TESORO GOLDEN SABRE

[Max]

Regarding this simulation stuff you guys are doing with the TX osc:
One important thing you'll eventually come across (if you just randomly swap component values to make improvements) is that you'll end up with a circuit that performs well in simulation but doesn't work in practice. My advice is - before you build anything, run a Monte Carlo analysis and a temperature sweep. Can LTspice do this?
If you modify this amplitude-stabilized configuration without running an MC analysis, you could build 10, and only 5 might work - if you're lucky.

By the way - nice coil Max!

Hi,
yes it does montecarlo analysis ... next time I'll use it before making mods or circuits to be sure or changes involved. Thanks.

About coil... yes... to be homemade with strange things it looks not too bad.
But what I like more is weight : 350gr total is very relaxing for arm... without wasting performances.

I've used the surfboard approach... polystyrene bubbles to keep weight low and epoxy to reinforce it and polypropilene bottom... and it works pretty cool.

The little work was on cutting polystyrene foils and I've made and hot cutter using NiChrome-wire and a PWMedd Mosfet... like in model airplanes starters... and it cut that like a laser

Best regards,
Max

[Max]

question for ivconic and max:

have good function tgsl underwater?
------------------ in proximity other md, e.g interferences?
-------------------- hot rocks?
-------------------- in exteme conditions hot or cold e.g what stability have
-------------------- ! because xlt white have faults after 1/2 hour these is work
-------------------- is good discrimination tgsl on iron one x one metre objet? to 30 cms depth?
------------ resistence tgsl in porcente humidity no risk of short circuit? eg burn
thanks for attention
detectoman

Hi,
Underwater ? No you cannot use it.... maybe you can use on wet sand e.g. of rivers (not in salt water environments)

Interference ... as other detectors ... I mean if you have another VLF running at 14KHz at less than 1meter that would be a real problem... otherwise not...for PI near you need at least 10-15meters far away... otherwise it will pick up the PI TX signal very easy.
On workbench it's about totally immune to "house" noise... apart extreme cases I wrote in a post above (flyback near, tv sets on, fluo lamps... and the like).

Hot rocks are a problem for TGS if they are very large and with much minerals of iron inside. Small things like a cigarette box to a VHS box or similar have no effect on it, same for pottery stuff , bricks... it's ok if you set GEB far middle.

Temperature has no great effect on it from 10 to 35°C... that's cause the zener voltage change really a few with temperature... and all the rest is rock soild... even if you heat up some stuff on PCB intentionally it remains quiet ! Only noise source is from internal intermodulations and part noise that you can minimize using special parts.

You could have problems at temperature changes (e.g. from cold early morning to warm morning say... when rise is of 10°C or more in less than 2hours, so >5°C/h) and for temperatures above 40-45°C cause of the increase number of minority carriers and the like.

Discrimination is perfect against iron (pure) on small items like coins. When you have large iron stuff e.g. poles or large e.g. iron plate (>30cm diameter) you'll detect at when the thing will start distorting too much the magnetic field... for the pole (e.g. height 2meters, diameter 6cm) also from 40-50cm... for the plate at less distance.... you can detect e.g. an hammer in disc just if it's big and when at few mm or touching the coil !

I think it will work till 70% humidity very good... and things could be worse only at >85%. I've tested at 90% humidity just one day ...and apart the stress of digging holes at 33°C 90% humidity I found it worked good... just some chatter sound from time to time... nothing else. I think that's impossible to damage TGS even at 100% humidity cause it doesn't use lot of power or hi-voltage... so it's safe as using an MP3 player in your kitchen... it can work there for years without problems ! That's what I think.

Best regards,
Max

[tiktak]

Max NICE coil!

[Max]

Hello Ivica and frends

No problem for showing the goldy pcb. Made it together with Nakki.
Here the latest version.... but there is still on high sens sometimes erretic noise.
Can it be that it is 50-60HZ ?? Is it a pcb design error?

Ap

Hi Ap.Berg,
thanks again for your work (and thanks Nakki too) I found it really cool.

The picture you posted also seems a very nice work about assembly of it.
Very good, congratulations.

