My Pulse Oscillation detector project.

[Teemo]

Pinpointer pictures

Hello everybody!

I'll post some pictures of my pinpointer. (Got the inspiration to make one from the video Juha made about making pinpointer with my circuit:
https://www.youtube.com/watch?v=nS4GWuD5Dk8. I did not have exact same tubes so I used what I found laying around and came up with little different.
Fortunately I found plastic water tubes of 4 sizes that fit perfectly tight inside one another and a plug to close the other end.
The 4xAAA battery holder and the circuit board fits nicely inside the tube. Only had to mount the C2 electrolytic capasitor to the other side of the PCB, and bend the leads of the MOSFET a little. Used coil with ferrite core. Speaker is piezo glued inside the cap with hot glue.
Basically quite durable and easy to make waterproof, only the button is weak spot at the moment. Also I have not closed the coil end with the heatshrink jet, to make it easier to experiment with the coil.
So here are the pictures. Hope you like it.

[mr.sneezy]

you must be under 25years or younger
where did you come from doesnt mean where do you live in the virtual networld
it means whre is you hometown

LOL, an accidental compliment, I'm MUCH older than that

I'm from Adelaide Australia.

I put up a thread for the TX-2002 BTW. I'll tinker with it a bit before giving up to a conversion of some type.

[bernte_one]

you must be under 25years or younger
where did you come from doesnt mean where do you live in the virtual networld
it means whre is you hometown

[mr.sneezy]

No problem, I'll start a new thread with the info I have. Schematic is not trivial, there is a lot more in this detector than say a Cen-Tech pointer. I'll photograph both sides of the PCB while I have it apart.

Where did I come from ?
Not sure what you mean, but I've been around on the web a bit, mainly in RC and PIC micro forums.

I'll be able to measure the L when I get back to my work place in one week. The coil can not be disassembled, so the circuit has to work with it as is.
Cheers,
Martin

[bernte_one]

hello martin,

where did ou come from?

would be happy if you could post the tx-2002 sheme and maybe good quality pcb pictures in a new thread.

if you got a L- meter check if inductivity is around 150-300µH i think all in this range can work somehow
i wind yv wire 0,5mm core directly around a 8mm ferrite core
compared to others it has good sens on small items

please post your results
good luck

[mr.sneezy]

Hi bernte_one.
I see you have used a ferrite coil with Teemo's design, which answers a question I had about that.

What I have in mind is to retrofit a cheap Chinese TX-2002 pinpointer with Teemo's circuit and see how it does. The TX-2002 is not a very nice thing (mine at least) as sensitivity is poor (like 10-15mm for a coin) and it's a motion circuit so you must keep moving the pointer to pin down the target (sort of counter intuitive).
I have picture of the TX-2002 circuit board if anyone is interested BTW. It's got a LM358 and a CD4011 as the core components.

The good thing about the TX-2002 is that it has a single wind ferrite coil of around 2 ohms, in a nice water proof tube, inductance is unknown at the moment (till I borrow a meter). Hoping it may be usable with this PIC circuit.

Cheers,
Martin

[Teemo]

Hello bernte_one

Thank you for the video.
Wery interesting construction. Nice to see.
I will gladly examine the code changes if you send to me, and of cource I will be happy when you put link to my site in your video.

Best regards

[bernte_one]

hello teemo
i have to make some experiments with the source code
but for the moment lokk what i have done (only prototype)

http://www.youtube.com/watch?v=9eG3-gmh7tA

if i get more depth by changing the code i will send you the changes if have done
and i will post a link on my video to your shop side if that would be ok for you?

my goal is to get 2cm for a small nugget and around 8cm for a 2€ coin
will see

kind regards

[Teemo]

hello teemo

can you give me some advice to increase the detection range
at the momnt i can get maybe 4cm on a 2€ coin with a pinpointer coil (16mm diameter, 5cm long, litzwire with ferrite core around 80µH)
the sound range (from little noise till full sound) is very small maybe 5mm range
is it possible to inrease this threshold sound range? a litle bit more noise is no problem if i get two more centimeters of range

at which parts should i focus my work?
will post a picture later
kind regards

Hello
The solution that comes to mind first is to modify the firmware PIC program. As you very well describe it should be possible to get some more range when to allow some more noise.
I've also have had this in mind. The current firmware is very well optimized to my original objective of scanning logs, the digital filtering allows very few noise.
This requires quite big modifications to the firmware. Basically the digital filters must be redesigned. In the assembler program there are variables f_result and t_result those are the basic measurements that are passed to the filters in the main program.

Best regards and thanks.

[bernte_one]

hello teemo

can you give me some advice to increase the detection range
at the momnt i can get maybe 4cm on a 2€ coin with a pinpointer coil (16mm diameter, 5cm long, litzwire with ferrite core around 80µH)
the sound range (from little noise till full sound) is very small maybe 5mm range
is it possible to inrease this threshold sound range? a litle bit more noise is no problem if i get two more centimeters of range

at which parts should i focus my work?

will post a picture later

kind regards

[bernte_one]

i think about 18650 bacause i had a lot of them
but the have a critical voltage max 4.2 is not enough
so my favourite is a small akku pack of 4*1,2V aaa nimh (eneloop?)
and a simple charger plug with max charge of 5V usb or micro usb??? - modern standard

what do you think?

[Waikiki_Sweep]

now i search for the smallest 5V power source so that all fits an a small tube enclosure

I am not sure will it work from 3.7V (charged 4.2V) 18650 Li-Ion battery. If yes it will be absolutely great because it is compact, rechargeable, lightweight and very powerful 3000-4000 mA/h!

I am using 3 cells starting at full charge 4.2 Volts (12.6 V) and discharging to 3.9 Volts (11.7 V) after 10 hours of work of my overclocked to 130 mA Surf PI.

At least microprocessor will work.
Operating Voltage Range:
- 2.3V-5.5V (PIC12F1840)
- 1.8V-3.6V (PIC12LF1840)

The problem is IRL640 will work from 4 volts or not also maybe some adjustments are required to software and / or electronic.

[bernte_one]

detector is alive

i used a ferrite core inductivity around 340µH (desoldered from some scrab electronics)
i think it should work fine as pinpointer
now i search for the smallest 5V power source so that all fits an a small tube enclosure
and i will make a better ferrite-coil

would say it is the best beginners project in category microcontroller/pinpointer

kind regards

[bernte_one]

ok
thanks for reply
i have choosen irl640
and some testing replacements for elko 1000 -3300uf 10-16V, the 1uf and the 47nf cap
will post results asap

kind regards
special thanks to teemo

[Teemo]

For IRL630 replacements the priority parameters are:
-Gate treshold voltage(Vgs): must be less than 4,5V (often called "logic level mosfet")
-Drain source voltage Vds: must be 200V

Other project news:
I have done some testing with the audio, managed to program the variable volume and tone using available resources. Only modification to schematic:It is clear that piezo speaker will not do, instead there will be dynamic speaker or headphones. New sound will use 8 or 10 bit PWM, not clear jet how the modulation will be. I guess the fancy circular buffers from the current version is not good for the new version -- the new algorithm must be simpler. To get the direct unbuffered information from the coil to the headphones/speaker.
And thanks all who participate in here forums. The tips I get here are most useful, even if I can't grasp all the ideas promptly.