Baracuda Build Blog

[Koala]

Hi,

I am just starting to put together the parts for a Barauda to be used for general use on UK beaches and places where my IDX will not work. There was a very impressive YouTube video of an original one discriminating iron but can not seem to find it now. It was very similar style to the one dfbowers posted.

I would like to get as close to the original specification as possible to start with.


Started to collect a few items. Found an old crutch for the shaft and a waterproof box with latching lid and the SilverDog PCB.


Seen Qiaozhi list of parts reading through the threads most people seem to recommend using the 7660A instead of the standard 7660 are there any other parts I have to be carefully what version I order.

Which will be better 2X 18650 lithium or 8X AA Nimh


On one thread there is mention that Q3 and Q4 should be matched and 270k 470nF 1K should be 1% are then any others. On Qiaozhi's part list there is no Q4 should they both be 2N5485 and how many should I order to stand a good chance of a matched pair.

Can not seem to find the specification for a coil that gives the washed out with iron (what cable will I need to order) or is it not that important and use the info in the Joseph J. Rogowski Making a Fast Pulse Induction Mono Coil article

One last question people who use there detector on the beach once set do you use the delay pot or could I get away with only a threshold pot.

Sorry for such a long list of question tried to find as much as I can myself but some of the information is conflicting and now have brain overload


Looking forward to this build would like it full working for a trip out in December

[mohandes]

7660 not different ( maybe one type is better but i use and not problem) just use for 79l05(for input pin) and 79l05 produce -5 volts to another parts.

i use 12v 7.2amp seald lead acid and very well

2n5485 = bf256b ( the best ) or bf256 , or mpf102 and use bf245 ,bf245b , bf245c , bf244
i think bc517 more better than mpsa13 so use that
if you see the last post can see which transistor dont need and wilson say remove it.


for coil you can use coil calc. 28cm diameter and 0.5mm wire and 30turn should be 450UH and 1.5ohm.(or use coil calc to use any wire you have)


Delay put not realy use you can remove it and sold wire instead of that.
just find best damping resistor and best palce for Delay and ne5534-6 waves( in oscope).after you can set detecto by threshold ,just turn it until your detector is stable.

i should just say you very bad depth (near 14cm by 2000Rial coin) and after IDX i will repair that.find TP poind(certain the out put like every point have +5 and -5 volts and ...)
regards

[Koala]

Hi after a bit of advise


Is this a good way to match Q3 and Q4

http://www.docshut.com/mpnsqt/transi...ian-fritz.html

As I will have 18x 2n5485 left over can I use one in Q7 location as well or am I better to sticking to the MPS102

Apart from the damping resistor can all the rest be 1/4 watt. Will this do for the damping resistor. http://uk.farnell.com/vishay-dale/cm...-1w/dp/1871301

[Koala]

Some parts have arrived from Tayda.

Good price. Good service. Best of all everything is in grip seal bags with clear labels.

[sinclairuser]

if you really want to replicate the original barracuda, a tip127 darlington instead of the irf fet, q5 should be mps102(this jfet is no longer provided for on silverdogs board you have to drill your board to add it and its resistors), the matching you were on about there is disagreement about mine are not matched, matching them made mine unstable.
its not as easy as it was personally i think the other board was better, as you had options on which version to build, satdave uks files have all the info to build the anchor barracuda, the main difference is silverdogs version is motion, and the original is non motion, the original prefers 9v- 10.8v, silverdogs has been run on 9v-12.
the other difference is how they feel to use, which is very different.

[Koala]

if you really want to replicate the original barracuda, a tip127 darlington instead of the irf fet, q5 should be mps102(this jfet is no longer provided for on silverdogs board you have to drill your board to add it and its resistors), the matching you were on about there is disagreement about mine are not matched, matching them made mine unstable.
its not as easy as it was personally i think the other board was better, as you had options on which version to build, satdave uks files have all the info to build the anchor barracuda, the main difference is silverdogs version is motion, and the original is non motion, the original prefers 9v- 10.8v, silverdogs has been run on 9v-12.
the other difference is how they feel to use, which is very different.

