complete project

[Davor]

I imagine it wrenching the target hither an thither, wringing out the greatest possible response from it.

Unless I'm terribly wrong, this detector does not do such thing at all. Instead it causes a Rx tank to ring in case of a target being underneath it. A ringing Rx coil is in a way a good thing because at start sin(x) ~ x (or a ramp) that makes for much lower initial voltages than traditional PI, while return pulse* energy is being conserved.

* In reality there is no such thing as return pulse at LF, just the energy being transformed by a Tesla - type transformer from Tx to target and back to Rx.

There is not much you can do about this transformation efficiency, except maybe building a better coil, but there just might be some approaches that may improve Rx sensitivity. I think applying a weighting function to Rx frontend may be that answer. I strongly believe that the ramp action of sin(x) ~ x could perform much better if only a first half sine is examined - even if it takes a lower resonance than Dave's solution.

[Kev]

G'day Kev
that sure is spectacular countryside you get to detect in
we have rellies in Christchurch, they have been ordered out of their home because of the quake damage, yet some houses in the street are undamaged.

Gid'day 666,
Yep, that's the way it went, all depends upon what lies beneath your house 10s of metres down. When the first Europeans arrived here way back, they filled in a swamp and built the city upon it, as it was the closest available land to the deep water port. Sadly if your house was over one of these subterranean streams or springs then water boiled up during a large quake or aftershock, and the ground turned to quick sand. Have you ever pattered the sand at the beach near the water line? You'll have a picture of liquefaction.

We get away to the hills as often as we can and leave all the stress of it behind us

I'm not convinced that (by looking to the patent) it is possible to increase depth by much with this particular solution - instead of exponential fall we have an exponentially fading sine.

You could be right, but the way I see it, a ringing coil and by extension the field, is going to have a much greater dV/dt than a critically dampened one. I imagine it wrenching the target hither an thither, wringing out the greatest possible response from it. Dave doesn't mention it in the patent, but at the time he was working on this there were a lot of experiments being done with constant current coil sources, he mentions in the patent high current pulses, perhaps he is using this typology?

What is really impressive is the full depth Fe discrimination.

Tinkerer is on the right track I think, maybe achieving the same results but with a public domain solution, I hope to have some time soon to experiment with his generously published findings.

Cheers
Kev.

[Davor]

I recently stumbled upon Dave Emery's patented Resonance PI. I was wondering if the TEM system uses a similar approach as far as Rx is concerned? I know Dave doesn't use Caps in the TX and the TEM coil isn't in a balanced configuration, at least that's what I remember, could be wrong. here's a link to the pdf. http://www.google.com/patents/US20090045813.pdf

One of my musings here on this forum is that PI Rx is not nearly efficient as it could be, and waiting for the perfect sampling moment is a main symptom of it. My thought is that some weighting function could squeeze much more of the target information than a mere exponential curve can. This resonant ... thing is in effect an energy conserving weighting function. However, I'm not convinced that (by looking to the patent) it is possible to increase depth by much with this particular solution - instead of exponential fall we have an exponentially fading sine.

[6666]

G'day Kev
that sure is spectacular countryside you get to detect in
we have rellies in Christchurch, they have been ordered out of their home because of the quake damage, yet some houses in the street are undamaged.

[Kev]

Hi Tinkerer,
Here are some images of the country I detect in mainly. I also like river gorges, which is similar, large obstacles, deep & shallow overburden, damp and unpredictable mountain weather etc.,

Mountain camp in auriferous country


Thick grasses, tussocks and peat mean that a deep seeking detector is required (don't look at my wife using a Gold Bug VLF, actually she did OK with it in the rocky places, nice and light for the female enthusiast)


The quarry, a quarter oz found on this particular trip.




I meant to say that peat usually means that basement will be fairly deep so a deep seeking machine is required, especially when a thick mantle of grass overlies it.

I use the slow motion filters on my Minelab at present in this area, as you do need to poke the coil in and about the grasses, it achieves much better depth this way too.

The main thoughts on miniaturization, is that fact that all the gear has to be lugged in on ones back, so the less area and weight the control box etc., consumes the more space is available for food

The rivers and lake shores would give up many troy pounds within a couple of metres of the surface, that's all that would be required. I'd even consider using a pelican case and just opening it up and making adjustments before entering the water, or wading up a gorge channel.

