Can pinpointer detecting thin chain?

[Nupi]

To everyone.

To avoid problems, it is important to keep the specified parts and construction.
I only want help the people who have everything according my information made, including the same parts .

Who want to experiment with other components or circuitry should only do it after.
The performance of this PP are excellent for the price, shown anywhere before.

regards nupi.

[Fabian]

Thank you both for your answers. I will implement its recommendations.

Nupi: Yesterday I made the coils with each turn very close to each other. I also tried with lower values in C2, and even took it off. He continued working "backwards"; just the frequency changed.

But do not worry, I will make a new board. I do this as a hobby, and as you Nupi, I have a lot of patience ...

Regards

Fabian

[Nupi]

Hello Nupi. I was working on the PP during the weekend, and I could not find a solution. I wrapped several coils, triple-core and single core (15mm ferrite) and the result was the same. I changed ALL components, including the BD139, the 4024, all capacitors ...
I will build a new PP, but I read this post by Davor and wondering if has something to do:

"I'd say your Q factor is too good. No kidding. This oscillator is very touchy on the coil Q and transistor gain, so the trimmer may not compensate if both are too good. You may try 100k in series with a trimmer, or you may go for a lower frequency by increasing the tank capacitance."

I already tried putting a 470K trimmer in series with R1 and did not work well... Can the problem be related to the transistor? Maybe put a transistor of other features, or something. I put a 2N3906 but it works just like the BC560.


If not, I'll build another PP on a perf board as Nezocas and you did. (Can PCB tracks influence the performance of PP?)

Regards,

Fabián

Hi, Fabian
What Davor says that is not related because We have already done with the resistors in series with R1.
How did you get the coil wound?
Are the layers of tight turns on each other or have a lot of
insulation between layers? In that case you have too much capcity between the windings.
Experiment with C2 with smaller values or try without C2.
regards, nupi

[chemelec]

Hi Gary, thanks for your reply. I have no problems with the operation, unless my PP runs "backwards" (stop ringing when I approach a coin into the coil) and I can not "straighten" the operation of the detector. From what I can measure the inductance of my coils is correct. Just resistance is a bit high compared to that achieved by Nupi.

In the coming days I will try new boards. Maybe my meter is not giving correct inductance values.


Fabian

Runs Backwards: INCREASE the Value of the LARGER POT to give More Range of adjustment.

[Fabian]

Hi Gary, thanks for your reply. I have no problems with the operation, unless my PP runs "backwards" (stop ringing when I approach a coin into the coil) and I can not "straighten" the operation of the detector. From what I can measure the inductance of my coils is correct. Just resistance is a bit high compared to that achieved by Nupi.

In the coming days I will try new boards. Maybe my meter is not giving correct inductance values.

Fabian

[chemelec]

Even a High Q, Air Coil will work with this circuit.

The Coil is actually a Single Coil, With a Tap off at the correct number of turns.
"Or more appropriately at the Correct Inductance Value".
And this Tap goes to the Ground in the Circuit.

The 2N3906 also works Good in this circuit.

EDIT: For Simplicity I would recommend Just the LED Indicator, Until you get it working.

[Fabian]

Hello Nupi. I was working on the PP during the weekend, and I could not find a solution. I wrapped several coils, triple-core and single core (15mm ferrite) and the result was the same. I changed ALL components, including the BD139, the 4024, all capacitors ...
I will build a new PP, but I read this post by Davor and wondering if has something to do:

"I'd say your Q factor is too good. No kidding. This oscillator is very touchy on the coil Q and transistor gain, so the trimmer may not compensate if both are too good. You may try 100k in series with a trimmer, or you may go for a lower frequency by increasing the tank capacitance."

I already tried putting a 470K trimmer in series with R1 and did not work well... Can the problem be related to the transistor? Maybe put a transistor of other features, or something. I put a 2N3906 but it works just like the BC560.


If not, I'll build another PP on a perf board as Nezocas and you did. (Can PCB tracks influence the performance of PP?)

Regards,

Fabián

[Nupi]

Adjusting the PP.

[Nupi]

OK, I'm going to bed now, bye.
nupi

[Fabian]

The inductance from L1 to L2a is 2.97 MH

[Fabian]

And how can we "give it back"? Where would I have to change settings to try?

The funny thing is that Detects great! A 1 euro coin at 6.5 - 7 cm. If it were not so annoying bird, I leave it as is!

When turning VR2, no "two-zone" detection. All is silent and suddenly starts ringing until the end of turn.

Let's leave it for now. Maybe in a few days an answer appears in our minds.

Many, many thanks for your time and support.

regards,

Fabian

[Nupi]

I want to be the inductance between L1 and L2a so the whole coil!!

[Nupi]

That the wires are not the same as mine is not the problem.
The coil looks perfect.

What I tell you is very important and should be well understood, otherwise you have to ask.

If you rotate R2 and starts beeping, you must rotate further up to the end.
When, adjustment is normal that you have two sides of detection. 1 if it works
the other way around, so that stop beeping when it detects something and if you continue turns R2,
you get the other side detection. This must be so.

[Fabian]

Does your ohmmeter do good '??
What I do not understand is the high resistance of the coil?
What kind of wire you use for coil and what are the dimensions of the coil?
Another question, can you measure the inductance of the coil again?

I think so...

1.2 Ohms / .241mH

2.7 Ohms / 1.6 mH

In this one, my last coil, I use .32mm and .35mm wire gauge (L1 and L2)

Dimentions in the pictures

[Nupi]

Does your ohmmeter do good '??
What I do not understand is the high resistance of the coil?
What kind of wire you use for coil and what are the dimensions of the coil?
Another question, can you measure the inductance of the coil again?