About noise... well... yes if you have some noise source near it will pick up some and you'll ear in speaker... but it's rare if you haven't e.g. fluorescent lamps just over coil... and the like... e.g. a TV set on just at few distance etc

Personally I think that TGS with good shielded coil if at least 1 order of magnitude better on this than any PI on the workbench... they have all serious problems with 50-60 noise. VLF suffer more of TV and other noise sources at 10s KHz (like electronic ballasts etc flyback circuits...).

I think that the noise we hear sometimes... when e.g. we rotate GEB trimmer to particular position during tuning is related to circuit problems...and coils are ok.

I've tested all coils I have suitable (9x8'' original, 8'' opencenter, 8'' DD, DD22cm, DD255x137, OO12cm...) all give that noise sometimes at certain trimpot positions... I noticed that using a ferrite toroid core... trying to null effect of it with various coils and got noise quite easy when I pass the sensitivity area for ferrite... just 1° turn more on trimpot and I get noise at max sens.

I strongly think is some kind of intermodulation inside the circuit between osc freq and others... and probably comparators are much involved in this cause they commutate at that frequencies.

Also , as you can see from simulations, the only oscillator produce already some intermodulation cause of feedback part.

So, if we want avoid this we have to find the sources of that problem that's all about purity of signal we have through the circuit.

Another thing that I've noticed is that when I touch with finger the aluminum case of disc pot noise disappears... same happens just nearing the finger to the geb trimpot... so sure there are problems that show up at particular phase shifts...and that could be related to intermodulation... cause at some phase shifts the effects could subtract one each other ... and at others they could sum giving that bleeping.

I've also connected the aluminium case of disc pot to gnd but that doesn't solve problem... works just with finger !

What to say... it's a real mistery !

Best regards,
Max

[tiktak]

Hi,

I have made the first PCB with NOTCH.
Why you remoove NOTCH section Ivconic?

[tiktak]

Hi,

Hi Max,
I am using DT9205A multimeter, it have 200 mV range in AC.And like you say 1M resistor and 15N capacitator paralel and conected to RX.And look for .000!
So If my problem is nulling then............

I have a few more questions for You and Ivconic:

1.Have you reach 35 cm for 1 denar in air with 1M modification of not?

2.When you wind coils you start winding from bottom and you moove up without turning back or you make few layers?

3.I can find KA and TEA 2262 can I use this for TLC2262 or they are different things?

Thanks

[ivconic]

Like somebody blowed whistle!!! Everybody left!?
I am going too....
Fade out....

[ivconic]

question for ivconic and max:

have good function tgsl underwater?
------------------ in proximity other md, e.g interferences?
-------------------- hot rocks?
-------------------- in exteme conditions hot or cold e.g what stability have
-------------------- ! because xlt white have faults after 1/2 hour these is work
-------------------- is good discrimination tgsl on iron one x one metre objet? to 30 cms depth?
------------ resistence tgsl in porcente humidity no risk of short circuit? eg burn
thanks for attention
detectoman

Underwater...? I never tested it!
Interferences.....depends what kind of those? For example, in my workshop there are some sources of noise,interferences...TGS showed absolute imunity on those! Superb!
Hot rock....very mum "cracks" can appear on those. Not disturbing much, at all! Again good!

Temperature.... i am using my TGS for over 3 months under various temperature conditions...No problems! I noticed slightly better perfomances when higher moisture...for example; early in the morning! But on the same field i came early in the morning, when sun rises and temperature rises also, soil start to dry; i noticed some unstabillity than? Ocassionall beeps!?
But if i come on the same field, in the middle of the day...than TGS works stabile....

Discrimination.....is good as it can be. Smaller iron objects disriminate perfectly - absolute. Large iron masses cant discriminate well, but nevr mind, audio on those is recogniseable - different than on "coloured" items...so it is easy to distinguish it..

Last question....well it depends on coil housing mostly. If you put it in a "pocky" enclosure...for sure it will suffer...But if you put it in closed, good isolated housing, than no problems at all! Same with coil...

Damn! I am still here....
I just cant give off...Rare oportunity...many members on same place at same time! Carl, Carl...! That's why i suggested chat mode here!