Presently I'm using hip mount Li-ion batteries on my Minelab, it's called a Pocket Rocket system produced by Coiltek www.docsdetecting.com/lithiumionbp.html
I can purchase extra batteries locally for about $35 US they are listed as being 6.6 AH when new and each one will run my GPX4500 for about 6 hours, 5 after a couple of years.

I recently stumbled upon Dave Emery's patented Resonance PI. I was wondering if the TEM system uses a similar approach as far as Rx is concerned? I know Dave doesn't use Caps in the TX and the TEM coil isn't in a balanced configuration, at least that's what I remember, could be wrong. here's a link to the pdf. http://www.google.com/patents/US20090045813.pdf

Sorry for the delay again, busy with quake repairs to the house, I'm situated in Christchurch New Zealand. We've had a couple of good shakes over the last couple of years.

Best regards
Kev.

[Tinkerer]

Hi Tinkerer,
Sorry for the delay in replying, I had to nip away for a week.
I don't want to hijack this design I just realised that if you were tailoring it towards old coinage and artifacts as per satdaveuk's suggestion, then I could adapt it for my needs.

The type of country I hunt, is somewhat like Northwest European Roman sites, having lots of tussock grasses and peat that reduce depth markedly. I'll link to some photos when flickr stops having hiccups.

I expect I would need a coil size of around 60 cms able to detect a 10 gram nugget (20mm coin) at about 45 cms. The Minelab GPX4500 will easily detect such a target at 40 cms and deeper with a 45 cm coil. The problem with the Minelab is its weight and poor ergonomics. Hence my original thoughts of miniaturizing Tinkerer's PI (SMD, 4-6 layer PCB) as many of my sites are many miles from roads well away in the mountains, and I need to lug enough power for up to 40 hours detecting. A flexible roll-up solar panel is an option in summer, but not in spring or autumn.

Showerproof would be ideal as mountain weather is unpredictable, however the possibility of a waterproof fresh water discriminating machine could open up vast areas.

As previous posters have said on this thread, you have already developed a detector already that has such potential, it exists across many posts and threads in the form of developmental blocks. The problem is deciding which blocks to collect and assemble to get a working optimised machine. I think the Guys, myself included were very interested in your assembling such blocks in one thread as a complete design. However, the potential of a TEM solution could over shadow all your previous work, and so I don't want to discourage you from proceeding down this course instead.

I am interested in your 12V front-end, since I will need to go with a medium power option. I suspect that using the TEM system will actually produce results only achievable with much higher powered front-ends, do you agree?

Cheers
Kev.

Hi Kev,
Your situation presents an interesting challenge.
Let’s take a closer look and see if we can understand the problems.
I say WE, because I hope that others who have similar interests and problems might join in to help finding solutions. Many minds= many ideas= many solutions.
I am adding my comments between your lines. I will take some guesses, please correct me when I am wrong.
Hi Tinkerer,
Sorry for the delay in replying, I had to nip away for a week.
I don't want to hijack this design I just realised that if you were tailoring it towards old coinage and artifacts as per satdaveuk's suggestion, then I could adapt it for my needs.

The type of country I hunt, is somewhat like Northwest European Roman sites, having lots of tussock grasses and peat that reduce depth markedly. I'll link to some photos when flickr stops having hiccups.
Peat, why would that reduce the depth? It is not mineralized. Could it be that it is conductive? I think it is acidic. We might consider it an electrolyte. What is the underlying rock?
Is the ground response fairly constant? Or is it highly erratic?
Tussock grass, I guess you have to walk around the tussocks and sweep the detector around the base of the tussock? This makes the actual sweeping motion difficult.
Would it help if the motion could be slow, like 0.5m/s? Is it possible to maintain a steady motion of the coil?
Motion speed control.

I expect I would need a coil size of around 60 cms able to detect a 10 gram nugget (20mm coin) at about 45 cms. The Minelab GPX4500 will easily detect such a target at 40 cms and deeper with a 45 cm coil. The problem with the Minelab is its weight and poor ergonomics. Hence my original thoughts of miniaturizing Tinkerer's PI (SMD, 4-6 layer PCB) as many of my sites are many miles from roads well away in the mountains, and I need to lug enough power for up to 40 hours detecting. A flexible roll-up solar panel is an option in summer, but not in spring or autumn.
I don’t think that miniaturizing the PCB will change much to the weight problem. Also a 60cm coil will most likely be more heavy than a 40cm coil.
Personally I lean towards SMD in general, but I still have a lot of through hole parts to use up. Just a few years ago, I thought that the SMD will be the end of my hobby. These things are so small I can’t see them without glasses. But now I need a large magnifier for everything, so it does not make such a big difference anymore.
The ergonomics. Could you make some simple sketches of your ideas of ergonomic improvements?

