Barracuda Volume

[DOOLEY]

hello Thomas,

ah................

abrupt, yes.

never had a scathing reply before, no.

shocked and offended, yes.

no need for the picture.
or that reply.


anyways,
back to the chase.

I understand now,
lost in google translation then I assume.....

originally I was using the circuit to drive an 8 ohm speaker,
putting a resistor between the emitter an the speaker would have limited
the maximum volume,
so I didn't put one in.

but yes an 8 ohm load driven from say 8v would theoretically take 1 amp,
suppose I could have put a 47 ohm in there to limit current to 74 ma,
for a 1.5w speaker this would have driven it at a safe 1.15w max.

it was never going to get that much drive from a 3904 with a 10k base resistor,
doing a quick calculation speaker was only ever going to see 55 mw at best.
and with 50% duty it was never going to blow the speaker away.......

ah well,
many apologies to all for not placing a load resistor there,
didn't think it would result in a ho down............

[DOOLEY]

your both welcome.



my enjoyment and reward in this hobby is trying new things,
devising new circuits,
modifying existing ones,
and designing from scratch.

it's quite annoying for someone to p1ss on my parade, ( can I say that, sorry George........LOL.....)

just thought I could help people out from time to time by sharing working solutions.

I asked many questions in the early days,
some poss quite stupid looking back now.

electronics is a never ending learning curve and process,
that's the fun and rewarding part,
(although when things don't go right it doesn't seem like it at the time.)

no one EVER knows EVERYTHING !!
and if they think they do, then they are an idiot !!

[Thomas]

Guys, you are getting a little over reactive towards KT, Dooley - when KT says "strange decision for me. you broke the Emitter of transistor from link FOR WHAT? where in electronics you see disrapted Emitter pin from another part of schema? give me please the examples where you found that." I think he is saying He does not understand why you left out the emitter resistor, not a common practice. and what circuit also has that arrangement so he can under stand it. Bluebenz KT is abrupt, he has that right and does not need a attitude change, you have to like the good and live with the bad. Live and learn.

[pebe]

Dooley, I fully agree with your method. It is perfectly valid.
I am surprised KT315 cannot understand it.

[bluebenz1]

Dooley...Thank you very much for your ideas regarding the volume control....I AM a total nooby and appreciate anyones suggestions...even if i don't have the skill to convert a schematic diagram into and actual working item...!!! Anyone who comes out with totally unhelpful remarks is noted by all on this forum...and just ignored....what a total @£$%"$%£@
I have read a few of kt315 posts and find it difficult to understand the meaning behind the Lituanian/English he's trying to use....so best ignored in my opinion.
kt315, maybe you don't mean to come over as abrupt...but you do!!>>>SO CHANGE YOUR ATTITUDE..or change the forum you choose to use...

[DOOLEY]

whoh whoh KT !!
ease off KT !!

WHERES ALL THIS ANIMOSITY COMING FROM ???

I decided to post a couple of times to help somebody out with a volume
related problem and I get YOU calling ME a dummy ???

I can't give examples of this circuit because I devised it myself,
I have not seen it used on any other detectors schematics so I can not
post examples,
somebody may of used it before in a design,
i'm not sure.

I may be new (7 years or so) to metal detector electronics but I am NO
NEWBY to electronics in general !!
NOR A DUMMY, thank you very much !!

me, like many others on here are striving to develop new idea's and circuits
regarding metal detectors and this sort of response is not called for.

is your aim to deter others from posting for fear of ridicule ??
or are you just having a bad day ??

I can not believe this response from you,
a long time and contributing member of the forum.

this is the sort of backlash that makes people think twice about
posting anything here,
and the content of the site will then suffer.

yes,
there are individuals on here that have great insider knowledge ,
there are professional electronics people on here from different fields of work,
then there are us mere mortals who partake in this very rewarding hobby.

just because we are not professionals or "in the game" neither makes us dummy's or
any less worthy of taking part on this forum.

[kt315]

can't give examples of this method in use in any other schematics --- then you are only nooby

crotcheteer

)))

[DOOLEY]

hello kt,

i'm trying to decipher your reply,
not sure what youre referring to........

going to hazard a guess it's relating to the diagram " AUDIO OUTPUT SECTION.JPG "
can't give examples of this method in use in any other schematics,
don't think i've seen any other detectors using it.

it's just the method I devised a while ago that worked well and
sounded nice ,
and provides proportional target response.
quite economical on power also.


the NPN is a simple voltage follower that applies target voltage to the speaker,
and the 2n7000 is pulsed by a clock signal for the desired tone output.
either a 555 or a divided TX signal would do.

