BARACUDA-Legend-1

[DOOLEY]

good question 6666,

chip specs vary quite allot depending on the designation AFTER the "normal" part number we usualy only refere to.

only the other day , i happened to be looking at TL071's , 7 different designations ,

all with different max voltages , and different offset's (3 to 10 mV),

buying online can be a chance , poor / average / good spec.

only found the difference when on rs site.

i'll certanly be double checking the full part number in future

[Rom_1]

Hi, new in this forum, i just received my baracuda kit from Silverdog. In my kit i have as Q3 a 2n5458 instead of the 2n5485. Can i use it to replace the 2n5485?
Thanks.

[porkluvr]

If you have two 2N5485, use them for Q3, Q4 and use 2N5458 in less critical slot, say Q5 or Q12.

2N5458 is not really a good substitute for the sample circuit around U4 (partnering with 2N5485) but it might work dandy somewhere else.

[ApBerg]

Hi AP
thanks

sorry for my poorly worded question
what I was trying to ask was
what are the complete numbers on the chips
for example ne5534XYZ
and LM358XYZ

thanks
cheers

Hello,

Made a small test... for U2 I only have the Ne5534p ...

for U4 I tested 8 IC's, they als work and not much differents .... I like the LM358 (j4k527) the TLC272 and the lF442 ... some re-adjustment with the tune(threshold) potentiometer is needed , but then they al get good sens....

Best regards

Ap

[Rom_1]

What is the best for Q3 and Q4?

[maikl]

What is the best for Q3 and Q4?

Hi Rom_1. It seems does not work very well Google translator (English - French). The best combination is Q3=2N5485 and Q4=MPF102. Best regards.

[6666]

Hi AP
with all your testing with matched 2N5485 and Mpf102 fets
if you had a choice between the two which would you prefer
for best performance ?
thanks

[ApBerg]

Hi AP
with all your testing with matched 2N5485 and Mpf102 fets
if you had a choice between the two which would you prefer
for best performance ?
thanks

Think there is not much differents between them, as long as they are close matched.
Also I had some J310 fets... after testing them it seems the al where close in tolerants .. they also worked in the baracuda..
If I had to make a choice it is the 2N5485 I use, just a feeling...

.... it is as porklver explains, look at his explanation here post # 193, a few posts earlier..

Best regards.

Ap

[6666]

Hi Ap
thanks , I have an opportunity to buy a bulk lot of fets
so it will be the 2n5485 fets, when they arrive
I will try and find a matched pair and attack the Bara
with the soldering iron

cheers

[porkluvr]

If you don't match the resistors in the differential amplifier... then it would probably be a waste of time to go to the trouble of matching the FETs.

When you purchase ten resistors of x (+/- 5%) value, chances are that most of them will fall within 2% of each other, but there is always the chance that one or two will be at the extremes of their rated value. Lesson of the story: match the resistors.

I read somewhere that Mr. Anchor (not his real name) would spend time with each detector. I wonder how much of that time was spent sorting out component...?

[6666]

Interesting about the resisters, are you only talking about R22/23 1K
silverdog kit has metal film, so should be reasonably close match ?

[porkluvr]

You would also want to have 270k matched. By the way, notice that the two 470nF are 1% units according to the schematic.

If Silverdog's resistors are 1% tolerance you should be in pretty good shape.

[6666]

Thanks its good to know these things

[6666]

I just rechecked my silerdog kit, the resistors are mostly carbon i think, some are metal film
so I retract my previous statement, I will get some 270k's and test them and see how close they are, cheers

[ivconic]

Couple days ago i received Barracuda and Surfmaster pcb's from Silverdog.
First, must say, pcb's are SPLENDID! Bravo Silverdog! I am delighted with quality!
So i made Barracuda.
Haven't all fets from same specs, so i put one 2N5484 and three BF256's.
Haven't TIP127, so used TIP125 instead.
Instead 6800uF - 4700uF.
Coil is 19cm diameter, 24 turns of 0.5mm (haven't measured exactly...could be even 0.6mm) wire.
Resistance is 1.5 ohms and inductance ~0.25 mH.
It is working pretty descent!
Yes, seems is a bit better than Surfmaster!
Very sensitive on smallest coins.
Not sensitive on hotrock and minerals (when Delay adjusted properly).
1e coin can detect in air up to 25cm! Very good!
Larger items - more detecting distance... some up to 50cm!
Tip125 is getting a bit warm, not to much. Will survive even without heat sink.
Overall... i am satisfied.