Can pinpointer detecting thin chain?

[Nupi]

Adjusting the PP.

[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

[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]

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]

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.

[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

[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]

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.

[Nezocas]

Hi,
Finally I had some time to finish the NUPI Pinpointer.
It ended up with a 21.5 cm long "tube" and with 3 cm in diameter.
It is fully water proof, this was all ready tested, I placed it at the bottom of a 3 meter depth swimming poll for a complete day, without no batteries inside.
I upgraded it with a reed-switch to power it on and off with a small neomagnet.
It is very stable and does not looses detection range for long periods.
When whether gets warmer it will be tested underwater at the beach hopefully finding some rings.
Lets see how it behaves in salt water.
I made a small video (turn volume up a bit) because this PP only have the vibrating motor on it.
http://youtu.be/OvG9h2lsELU
I didnt atchived the 11 cm´s detection to an european 5 cents piece (only 7.5 cm), because if I tune it up a bit the PP gets very "nervous" .... but I am very pleased with it.
In the past I wanted to buy the Vibraprobe or the Vibratector, but they are both up to 200€ .... and this pinpointer it is very cheaper to make and has got more detection range.
THANK you so much NUPI, for this great PP

[Nupi]

You have a very nice compact and unobtrusive PP made.


I made itself seawater for testing with salt from the health food store. (see-salt)
The results were exactly the same as with the real seawater.
If you mixes masonry through you have real sea sand. Try it out!!!
The amount of salt in sea water is average 34.5 grams per kg.


That you didnt atchived the 11 cm´s detection to an european 5 cents piece may have to do with
the construction of all components together. The magnet should be as far away from the coil as possible.
The more compact you the PP make the more agitated he is. He needs space!!!

It will take some time, I think, that people get an eye for what great qualities the NUPI PP owns.

Actually I should have commercialize the PP.

I wish you lots of fun with searching.
Best regards, Nupi



nupi PP made by Nezocas

[Nezocas]

Hi NUPI,

When I recived the PP from you, I did some testing with it and it only detected to 4 cm (I didnt touched the R1 and R2).
Now its up to 7 cm´s... it is very good.
I will make the 50 Km´s trip to the ocean very soon...and then report back to you.
Underwater finds will only be made with good weather.

Regards

[Nupi]

Hi Nezocas,
When you turn on the PP you must adjustment R1 to the maximum sensitivity.
If you search on the beach you have the PP hold a 1cm of the sand and so adjust R1 that it just not detected.
By doing this, you have the PP "ground balance" and adjusted for optimum sensitivity.
If you go under water in the sea, you must do the same. You should maybe also adjust R2.
It's a matter of trying. If you know how to do it adjust is very quickly.
You might also super tune manually, then it is even more sensitive.
But the downside is that you often have to dig very deep.
I'm a bit lazy so I'm not use that method.

regards, nupi

[Harp]

Hello Nupi,
http://www.youtube.com/watch?v=BWW8EOdp30g
In the video where you presented the sensitivity of PP, you used a marker-pen with which you recorded the distance on the paper. It seems to me that this marker is in aluminum housing, all except the very top, and I noticed that your PP is not detected, even if it was very close to the coils? What is the lateral (side) sensitivity of your PP, if not a problem? Or, marker is plastic one?
Thank you!

[Nupi]

Hi Harp,
The pen is completely made of plastic. It is the: edding 8400 CD / DVD / BD marker.
The lateral (side) sensitivity of the PP is 30% less than the front.

regards, nupi.

[Davor]

I've got the automatic tuning working in simulation.
Now, to do it properly I'd need a cheap rail-to-rail FET input single op amp, and so far I avoided them whenever possible. In my neck of the woods they are usually difficult to obtain, and cost a lot. So far only TLC271 fits the bill, but I'm open for suggestions.
The solution uses one single op amp as an integrator/SAH, one CD4069 and a FET as a switch. So all in all it is not far off from the manual design. It also has a coarse trimmer to set the working conditions right, and a sensitivity trimmer to set, well, sensitivity threshold. I designed the whole thing based on the Colpitts oscillator for simplicity.