Building the Geotech Barracuda Rev A (from silverdog)

[ionut_mtb]

shield need to be connected to ground and between wire and shield need some insulator. (if emailed copper wire) maybe copper tape is to thick.

[azigta]

Hi, Today I ran more tests with the shield, connected and disconnected, and now it even beeps when disconnected, something is really wrong with it. I removed the copper tape, and it's working again. No idea what happened, maybe there was some short there, no idea.

Is it bad not to put metal shielding on the coil? I was thinking about wrapping the coil in electrical tape and then cover the whole thing with silicone to make it waterproof. Is it necesary to shield it with metal? I'm going to do tests with aluminum not sticky foil, and see if it works, but for today I had enough with this xD

[kosacid]

for my ground i just use the same wire and rap a coil round the coil and put that on the ground wire
http://i943.photobucket.com/albums/a...306_095055.jpg

[azigta]

Updates:

I shielded it with aluminum foil and it doesn't do weird things now. Then I wrapped 2 layers of cable organizer plastic around the coil, then electric tape around, and then did a mold and submerged the coil in non acid silicone. I hope everythings turns out well. I'm sure It won't look pretty, but hopefully I can "polish" it when it's solidified. It's the first time I do this so I'm unsure as heck about if it's going to turn out good or I'm going to ruin it but at least it's only the coil, and it's easy to make, so I decided to take the risk. I bought the silicone a while ago and it was about time that I had to do this.

I will probablly have to flip the coil and put silicone on the other side because the mold was too tight and although I putted silicone previous to insert the coil there, I don't think it was enough xD

Whatever, it's being fun, the thing works nice, and I am very enthusiastic about going there with my metal detector and hunt! So whatever turns out, as long as it works, I will be happy.

I will probablly change the control box to a little bigger one, and I got an analog chinese uA/uV meter that I hope I can use here with a switch to alternate between audio+meter/only audio.


For now I don't have a decent cable to run from the coil to the control box , so I will buy one the next time. Tv coax cable is ok?

Thanks to all the members who have helpped me continue with the project, I almost gave up... I will post more updates.

[marcosalvadori]

Hi, i am building my first Baracuda (Silverdog) and i have some problems.
I am tuning it but when i make the steps of the silverdog guide, i find a problem.

I think tha my problem is on LT1054. In pin 7 (osc) i find a triangular signal like this: https://goo.gl/photos/WDGKdpRf9gsx3Ksc7

I think that triangular signal is bad.
What do u think about?

Thanks in advance

[homefire]

Good to go. Are you getting the -5 V ??

[marcosalvadori]

Thankx Homefire for your answer.

I get -5v and the Baraduca works but it does not work well.
I tried to swing a screwdriver over the coil and Baracuda fount it.
But if i try with one money i have no sound.
So i think that i am tuning in wrong way and i investigate all the circuit to be sure that all the component are correct and there are all ok.
During my investigation i found a triangular signal on U7 pin7 and i thought that it's strange, so i asked here.

But probably my problem is elsewhere.

During the tuning i found that the circuit work with a very little delay of 5us. If i use R14 for set 20us delay (like the instructions) Baracuda don't works.

Somebody has similar problem or has an idea?

[marcosalvadori]

Sorry I was wrong I meant U5 pin7 (LT1054)

[marcosalvadori]

Ok, i tested all the components and many signals.
I tested Baracuda with big metal pieces and it detect good.

But if i try to detect 2€ money it doesn't detect the money.

I think that i made a bad coil.

Somebody can tell me a good coil specifics size for diameter, size of the wire and turns?
I need to start tuning from a good coil.

Thanks

[dfbowers]

Check your delay setting. Try 21 turns for a 10" coil or 23 turns for an 8" coil. For a 1e coin you should get 10" - 12".

[marcosalvadori]

Check your delay setting. Try 21 turns for a 10" coil or 23 turns for an 8" coil. For a 1e coin you should get 10" - 12".

Thank You very mutch.
What do you thnk about wire diameter?
0.4mm?
0.2mm?
It's the same?

[Koala]

Thank You very mutch.
What do you thnk about wire diameter?
0.4mm?
0.2mm?
It's the same?

.4mm works fine

[marcosalvadori]

Many thanks.
I realized a 10” coil with 23 turn and the sensibility of MD will be more strong


Now it can find a screwdriver from 60-70 cm.
But it can find a 2€ money only at 3cm-5cm so i need more sensibility.


I check the delay with a scope and i find that the best performances are at 7uS-10uS.
The specifics of Baracuda are for 20uS so i think that i try to find optimal value of damping resistor.
It this the correct way? Do u think that i can increase sensibility by optimizing damping resistor?

[marcosalvadori]

I am looking for fix my Baracuda.
I found that the best performances are at a delay of 5us-8us.
I think that this is too low then the specifics :-(

I investigate the wave form on the coil and i find this: https://goo.gl/photos/JMzYNLqdhTSfjRUH8

I think that it is too smoothed... what do u think about?

[ionut_mtb]

did you adjust dumping resistor like in picture? is possible that your delay is not working good. repace dumping resistor with the schematic in picture. and check output ne5534.