LOOKING FOR GOLDSCAN 4 Schematic.

[ivconic]

Probes across the coil directly...

[pito]

knowing current consumption with and without coil can gif info how much power is consumed by Tx. Right now I am testing the coils.

[pito]

knowing current consumption with and without coil can gif info how much power is consumed by Tx. Right now I am testing the coils.


these two coils emit the same power, similar turns with numbers 25 and 20 and wire diameter, 1 mm damping resistor or no damping resistor - there is not much difference.
So capacitance of the coil has no effect on Tx emitted power .

Probes across the coil directly... = 20x10x7 = 1400 V?
I am using 50us pulses, it is look you to, but I have 350 V on the coil and 50mA current.

[pito]

I will make a coil with 0.5 mm wire diameter ....

[ivconic]

knowing current consumption with and without coil can gif info how much power is consumed by Tx. Right now I am testing the coils.


these two coils emit the same power, similar turns with numbers 25 and 20 and wire diameter, 1 mm damping resistor or no damping resistor - there is not much difference.
So capacitance of the coil has no effect on Tx emitted power .

Probes across the coil directly... = 20x10x7 = 1400 V?
I am using 50us pulses, it is look you to, but I have 350 V on the coil and 50mA current.

No, it is somewhat above 200Vpp...
When it was at 20V ; multiplier was at 1x.
But the upper peak of the trace goes far out and above the oscilloscope display.
This is brand new oscilloscope but somehow I don't manage with it well, not the first one I have though. Had dozen so far; but never really did anything on the PI subject with those.
Usually all the previous PI diys that I made were pretty easy and straightforward and works nice from the very first switching ON, I didn't need to "scope" anything on them.
But then again; all those PI diys were pretty simple designs. No sweat.
Pulse Star II is indeed powerful and good "depths" PI detector, but a real sweetheart when we talk about diy, nothing to additionally worry or adjust, it works like a charm from the very first switching ON.
So that's why those easy diys made me too lazy and I stayed pretty ignorant when we talk the details.
So, consider me as absolute beginner in this!
If I switch to 10x then the pulse is so narrow I can't see it right. Tried everything what could be done to get proper and "sane" oscillogram.
Upper line is dimming as it goes far up, so it is not easy for me to figure out correct voltage.
Either I do something wrong... either the pulse width is too short. Far bellow 50uS.

[ivconic]

In the last half hour, I quickly wound another coil of PVC-insulated stranded wire.
I had one piece lengthwise, I didn't want to cut, I rolled the whole piece.
However... I didn't get anything good!
No gain at "depths" in the air, worse stability of the detector and considering the size of the coil; poor ranges in the air on previously described "targets".
Carl, of course, was right once again. This was a futile attempt.
A smaller coil, no bigger than 20cm, actually suits me, because of the terrain I have here.
And to achieve the greatest possible range with that coil on the mentioned targets.
I made the one from the picture because I have such a plastic coil former.
But it's all in vain. This is wrong.
I will have to go back to the excellent PDF article by Jospeh and read it again (I have read it many times in the past, but as the years go by; I have less and less gray cells...)

[pito]

Comparison 1mm wire and 0.5 wire
coil 25 turns, 22 cm diameter
1 mm wire, 290 uH,0.7 Ohm, 0.45V
0.5mm wire, 260 uH,1.3 Ohm, 0.42V
very small difference in Tx power

how many turns has your red coil ?

----------------------------------------------------
coil, 35T, 0.5 wire, 1.7Ohm, 0.58 uH, 0.35V

[pito]

50 us corresponds to 10 kHz (50x2 )
inductor impedance ,
510uH = 32.1536Ω
290uH = 18.212Ω

coil 20 turns, wire 1mm, 30cm diameter, 0.8 Ohm, 510uH, 0.6V

[Carl-NC]

Reduced range is because of the mixing two channels.= increase gain of U13 A ?
Add in parallel to R55 a 10k resistor.

