TESORO GOLDEN SABRE

[Majster]

Hello again everyone
These are the words of a wiser than me! I am pleased to read the words of encouragement, seriously!
Unfortunately, I do not have a real two-channel oscilloscope, but only a DIY sound card simple circuit. That's why I read so much about nuling by ear, or with the AC millivoltmeter. But having only what I have, I had to try anyway. I connected the circuit to this sound card, launched the SoundCard Scope soft and watched what I can see. This is by no means a decent oscilloscope, but I think (yes, unfortunately I can't be sure, I just think) I can see both waveforms and that they have a phase shift, but I can't tell if it's 20 degrees or anything. Sampling is too sparse / slow. But it's a good program anyway, the frequency values of both coils it measures are the same when I measure them with an independent frequency meter. That is why I am trying with this AC millivoltmeter.
Overall it is like this:
1. The detector can see various pieces of metal, ferrite, copper, etc.
2. The sensitivity of this vision is poor (5-10cm).
3. The supply voltage (+/-) on the PCB is + 8.0V and -7.0V.
4. The diss mode is working similar, but I haven't nulled the coils yet, so there's no point in balancing the ground. To early for this.
5. The coils, depending on their position, sometimes oscillate longer, which is manifested by a pulsating sound.
Based on my observations, can I conclude that my PCB is OK? Is my problem only with the coils? Or differently: is it possible, being a layman, to make a PCB that works as described above (1..5), and yet it is not correct? I'm asking because it's my first VLF and I'm still learning.
I greet everyone.

[waltr]

Sounds like you got iy working. Swapping leads on the transistors is very common thing and great you found this. You are on your way.

The next Big step is TX to RX Coil nulling. This also really needs a two channel O'scope and is a very fiddly operation if you have never done it before. Do not rush and play with the null adjustment until you understand what it is doing.

[Majster]

Hello again everyone,
As I wrote earlier, I bent the coils to have their inductances closer to the values of 6.0 and 6.5mH, it turned out to be equal. I didn't even have to massacre them somehow, all I needed was a simple gum rings and old, empty plastic pens. The frequencies of the coils were then about 14.3 and 14.0 kHz. A little bit of a difference, intuition tells me it should be a bit bigger. So far, I have not fixed the TX permanently because experience and intuition tell me that I will unstick it more than once. I was not wrong. I planned to apply TX and RX and look for a position where the voltage of 7/IC101a / ground would be minimal. But it didn't work. The AC voltage is almost constant 4.6 - 4.7V (1000 x higher than 5mV), with a frequency of 13.7kHz, regardless of the position of the coils. Maybe I solder something wrong after all? What could I have done wrong? Maybe you have any other suggestions? Maybe the board is not assembled correctly?
I greet everyone.

[Majster]

Hi Qiaozhi,
I have looked at these documents, I know them, although I do not understand all of them well, thank you.
Greetings.

[Majster]

Hello again everyone,
And I did as I planned. I put all the ICs in the sockets. I connected the power and the loudspeaker. I connected the TX and RX and put both coils in makeshift form. At this stage, I was not fixing anything permanently. The coils are only lying slightly overlapping each other. I turned on the All metal mode, all 3 potentiometers at half scale. I turned on the power. I moved ferrite over the coils, a piece of steel, a piece of copper. Hear single or double beeps, copper seems to be giving a double signal. It is not very regular, the sensitivity is also not good (5-10cm), but I know this is just the beginning of the tuning and I cannot expect everything to be great at this stage. Then I moved a watch, a telephone, etc. over the coils. I can also hear signals, the sensitivity is better, but they are large objects. The coils sometimes go into some deeper resonance and the throbbing sound does not disappear when I take the items away. I can turn it off with the Diss knob, it's kind of weird. It can also be turned off by moving the coils apart.
Then I switched to Diss mode and looked for positions where the ferrite would be rejected and the copper would not. So far I have not succeeded: it either rejects everything or nothing. But I know that the coils are only lying together, so it would be naive to expect them to work well right away.
I understand these initial tests that the board is assembled correctly and all components are OK.
To the island / position 7/IC101a I soldered the lead/cable for connecting the multimeter. I am going to look for the minimum AC voltage value between this point and ground now. But I think first I should bend the coils so that their inductances are closer to the values of 6.0 and 6.5mH, what do you think? Once this is done I will attach the TX permanently in its semicircle to the base so that I can bend it a bit in diameter, what do you think? Then I plan to put RX on it and look for a position where the AC voltage of 7/IC101a / ground will be minimal. When it succeeds, I will have to fix the coils permanently and start tuning the potentiometers.
Maybe you have any other suggestions?
I must add that I wound the coils with 0.4mm wire, and their final resistance is slightly below 20 Ohm, I hope that is not a problem.
The fun is in motion, I like it more and more
I greet everyone.

