Delta Pulse

[kt315]

I am trying to make it detect gold but without any success...???

hello Dean, thank you lots for pics of your job. it's perfect!

can you give pics of this gold sample you use? what weight, size, is of it? yes, normal famous fact that a PI detector is more sensitive
to ferrous than to gold. nothing new I do not see here, Eric, Carl, wrote about this fact many times.
also. have you did learn Eric's Foster diagram coil size vs target size more sure?

[calebsone]

any progress with the mod dean and if so what steps did you take?

[Dean Sarelius]

Hi All,
I have tried replacing the op amps especially DA2(LF357) and DA4(TL062) but without any success. I have also tried swapping out DA3 and DA5 but this made no difference either.
Here are some pics of my gold its not much but it is still more than the M4 screw which I am testing..!

[pigeon]

hi all

it is ok to use irfp460 or no?

thank you

[kt315]

hi all

it is ok to use irfp460 or no?

thank you

try it. it is better on data vs IRF740 but needed in experience.

[kt315]

Dean, a metal detector is reacting at big target, not on all massive of the gold nuggets you maybe waiting. that is hard fact that all targets being folded together do not pool in one volume, for a detector reacting. so DP will react only on big sample from all samples, because such working of eddy current in the metal target and a EMF reply of it in the coil.

more theory on that in comments of Carl M. and in the book ITMD you may find.

http://www.geotech1.com/forums/showt...ghlight=silver Cache Test is good example...

regards

[mschmahl]

Hi kt315.
I´m building the Delta Pulse with your nice PCB. I have some question´s.
Why you have C12 with 47uf and not 100uF (see picture)? Is it critical?
You have built it with standart R6/AA batteries and big caps nearby. What are the values? (see 2. picture) There are some other hidden parts? I will use also R6/AA batteries.
How critical is R23-R26 with 4,72k? can i use 4,70k or 4,75k also?
How to tune R37?

[kt315]

in an especial folder at the DVD you may see a text and a diagram of Eric Foster ...\#miscellanea\Eric Foster_range_curves\.
so you have to decrease a size of a coil to increase a depth on a nugget instead of the increasing like you are thinking
a big size will give to you big depth. NOT. there is NOT un-linear dependence, there is some size that will be OPTIMAL for some size
of the nugget.

Re: Question on coils
Posted by: Eric Foster
Date: May 18, 2005

Here are the curves I have used for many years. The range reaches a maximum when it is
equal to the radius of the coil. Coils larger or smaller than this optimum will result
in less range. To show how this works, along the bottom axis you see coil diameter,
which is obviously 2 x the radius. So for an 11in coil, if we go up the vertical scale
to A, we have 5.5in. Also note the diagonal line and the series of ever increasing
semicircles. Everything to the left of this line shows increasing detection range up to
the maximum where it intersects the line, then decreasing range to the right, where the
semicircles are shown dashed.
If a certain metal object is just detected at 5.5in with the 11in coil, then going
larger in coil size will cause a reduction (going down the dashed side), and going
smaller in coil size will have a similar effect. Initially, it won’t be much, i.e.
going from an 11in to an 8in coil will only make 0.5in difference but below 4in
diameter, the range will drop rapidly.
Now, suppose with the 11in coil, you can detect an object at about 12.5in (B on the
vertical scale. This indicates that the coil is not an optimum size for that particular
object. If we carry on up the curve (direction of arrow) we can see that by using a
20in coil, we could gain another 2.5in (C). The curve peaks at 15in with a 30in coil.
But the extra inch gained hardly makes such an unwieldy coil worth while.
Other factors come into play of course. The curves assume that the number of turns and
the coil current is the same in all cases; which it isn’t necessarily. For the same
inductance value, a smaller coil has more turns, which counteracts to some degree the
loss in range. Also a smaller coil will pick up less electromagnetic noise, earth’s
field noise and ground effect, which make for a smoother threshold.
The end result is, that with a small nugget that can be detected at between 5 and 7in
with the 11in coil, so that it is on the top part of the curve, an 8in coil may well
give a similar range. That is not to say that smaller coils do not have other
advantages. Small coils and probes are very useful in rocky areas or searching in
undergrowth. They have less drag too for water hunting, and less pickup from
mineralised soil or conductive sea water plus better signal separation on close or
multiple objects.
One other point regarding PI, is that the small object sensitivity is largely
determined by the sample pulse delay. If an object is so small, or thin, or made of
high grade stainless steel, such that all the signal has decayed before sampling takes
place, it would not matter how small a coil you made, it would never be picked up.
Eric.

[kt315]

hello ms...l

Hi kt315.
Iґm building the Delta Pulse with your nice PCB. I have some questionґs.
Why you have C12 with 47uf and not 100uF (see picture)? Is it critical?

I did set what I did take first =) 10-25V caps will be OK here. not so critical... 47-100uF and more value caps...

You have built it with standart R6/AA batteries and big caps nearby. What are the values? (see 2. picture) There are some other hidden parts? I will use also R6/AA batteries.

in my case I used two 10000Uf 25V caps everyone.

How critical is R23-R26 with 4,72k? can i use 4,70k or 4,75k also?

yes. certainly. but you have to choose them in a couple - R23 with R24, R25 with R26. for example if one is 4,628 another is 4,630 that will be OK.

How to tune R37?

you will see. that is some kinda intuitive tuning. on a reaction at a target (big target and max reaction) the arrow of the microamperemeter has not to foul hard at right side of a scale ("throb"). leastwise there has not to be so big reloading of the uAmeter.

[mschmahl]

Thank´s a lot KT315. So i can continue to build the dp.

[pigeon]

hi all

I can use 24volts for delta pulse?



thank you

pigeon.

[kt315]

for what you mean? do you hope to encrease the depth or can you not find out 12V battery anywhere around??

[maximusdesmus]

had some spare time and completed 2 dp pcb's the problem is one is working but acting strange when the object is getting closer to coil it gives normal stronger signal then when i dont move it just keep the object still the signal starts fading and dissapears then i have to move the object again to get a signal , coil is 30cm 5.3ohm

the other pcb doesnt see the coil at all it turns on and i can set the pots to get constant oscillations but it acts the same with or without coil and its doesnt see metal objects nor does the power knob react at all and the voltage regulator is completelly cold tried changing voltage reg ,ic 's and checking all the components again its all ok cant find the problem. ???

thanks in advance

[pigeon]

hi all
I have a classic delta pulse that work well i am using a 2metre coil .the problem is that there is an old stoned tunnel.i scanned it with coil,its sound is increasing more and more for about 12metres them it decreases so much.do you think that sound is because of a metal or just that thr ground?
Thank you

[pigeon]

hi all

please help me

thank you.