Delta Pulse

[nelson]

Thanks

Hi Geo and thanks for your support.
I think i ll star checking everyting again, because after listening to all yours supports, it must be something wrong with upper side PCB connections. So when i get everything connected i ll post what was wrong. I know is something that i made wrong.
Regards and many thanks to all of you who help me, and when i get any doubs i ll post again.
Nelson

Hi Nelson. At my DP 556 is always cold. I don't understand what to looking for it?

[Esteban]

Nelson, check all the connections, but first clean very well and eliminate path of solder resin. With a magnifier see possible shortcircuit.

[nelson]

Delta pulse in sprint layout format

I forgot. I have delta pulse pcb made on sprint layout software. This is the one made by KT315. Is this pcb ok or has some problems?
Regards
Nelson

Hi Geo and thanks for your support.
I think i ll star checking everyting again, because after listening to all yours supports, it must be something wrong with upper side PCB connections. So when i get everything connected i ll post what was wrong. I know is something that i made wrong.
Regards and many thanks to all of you who help me, and when i get any doubs i ll post again.
Nelson

[nelson]

Hi esteban

Hi Esteban. Yes i ll do what all good fellows are telling me.
Best regards
Nelson


Hola Esteba. Si voy a hacer todo lo que los buenos muchachos me han indicado.
Coordiales saludos
Nelson

Nelson, check all the connections, but first clean very well and eliminate path of solder resin. With a magnifier see possible shortcircuit.

[ivconic]

?

:confused:
Your 556 might be failured due previous mistake. This is oscillator setup,might be some failure arround it.First power supply and filters arround...???
It is gonna be some job to find problem.
I wish you luck and nervs.
I also have problem.After a while i did some experiments more.My coil is detecting nice but on some pots. positions i gain strange sound.Double,poliharmonic sound??? It looks a bit unstabile...
Geo give me a hint, i guess you can calculate inductance, i have former 26cm and wires 0,23mm and 0,35mm....270Hz, 1K2 damper.....What do you think?
How many turns i need to make "calm" coil? Without ringing and singing?
regards

[1843]

:confused:
I also have problem.After a while i did some experiments more.My coil is detecting nice but on some pots. positions i gain strange sound.Double,poliharmonic sound??? It looks a bit unstabile...

ivconic,
You must use the one 1N4148 diode between the pin 7 and 6 of the D8.(Anode to pin 7 and kathode to pine 6)
It can eliminate the harmonic sound.
hope this help,
Regards

[Geo]

:confused:
Geo give me a hint, i guess you can calculate inductance, i have former 26cm and wires 0,23mm and 0,35mm....270Hz, 1K2 damper.....What do you think?
How many turns i need to make "calm" coil? Without ringing and singing?
regards

Hi Ivconic. What to say. Your detector is better than mine. But 30 turns at my 25cm coil are OK.Very stable and calm with full sensitivity and power. Try it. But i think that there is other problem. Why the other 4 DP works fine ???
I can say only one (Good Luck).

[ivconic]

Good..


Thanks 1843 !

Geo your question is good! Other DP's i sold with large coils, really works good on large objects,deep detection....excellent!

But this is first i want to make to work good on smaller items like coins.
I also made coil 26cm,0.35mm wire, 31 windings. Works very clear,calm,no harmonics in sound,detection on midle and large items is very good.But still poor on coins. Slowly step by step things become more clear to me....I have to rise frequency more,of course....But still number of windings is confusing me. It showed to me so far that best coils have more windings than mentioned anywhere in documentation.Usually 31-45 windings makes coil very good and stabile,detection much better.....When i obey various documentation and make coil with less windings....18-25, usually coil performances are very poor,also influences on DP performances too, start being unstable,"singing" like canarian etc...

I've been reading and listening many people here;Carl,bbsailor,you,some bulgarian people, also reading much more documentation on PI's too.
Neither once i saw project with higher number of windings than usuall,up to 30....but when experimented oposite, almost always showed to me that higher number of windings gives better performances....of course up to some limit to 45....one more or less....???
Usually i make coil as noted,later it shows poor performances and i "switch" to my hunch and add more windings....and usually gain better performances...
What to say? Still not clear to me...?
Anyway regards friends

[bbsailor]

It's not just the coil

ivconic,

Sensitivity to a target is not just based on the coil. Each target has a total decay time that must be energised by the TX pulse width, to obtain a good response from that target.

Here is an example. Two common U.S. coins are the U.S. one cent penny and the U.S. 5 cent nickel.

The older penny is made of copper and has a 350us (micro seconds) total decay time. A good TX pulse width of about 350us would fully energise the penny for maximum detection depth.

The U.S. nickel is made of a different metal and has a total decay time of about 100us. Here a shorter TX pulse of about 100us would fully energise this target.

