Surf PI Pro

[Qiaozhi]

Hi Everyone
Looks like Surf PI, was designed to work with low inductance coils, as seen in the following link:
http://www.geotech1.com/forums/showt...ematic&p=82315 # post82315 (post Nº"58")
The original coil consists of 20 turns of wire 0.5 mm and diameter of 23 cm., As mentioned by a forum member, which corresponds to about 250 uH, as MiSCeL calculator. This explains why the pulse width set by the R2 of 3.3 K is approximately 50 ns, so the first thing to evaluate is the coil, or try to get an original.
I'm using a 380 uH coil and get the most out extending the pulse width to about 100 ns.
Had problems of instability because of the telephone handset, which captures the emission coil is oriented according as, the solution was to use a piezoelectric handset.
Besides adding an R of 3.3 K between emitter and base of T1, 2N3906, for the reasons explained before, replace R20 47K by 22K to fix the threshold range. R18 remained in 47K.
Resistor R25 was adjusted to about 13K, through a preset delay and replaced by potentiometer 50K
With these values the minimum of delay setting corresponds to 15 ns, and the maximum at about 80 ns.
The PCB used was ApBerg.
It's all the changes you make, it's a nice and very sensitive detector.
José

By the way, the pulse width and sample delay are measured in "us" (micro-seconds) not "ns" (nano-seconds).

[Jose]

Qiaozhi
Thanks for the clarification, and sorry for my bad english.
It happens that to translate into Castilian, us, has an entirely different meaning.
Meaning of "us" first-person personal pronoun in the masculine and feminine and plural number.
Henceforth I will write "us"..
Jose

[Davor]

you can also find the μ sign in windows' character map, or anywhere else, and copy/paste

[sdesic]

Surf Pi Pro after few days of testing... found aluminium foil, hand cream tube, hand lotion wipes alu package, few hunters bullet casings, handgun casings, bottle caps, few chain loops, bots... nails lots of them in old house... hunted in forrest area
my first finds ever ... works fine with all of those finds in depth about to 15 cm.

I have one problem.
When I touch coil coaxial wire or BNC connector to PCB it produces beep.
I tried reversing polarity of coil connection to PCB and it goes away so does the sensitivity... goes to 2-3 cm max
Coil is not shielded and also acts with (wet ?) grass or ground.
Coil is 20 cm 21 turns.

Made coil with 25 turns 20 cm diameter. Same happens...
It is not problem when you get used to it.
Any solution ?

[Jose]

Check that the BNC connector housing, is connected to the GND of the PCB.
Use coaxial cable between the PCB and the BNC connector, or stranded wire.
21 laps for 20 cm coil, should work well, see my post No. 216.
Jose

[sdesic]

In this case my outer part of BNC is not connected to ground
other one is connected to ground...
I will try connecting with coaxial cable
if I connect both to GND there is no signal ?

I tried reversing polarity of coil connection and outer part is on gnd I get much lower sensitivity to metal

[Jose]

In this case my outer part of BNC is not connected to ground
other one is connected to ground...
I will try connecting with coaxial cable
if I connect both to GND there is no signal ?

I tried reversing polarity of coil connection and outer part is on gnd I get much lower sensitivity to metal

Sdesic
Do not understand the question. The outside of the BNC, should be grounded or GND, or to negative battery.
Look closely at the PCB.

[sdesic]

That solves problem with coil connector and cable sensitivity to touching by hand and ground.
BUT it lowers sensitivity, I have now up to 5 cm detection of 1 EURO.

I have tried 9V battery and it is working far better than on 12V batteries with same coil.
With 9 V I can use delay pot, not only at max resistance.

[tifred]

Sdesic Bonjour, J'ai eu le même problème sur mon barracuda. J'ai inverser le fil du connecteur sur la boîte de bobine et j'ai résolu le problème.
Je n'ai pas de faux signaux quand je touche le câble :-)

[Jose]

That solves problem with coil connector and cable sensitivity to touching by hand and ground.
BUT it lowers sensitivity, I have now up to 5 cm detection of 1 EURO.

I have tried 9V battery and it is working far better than on 12V batteries with same coil.
With 9 V I can use delay pot, not only at max resistance.

Sdesic
If you connect BNC PCB as drawing, fine.
In green is the GND path, which is the same as the negative pole of the battery.
After the BNC coaxial cable to the coil, should continue in the same way.
If the problem persists, try adjusting R2 for best performance, with 12 volt battery.

[Qiaozhi]

Sdesic Bonjour, J'ai eu le même problème sur mon barracuda. J'ai inverser le fil du connecteur sur la boîte de bobine et j'ai résolu le problème.
Je n'ai pas de faux signaux quand je touche le câble :-)

Please make your posts in English, as requested in the Forum Rules. Not everyone understands French.

[sdesic]

Sdesic Bonjour, J'ai eu le même problème sur mon barracuda. J'ai inverser le fil du connecteur sur la boîte de bobine et j'ai résolu le problème.
Je n'ai pas de faux signaux quand je touche le câble :-)

Tifred,
thank you, I have tried that, and it helps, now I can't switch polarity of coil wires ...
it is fixed in glue and plastic ... if I switch inside of detector it will be both coil wires on GND.

Jose,
I replaces trimmer with 3k8 resistor.. must turn back time again
today is hunt day, so I will try 9 V hunt.
Less weight.

I am making another Surf Pi Pro that will be experimental with your added 3k3 and another pot for better tuning.

[tifred]

Sdesic Bonjour, J'ai eu le même problème sur mon barracuda. J'ai inverser le fil du connecteur sur la boîte de bobine et j'ai résolu le problème.
Je n'ai pas de faux signaux quand je touche le câble :-)

sorry !!!
Sdesic Hello, I had the same problem on my barracuda. I reverse the wire connector on the coil box and I solved the problem.
I do not have false signals when I touch the cable :-)

[sdesic]

sorry !!!
Sdesic Hello, I had the same problem on my barracuda. I reverse the wire connector on the coil box and I solved the problem.
I do not have false signals when I touch the cable :-)

I have done some field testing - still having ground detection on few occasions.
Maybe it is my coil moving inside of coil casing.


Today it was working with 9V battery
and this is my finds ... 2,5 hours hunting in one place - woods
fist coins and first pull tabs

[Jons]

Battling through all 15 pages of this thread, left me with one question. What is the score between those who successfully made a properly working specimen of Surf PI Pro (original or XX), and those who didn't? Seriously!

A short explanation: I made Stuart's 1. (EE TH) MD, and I'm having some issues with sensitivity. I'd like to make something else for comparison. Getting past page 2 or 3 of this thread, made me wondering whether Surf PI Pro would be the right choice. At this moment I deeply fear to fall into MD builder's "gambling frenzy", e.g. though it's time to leave the casino, you wanna spend even more to win back the losses... In my case - whether it's time to visit the nearest dealer with MD's before homebuilding expenses rise sky high.