Barracuda Legend Kit Problems

[ivconic]

Best compromise with delay setting I could find. 12V battery 8.5 coil

~[ATTACH]35809[/ATTACH]
~[ATTACH]35810[/ATTACH]

All maxim threshold change while sweeping. Loud beep is approximately 1" less

Can get nearly 14" on the gold ring but then the fibula is down to 3"


If I was only going to use it at the beach I think I would tune just to the rings both would be a solid beep over 10" which is about the max you can easily dig out.


Not sure how low the battery can go before the delay settings alter but at 8.75V there is about 1/2 a turn of the trim POT difference with no warning.

Precisely! Good job!
Heat sink is HUGE! No need for that.
"...Can get nearly 14" on the gold ring but then the fibula is down to 3"..."
Obviously.
Have you tried different delay for fibula?

[Old cart]

Best compromise with delay setting I could find. 12V battery 8.5 coil

~[ATTACH]35809[/ATTACH]
~[ATTACH]35810[/ATTACH]

All maxim threshold change while sweeping. Loud beep is approximately 1" less

Can get nearly 14" on the gold ring but then the fibula is down to 3"


If I was only going to use it at the beach I think I would tune just to the rings both would be a solid beep over 10" which is about the max you can easily dig out.


Not sure how low the battery can go before the delay settings alter but at 8.75V there is about 1/2 a turn of the trim POT difference with no warning.

That sounds normal if the fibula is small, say 1/4" or so in diameter.
Do you have a US nickel? Hard to tell from your pictures. That is a target I know well.

[Old cart]

Here are some scope shots from my Barracuda Kt 315 version. Im on the road again and all of my testing has been indoors in bad EMI and also lots of rebar in the floor.
Performance depth is pretty much on par with most other posters. Nickle at 10 inches in bad Emi.
At first I thought the motion non motion did not work but turned out I needed to move the coil 4 feet off the floor due to the rebar. It picks up large metal very well but strangely only has a depth of 4 inches on all my other test targets from gold rings to coins all hit the same.


Tx Pulse
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Tx and main sample delay
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Sample delay and main sample
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Earth field delay and main sample
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Earth field sample
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Pre amp out and voltage across coil. (maxim 410)
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And here is a picture of the peramp out with my dual front end plug in made for the HH (maxim 412). I know its not optimized for the two circuits but boy does it change the threshold to a nice clean hum similar to a Vlf and not hardly effected by the noise in my test environment. Depth response is about the same but for the deeper targets its a threshold worble or drop. Target sample range also changes, Good only from 7.2 us to about 30us no response after that.
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This post may be out a little out of place but it seemed relevant to the discussion on the schematics working or not.
I'm still learning and may be missing things but this board seems to work Just build it and power it up and calibrate it.
Went as smooth as my HH Surf pi or Mpp. All of these kits worked from the get go.
And thanks to you all for that!
Best
godigit

These look pretty good. Is the KT315 version of the BOARD or the schematics? I ask this because KT315's board appears to have been much better laid out than the original. The scope photos I have seen from his board are much better than other layouts. He has also done a better job of bypassing many of the IC's.
I want to emphasize that I have never said that any of these designs would not work, only that the some of the designs are not optimal for reproduction. Some will work, she may even work great, and some will break. The Baracuda certainly fits into this category.I think that given the vast differences in electronics background and debug skills our members have it is wise to have designs that are dead easy to build and have work.
In that regard maybe we should have voting buttons on each project that allows builders to give feedback on how easy it was build a design and get it working. EASY MODERATE HARD I NEVER got this to work!

[raygdunn]

Ray, I think all this would do is to increase the delay. Caps in parallel just add so 1nF plus 4.7 nF = 5.7nF. So did you match the main and EF pulse widths? That mod I mentioned really just adjusts the signal going to the samplers (main and EF) by adding
Resistance to make the channels match.

Hi Old cart,

Sorry I'm getting a bit behind with replies.

I've put some 100ohm pots presets on order. I've got nothing like that. I'm dubious about proceeding with much in the balance area, whilst the first sample pulse width varies with the Delay setting, though I do appear to have balanced things with the ceramic magnet at round about the optimum delay. With the detector balanced, I unearthed some low voltage batteries and did a field test. Yes it has eliminated the swing noise.☺

My capacitor experiment went wrong on two counts. I need to reduce the value, not increase it. That will shorten the current delay setting and then I can increase the Delay pots to compensate. The 40106 appears to dislike low value resistors. I'm thinking this would square up the leading edge of the first sample pulse and reduce the variation of its width (which upsets the balance of the two pulses to some degree). I'm having second thoughts on extracting another component at the moment☺

On my last component extraction, I found your tip about using a toothpick very useful, for clearing the hole. Some small new side-cutters also helped... Thanks.

Ray

[kt315]

thank you Godigit for nice report. try to tune frequency on exactly 600 Hz (enlarge R7 value). that has to decrease EMI interference.
can you give maxim412 opamp schematic you connected? i maybe will do a especial dip-8 submodule/board fitting opamp place with it...
also you may change R15 and R16 on inductors >80 uH (micro-).

[kt315]

Is the KT315 version of the BOARD or the schematics?
---
board = schematic. i did exactly layout of original, but in my opinion power lines was no so optimal and were retrassed in some places based on the concept of reducing interference&noise.

[Old cart]

Is the KT315 version of the BOARD or the schematics?
---
board = schematic. i did exactly layout of original, but in my opinion power lines was no so optimal and were retrassed in some places based on the concept of reducing interference&noise.

well it must have worked!

[godigit1]

Hi Old cart,
It is KT315s board but I am using the 74hc14 p instead of the 40106 and a bc517 in place of the mpsa13. Also the 410 amp but it did work fine 5534 as well.