[detectoman]

question for ivconic and max:

have good function tgsl underwater?
------------------ in proximity other md, e.g interferences?
-------------------- hot rocks?
-------------------- in exteme conditions hot or cold e.g what stability have
-------------------- ! because xlt white have faults after 1/2 hour these is work
-------------------- is good discrimination tgsl on iron one x one metre objet? to 30 cms depth?
------------ resistence tgsl in porcente humidity no risk of short circuit? eg burn
thanks for attention
detectoman

[Qiaozhi]

Hello Ivica and frends

No problem for showing the goldy pcb. Made it together with Nakki.
Here the latest version.... but there is still on high sens sometimes erretic noise.
Can it be that it is 50-60HZ ?? Is it a pcb design error?

Ap

Looking good!

What sort of erratic noise? Is it random?

[ivconic]

"....Get one. I've no idea how how you can build detectors without it...."
I do ask myself simillar question oftenly!?

Actually i have 2 oscilloscopes. But both are obsolete. I didnt mention them so far cose i do not count on those seriously....Some less important things can be measured with them, but now we are dealing with more delicated values here, and those are unuseable for that matters...
Yes i have to buy new one asap...or i better leave this job for good!

I 'll try to follow your advices there....I am going this moment to my workshop to try to do some things!
Bye!

P.S.
Thatnks a lot friends!

[Qiaozhi]

Regarding this simulation stuff you guys are doing with the TX osc:
One important thing you'll eventually come across (if you just randomly swap component values to make improvements) is that you'll end up with a circuit that performs well in simulation but doesn't work in practice. My advice is - before you build anything, run a Monte Carlo analysis and a temperature sweep. Can LTspice do this?
If you modify this amplitude-stabilized configuration without running an MC analysis, you could build 10, and only 5 might work - if you're lucky.

By the way - nice coil Max!

[ApBerg]

Goldy

Hello Ivica and frends

No problem for showing the goldy pcb. Made it together with Nakki.
Here the latest version.... but there is still on high sens sometimes erretic noise.
Can it be that it is 50-60HZ ?? Is it a pcb design error?

Ap

[ivconic]

I'll do that today....this evening i'll post results...
Now i am going back to my workshop! (i am in living room now)
No smoking here (my wife's rule)....No place for me here...That's why i have to leave...i need fresh air (smoke)...
See ya in the evening...

[Qiaozhi]

One thing is still buging me;
again i went outdoor with TGSL. It is still producing false signals from time to time on the ground? I checked everything. Cant find what is the problem? So i have made TGSL on 2 different pcb's. One (bigger) from first page of this thread and second, smaller.....I removed all components included in notch section from larger pcb. Comparing those i saw that device with larger pcb is acting much better than device with smaller? First one is not producing to much false signals at all. Smaller one is producing to much false signals.
What is interesting; i can not provoke false signals to be produced by bending cable,shaking coil,punching it....remains silent. Not sensitive on any kind of "torture"...But when small item moved in coil vicinity, just about to provoke weak detection....device detect it weak and when item removed, device continue to "beep,beep,beep...."-ing all the time. Outdoor, when coil is in the air, i get simillar behavior, but when lower to the ground it stops beeping. Moving forward with coil 3-5cm of the ground, touching grass it is producing false signals oftenly?
Device with larger pcb is acting simillar but noticeable less false signals....very rare...on some fields almost none?
I collected those 254 coins in not time, with larger pcb.
I tried everything possible to find source of problem....without success.
I guess my huge problem is cose i dont have good osci. to accuratelly measure all suspectable "spots" here.
I am posting smaller pcb with component layouts, maybe some of you will spot some mistake on it. I got very tired of looking in it, and havent find anything bad yet....

Hi Ivconic,

I know I keep coming back to this ... BUT - what you are describing sounds exactly like the comparators are going into oscillation. Problem is that you don't have a scope yet. Get one. I've no idea how how you can build detectors without it.
The comparators on the outputs of the GEB and DISC channels have a threshold which is set by the sensitivity control. The GEB channel appears to have R40 there to provide some hysteresis to prevent this, but there's nothing for the DISC channel. Don't know whether this is a problem or not, as I haven't looked closely enough yet. If you bring a coin towards the coil to get a faint response, the comparator can easily start oscillating. It might even be worth just swapping the IC for another one. I've managed to cure some instability on another detecting by just changing the comparator. With a scope, you'll see the problem immediately.