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[Qiaozhi]

Maybe i'm wrong but is it possible that I have a PI metal detector coil instead of VLF? As I said before, resistance of both coils are almost the same, around 6 ohms... Coil is DD type.

A PI can also use a DD coil.
What is the inductance of the windings? That will tell you the answer.

[TheBreMar]

Well I have made the electronic by "caesar" or so called S.M.W. schematic because the coil is "universal VLF" type. Man who gave me coil said that, but resistances just confuses me. I expect at least 30 ohms on Rx side but all I have is around 6 ohms. About PI coils, there are 3 types of them, mono, DD and one more, can't remember so I was thinking that I might be combining wrong types...

Unfortunatly I don't have a L meter Maybe I could measure it tomorrow if I go to the faculty...

[jap]

Hi TheBreMar
-the link may help http://www.md4u.ru/viewtopic.php?f=8&t=5798
best time
j.

[Freddy67]

[QUOTE=jap;157438]
Be sure to wire diameters exactly

Hi Jap and others.

Yes, I have the right sizes. I still have 7.5 ohms Tx and RX I dropped to 5 ohms by removing turns. I redid the welds thinking a dry solder, I replaced by 470 nF 220 nF and the problem is still the same. As soon as I touch R16, the detector emits a loud sound and can not detect more than 10 cm. I still do not Lmeter to check the inductance.

[jap]

Hi Freddy67
try to put each capacitor c in on coil RX , TX like pic. Will greatly improve the situation.
-Be sure to Ground and Ground virtual.
- R16=47K GEB Adj.
best time
j.

[Freddy67]

Hi Jap

Thank you for the information. I implemented the components as shown in the post # 105 and I replaced the capacitor 470 nF by 220 nF .
I just ordered a L, R, C, and transistormeter, but as it comes from China, I have to wait 6 to 8 weeks.

Best time

[Freddy67]

Hello to all

I found some errors

R 2 is 27 k on the circuit and 2.7 k on the scheme
R 20 is 1.8 k on the circuit and 3.9 k on the scheme
R 28 is 4,7 k on the circuit and 1 k on the scheme

What are good values ?

Just for info: the BD 140 cooler is supply side negative (outward pcb)

With thanks and greetings

[TheBreMar]

I have made some measurements, my Tx coil have 1,52 mH and 1,6 ohms, and Rx coil have 2,4 mH and 2,03 ohms. Coils are tester on 1 KHz. Coil is DD type, 16 inch by 14 inch.

[jap]

Hi TheBreMar
-What you got from the results is not like Standard coil is 0.9mH;2,1ohms/ 14,72mH;30,6ohms.
This does not comply with this project . best time
j.

[jap]

Hi Freddy67
-No errors
the first values follow ver1,the second values follow ver2,He modified for the better.the good values the second values ver2.
best time
j.

[TheBreMar]

I decided, I'll make my own coil by some of yours recipes. All I have to do now is to steal some copper

Unfortunatly this coil I have is not mine so I can not use it to put new coils. I have one question, why there must be a gap about one cm in length when we put aluminum foil on coils??? Give me a link, I'll read it with joy!

[Freddy67]

Hi Freddy67
-No errors
the first values follow ver1,the second values follow ver2,He modified for the better.the good values the second values ver2.
best time
j.

Hi Jap

I took the implementation of post 105 and the scheme post 107 (last known) and it is just between the two there are differences. I do not know if this is the scheme or implementation that are good.

[jap]

Hi Freddy67
not worry,,, OK,,, you do SMW V2,, reply#105 PCB, is corrected schematic in reply #107,,
---SMW V2 PCB,schematic are ok,(follow).
-about handmade coil ,original coil read reply#108
best time
j.

[jap]

I decided, I'll make my own coil by some of yours recipes. All I have to do now is to steal some copper

Unfortunatly this coil I have is not mine so I can not use it to put new coils. I have one question, why there must be a gap about one cm in length when we put aluminum foil on coils??? Give me a link, I'll read it with joy!

Hi TheBreMar
the data about coil make "TGSL 101" (parts 1&2).
link may help http://www.geotech1.com/forums/showt...mplete-Details
best time
j.

[Qiaozhi]

I have one question, why there must be a gap about one cm in length when we put aluminum foil on coils???

If you don't leave a gap in the foil, then it looks like a shorted turn. This will completely ruin your detector's sensitivity.