baracuda rev A silverdog bad performance

[nonkapo]

Thanks waltr, however the Chinese toy is next to me and i'm adjusting with the pot, so far, that's why i do not suspect the damping resistor. I do not solder the resistor on the board, still with the damping tool. The other problem is the DSO cant get triggered below 50uS no matter what i do. Taking my TEK in the courtyard will be challenging but i'm close to do that. The other issue is that i must run away from the parking shades(all solid steel pipes) and not sure the extender is long enough.

[kt315]

1. How do you match the FET's and how critical it is?????

bara is simplest detector for a beginner and no reason to think about FET's. either, run back in technical university on 1 stage.

2. If the damping resistor is set what might be the reason for the coil ringing?(happened only with the basket coil).

we do not see your basket coil and sure it is wrong. coils ringing's reason is self resonance SR because any coil has self capacitance.

coil ringing is sinusoidal signal on SR frequency.

we call this cap 'parasitic' or 'unwanted'. range of SR is approx 500-600kHz.
we do a basket coil just for one reason - to decrease the cap value to minimal one.
a coil with minimal cap we call 'fast'. Fast Coil.

[nonkapo]

Thanks KT315. About FET's i read somewhere here about matching two of them in the cuda, otherwise in my experience i only match bipolar transistors, mostly in audio applications.
About the basket coil I'll post a photo. It is done on the standard 18cm ring printed directly from the PDF. The thickness of the material might be not enough. I use magnet wire 0.5 for it and planning to try with stranded or litz but only when i get the idea what i do wrong.

[geoscash1]

I do not Need a Bara any more.

I want to build a detector that finds a 1Gr gold nugget at 70cm depth

Gr=gram or grain?
I want to build a detector that finds a 1Gr gold nugget at 70cm depthMe too

green, yeah, me tooo.... Now that would be the holy grail....

I think nonkapo is mis-understanding the basket (3dss) coil for use with the bara... I have not built this new version (yet... but have built 2 of the previous versions of the bara and neither one of them liked the 3dss coil. When I tried my bara at the beach with an 8" 3dss is was beeping/buzzing/ringing constantly from the moment it was turned on, it was horrible. I had to use a bundle wound with both.

[dbanner]

Basket(3dss) coil is supposed to be fast coil and should be properly shielded as well. But on water's edge at the beach cannot use short sample delay. So for aqua hunting, better to use bundle coil made of silver coated stranded wire Teflon insulated. Just because they are simple to construct and fast enough not to mention easier to make shielding wrap and watertight housing.

[nonkapo]

Thanks all for your opinions and help.
To KT315 - please see the coils and give me your opinion. I've done all as per the instructions which seem more than clear. The enameled one is exact copy of the Plantilla coil pdf. The other one is expanded form of the same to reach 30cm OD.

Further there are some photos of the nearly completed "end product" ;-). Shaft made of 1/2 and 3/4 PVC pipes. Coil housing made of Cake pot. Pipe clips 1/2 & 3/4 are used for control box and coil attaching. The weight is around 1,5 kg but can be reduced by using piezo instead of speaker and fishing rods instead of PVC.

[kt315]

http://www.geotech1.com/forums/showt...baracuda/page2

your coils seems bad for me. i grasp you did not do a transfer step after every 5 turns.
you read unattentionally the forum. thats bad. i told about basket coil millions times but people do mistakes
every time. even i did ESPECIAL photo where i showed how to do transfer step but
anyway people are not able TO SEE it like the blind squerrel. people are merciless in their pursuit of the stupor.
http://www.geotech1.com/forums/album...chmentid=43266

[Qiaozhi]

I'm not quite sure why some people are obsessed with making basket coils for the Baracuda.
This type of coil is popular with DIYers who want to minimize interwinding capacitance and hence achieve the early sampling required for detecting gold nuggets. However, there are at least two problems here:
1) The Baracuda has a single-stage preamp, which does not lend itself to early sampling.
2) Even if you could set up the detector to provide sub-10us sampling, the design does not include a ground balance circuit.

It's a bit like putting racing stripes on a small family car. It won't make it go any faster.

[nonkapo]

Guys, you kill everything childish in me . I do all of these in my free time, as a form of experiment. It is not necessary i use them for the Barracuda, but that design, together with the Surf is the only working PI circuit i have at the moment. Going back to the sentence KT315 was using with regards to the USSR army - "if the conclusion does not come trough my brains, let it come thorough my hands". The bundle coils are not so challenging and time consuming, that's why they are less interesting to make.

To KT315 - No offense but there are at least 5 threads in the forum, where you personally recommend the basket coil as the best one for Barracuda;-). About the transfer - I'll get you special close up photo of those sections just to figure out whats wrong. I feel,like i misunderstood the words layer(слой) and turn(виток).

To George - yes I'm aware about. Funny enough even with the bundle coil from stranded wire i manage below 10us sampling, but as you say it sort of react to the soil cause of the lack of ground balance. In other words there is no point pushing down the delay below 10us, especially for the beach(which is not my main field of search anyway).

Again no offense all, your advises are priceless for dilettante like me. Since the project was set and working i concentrate on trying different coil designs before i go to the next level. So i have done bundle coil from enamel, UTP, stranded awg24, stranded awg22 and basket from enamel, stranded awg24 and UTP basket, flat spiral from enamel, UTP, stranded awg24 and stranded 22.

[kt315]

i say again NK. i had did ESPECIAL THREAD where i DID CLEAR TOLD how to make RIGHT basket coil.
i did so because this forum is similar to a swarm of angry bees flying in different directions.

I feel,like i misunderstood the words layer(слой) and turn(виток).

after every new layer you must do A STEP and then to begin new layer. LAYERS MUST NOT BEING PUT NEW-ON-OLD.

[nonkapo]

After using the Cuda for around a week, i just realize how deaf my Bounty Hunter Quicksilver is. Cant say for the small items, but for the bigger one... it force me dig few deep 70 - 80cm holes :-). Even i get a big bucket and remove the bottom cause digging a sand is challenging. One side you do, at the other sand come back down;-). The bottomless bucket help you a bit with that.

[dbanner]

After using the Cuda for around a week, i just realize how deaf my Bounty Hunter Quicksilver is. Cant say for the small items, but for the bigger one... it force me dig few deep 70 - 80cm holes :-). Even i get a big bucket and remove the bottom cause digging a sand is challenging. One side you do, at the other sand come back down;-). The bottomless bucket help you a bit with that.

I have bad experience with fake 5534 chip, causing poor sensitivity, coil after coil did I make wasting time and growing older in the process.
It was only when I ordered new chips for another project I decided to try the new chip on bara, and realized huge difference.
I don't see myself toting a bottomless bucket around the beach. People may think me insane.

[Tibuck19]

I have bad experience with fake 5534 chip, causing poor sensitivity, coil after coil did I make wasting time and growing older in the process.
It was only when I ordered new chips for another project I decided to try the new chip on bara, and realized huge difference.
I don't see myself toting a bottomless bucket around the beach. People may think me insane.

Had the same problems with 5534 from china and other chips as-well, and there were 18 10 turn Pots, only 5 were good! all from the same Chinese seller, called Alice1101983

[nonkapo]

Yes, the 5534 problem was long override during the surf pi project. Lucky I bought only five ic's at a local shop. The rest cost me three times more but work as a charm. I'm getting JRC one here and original TI from Farnel.
About the bucket there's no one in the desert to think I'm insane. My colleagues already know I am, after I buy MD to find my lost company phone. Now they start asking me to borrow my machine to find guest's lost items��