[kt315]

strange decision for me. you broke the Emitter of transistor from link FOR WHAT? where in electronics you see disrapted Emitter pin from another part of schema? give me please the examples where you found that.

[DOOLEY]

just thought i'd post an extra diagram,
if anyone wants to use it.

gives a very nice pleasant sounding audio output ,
proportional response,
and has the "minimum" diodes on the volume pot.



volume pot doesn't have to be 100k,
could be anything say 10k upwards,
but 100k wastes less power,
if that's important to you.

R1 AND C1 added to reduce the sudden impact on the +
voltage rail and feedback noise.
may be omitted ,
personal choice........

[DOOLEY]

hang on a minute ,

just had a thought,
2 or 3 diodes works well when using a single NPN
for the output drive,

but,
BARRA uses a darlington,
going to need to use 3 to 4 diodes for that.
(maybe more, personal choice)

then 3 diodes will let 0.6v through un hindered to the speaker,
4 would let 1.2v through.

[DOOLEY]

hello all,

I have attached a pic below to modify detectors audio response.

its quite simple, and it works !!

done this on my last 2 detector designs.

basically add the 100k pot for volume,
this is set for your preferred MAXIMUM volume level.

the diodes on the volume pot that goes to earth serve to allow a MINIMUM
volume to pass without being regulated by the volume pot.
so sets your minimum volume.

2x diodes is about 1.1 volts,
after which point the volume pot starts to limit.
this allows faint signals to pass un hindered .

depending on preference any number of diodes (1,2,3,4) can be added in series,
dependant on the headphones used,
personal deffness etc......etc......



picture shows rough version of the barra audio,
that many different versions out there,
I just picked the 1st I came to.

enjoy.

[Koala]

went out for the first time with a detecting group on farm land and my home brew barracuda ...some interesting observations.... it was no match for the xp deux's...however...it did find various bits of rusty farm metal including a horse shoe...so if its big and rusty...I'm your man....mind you no one else found anything more than a couple of old pennies......I used head phones and the buzzes almost blew my ear drums out..I couldn't wear them over my ears, bloody awkward trying to get headphones to sit anywhere other than on ones ears...i found that if i moved the coil end of the detector with a bit of a twitch it would buzz as if detecting something also a feint buzz at the end of each gentle sweep....summery pleased that it found anything at all...but seemed very unrefined.
Powered with 8 AA batteries, coil-200mm 0.4mm enamelled wire, can't remember how many turns unshielded.

Think you will be surprised on a cut quarter in mineralized ground between you detector and a Deus. After its been fine tuned.

Had a look through TK Maxx headphones and earbuds today. Only one set said it limited to 85dB but there was no mention of how it was done so suspect its just an inline resistor.

Several around the £10 with a volume control but you will loose the faint signals.

I sometimes run my IDX with 0 discrimination. I pinpoint a target then work out how big it is. If its a large or long an thin target I walk on by. Tend not to dig too much junk plogh shear or horseshoes. Seen some nice iron artifacts but not by me yet like a medieval cast iron thimble and some lovely rose mounts.

[bluebenz1]

went out for the first time with a detecting group on farm land and my home brew barracuda ...some interesting observations.... it was no match for the xp deux's...however...it did find various bits of rusty farm metal including a horse shoe...so if its big and rusty...I'm your man....mind you no one else found anything more than a couple of old pennies......I used head phones and the buzzes almost blew my ear drums out..I couldn't wear them over my ears, bloody awkward trying to get headphones to sit anywhere other than on ones ears...i found that if i moved the coil end of the detector with a bit of a twitch it would buzz as if detecting something also a feint buzz at the end of each gentle sweep....summery pleased that it found anything at all...but seemed very unrefined.
Powered with 8 AA batteries, coil-200mm 0.4mm enamelled wire, can't remember how many turns unshielded.

[Koala]

Finding specification of audio limiting headphones is hard. Suspect most are just a resistor add so will affect the softer sounds also.

dB Logic SPL2 looks interesting. Does not affect the lower sounds and no batteries required and very cheap. Not sure it will work for detectors as on one site did say it took awhile for the limiter to kick in. Still searching for its proper specifications. There was also an inline module for $20 but can't find any listings in the last year.