TESORO GOLDEN SABRE

[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.

[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]

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

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]

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]

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!

[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]

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!

[Ruben2000]

After building new coils, now I have better results, although, not perfect yet.
My inductance meter (gm328a) sometimes measures the inductance, sometimes not (I think I need to buy a better one) and also need to buy an oscilloscope.
Anyway, measuring the frequencies (connected to the TX pins), I got the values of 15.6 for TX and 14.3 for RX and below is a video of some detection distances for some coins (a portuguese "20 centavos", a french 5 Francs, a quarter dollar and finally a brazilian "40 reis"), for all of them I get a distance about 20cm (more or less) so I thing is still a poor detection compared to others I have seen of detecting a coin at about 30cm.

Here is how I'm securing the coils in place (to prevent deformation) while testing:
[ATTACH]56049[/ATTACH]

Well, I think the next step is to buy better testing tools like a better inductance meter and an oscilloscope.

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

[cristiano.sar]

After building new coils, now I have better results, although, not perfect yet.
My inductance meter (gm328a) sometimes measures the inductance, sometimes not (I think I need to buy a better one) and also need to buy an oscilloscope.
Anyway, measuring the frequencies (connected to the TX pins), I got the values of 15.6 for TX and 14.3 for RX and below is a video of some detection distances for some coins (a portuguese "20 centavos", a french 5 Francs, a quarter dollar and finally a brazilian "40 reis"), for all of them I get a distance about 20cm (more or less) so I thing is still a poor detection compared to others I have seen of detecting a coin at about 30cm.

Here is how I'm securing the coils in place (to prevent deformation) while testing:


Well, I think the next step is to buy better testing tools like a better inductance meter and an oscilloscope.

[cristiano.sar]

Hi friends,

I just want to share my almost finished TGSL with you.
It is working (detecting) but I need to adjust and finish the coils (shielding, etc...)
By the measurements of my multimeter, the TX coil is oscillating at about 17.6khz and the ideal is about 14.5.
Here is a simple demo of it detecting a brass pestle (from a mortar):

and a picture:

Thanks all that helped me by answer my doubts.

[folharin]

a bobina de desmagnetiza?

[folharin]

I last tried aluminum yoke coils for 14 and 20 inch tube televisions ... which worked very well ... so the coil is not as critical

[folharin]

the tgsl I made here in Brazil more than ten pieces ...