Easy Detector

[Friday]

Hi Dear Friends,

I saw this circuit.Its very easy but I don't know its performance.Is this detector be useful?

[Qiaozhi]

Hi Dear Friends,

I saw this circuit.Its very easy but I don't know its performance.Is this detector be useful?

I have not seen this one before. But did you notice that the lower left L358 has it's output shorted to ground?

[Ustura]

But did you notice that the lower left L358 has it's output shorted to ground?

This LM358 circuit provide for virtual ground...

[Qiaozhi]

This LM358 circuit provide for virtual ground...

Yes, of course. The power supply is single-ended.

So - do you know this design? Where does it come from?

[kt315]

Where does it come from?

as schematics' archivarius, kinda of, I must note it came out one from two our PDF schematics' archive files. it is noname one. maybe oldie tesoro?? I see 4024 there, tesoro fist sign IMO.

[ApBerg]

Hello Friends,

The circuit is from a Scope minidisc, is a nice little detector.

Ap

[peroon]

Coils datas? Any?

[ApBerg]

Hello Peroon

I the past I made some coils for this detector, there is original a 15 cm coil. The oscilator is the Hartley type, so the transmit coil has a centertap. For a 20 cm coil I used (if I remember wel) some 100 turns 0.25mm for both the transmit and the receive coil.
The transmit coil has a center connection to ground 50trns gnd 50trns.
The transmit freq is between 17 and 19 kHz, you can adjust this freq with a cap. in the coil.( do not forget to screen the coils )
The sens with the 20 cm coil was some 22 cm for a man wedding ring... in air, so not bad for a detector this sort. Al very common parts !

regards.

Ap

[Friday]

Hi...

Can I use DD coil for this detector? Centertap coil is difficult...

Regards...

[Friday]

Hi...

Can I use DD coil for this detector? Centertap coil is difficult...

Regards...

???

[ApBerg]

Hello Friday.

The coil is a DD coil.
The TX coil has 3 connections , look at the circuit. There are 2 connections for start and finish and 1 for a connection to ground , this ground connection is made after some 50 turns from the 100 turns total. (The TX coil is in fact 2 coils)
So wind 50 turns then take a loop out ( for the ground connection) then finish the last 50 turns in the same turning direction as the first 50 turns.

Good luck.
Ap

[Friday]

Thank you ApBerg...

I am understand you.I made 6 mH coil.Both are 6 mH.Coil capacitors are 15nF.Frequency is 16.776 kHz.

Best Regards...

[ApBerg]

Hello Friday

Nice that the coil works. For a long time ago I made a pcb for this circuit, recent I turned it to Sprint Layout 5... look at it , I think R27 has to be 100R not 100k , check it all before you use it !

Regards.
Ap

[ApBerg]

Forgot the pcb ....here it is as sprint layout file...
Check R27 must be 100R I think

Regards.

Ap

[Friday]

Very nice ApBerg.Thanks a lot for pcb.ok, I wil try both resistor(100k-100R).

Regards ApBerg...