DP interesting beeps

[okantex]

Hi All,
it beeps to wet ground.
also beeps to plant if it contacts to plants.
sometimes if I put coil to ground it beeps even with big coil.

when I pass over a metal it beeps,but stops beeping slowly after leaving target area.can not stop suddenly.
yesterdays something interesting happened.
I pass coil over target,after leaveing target I mean 1.5meters or more.scale did not get down and machine continued to beep till I push tune.it happenned 3 or more time for same target.I do not know what is it.
and somethin interesting ,too
after testing machine for half an hour.I close machine between targets.
for 15 minutes time.I could not stop machine beeping. in air when I succeeded to stop it.something happened.
in air ,no metal around, after opening it.
I started counting 1,2,3,4,........
when I came to 8 somethimes 10 ,it started beeping. this happened may be ten times or more .at every try I made one after other.
can can be the problem.
for IRF ,I use heatsink.coils are 4.2 ohm and 5 ohm

[Max]

Hi All,
it beeps to wet ground.
also beeps to plant if it contacts to plants.
sometimes if I put coil to ground it beeps even with big coil.

when I pass over a metal it beeps,but stops beeping slowly after leaving target area.can not stop suddenly.
yesterdays something interesting happened.
I pass coil over target,after leaveing target I mean 1.5meters or more.scale did not get down and machine continued to beep till I push tune.it happenned 3 or more time for same target.I do not know what is it.
and somethin interesting ,too
after testing machine for half an hour.I close machine between targets.
for 15 minutes time.I could not stop machine beeping. in air when I succeeded to stop it.something happened.
in air ,no metal around, after opening it.
I started counting 1,2,3,4,........
when I came to 8 somethimes 10 ,it started beeping. this happened may be ten times or more .at every try I made one after other.
can can be the problem.
for IRF ,I use heatsink.coils are 4.2 ohm and 5 ohm

Hi,
if it sound with wet soil or plants...I think could be a shielding problem. If you haven't shield good your coil(s) you get capacitive effects when approaching soil or plants or other things (your hand also) instead of only air.
The fact that it sound repeatly when near targets and continues sounding means that maybe some imperfection was made in the circuit...don't know where can be. Use of heatsink can't be a problem if external temperature changes are not so rapid...so I think could be a saturation problem...means that something goes in saturation (e.g. an op. amp) and then current flow increase (or decrease) in a way that something locks in the circuit. I've sometimes same behaviour on my GS4 and just resetting it is a solution. I've noticed that it happens easy with iron-magnetic materials ...e.g. rusty metals...cans...and the like and not easy with good targets. Think that lock could be produced by overloads in middle stages.

Maybe you can workaround this by implementing another reset strategy (a push-button somewhere and maybe a resistor for limiting current) or changing op. amps with some rail-to-rail amplifier (e.g. TLC2262) instead of tl082 and the like.

Best regards,
Max

[Tim Williams]

I agree with Max. The plant and wet soils are a shielding problem with the coil. The drifting causing the beeping may be in the sample/holding stage of the circuit. Or depending on how you made the board "wiring" you may have a bad capacitance problem.

Tim

[ivconic]

???


Should not act like that?
Must be something wrong...
Shield not needed if frequency is low enough....under 200Hz....I never used it so far. But my DP's are stabile as rock. Neither one false signal...no matter if ground is wet or not...Usually keep frequency under 120Hz.....arround 100 or even 90Hz....due deeper penetration and avoiding small items, also due stabillity in most of grounds ive been working so far...
I made 9 DP's so far...All very stabile and very,very deep...
Already posted all datas and results earlier in Delta Pulse thread, no need to repeat everything....
So Okan, you have to recheck everything from a start...If using high frequency you MUST use faraday cage on coil...you MUST! Also my datas for coils not suitable for higher frequencies...Ask another datas...
regards!

[1843]

I have made two DP so far.Both of them are the same with okantex's...
I tested them with 1m x 1m coil and 90Hz frequency but it beeps when become close to soils (30cm) and at wet areas doesn't tune.(If I press the zero button, doesn't effect)
It is possible there is an error in the schematic which we don't know...
I made second DP carefully from start.