Showerproof would be ideal as mountain weather is unpredictable, however the possibility of a waterproof fresh water discriminating machine could open up vast areas.

Would the freshwater machine be used for diving? How deep?
I used to build my own detectors and housings for recovering treasure from the bottom of the oceans, so I know what is involved.
Waterproof controls are expensive. This means we would try to have a minimum of controls. Make it extreme simple for a start.

As previous posters have said on this thread, you have already developed a detector already that has such potential, it exists across many posts and threads in the form of developmental blocks. The problem is deciding which blocks to collect and assemble to get a working optimised machine. I think the Guys, myself included were very interested in your assembling such blocks in one thread as a complete design. However, the potential of a TEM solution could over shadow all your previous work, and so I don't want to discourage you from proceeding down this course instead.
Some of my earlier ideas were not bad, but in general, there is constant evolution, better understanding and accumulated knowledge, so I really recommend going with the latest design.

I am interested in your 12V front-end, since I will need to go with a medium power option. I suspect that using the TEM system will actually produce results only achievable with much higher powered front-ends, do you agree?
The TEM method is very power efficient. Until now I have not tried to cut down on the power consumption, instead I have been trying the increase dept and the signal response amplitude and S/N, this ay eliminating a lot of problems that come with very high amplification.
I am working on a LP (low power) Lite solution. This might just be what you need.
Could you give some more information about your battery ideas? Let’s say we chose 12 batteries. Would you use LI-Ion? What is the maximum weight of batteries you would consider OK?
Tinkerer

[IBGold]

That is what I did just built it onto a small bit of D/Sided board as a plug in so we can test various designs have fun.

Regards, Ian.

[satdaveuk]

Actually im going to be applying that sound output stage to the mini pulse 3 project, main pcb is full populated will make another small pcb for the audio, bit over the top but can always turn the volume down

[satdaveuk]

Thats great
I didnt bother you both for the last couple of days because gathered you would both be busy working on the project, if theres anything you think I could help just ask, although my technical ability with this design is limited always willing to try and learn.

Warm regards

[IBGold]

The TEM-TX board the GG Group are working on with Tinkerer will have three switchable power levels and I hope to be making the new prototype boards in the next couple of weeks and Tony I have built three different audio stages for testing including the one suggested by satdaveuk.

Regards, Ian.

[Kev]

Hi Tinkerer,
Sorry for the delay in replying, I had to nip away for a week.
I don't want to hijack this design I just realised that if you were tailoring it towards old coinage and artifacts as per satdaveuk's suggestion, then I could adapt it for my needs.

The type of country I hunt, is somewhat like Northwest European Roman sites, having lots of tussock grasses and peat that reduce depth markedly. I'll link to some photos when flickr stops having hiccups.

I expect I would need a coil size of around 60 cms able to detect a 10 gram nugget (20mm coin) at about 45 cms. The Minelab GPX4500 will easily detect such a target at 40 cms and deeper with a 45 cm coil. The problem with the Minelab is its weight and poor ergonomics. Hence my original thoughts of miniaturizing Tinkerer's PI (SMD, 4-6 layer PCB) as many of my sites are many miles from roads well away in the mountains, and I need to lug enough power for up to 40 hours detecting. A flexible roll-up solar panel is an option in summer, but not in spring or autumn.

Showerproof would be ideal as mountain weather is unpredictable, however the possibility of a waterproof fresh water discriminating machine could open up vast areas.

As previous posters have said on this thread, you have already developed a detector already that has such potential, it exists across many posts and threads in the form of developmental blocks. The problem is deciding which blocks to collect and assemble to get a working optimised machine. I think the Guys, myself included were very interested in your assembling such blocks in one thread as a complete design. However, the potential of a TEM solution could over shadow all your previous work, and so I don't want to discourage you from proceeding down this course instead.

