Barracuda Legend Kit Problems

[Koala]

30cm is what I was getting with a ladies wedding ring.

[Old cart]

Impulse, sounds like you are making progress. The performance you are seeing is in the ballpark of the best you can expect. My guess is a tweak of the damping resistor and it will get very usable.

[Impulse]

ok i have tried connecting just one end of the shield and 'nothing' and with the shield connected both ends it is better/more stable so i tried taking one loop at a time off the coil to bring the uH down to 'balance' (Im guessing at this point) the coil and i started with 24 loops 10.5" then as i go down (taking loops/coils off) nothing nothing nothing Then i get to 17 and it gets better so i keep going and i reach 15 and i get a scattered/sketchy signal but about 25-30cm away gold ring, also the coil now picks up a 5p (which it didnt before) at about 20cm so i continue to take loops off and it gets worse about 2 loops in so is the 'sweet spot' about 17 turns? i have also taken the insulation tape off the coil so i can do this. I feel slighty hopeful at this point yay. The o-scope should be here wednesday so i will be able to test the circuit (with your help ) and set it up properly. also with each coil/loop i took off i adjusted the top and bottem pots to get the best distance.

[Old cart]

Yes this is important. In addition to grounding the cable at the PCB ground, you might try connecting the shield at the cable end as well. Try both connections at the coil, one at a time.

[Qiaozhi]

Ok I have tried the new wire hasn't helped I just get a static like noise if I adjust the delay pot at a certain point I have even tried another coil which didn't help.

This might be a stupid question ... but you have actually connected the cable screen to 0V at the PCB?
I see something that looks like it's connected between the cable screen and the PCB in your image, but I'm not sure if that's a wire connection or the plastic covering of the screen.

[Impulse]

Ok I have tried the new wire hasn't helped I just get a static like noise if I adjust the delay pot at a certain point I have even tried another coil which didn't help.

[Impulse]

i take that as a no then?

[kt315]

Re: Eric Foster PI Search Coil Wire
Posted by: Eric Foster [ Send a Message ]
Date: November 25, 2012 02:15AM
Moderator
Registered: 10 years ago
Posts: 311
Hi Sven,
The orange cable is a specially made RG58 coax. It is made for the offshore industry, specially for underwater use, with a polyurethane outer jacket rather than pvc. This is much stronger and hard to penetrate by contact with sharp edges. Water at pressure would very quickly siphon along ordinary coax if there was even a small cut, and enter the coil windings. Salt water would write off both the coil and the cable and even enter the electronics unless a water blocking connector was used. Of course the orange coax is considerably more expensive, but I thought it was worth it as even for shallow water work it gives added protection.
Eric.

[Impulse]

Hey old cart I have managed to get this it is a two core foil covered 1mm cable with a mesh shield any good?

[Old cart]

I will get some coax tomorrow and try that but i do not have a shield (yet)? also how does the polarity affect the coil as it is a mono loop 'bunched' coil?

The coax ground will do most of signal shielding. The coil may be polarity sensitive if there are significantly more windings on the outside of the coil they will act as "self" shielding. If the coil is just randomly wound the coil polarity itself may not make much difference.

[Impulse]

o and i have ordered the scope! delivery for wednesday!

[Impulse]

I will get some coax tomorrow and try that but i do not have a shield (yet)? also how does the polarity affect the coil as it is a mono loop 'bunched' coil?

[Old cart]

I looked at your picture again. Are you not using coax for your lead in to the coil? You should use coax and make sure the shield is on the ground side. Also coil polarity is important try it both ways,

[Impulse]

ok thanks i will order it asap, once i get the scope what or where should i connect it to? (i know sorry but i am still new to this)

[Old cart]

Ringing is a waveform that continues after a waveform transition. It is called that because it is a decaying sine wave: similar to a bell ring. You can not hear it but you can measure it when you get your scope.