[okantex]

pcb is okay.because I ve controlled all lines before adding components.
pr1 is strapped ,so constant frequency around 98hz.coil is 60*100 rectangular.I think enough big not to use shield.

does your big coils cause beep if you put coil on ground (distance =0)
and something else
when all pots are at middle
on air it is ok.
but over ground IT sometimes need to adjust.
so soil is highly mineralizied.

[okantex]

btw there is a big problem with big coil.
I can not get close to iron object less than 150cm.it is sensitive to sides.

[Unregistered]

opened box.see that bottom of speaker touched to + of battary.
I think this is the cause of over loads and beeps.
but there must be something else casue beeps for wet ground and plants.
I try it again today.
okantex

[1843]

does your big coils cause beep if you put coil on ground (distance =0)
and something else
when all pots are at middle
on air it is ok.

My DP is like yours...

I checked D5A output, It is in saturation...Maybe it causes these problems.(I cannot increase the gain)

[Max]

Should not act like that?
Must be something wrong...
Shield not needed if frequency is low enough....under 200Hz....I never used it so far. But my DP's are stabile as rock. Neither one false signal...no matter if ground is wet or not...Usually keep frequency under 120Hz.....arround 100 or even 90Hz....due deeper penetration and avoiding small items, also due stabillity in most of grounds ive been working so far...
I made 9 DP's so far...All very stabile and very,very deep...
Already posted all datas and results earlier in Delta Pulse thread, no need to repeat everything....
So Okan, you have to recheck everything from a start...If using high frequency you MUST use faraday cage on coil...you MUST! Also my datas for coils not suitable for higher frequencies...Ask another datas...
regards!

Hi ivconic,
yes I agree that most of the times with 100Hz or so frequency you don't need shield at all. But sometimes you need. I have too some unshielded coils that I use sometimes with delta (and other PIs) but sometimes I get falsing even at 100Hz frequency...e.g. on wet salt beach. I don't often search in salt beaches but where I have to do I need shield. Also sometimes I've noticed (with delta too) that some worms , plants, wet grass , soil need shield too. I think that much depends also on coil construction...on cabling ...at the end on total capacitive effects involved.
I think that okantex have such problems cause his coil wire...and maybe coil cabling are not good for soil conditions where he's searching with.
So the simple thing is that adding a shield is not so bad in these cases.

E.g. I've modified GS4 to make a test at 150Hz (to reduce consumption) and have a lot of problems with falsing on unshielded coil...then I switched to my standard one for GS4 (8'' round with mylar shield) and get it perfect working !

I've tested in backyard...not beach...and got many falsing at 150Hz with GS4 and unshielded one.

So, yes, sometimes you can avoid shielding...but sometimes not. Also I think that he have some pcb / circuit problem cause seems it locks easy ...too easy. Sometimes I've same behaviour on GS4 but then resetting everything come back ok.

Best regards,
Max

[okantex]

give me time to see .
lock could be from touch of speaker's back metal to battery + socket

[Max]

give me time to see .
lock could be from touch of speaker's back metal to battery + socket

Hi,
ok. Maybe was due to speaker false contact...but I have seen many on other detectors...e.g. GS4 to be confident that could be a saturating secondary effect...you know...an op amp saturates ...then the output cap(s) charge and so the lock occourrs cause of the overload charge.
Anyway, on GS4 there is a reset push-button just for this ! Where on delta I remember just the auto-push and not reset.

Ok. Keep me informed of any progress. If you can ...change TL0x2 with TLC2262...and see if there is any difference.

Best regards,
Max

[ivconic]

???

?