I am interested in your 12V front-end, since I will need to go with a medium power option. I suspect that using the TEM system will actually produce results only achievable with much higher powered front-ends, do you agree?

Cheers
Kev.

[Tinkerer]

TINKERERS_TEM_TX_LP

Here is another little piece of the detector. A LP (for low power) TX board.

As I showed above, there is quite a difference in power between 12V and 30V TX. So this is the low power TX, running on 12V. Still capable of reaching very deep.

Enjoy

Tinkerer

[Tinkerer]

Great stuff Guys,
You're a powerhouse Tinkerer, the ideas just keep on flowing, magnifique!
To get involved in this project should I build a UNI PI and TEM TX? I'm pretty blank on the ideas front but would like to contribute something towards it.

My quarry is deep largish nuggets, they would not be dissimilar to old coinage and bronze age artifacts, so perhaps this would be a multipurpose machine, no?

I've long wanted to do a modular design with the motherboard having the power supplies and the other blocks, Tx, Rx, uC, Audio etc., being pluggable modules into the MB. Then various upgrades and experiments can be done on any one block without scrapping the whole board and starting from scratch, much like what you're doing now Tinkerer.

I though need to do a compact version for high mobility, surface mount etc., which has always been a bit of a pain for me since when down scaling circuits I've found many problems arise when placing components close together....it requires much skill I believe to do really good compact layout on mixed analogue/digital solutions.

Cheers
Kev.

Hi Kev,

the mother board idea keeps coming up from time to time. It has a lot of merit, but on closer look, the individual needs are often so different that it is really difficult to design a detector to fit all needs. Unless one makes so many compromises that the final result becomes a very watered down "super lite" model.

The basic idea for the TINKERERS_TEM_IB-PI, is for a detector to walk the open fields. Is this where you are going to look for nuggets?

If you go through all the trouble to build your own detector, I am sure you want it to be as close as you can get, to your individual needs.

What are these needs? If you give me some hints, I can come up with ideas of meeting these needs.

Does it rain a lot where your nuggets are? A water proof detector might be the answer. This means few controls.

Are you detecting in the woods? The ergonomics of large coils become problematic. How deep do you want to detect? The depth is relative to the coil diameter.

Can we find solutions to all your needs? Well, we can give it a try.

Tinkerer

[Kev]

Great stuff Guys,
You're a powerhouse Tinkerer, the ideas just keep on flowing, magnifique!
To get involved in this project should I build a UNI PI and TEM TX? I'm pretty blank on the ideas front but would like to contribute something towards it.

My quarry is deep largish nuggets, they would not be dissimilar to old coinage and bronze age artifacts, so perhaps this would be a multipurpose machine, no?

I've long wanted to do a modular design with the motherboard having the power supplies and the other blocks, Tx, Rx, uC, Audio etc., being pluggable modules into the MB. Then various upgrades and experiments can be done on any one block without scrapping the whole board and starting from scratch, much like what you're doing now Tinkerer.

I though need to do a compact version for high mobility, surface mount etc., which has always been a bit of a pain for me since when down scaling circuits I've found many problems arise when placing components close together....it requires much skill I believe to do really good compact layout on mixed analogue/digital solutions.

Cheers
Kev.

[Tinkerer]

TINKERERS_TEM_IB-PI

TX and Bucking Coil

TX – 24 turns, CLOCKWISE, #14Awg, Audio cable, fine stranded. Wind 4 turns wide and 6 turns high
Inner dimension for winding 95cm x 45cm
Bucking coil wound with the same cable, ANTICLOCKWISE, 6 turns in line high, single layer.
Inner dimension for winding 70cm x 30cm
Total cable needed, about 87 meters, about 1.4Kg.

TX voltage and cable gauge.

The choice of the TX voltage

At TX 190us, about 5000 PPS, Pulses Per Second
At 30V, AWG #14, cable we get about 5.2Amps peak coil current. 1300gr copper, 4.2 Watt
At 12.5V we get 2.17A
At 11V we get 1.91A
With 12.5V and AWG #16 cable, we get 2.13A. 822gr copper, 750mWatt
With 12.5V and AWG #18 cable, we get 2A. 460gr copper, 1.2Watt
But this is not all. The increased resistance also reduces the efficiency. More losses, compare the Watt power consumption.

Tinkerer