TESORO GOLDEN SABRE

[cristiano.sar]

Here I send you a link so that you can build this inductance meter. I have built it and it is very accurate. So that you are not using threads in the spools, use super glue or fast glue to hold the wires together, it will be easier and less time will take you.
https://youtu.be/hMa-AWyuxaA

Thank you so much!

[cristiano.sar]

I have found a very cheap Tesoro coil here in Brazil (Tesoro widescan Epsilon 11x8 (https://www.fortunadetectores.com.br...rto-e-protetor). Does anyone know if this coil can be used in the TGSL without any modifications to the circuit? Thanks!

[cristiano.sar]

I bought the elliptical coil I have shown in the previous post ( Tesoro widescan 11x8 ) and tested it with the homemade TGSL and that commercial coil appears to have a "poor" performance. I tested it for example with a 1945 5 francs AL coin and it is detected at about 16cm while with the homemade coil it is detected at about 25cm.
Is this normal due to the format (elliptical) and the size of this coil? Or may I need some adjustment in the board (oscillator capacitors or something)?
Actually, my pack of AA batteries is not at full 12V, around 10.5V (don't know if this can cause some difference).
Here is the video with the test:

Thanks!

[Nandor]

Hello

You need to adjust the RX capacitor value on your pcb. Add or remove some nF on the front end capacitor. That coil should perform really well.

[cristiano.sar]

Hello

You need to adjust the RX capacitor value on your pcb. Add or remove some nF on the front end capacitor. That coil should perform really well.

Hi Nandor,
Thanks for the help.
The problem was really related to frequencies, so I added a 3.3nf capacitor in parallel to the existing one and now, the same coin that yesterday was detected at 16cm, is detected at 30cm.
Another thing I noticed was the 22nF cap on the TX side, it was also a wrong value making my TX to oscillate at 15.37Khz, I replaced it with a new 22nf capacitor and not it works at 14.78Khz.
So my plan for now is just to buy a good LCR meter so I can measure the exact inductance of the RX coil and calculate the best RX capacitor so the frequencies are the best.
I'm learning a lot of things from you all.

Thanks.

[Nandor]

Really nice to hear that you made it work properly.
I used to calculate my coils, first meausre the capacitor with a multimeter and than measure the frequency that makes youe oscillator and you can calculate the inductance of your coil.

best regards

[cristiano.sar]

Thanks, good idea to "reverse" the calculation.
Here is a video with the final result: https://www.youtube.com/watch?v=osvZlM5DcqY
Thanks!

[sinclairuser]

hi cristiano, i have two of these i bought a kit of parts from ebay to build one, but for some reason there was a complete one in the parcel as well, anyway they are really cheap either as a kit or as a built unit.
but they work really well i was sceptical of them at first double checking the readings, but now use them all the time for matching transistors and resistors plus checking components, they are quite accurate at testing the inductance of coils too.
the only downside is you must use a good quality battery and keep an eye on it, the inbuilt battery volt meter tells lies, it will say 8.4v but really be 6.9v so just use a duracell or energizer and disconnect it when not in use.
low power makes the meter readings wrong.

[cristiano.sar]

hi cristiano, i have two of these i bought a kit of parts from ebay to build one, but for some reason there was a complete one in the parcel as well, anyway they are really cheap either as a kit or as a built unit.
but they work really well i was sceptical of them at first double checking the readings, but now use them all the time for matching transistors and resistors plus checking components, they are quite accurate at testing the inductance of coils too.
the only downside is you must use a good quality battery and keep an eye on it, the inbuilt battery volt meter tells lies, it will say 8.4v but really be 6.9v so just use a duracell or energizer and disconnect it when not in use.
low power makes the meter readings wrong.
[ATTACH]56476[/ATTACH]

Thanks!
I have bought a similar one that is based on an ATMega 328 board but it has some bad readings, everytime my coils has more than 24ohm of resistance, the device does not measure the inductance (lol), but really maybe due to using low quality / lower voltage batteries as you said. For now, I bought a better one ( a lot more expensive ) but at least it is working perfectly.
Thanks for the help.

[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?

[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]

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]

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]

Thank's for your reply!

[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.