before I open it up.
Battery can wait.. First make this project work. But you properly right Skippy. (1000ma).
Next step must Be to scope this XP coil. One little problem. I removed the Battery cable, but some result should come out.
Step 2 is to connect a cable to the XP coil, and work with that.. Ground, shield, and learn.
Then If all this succesed, starting to make my own small coil. I would get help from Qiaozhi nice work, http://www.geotech1.com/forums/showt...oil-Calculator . I used this before and it was a great help.

the bigest problem would Be the shielding. This matter I had problems with before. And in this case, the XP coil dont seem to got a shielding wire connected to the board. I'm confused..
Henrik.

[Skippy]

Probably just the receive coil is shielded, and the shield is connected to the cold end of the RX coil. It's possible the coil case is conductive, graphite loaded (could you check for resistance with a meter?), and there may be a connection to this somewhere out of sight. This would likely connect to RX ground, too. It would be interesting to see how the voltage on the TX varies with the "coil power" setting. I assume that the receive gain (software, probably) is adjusted accordingly, to give the same sensitivity, eg if TX voltage is halved (1/4 power consumption) the RX gain is doubled etc.
What kind of small coil are you thinking of making? There seems to be a lot of praise for elliptic shaped ones, eg. the Teknetics T2 style, and the newer 11 x 5 from Tek, and the SEF 'butterfly' style. Maybe a copy of these, in 'miniature', eg. 6" x 4" (150 x 100mm) might give better results than a plain 'circular' DD.(like the original Deus coil)