I never tested it on the beach. I live deep in mountains, far away from any beach. Might be due terrain,might be my terrains are not mineralized much??
At my DP's PR1 exist, never straped. I am using it to fine readjust oscillator on current coil. Pay attention on this! This might be your problems!? You can not make proper coil 100% for DP at first glance...so i noticed quite better performances when readjust a bit frequency on current coil i am using at the time...After that it is working perfect, comparing to PUlse Star II...much,much more stabile and overall better...No false signals at all.
Also i payed huge attention on cable. I am using special microphone cable made by Televes, very fat with very fat Cu shielding, also very fat Cu main...
Perfect cable for low frequencies....up to 22kHz...
What elese could be a problem...? I am using LF357/356 in RX...Also i put ordinary 1N4148 diodes in limiter...nothing special?
I am using TL062 and those working excellent...My transistors are BC546 and BC557....always using those...
Capacitors are p.propillene...all of them, except pF values, those are ceramic.
Mainly i draw my pcbs manually with thin marker.....
As you see no secrets, everything ordinary....???
I am using 0.55mm Cu wire for 77cm coil and 0.4 for 32cm coil...
I am avoiding thicker wires...no matter what other claim here...My experiences are different so i am listening myself mostly...
I agree; no big deal to make f.cage.....so if no other solutions, i am affraid you'll have to make it at the end..
regards!

[Max]

?

I never tested it on the beach. I live deep in mountains, far away from any beach. Might be due terrain,might be my terrains are not mineralized much??
At my DP's PR1 exist, never straped. I am using it to fine readjust oscillator on current coil. Pay attention on this! This might be your problems!? You can not make proper coil 100% for DP at first glance...so i noticed quite better performances when readjust a bit frequency on current coil i am using at the time...After that it is working perfect, comparing to PUlse Star II...much,much more stabile and overall better...No false signals at all.
Also i payed huge attention on cable. I am using special microphone cable made by Televes, very fat with very fat Cu shielding, also very fat Cu main...
Perfect cable for low frequencies....up to 22kHz...
What elese could be a problem...? I am using LF357/356 in RX...Also i put ordinary 1N4148 diodes in limiter...nothing special?
I am using TL062 and those working excellent...My transistors are BC546 and BC557....always using those...
Capacitors are p.propillene...all of them, except pF values, those are ceramic.
Mainly i draw my pcbs manually with thin marker.....
As you see no secrets, everything ordinary....???
I am using 0.55mm Cu wire for 77cm coil and 0.4 for 32cm coil...
I am avoiding thicker wires...no matter what other claim here...My experiences are different so i am listening myself mostly...
I agree; no big deal to make f.cage.....so if no other solutions, i am affraid you'll have to make it at the end..
regards!

Hi ivconic,
I agree with all you said. No big secrets in DP...and very stable and good machine. Just need a bit of care and some experience for coil making and tuning. I'm sure you have done it right ...many and many times...without problems cause I know your have great experience in metal detectors experimenting and construction. Also I've TL0x2 on many detectors too...and also a lot of normal components like BCxxx that work great in this stuff...no need of special ones most of the times.
A point that I've missed in the last post was about first delay. I saw old Eric Foster's posts on findmall that talk about first delay vs shielding importance.
In most deep-seeking detectors (DP, Xr-71, PS2, Lorentz...etc) that use e.g. 1mx1m coil...or other big ones ...the minimum first delay is longer that in e.g. GS4 or deepstarII cause those last are for small target searching...and need small delays for e.g. gold detecting at big depth.
What happens with small delay is that detector easy need a proper shield on coils...cause if delay is e.g. 30-35 us or even a bit less...there's no need of shield...and capacitive effects can be ignored...but if you use e.g. 10-15us you almost often need a shield cause capacitive effects coul add to your mos-coil-cable---then total capacitance---thus altering output at pream occourrs quite easy, also on normal soil...not too mineralized.
I've noticed many times...that the lower the first delay...(e.g. 10 us) the more the sens to false signals due to plants...wet soil...in one word: capacitive.
So I almost always use shielded coils...cause I've modified all my PIs to work with small delays.
Older PI and deep-seeking have bigger delays that makes some of these no need shield. Also underwater ones have often delays greater than 30us. Just to simplify things...
Would be interesting too...hear from okantex and others that have problem with DP...which kind of first delay they have...to figure out if this is the problem.

Best regards,
Max

[Geo]

Hi all. A little about coil shielding.
I agree with ivconic that Delta Pulse dont need coil shielding. I use it without problems. But the reason that dont need shielding is the time delay and not the frequency. DP works with delay 30us. If the delay is lower than 20us then the coil needing shield......but now ..NO
Regards