Hi Kt 315,
Your welcome the build went nice. I realize I'm a little off on the pulse rate and my second sample one thing I was going to try was a couple different Ics and also order some 40106s to try as well. Most of my Emi problems I'm sure are environmental as my Mini pulse is also badly affected. I'm close to a airport where I'm at now and on the scope there is a wave that pulses backwards on the trace.

Thank you all for the help. I need all I can get . You may of hit it with R 15 and 16 though as I could not get any 24 ohm resistors at the time so I have parallel resistors there. I now have 24 ohm resistors but 5 % and was thinking of trying them. Im also only getting 240 volts of fly back but assume its due to only using a 300 uh coil when the circuit was designed for 450 uh. Or my pulse on time may need adjusting a little too.

The Dual Front end was made for the Hammerhead 1 as a plug in and is under this thread.
http://www.geotech1.com/forums/showt...ront-end-gt-gt
It is not optimized for the barracuda (Or The HH1 for that matter it was copied from the HH2 Schem) but does seem to really help the threshold and Emi. I don't have the engineering skills to do it myself I can only copy things at this point in my learning but I have good attention to detail and a good pcb background. I think the gain could be increased to it and it could be good mod for the barracuda.
Thanks Again
Digit

[Old cart]

Hi Old cart,
It is KT315s board but I am using the 74hc14 p instead of the 40106 and a bc517 in place of the mpsa13. Also the 410 amp but it did work fine 5534 as well.


http://www.geotech1.com/forums/showt...ront-end-gt-gt
It is not optimized for the barracuda (Or The HH1 for that
Digit

I noticed nice clean waveforms from KT315 and he uses 74hc14 as well. Maybe they are a better match. Getting the coil damping optimized is important whether you have a one or two stage preamp. I noticed on the trace you published earlier there was significant overshoot at the preamp. A little overshot can be good. It might be better to use the damping adjusting tool to try and optimum
y damp the coil/ cable/preamp combo.
The good damping tool is just a 10k 1watt pot in series with a 200 ohm resistor. Tack solder it across the board at the coil connections. Starting with the two set to max resistance slowly decrease the setting while observing the preamp out and the coil voltage as well and use a sweep speed of maybe 10uS per div. adjust until the pre output shows a smooth transition and the smallest pulse width.
A very useful reference is the book Inside the metal detector.

[godigit1]

Hi Old cart,
Thanks for the reply. I had damped the coil for the 410 amp and just plugged in the 412 So it was not damped properly. I keep blowing pots for some reason. Ive been using the same set up but with a 1.2 k in parallel. But only 1/2 watt pots so maybe that's it.
The two stage amp I am using was for the hammerhead so caps and resistors need tweaking . It worked well on the HH and quieted it down too but the wave form was not right there either. There is a picture in the link above. With proper design it could be a nice adaptation to the Barracuda or maybe the surf pi as well I never tried it on mine but I think I will put the smp back together and give it a try just for fun.
I do have a copy of ITMD it has helped but I haven't been able to spend the lab time with it I need and it deserves.
Thanks again

[Koala]

That sounds normal if the fibula is small, say 1/4" or so in diameter.
Do you have a US nickel? Hard to tell from your pictures. That is a target I know well.

No put the bottom right is a Canadian dim if that's the same and next to it is a Latvian.

[Koala]

Precisely! Good job!
Heat sink is HUGE! No need for that.
"...Can get nearly 14" on the gold ring but then the fibula is down to 3"..."
Obviously.
Have you tried different delay for fibula?

Yes

Best I can get is only an extra 1/2" but is not worth it with the loss of depth on other targets

It is a tough target. My VLF with a 6" coil only tests at the same depth.

It was only a couple of inches down when I found it. Still only gave an iffy signal.(IDX 10" DD poor ground condition)


Yes heat sink is not needed. FET only gets slightly warm.

[ivconic]

Yes

Best I can get is only an extra 1/2" but is not worth it with the loss of depth on other targets

It is a tough target. My VLF with a 6" coil only tests at the same depth.

It was only a couple of inches down when I found it. Still only gave an iffy signal.(IDX 10" DD poor ground condition)


Yes heat sink is not needed. FET only gets slightly warm.

It could be also because of possibility that fibula was made from alloy with larger percentage of Cu.
Not "good" bronze but with higher percentage of Cu.
I noticed that Cu is tough target for some detectors.
There is (sort of speaking) "male" and "female" copper alloys!?
That's local slang formed around prejudice at local diggers.
So, one of those two (can't exactly recall which one) is very easy detectable with PI detector and another one is not.
Another one is almost impossible to detect it with PI detector.
I guess it's just variations in alloy compounds and relation between it's compounds.
But i noticed that certain Cu alloys are indeed very tough targets.

[porkluvr]

whoops, I intended this for one of the other Barracuda threads.

Polymer posted a '7660 Do's and Don'ts around here somewhere, but now I can't find it. That's what I was referring to in the drawing.

[wakko]

Could someone please tell me the correct delay to use between the main sample pulse and the earth field sample pulse? I've seen a few figures on the forums from 100uS, 150uS and 180uS. Maybe it's best to trim the delay to whatever works best in the field?

Currently I have:

TX pulse: 100us width, 640pps.
Main sample pulse: 45uS width
Earth field sample pulse: 45uS width
Delay between Main sample and earth field sample: 150uS

Air depth results using an 11inch coil...

Thin gold ring - 10 inches faint, 8 inches solid.
1p coin - 8 inches
10p coin - 10 inches
£1 coin - 12 inches
£2 coin - 14 inches

I think these results are acceptable.... any thoughts?