Each coil has a time constant (TC) that is calculated by dividing the coil inductance by the total coil circuit resistance. If the MOSFET on-resistance is .5 ohms and the coil resistance is 4.5 ohms, such as in your 31 turn 26cm coil, the total coil resistance is about 5 ohms. I calculated that your 31 turn 26cm diameter coil has 706 uH of inductance. This inductance is very dependent of the insulation thickness of your wire. I assumed that the outside diameter of you .35mm wire is 1mm in my calculations.

The time constant of your coil is 706 divided by 5 ohms or 141.2us to reach about 62 percent of the full current. That means that the TX pulse width must be 141.2us long for the coil to reach 62 percent of its maximum current value. If the coil were on for another 141.2us or for 282.4us the total curent would rise to about 85 percent of its maximim potential. Finally, if the TX pulse were 3 time constants (TC) or a total of 423.6us, the current would reach about 95 percent of it's maximum value.

Your 26cm coil with 45 turns has an inductance of 1444uH. The coil resistance is 6.6 ohms plus 0.5 ohms for the MOSFET for a total coil resistance of 7.1 ohms. The TC of this coil is 1444 divided by 7.1 or 203.4us.
As you can see, adding more turns increases the inductance at a faster rate than the resistance rises, so the coil TC is getting longer.

Adding more turns makes your coil more sensitive but it also makes a higher voltage spike (back emf spike) that should be under the voltage rating of your MOSFET so the MOSFET stays relatively cool. As you change the TX pulse width, the amplitude of the voltage spike also changes. Higher TX widths make the spike higher. Different coin metal will be fully energised by different TX pulse widths.

Tell us the following:
TX Frequency
TX Pulse Width
Coil Inductance
Coil Resistance
Coil Wire Outside Diameter
Coil Wire Bundle Diameter (cross section of coil bundle)
Number of coil turns of your best coil
Size and type of metal in your desired targets
Distance desired targerts are detected from 26 cm coil
MOSFET type you use
Length of wire from coil to control box and resistance
Voltage powering your PI

You may be able to make some changes in the TX pulse width of your PI circuit adjsutment and obtain the same performance from a variaty of coils that are all operating on the same point of the TC current curve. But first we need to know some more facts (above) about the conditions of your best coil.

You may be able to add a small resistor ( 2.2 to 5 ohms) in series with your coil to: (1) reduce the peak back emf voltage (2) increase the total coil resistance to shorten the coil TC so it is between 1/2 to 1/3 of your total pulse width time. You may even need to change TX frequency (higher) and the integration time to accomodate a small coil moving at a faster sweep speed.

Provide a little more information and maybe we can help you find a coil that works best on smaller coin targets.

Happy New Year

bbsailor

[ivconic]

...

:confused: :confused: :confused:
Yes,bbsailor! I also noticed different behavior on different coins and small items too.
You got it right;matter of material(metal),shape,size.....True!
"..If the MOSFET on-resistance is .5 ohms and the coil resistance is 4.5 ohms, such as
in your 31 turn 26cm coil, the total coil resistance is about 5 ohms. I calculated that
your 31 turn 26cm diameter coil has 706 uH of inductance."

You are pretty close! 31 turn of 0.35mm(0.4mm with varnish insulation) on 26cm former.
And resistance is arround 4.1 ohms with "microphone" cable connected (fat,high quality).
Coil Wire Bundle Diameter is arround 6mm...
I checked this coil on DP before put in housing,detection was very good. Today when coil
is closed and glued in housing, detection is a bit weaker...have a feeling that coil is
"choked" a bit??? Also it started "canarian" song from time to time???
Mosfet is IRF740,supply is 12 volts (Delta Pulse).
Some other measurement i can not provide now, i left without elementar measuring instruments
this summer. I had huge electric "wreck" in my workshop.All instruments busted.
So now i do have only frequency meter and unimeter(volt,ohm,ampere...).Sheesh!
It will need some time&money to "stand on my feet" again...
What really interesting me is relation and changes between "open" coil (without housing) and
finished coil,put in housing,glued and closed...Quite different performances?
Also ocassional "canarian singing" and simillar may occur with the very same coil or with
slice different coil than previous one,which showed excellent performances???
What is main factor? What is source of problems? Inductance? Sudden change of it? Caused
by some subtle changes?
Resistance is not. Always remain same.Power supply is not. I do experiment using very good,
accurate, sealed lead acid battery, 12 volts,7.5 Ah.
I am also using high quality coaxial cable ("microphone" cable),already proven on many
coils and devices,both PI's and IB's. Cable length is usually 1-1.2meters. I am using
high quality connectors also.Cable and connectors made by Televes mostly.
The only reason of loosing good performances might be step when put coil in housing.Covering
with "Body" kit or simillar. I am using mostly liquid plastic (2 component)...Might be
something in that material?
I do not "extra" covered windings, just put in housing and coat,smear with mentioned material.
Is this the problem? Or maybe coil was not optimally assembled from the begining?
It was assembled close to "passable", but not close enough, so when reach end of performances
it starts "singing" and loosing performances very fast?
In this case i should calculate coil to be in the middle of "good" performances to avoid any
further "drift" when finishing it.Yes "drift" is good term to explain differences between my
"open" (naked) coils and finished one....
I do not have any doubts in my DP's.They all the same. Good constructed,giving good voltages,
good,proper signals....power consumption is 90mA without sound(detection) and 105-110mA with
loud sound(full detection)....I think this is optimal.
What to say? I still have problems making coils! This is fact! Large coils(from 45cm and up) are
working very good. Smaller coils not!?Large coils are closed in pipe,without glue or plastic.
Maybe that is "geag"? Who knows?
I did some comparsions and checks with PSII and DP. PSII,electronically speaking,is great
machine, state of the art. German constructors involved big effort and made very neat PI.
But on the field,there is not big differences between these two machines. In some cases PSII
is out of question,the best...but in some cases DP showed even better performances.Usually on
wet,mineralized terrains...
...
regards

