BARACUDA-Legend-1

[mohandes]

Mohandes,
Typically, the resistor is 330 Ohms. Contact oscilloscope to pin 6 NA 5534. Instead resistor 330 ohm put resistor 220 ohms in series with potentiometer 1 kilohms. Potentiometer is placed in position - max. Begin to reduce the value of the potentiometer until the oscilloscope signal is clear and no parasitic peaks. Measured values of the pot and add to it 220 ohms. You'll get the value of the resistor that you care. Change resistor 220 ohm and potentiometer with another resistor, which has an estimated value of you. You're ready!

thanks
but the depth is very bad , and ne5534-6 dont like wilson,s wave.
i (use 2.5k pot) to find it but not find and change 3 coils together but again not success
regards

[Wilson]

Mohandes, do what Toros recommended, do not be questioned. You ask for help with a question and when someone responds to you do not care and throws another question, you never know if you followed the recommended. You have in your hands an oscilloscope use it and try to fix the problems.
Hug.

[mohandes]

Mohandes, do what Toros recommended, do not be questioned. You ask for help with a question and when someone responds to you do not care and throws another question, you never know if you followed the recommended. You have in your hands an oscilloscope use it and try to fix the problems.
Hug.

oh my dear friend wilson
thanks , but i do every thing and detecting like mr bion.(and not good , maybe this detector cannot find more or ...)
thanks for your helps and thanks Mr Toros
best wishes

[bion]

Wilson.Do you want to send me the baracuda PCB long board please. I will try downoad but i cant open the archive.Thanks.Mi email: [email protected]

[mohandes]

Wilson.Do you want to send me the baracuda PCB long board please. I will try downoad but i cant open the archive.Thanks.Mi email: [email protected]

me too please
[email protected]

[satdaveuk]

In this case 330 ohms should be pretty close.

I like to adjust the damping resistor by looking at both the output of the preamp AND the voltage across the coil at the same time. Some tips:

1 Make sure your scope probes can take the voltage of the fly back pulse which can be hundreds of volts. Most x10 probes can do this.
2. Ground both probes to the same point on the detector near the coil attachment point and use shortest leads possible.
3. Adjust the scope attenuators and offset/position controls so the waveforms fill the screen vertically as closely as possible.
4. Adjust the time base so once cycle of the transmit waveform fills the screen. Later you may want to zoom in and observe just the fly back pulse to tweak it the best.
5. Use bandwidth limiting. The lowest bandwidth is best as long as it is greater than 2MHz or so. Most hobbiest scopes have 20 MHZ bandwidth limiters and they should be left on most of the time for detector work.
6. Trigger on the start of the transmitter pulse using the -/+ slope and trig level controls. Also use normal triggering NOT auto.
Adjust trigger level so there is no jitter.

7. Do not move probes around or change setting at all unless the waveforms goes off the screen.

While looking at both waveforms adjust the damper r slowly until you see a smooth transition with no ringing and the narrowest ring back pulse at the same time. You will also notice the output , pin 6 , of the preamp at this same time interval will also become narrower and wider while you adjust dampening. You want the setting that produces the narrowest ring back (fly back) pulse and little or no overshoot And the narrowest preamp output. This will allow you decrease the sample delay to its minimum, but no less than 10-12 uS if you want fine gold. On photo 6 if the yellow waveform is the early sample pulse you can decrease the delay 4-5uS so the leading edge of the sample pulse coincides with the point where the preamp out just breaks from the lowest level. You can also shorten the sample pulses to 10-15 uS if you want maximum gold sensitivity.SMALL adjustments to the offset can also help eliminate the wrinkles you see in the preamp out and smooth the response of the detector.

These settings let me increased my depth on a small mans gold ring of 6 grams from 24 to 30 cm. so careful setting pays back with huge rewards.

One last thing, once you confirm these setting are good in the field. Then it is best to replace the adjustable pot with a fixed resistor or combination of resistors that is closest to the measure value of pot. Be careful to keeps the leads as short as possible. You have to remove the pot from the circuit before you measure it so be careful not to disturb the setting you have been so careful to make.

Good luck!

