Whites Surf PI schematic

[multieagle]

Okay, my board is working and detecting. I have been watching videos on Youtube to get an idea what to expect. One thing I noticed is the Threshold/Tune variance. On my build, which has a guitar pot A254 (250K), I cannot reduce the threshold to silence. It has a constant background tone. The Youtube examples range from where mine is down to silence, with maybe a tick or two.

Not being an electrical genius, looked up the various types of pots and found the 254 variety comes in A & B. A254 is apparently logarithmic and B254 linear. If I change the pot to the linear variety would that make a difference in my threshold range? Or is my problem elsewhere? Or, is it normal for a Surf PI 1.2 to have this variance, depending upon build factors?

[daverave]

you should be able to adjust threshold to silence...i can adjust both my 2 surf pi's to silence...i used linear pots

[multieagle]

I might add I'm using a shielded 300uH coil (measured at coil before coax connected). Coil is copper tape shielded with ground connected to the shield. The coax is shielded with multi-strand central conductor. The board ground wire is connected to the coax shield. The coil was designed for a different metal detector. I might add, nothing is overheating on the Surf PI board.

Any ideas?

[daverave]

whatever you should still be able to get zero threshold...must be circuit fault or wrong component value

[multieagle]

Thanks for not jumping all over me!!! It was a faulty pot. Now working great. Should have tested before jumping aboard here.

[daverave]

been tweaking my surf pi and modified it and now i can get 20" depth on a old english nickle half crown so very pleased with its proformance.

[sdesic]

Hi Dave,

nickel half crown (1947-194 is about 32 mm ?
What is difference between surf pi and surf pi pro in depth for you ?
Can you please explain your modifications on surf pi.
How big is coil, how many turns and what type of wire is it ?

I was building bigger coil for more depth for my surf pi pro... coil about 32 cm...

[6666]

been tweaking my surf pi and modified it and now i can get 20" depth on a old english nickle half crown so very pleased with its proformance.

Would you mind a few details please.

[bernte_one]

been tweaking my surf pi and modified it and now i can get 20" depth on a old english nickle half crown so very pleased with its proformance.

video evidence

[Radvis]

Hello everyone,
i have read all posts in this thread, but still can't figure out whats wrong with my surf pro. The problem is that i get like few centimeters depth on pliers and everytime when i move my coil or its cable to any direction it makes sound response. Tried going outside where no metal objects or wireless or anything like that exists.
Surf 1.2 pi from Silverdog
Offset set to 0 volt.
Coil diameter 230mm
Turns 21
Enamel wire 0.5mm
Wire length 1586cm
Around 230uH inductance
1.37ohm
coil connected with coaxial cable
Detector responses to all pots and trimmers.
Maybe my soldered contacts overflowed? (see picture below, marked red where contacts ar soldered together)
And video showing how it all looks like. (metal clamp used temporarely, because i haven't glued cable yet, no difference without them)
http://www.youtube.com/watch?v=gPBan8I4pKY
I am sorry for my english and thank you for any suggestions what could be the problem.

[Tepco]

Metal clamp !?! You have lump of metal in the coil and expect this to work? Remove it and try again, your detector seems to work fine. You will notice different behavior of delay and threshold controls without metal clamp too.

[Thomas]

"Maybe my soldered contacts overflowed? " the red circled areas are OK. how about the other side.

[Radvis]

"Maybe my soldered contacts overflowed? " the red circled areas are OK. how about the other side.

Here you go,if they say anything



Tommorow ill try adjusting trimmers without metal clamp. Thank you

[Radvis]

I already attached my cable to coil so no metal clamp is used anymore, adjusted offset to 0 volt, but still the same result. Adjusting delay makes some difference, but nothing better. Still beeping everytime i move my coil or my cable and dont get any depth. Tried outside, where are no metal objects, wires or something like that.
Now i am wondering if my coaxial cable can be the problem. I am using cable as in this picture. It has a layer like foil... What cables do you guys use? USB?

[Qiaozhi]

I already attached my cable to coil so no metal clamp is used anymore, adjusted offset to 0 volt, but still the same result. Adjusting delay makes some difference, but nothing better. Still beeping everytime i move my coil or my cable and dont get any depth. Tried outside, where are no metal objects, wires or something like that.
Now i am wondering if my coaxial cable can be the problem. I am using cable as in this picture. It has a layer like foil... What cables do you guys use? USB? [ATTACH=CONFIG]28525[/ATTACH]

That cable should be fine, but try connecting the coil directly to the board using a short length of flex to eliminate the coax cable from the equation.
Also, what value of damping resistor are you using?