BARACUDA-Legend-1

[ApBerg]

Hello ApBerg

Thank you for the info on your experiments using different FET's for gating the signal. Wonder why the best results are when using 2 different FETs? I will get the datasheets and see if i can see any reason. Surely they are both doing almost the same job?

Regards, Jim.

Hello Jim

I think it works as follows:

The LF412 (or lm358 ) opamp works as a differents opamp it see's the receive signal from the NE4434 at short time windows .
The timings for that time windows are made with 40106. The fets are the switches that opens that windows so the Lf412 can see the receive signal coming from the NE4434 at time's that have some delay from eats other . The differents in that receive signal makes the 'detect’ signal. It is imported that there is only differents in the signal.. so if components have not the same property's they also give a differents in signal... think that is not what we want...! Think the fets also need a close match ??
Results: select the parts that are in that two 'lines' (ne4434 to lf412) as close as possible..this will give the best sensitivity

If I am wrong of if some have a better explanations...let us know..

Some info http://www.geofex.com/article_folder...h/fetmatch.htm not spot on.. but it give's some info about matching fets..

Best regards

Ap

[bernte_one]

maybe not the perfect one
but i use a 23cm coil classic single loop (not planar) with 30turns of
H05V-K Litze LIY 0,5 mm (lappkabel or ölflex - product names)
gives 490microH and 1R
the delay trimmer is nearly set to zero
gives a good signal light above 30cm for a 2€ piece

after holidays it will try higher diameter



...ahh 6666 was some seconds faster

[6666]

Good question bob
cct says 24 turns 26 swg 7.5 inch form

Andy would you mind posting a good picture of your completed working Pcb
thanks

6666

[plumabob]

Specs for the ultimate baracuda coil anyone? Waiting for some parts to come in. In the meantime I thouight I'd start working on the coil.

Thanks

Bob

[6666]

Hi
so you have found two different fets gives better sensitivity

which fets did you find to be the best combination ?
and how did you connect the Source and Drain for both fets


What was the difference in sensitivity with using a pair of the same fets
compared to using different fets?

thanks
you may have found an important discovery

[bernte_one]

thx to forum

[TH Jim]

Hello ApBerg

Thank you for the info on your experiments using different FET's for gating the signal. Wonder why the best results are when using 2 different FETs? I will get the datasheets and see if i can see any reason. Surely they are both doing almost the same job?

Regards, Jim.

[6666]

Ap i made a new thread in General Electronics

[ApBerg]

Thats a great idea about the sockets

Hello,

Yes, the sockets make testing very easy, no messing up tracks/pads if a other part are inserted.. .But only for bench testing, not for real use ..

As you are from Down Under.... have you seen or have info about the silicon chip logger from December 2010... I made now 2 prototype's , but they are not working good.
I have the 3 magazines and have seen on their website the update's...
Can be that I have made some error in the pcb layout..( pcb is not in the magazines) I like to bay a original pcb board (or kit) but this is not easy...
Think it is a very nice project, that logger, it can log the GPS data and also a lot other inputs e.g. from PI or Magnetometer..

Sorry ... I know it is off topic..

Best regards

Ap

[6666]

Thats a great idea about the sockets

[ApBerg]

Baracuda kit is here Andy! I gotta say this board is a beauty. Can't wait to get started on it! Before I do, are there any changes I should be aware of?

Thanks,


Bob

Hello Bob,

Look carfull for the 2n2222 connections E/B/C the symbol on the pcb is NOT leading for how you place the 2N2222, the text for E/B/C is good so look on the data-sheets transistor that you use.
The fets that switch the signal after the NE4434 are importend for good sensetivety, I tested some, not working was the BF245c the b and a versions were O.K.
Think if you can select the 470nF caps on close tolerance( same value) this is good for the sensetivety...

Lots succes and have fun...

Ap

[plumabob]

Baracuda kit is here Andy! I gotta say this board is a beauty. Can't wait to get started on it! Before I do, are there any changes I should be aware of?

Thanks,


Bob

[Janou]

Thanks for theses informations !

[ApBerg]

Hello Janou,

Look at the surfmaster and baracude info for coils, it is easy to make a coil for a PI detector, if you realy want to make a good fast coil look at the info from BBsailor.

For baracuda adjustmenst... look at the scope photo's, but there can alway's be better way's ?

[Janou]

Hello, i'm new on the board

I'm totaly a beginner for treasure hunting, but after would build a hammerhead D, i finaly choice the baracuda and order a kit to silverdog.

I really like the simple schematic of Baracuda, si i'm here now

One query to ApBerg, i love your coil, do you compare with more "standard" wire, is it a choice for experimentation or something like that ? Do you think it's a good choice ?

Other more global query about calibration of the detector, have you a calibration sheet or something to do correctly the job ( i have a scope etc ) sorry if the query is not interesting