Nice tutorial old cart very professional
I've not been on Geotech for the past few months due to work load, really missed you lot.
Nice to see some new faces on here also with success story's regarding the famous Barracuda.
As some of you know on here I made a second Barracuda but this one is based on using Silverdogs layout Q1 mosfet instead of Darlington transistor and omitting Q5 etc..
All transistors including Q1 have been socketed so easy conversion from original to Silverdog for experiments on pros and cons between the two versions and find out why the original works as designed a non motion PI and silverdogs is motion type format.
Not spent much time yet on the tests but first thing that is very noticeable is using the FET version certainly requires 12v supply as allot of you here have already quoted, unlike the original that works quite happily with a 9v supply.
The FET version is not so critical with coils in fact just winding a few turns of ordinary telephone wire round a empty toilet roll will get it up and running.
The one thing that is noticeable using my 2" coil which gets 5" depth in real ground conditions with the original design It seems to be able to get that little bit more with the FET Q1 but on the other hand im getting no audible or difference between coloured and non coloured metals which is what I expected.
Have also confirmed that the modified design does in fact produce a motion detector whilst sticking to the original lay files/design gives a non motion detector as originally intended.
The reasons for these differences I suspect and will be proved shortly will be tied up between Q5 and its relevant components far as motion/non motion, Discrimination IE washed out sound in presents of Iron due to two factors Q1 which was Darlington type transistor and coil specification which is critical for the machine to work as designed.
The supply voltage/current usage is also certainly down to Q1 which gives the knock on effect that the volts converter chip is working allot harder and I would think that a coil much under 1.5ohms would damage it or at the least not much of a life span, which brought me to the conclusion of why so many here have had to replace them.

Hope this helps, still got more experiments to do and will let you all know in due course together with a few pictures.
Regards

[wakko]

Hi everyone,

This is my first post in the forums, I have to say that there's a lot of useful information here After deciding to try metal detecting I've been following this thread with interest. I have bought the Baracuda kit from Silverdog (great kit) and threw it together in a couple of hours the main job now is to build a good coil.

Regarding the ferrous/non ferrous feature, will changing Q1 to a TIP127 and making a coil to the recommended specs give me the audible discrimination the original Baracuda had? If so, I wonder if the discrimination is a good trade off against making a larger coil with greater depth capabilities. I'm assuming you'll lose the audible discrimination if you move away from the original coil specs.

Regards,
Brian.

[bion]

Somebody can post the the Baracuda longboard PCB ,please.Thanks.

[Constantin]

Hi Bion. You can find a longboard version on elforum.

[Wilson]

Hello Bion and Mohandes, PCB longboard is on page 29 # 704
Hug.

[bion]

Yes but i cant open the archive.

[Koala]

You will need The Sprint-Layout-Viewer is free from here bottom of the page

[mohandes]

hi to all
any guru find the best component transistors to use ?(my barracuda dont work well without bf25c and bc517,;low depth)
regards

[Toros]

hi to all
any guru find the best component transistors to use ?(my barracuda dont work well without bf25c and bc517,;low depth)
regards

Mohandes,
So far I've done three detector Barracuda. One with a long board, which I did mod as Wilson showed and two detectors on Ap Berg`s board. I used both - the original scheme of transistors and transistors BF245C. In all cases, the boards work, but the maximum distance at which the detectors see a euro coin is about 28-30 cm. I used braided antenna U = 28 cm, 0.7 lacquered wire
I'm not convinced that this detector can give better results. It was developed as a beach detector. Objects that can be found on the beach are not so deep.
What are you looking transistor BC517. It is no longer produced. Look for MPSA 13 or MPSA 14. They are modern production and they doing a very good job.

[mohandes]

Mohandes,
So far I've done three detector Barracuda. One with a long board, which I did mod as Wilson showed and two detectors on Ap Berg`s board. I used both - the original scheme of transistors and transistors BF245C. In all cases, the boards work, but the maximum distance at which the detectors see a euro coin is about 28-30 cm. I used braided antenna U = 28 cm, 0.7 lacquered wire
I'm not convinced that this detector can give better results. It was developed as a beach detector. Objects that can be found on the beach are not so deep.
What are you looking transistor BC517. It is no longer produced. Look for MPSA 13 or MPSA 14. They are modern production and they doing a very good job.

many thanks
man can you put here for me pics of your detector.
i have bf245b ,and it is should be work well like bf245c but dont .
best wishes