Thanks for the information

Most of the parts came in before Christmas and the board is mostly soldered up. Went with the TIP127

Think I will solder some leads with headers on one end to the PCB and match the FET's in the board then remove and solder direct to the board. Got 20 FET's will be interesting to see the difference.

Missing a few parts that had to be ordered from other supplies. Been away for a month time to start this project back up.




Undecided as to the cable I needed to order for the coil that will give me the washed out sound. Some help here would be appreciated.

[sinclairuser]

i used both rg58 on one barra, and usb cable on the other both work. the coax is a bit stiffer.
replied to your post in the mduk forum today offered you a tip127 but i see you got one.
some prices for the tip127 on ebay are scandalous even for obsolete components.

[Koala]

Sorry did not word the question very well

Found some RG58 patch leads cheaper than paying for some cable so will just cut the ends off


What I need is the specification for the wire to wind the coil. Seen several on different treads from Teflon covered, CAT6E and speaker wire.


Used Tayda Electronics TIP127 = $0.35 only took a couple of weeks to arrive. Everything in clearly labeled bags. 90% of the components needed were in stock shocked at how much cheaper than Farnell it turned out. Well pleased will be using Tayda again.

Thanks in advance

[sinclairuser]

my pi mono coils are wound from 1mm teflon magnet wire, 8" 545uh-1.24 ohms, also made a 14cm coil .5mm wire 451uh 2.3 ohms.
a 12" basket is on my bench but uncompleated, but you can wind a pi coil out of allsorts of wire plastic insulated for instance, as long as you hit the coil specs your good, as long as its not to heavy(armache).
i tryed cat 5and6 but the ohms were way off.
old crt televisions have a loop around the screen, this winds good coils and if you find an old tv its free.
to sheild the coils i use a layer of insulation tape a layer of paper tape then i paint them with graphite lacquer(clear acrilic with graphite powder added) a fine copper wire(no teflon coating applied under the lacquer)connects this screen to the coil wire.
i have tryed unsheilded coils but its just to noisy round here for them.
p. s. the original barra had a 6800 cap, my kits came with 4700s, satdave uk sugessted higher ratings would be better he used 8600 i think, i have an 8200 in my 2nd barra and seems a bit more responsive.

[bernte_one]

hello
you should all try a 2200µF cap and a coil under 400µH, is not deeper but i has other advantages
http://www.youtube.com/watch?v=3RFWNjv2yso

[sinclairuser]

thank for the vid, i'l try that the second barracuda i built is for messing around with, the first is my primary beach detector.

[Koala]

Thanks a lot for the information from you both

bernte_one very impressive video thanks for posting

Did you have the extra FET installed that now missing from the silverdog PCB (Q5)

See what you mean about other advantages. Do you remember the type of wire you wound the coil and diameter. Think I will start with this as it clearly works very well.

Thanks again both for taking the time to respond

[6666]

hello
you should all try a 2200µF cap and a coil under 400µH, is not deeper but i has other advantages
http://www.youtube.com/watch?v=3RFWNjv2yso

Good video

[bernte_one]

@ koala
i have all parts installed (first version of the sold kits)
and i use for all my pi detectors in last time yv wire 0,5mm inner dia/1,2mm outer dia- best relation of L, R, Q and weight/size i think

@6666
thanks

[Koala]

Finally got round to putting some time into the project.

Could not get it to work well at first

Only had a loose coil on the table tried tweaking the delay and offset best I could get was and inch or so on a UK 2p. But could tell the difference between a older copper coin and a modern iron clad coin. If you place the iron coin on the coils edge it beeps as you move it away where as it is opposite with the copper coin and it only beeps when approaching the edge. When sweep iron across the coil it gives a broken sound and copper a nice beep

Thought I might have a problem with the fridge and washing machine nearby so move to another room no difference. Saw a old flat PP3 so tried it. Nothing except for threshold is at a lower volume. Readjusted the delay and offset by trial and error and now have 9" on a coin with a 9" coil same on a medium gold ring but now have lost the ability to difference between the iron clad verses the copper coin.

Measured the other battery pack. 10.5v plugged it in threshold goes loud again turn is down to just barely audible and nothing coin touching coil not detected. Put the flat PP3 back in works fine.

Why will it work with 8.6V but not 10.5V

And how can I get the the iron discrimination back