[PulseStarIIUser]

BIG PSII COIL

Dear Ivconic,

You said that big coils work well for DeltaPulse and PulseStar machines. Can you give me some hints about constructing a big coil for PSII? I am most interested in making a 2m x 2m coil, such as the universal search loop. I am only a beginner :confused: interested in experimenting with coils. Below is a post I made earlier this week. Thanks for reading this.
--------

Hello,

I own a PulseStar II, and I would like to get a larger coil, say 2m x 2m. The “Universal Coil” sold by the manufacturer appeals to me (http://www.tb-electronic.de/prodinfo/ps2/univcoil/unien.htm), but they charge over $350 for the coil. I am sure one can be built much cheaper. But first I have two questions:

1) Is it practical for me to try building a larger coil without access to an induction meter?
2) Am I likely to damage the PSII electronics if the inductance of my experimental coil is too far off?

I was thinking of starting with 8 meter length of 14 strand wire (metric 16/0.2) and connecting wires end-to-end until the coil performance is maximized. I would leave any unused wires free (unconnected).

I am not an electronics person like most of you but I like to try simple projects (but only if I am unlikely to damage the PSII electronics).

Thank you for this very interesting forum. I am impressed with the electronics knowledge here and willingness to share information.

Bob

[bbsailor]

Cover Coil Winding

Ivconic

I do not "extra" covered windings, just put in housing and coat,smear with mentioned material.
Is this the problem?

Yes, this could be the problem.

Try to isolate the wire windings from being in direct contact with the liquid glue.

You can try to wrap the coil with electrical tape or use spiral wrap like in my article.

Also, try using stranded wire with a thicker insulation to make the coil. It will take a few extra turns as the wire coil bundle will be a little thicker with the wire more spread out.

I hope this helps? Let us know?

bbsailor

[dan129]

My DeltaPulse

[ivconic]

...


Hi PulseStarIIUser,
i will try to answer some of your question;
first i am posting here original setup for 1x1meter coil for PSII. This was sent to me
from one of my friends from Macedonia,Goce,tribute to him!
About 2x2meters coil...well,pretty simillar setup.I do have original 2x2m coil for PSII,
to tell you the truth, i had not benefit much from it so far. 45cm coil suits 90% of
my needs.I can agree that 1x1m coil can also be very usefull.But 2x2m coil is pretty
hard to deal with.It will take 2 man,large space and a lot of luck. But search yourself.
If you want to make it,go ahead.Resistance is 2.5 ohms including cable.
"1) Is it practical for me to try building a larger coil without access to an
induction meter?"
Why not? If you have accurate datas...I left without it for some time,i made a lot
of coils so far, mainly good ones, these days i have some problems with small coils only.

"2) Am I likely to damage the PSII electronics if the inductance of my experimental coil
is too far off?"
No,youre not! Do not be affraid! Just keep coil resistance over 1.9 ohms and experiment
freely! Some of them will work better,some of them not...

"I was thinking of starting with 8 meter length of 14 strand wire (metric 16/0.2) and
connecting wires end-to-end until the coil performance is maximized. I would leave any
unused wires free (unconnected)."
Better use them all. Or find proper wire.
Regards!
P.S.
I connected 45cm PSII coil to my DP. 1.9ohm is resistance.I checked fet not to become hot.
Detection was average and fet remained cool for over the 5 minutes...This coil not suitable
to use with DP.I already made better coil for it.

BBSAILOR
"Try to isolate the wire windings from being in direct contact with the liquid glue.
You can try to wrap the coil with electrical tape or use spiral wrap like in my article"
Yes,i was thinking that way...Thanks very much on tips bbsailor! I'll report experiences..

Way to go DAN129 !!! Very nice pcb! Neat,clean...better than mine!
What are your experiences with it? Frequency? Coil datas? Depths?

[PulseStarIIUser]

Dear Ivconic,

Thank you very much for your reply. Your advice gives me confidence to experiment a little bit.

Best Wishes,
Bob