[Qiaozhi]

Everything you need to know about the TGSL is located here on Geotech -> TGSL - Complete Details

[Majster]

Hello again everyone,
Thanks for the answers. The first thing I did was to carefully check the schematic and catalog description of 2N2907 and 2N2222. It saw, as I expected, that I have swapped CBE> EBC feet in both pairs of 2N. I have both BC547 correctly. I took out both 2N pairs and inserted them correctly. I tested the voltages and the generator / oscillator for both coils. I have a voltage of about + 8V and -7V. My coils have TX 14.2kHz and RX 13.6kHz, but when bending these values change a little, which is okay. During the winding, I checked their inductances and they had the values of exactly 6.0 and 6.5mH, they changed a little after binding, applying the screen and gluing. On the TX I have a voltage (AC) of 7.7V, which, as I understand it, gives an amplitude of almost 16V, which is also correct. The loudspeaker is silent, but I did not have both coils connected, only the TX. In the left IC sockets I have + 8V and -7V power supply, I assume that it is good.
I know that the best documentation for TGSL was done by Don Bowers and Ivconic (eternal praise for them, and their teachers, their families, children, grandchildren and so on to the sixteenth generation), but this is documentation for professional electronics rather, and I'm just an amateur . The instructions I've read so far (and as you know, reading and following them are two different things) were something like this (for example):
1. Solder elements 1, 2, 7 and circuit A, check the voltage on pins 4 and 7 in IC3 socket. It should be (something) V.
2. Connect this and that, check the frequency on pin 3 of IC5, adjust to the value with potentiometer 2 (or other).
3. Solder elements 6, 11 and 21, check something, etc.
This manual is not like that. I miss the IC marking on the PCB (yes, there are their names, but there is more than one on the schematic diagram of similar elements). I miss the indication of control points on the PCB in this manual. They are in the diagram, but I miss a detailed explanation of what value to expect at which point on the PCB. Even this documentation mentions differences in two similar (but not identical) PCBs. I know that a professional electronics engineer can handle it, but my profession is far from electronics. But I also know that this is how a people learns: by reading, trying and making mistakes. When everything is going well from start to finish, you can't learn a lot. But I am very far from being criticized, because I know how much work the authors of the project and documentation put into it all. I'm impressed. This is very good documentation, I wouldn't even start without it. It was only reason that I decided to do with TGSL, and I considered the Russian Terminator 3 and several Polish VLF MD projects (also quite good), for which the documentation was weaker (although in my language).
Loading photos doesn't work, I noticed it. I have a problem with this even though I am using the correct function.
Regards Ruben2000, Waltr and everyone.

[Ruben2000]

Hello Majster!!!
You must go step by step here in the forum is all the documentation about TGSL.
You must go reviewing point by point and always verifying each component.

The images of your PCB are not appreciated, reload it.

I used 2907 but it wasn't with 2N, it was another code and I also tried with A708Y and it worked the same. At that time I couldn't get exactly the components on the list and had to adapt.

[waltr]

I also solder all parts in but use Sockets for the ICs. This is have I built the TGSL using Silverdog's PCB.

The BEST info is concise form is Dan Bower's TGSL 101.pdf documents. Find, download and study.

First is the TX Oscillator MUST run. Pull all ICs, except U108 (the 7808 regulator) and trouble shoot the oscillator (section 1 of the TGSL101 schematic). You may have wrong values components or have them mis-wired.

After Oscillator is running at 14.5kHz the install the clock divider. This drives the DC-DC boost converter to get the -5V.
Now continue installing ICs from RX through to audio ensuring each stage works.

[Majster]

TGSL

Hello all,
I'm new to the forum. I'm a very (really very) beginner, but I've already done a few or more impulse detectors, and they work very fine. I can solder, etch boards, I understand the operation of basic, simple elements, I can recognize them. I can wind coils and I know what inductance, oscillator frequency is, etc. I have several multimeters (frequency, inductance, capacitance etc.) and I can use them. They are checked and tested on other older projects. Unfortunately, I do not have a real oscilloscope, but only an adapter for the computer sound card. But I'm not an electronics engineer. I decided to make a TGSL detector. I found information on the website:

https://simplemetaldetector.com/induction-balance-metal-detectors/tesoro-golden-sabre-light-tlsl/

I have prepared a PCB. Unfortunately, I do not have an iron or a laser printer, so the board is drawn manually. It was inconvenient for me to draw narrow paths on one side of the board, so I added two more adapters (bridges). Before I soldered anything to it, I tested all the tracks. They are all normal and have no short circuits or interruptions. Then I soldered the adapters (bridges) marked in the diagram (one goes under the IC socket). I checked again if everything was working. Then I soldered all IC sockets (I never put IC's without the sockets). I checked again that all paths were correct. It turned out that they are correct, have no short circuits and are conductive along their entire length. All fields connected with adapters have correct connections.