This increases the gain in GB mode, but it also increases the gain of AM mode so that switching from AM to GB still suffers a depth reduction. It's the same as just increasing the SENS adjust. And whether you can just increase the gain depends on whether the detector is already noise limited, and it probably is. Also, GB mode is usually noisier than AM mode because you are now adding 2 channels that have their own uncorrelated noise, and the GND channel is noisier because it is added in higher proportion (per the GND pot and R52).

Hi Karl. I'm a bit confused.. About penetrating through the ground. What do you think is the best method Unipolar like tdi bipolar like Gpz 7000 THS method or more burst pluses in delivery? Or does it not make much difference?

I do everything now bipolar, whether it is voltage pulses (like traditional PI) or current pulses (like GPZ). It eliminates the need for EFE samples and so you can run the TX frequency much higher. I'm currently working on a design that runs at 8kHz and could easily run higher. I would love to get back to THS (or even HS) but am time-limited.

[Carl-NC]

Yes, the way the toggle is defined is a bit illogical.
"Off" is "All Metal mode" and "All Metal mode" is actually GEB mode.
I talk about "GEB" mode all the time but I respect how it is defined on the schematic.



"...Might help to post all your timing numbers...."

Would like to, but don't know how to do that with 2-channel analog oscilloscope.
TX pulse width seem to me too short, I "hunted" it on the oscilloscope last night and tried to adjust a bit wider on display, tough.

OK, I see now. OFF is AM mode, AM is "Low+High" GB mode, and SEL1 & SEL2 are LOW-only GB modes, I assume with different timings.

Connect a 10k resistor to the gate of Q4, and a 10k resistor to the gate of Q8. Connect the 2 resistors together, and feed that to the oscope. You should be able to figure out the sample delay from that. Move the second resistor to other sample gates to get the other timing.

[pito]

This increases the gain in GB mode, but it also increases the gain of AM = just for testing GB, if it is working than additional resistor can be added as needed.

[ivconic]

Comparison 1mm wire and 0.5 wire
coil 25 turns, 22 cm diameter
1 mm wire, 290 uH,0.7 Ohm, 0.45V
0.5mm wire, 260 uH,1.3 Ohm, 0.42V
very small difference in Tx power

how many turns has your red coil ?

----------------------------------------------------
coil, 35T, 0.5 wire, 1.7Ohm, 0.58 uH, 0.35V

So... 35 I think, lost count. It was random try, just to see what do I get from full length of that cable.
Of course it is useless try.
Carl pointed one thing and I will follow that in next attempts, because it correlates to what I really expect from this detector; it is smaller diameter coil.
Probably less than or close to 20cm diam.
Will try to find proper wire for 0.3mH and 3.5 ohms resistance for such coil.
End goal is to detect mentioned coins at 15-25cm in soil... if possible.
With such smaller coil. I don't need anything better then that.
Of course if that is possible.

[ivconic]

OK, I see now. OFF is AM mode, AM is "Low+High" GB mode, and SEL1 & SEL2 are LOW-only GB modes, I assume with different timings.

Connect a 10k resistor to the gate of Q4, and a 10k resistor to the gate of Q8. Connect the 2 resistors together, and feed that to the oscope. You should be able to figure out the sample delay from that. Move the second resistor to other sample gates to get the other timing.

Will do.
My appetites are growing and I am now realizing the need for a 4/8 channel digital oscilloscope.

[pito]

my coil, 35T, wire 0.5, 1.7 ohms, 0.58 uH, 0.35 V = your coil has similar inductance but much higher resistance, what is the diameter of your wire, is it copper wire?

[ivconic]

my coil, 35T, wire 0.5, 1.7 ohms, 0.58 uH, 0.35 V = your coil has similar inductance but much higher resistance, what is the diameter of your wire, is it copper wire?

I don't know why you insist on that coil, it turned out to be bad in working with the detector.