The instruction in the found documentation does not specify the exact order of placing the elements or the fields in which indirect measurements are made, so I soldered them all at once. I wound both the TX and RX coils according to the instructions in the found documentation, covered them with a screen, marked them accordingly. I measured the inductances of the coils and it seems to me that they will be OK when properly formed. They currently have inductances of around 6.2 and 6.8mH, but when slightly bent, I can easily get the required 6.0 and 6.5. I have prepared the appropriate cable with the screen. I looked at the Geotech1 forum in the thread above. Unfortunately, a thorough reading is not possible, because this thread has existed since 2007 and there are several thousand posts in it. I know that TGSL has been evolving for quite a long time and that my PCB version is one of the newer and proven ones.


I soldered all the elements into the PCB (I know that this is not the best way, especially when I install a system for the first time, but I had no other choice), and I had no major problems with finding the missing information (some capacitors are not marked, but result from the diagram / scheme, similarly GB connections, the discrimination are not precisely marked, but they result from the diagram). I dealt with it. I used all the elements in accordance with the list of elements found in the documentation. I did not use any replacements at this stage, although I know that some of the components are interchangeable (some transistors and IC), but I haven't done it yet.


Today I made my first attempt to run my TGSL. According to the information on the forum, I connected the 12V power supply to the PCB, the speaker, the TX coil, all potentiometers and switches. And this is where the problems begin, which was to be expected, because almost every new project is born in this way in pain. TX coil is not working, there is no oscillation, the frequency measurement shows 0.0. I measured the voltages on the CD4024 feet and unfortunately I do not have -5V anywhere. I have + 8V, which generates IC 7808, but unfortunately I do not have -5V. The voltages on the CD4024 are as follows:
1 7.9V
2 0
3 0
4 8.0V
5 8.0V
6 0
7 0
8 0
9 0
10 0
11 0
12 0.3V
13 0
14 8.0V


I don't know what's going on, can someone help me and tell me what to do next? Attached, my PCB, top and bottom. Maybe I did something wrong after all? It is probably so, because the information on the forum shows that TGSL is a proven and tested project many times. My paired transistors are 2N2907 (pnp) and 2N2222 (npn). Here I found information that they have the opposite feet than in the classic BC, and it's true, I knew about it. But it was also written somewhere above that even the same 2N2222 (or 2N2907) model can have different outputs, and that it depends on the end market (EU or USA), which seems unlikely to me, because they are probably all glued somewhere in China.
Can the positions of these paired transistors be put in BC557 instead of 2N2907 and BC547 instead of 2N2222? If so, maybe switching them would help. I have no other ideas at this stage. I would be very grateful if someone more experienced would help me, for which I thank you in advance.
I greet everyone.
[IMG]file:///D:/Film/Elektronika/wykrywacz/TGSL/Moj%20TGSL/IMG_20220129_105537.jpg[/IMG]
[IMG]file:///D:/Film/Elektronika/wykrywacz/TGSL/Moj%20TGSL/IMG_20220129_103549.jpg[/IMG]
Sorry for my English, I use Google Translator and that's why I try to build easy sentences so that this bot doesn't have too much trouble.

[Locator]

Thank's for your reply!

[Carl-NC]

I mean DDS generator with capacitor and coil tuned to the operating frequency we want as transmitter.

Yes, you can do that. Modern designs often drive the TX circuit from the micro at a fixed frequency but still resonate the coil at that frequency. In practice you may need to "tweak in" the capacitor using multiple parallel caps to match the resonant frequency. The micro pulses the TX current with a 25-50% duty cycle. A DDS generator could use either a voltage drive or a current drive. I think the benefits of using DDS will be minimal, perhaps a little less distortion. But that might be important in making a super-quiet ground balance.

[Locator]

I mean DDS generator with capacitor and coil tuned to the operating frequency we want as transmitter.

I mean that there is not a problem because a VLF detector measures the increase in amplitude at the receiver
coil and for discrimination the phase difference between two coils(transmitter-receiver),i think.


Thank's in advance!!!

[Carl-NC]

Hello,
i would like to ask you about this circuit and generally vlf detectors,if we can put in the position of the oscillator a crystal oscillator or a DDS generator
that produces exactly the same transmitter signal but with DDS generator and not with a self-oscillating transistor.Is that possible?

Yes, but an un-resonated drive will use a lot more battery power.

[Locator]

Hello,
i would like to ask you about this circuit and generally vlf detectors,if we can put in the position of the oscillator a crystal oscillator or a DDS generator
that produces exactly the same transmitter signal but with DDS generator and not with a self-oscillating transistor.Is that possible?