Can pinpointer detecting thin chain?

[Qiaozhi]

Davor, this may be a little premature because you have not yet posted your simulation file, but you did post a screen-shot... so would you please give a quick explanation of how "click" works in your .param and K2 statements? I don't know what you did and I can't seem to figure it out! (I'll bet I'm not alone.)

Thanks!

The parameter named "click" is the coupling coefficient between L1 (the detector coil) and L2 (the target). The .STEP command causes the simulator to make 3 runs, first with K=0 (no target), K=0.001 (weak target), K=0.1 (stronger target).

[chemelec]

I can even weigh that, but the jeweler does.


You weigh the chain without closure.
You count the number of links.
Your divided weight by the number of links.
Now you know the weight of each link.

Tell it to anyone else.


Post #86

Weighing my Whole Small Chain, "150 Links", it works out to .0095 Grams Per Link.
So Slightly heavier than Nupi's chain.

[porkluvr]

Davor, this may be a little premature because you have not yet posted your simulation file, but you did post a screen-shot... so would you please give a quick explanation of how "click" works in your .param and K2 statements? I don't know what you did and I can't seem to figure it out! (I'll bet I'm not alone.)

Thanks!

[Thomas]

Thanks Davor for the Colpitts front end version, and the explanation for the original Nupi. What do you think about using a 4060 with the internal OSC ?

[Davor]

It is possible, but it is often more rewarding to do some makeover for the specific purpose of improvement.
I rearranged your detector's front end to a Colpits type, and it is far more interesting to me because it uses a single coil, and in this configuration it operates in near saturation mode. I guess it will have better stability, but I'd have to test it in real life. If you are up to it, please let us know if it works and how it performs.
I only made a few small changes against the original layout, but the mode of operation is quite different.
A single coil is much easier to make, and it would lend itself nicely if you ever wish to make a grown-up detector with a large air coil and a stem out of this project.
Here is the schematic, lower pane is with no target and the upper with a target near by:

[Nupi]

Basically it is an absorption detector.
Tr1 forms a Hartley oscillator and it is biassed so that it operates in linear regime that is prone to amplitude changes. When a metal object is introduced to the coil, the amplitude of oscillation is reduced because of the eddy current losses, but more importantly, the transistor power consumption is enlarged, and thus the emitter voltage gets shifted. This arrangement is not new, and most pinpointers work at this or similar principle. The change in the oscillator working conditions is translated into some sort of indication.
What is new and very good here is the way this working point gets detected
It is the role of 4024 that forms a relaxation oscillator with narrow strip of input signal levels that brings it from non-operation to saturation, and in a process it provides a very sensitive indication. It operates on the oscillator's envelope rather than the DC level, pulse durations are set by pulse counting method, and in a process it provides pulsed audio. Brilliant.
Attached is the LTspice solution with selected traces for almost no target (lower pane), and a close by target (upper pane). I'll place the Spice files soon.
Enjoy

An excellent study and explanation, genius. Thank you very much.

I do not know if it is still possible with the LTspice to tell
something on the role of the coilloop on the circuit and the filtering
of the voltage on the sensitivity at the time of detection?

[Davor]

It is a great pinpointer and very nice documented project. I think also it needs a notes with explanation how electronic part works to let users to understand it better and fix it more easy if problems occurs. Thanks!

Basically it is an absorption detector.
Tr1 forms a Hartley oscillator and it is biassed so that it operates in linear regime that is prone to amplitude changes. When a metal object is introduced to the coil, the amplitude of oscillation is reduced because of the eddy current losses, but more importantly, the transistor power consumption is enlarged, and thus the emitter voltage gets shifted. This arrangement is not new, and most pinpointers work at this or similar principle. The change in the oscillator working conditions is translated into some sort of indication.
What is new and very good here is the way this working point gets detected
It is the role of 4024 that forms a relaxation oscillator with narrow strip of input signal levels that brings it from non-operation to saturation, and in a process it provides a very sensitive indication. It operates on the oscillator's envelope rather than the DC level, pulse durations are set by pulse counting method, and in a process it provides pulsed audio. Brilliant.
Attached is the LTspice solution with selected traces for almost no target (lower pane), and a close by target (upper pane). I'll place the Spice files soon.
Enjoy

[Nupi]

I Can't Weigh that Small of an amount.

However,......................

I can even weigh that, but the jeweler does.


You weigh the chain without closure.
You count the number of links.
Your divided weight by the number of links.
Now you know the weight of each link.

Tell it to anyone else.


Post #86

[chemelec]

********** Rectification ********

The smallest chain link from the small chain of the video does not weigh 0.07 grams but only 0.007 grams. and detected at 0.5 centimeters.

I Can't Weigh that Small of an amount.

However, "Harp", Asked me This for my Pinpointer.

Distance (mm) of detection for:
Aluminum foil of chocolate: 3x3mm, 2x2mm and 1x1mm
Copper wire 0.4mm diameter: 3mm, 2mm and 1mm Lengths. (26AWG)

I Didn't do the Aluminum foil as I don't have any of it from chocolate bars.
But I Did do those Copper Wires and posted my results in my article.

Nupi, How well will your Pin Pointer do on these TINY Pieces of Copper?

However, Calculating it out:
Based on Weight of 1000 feet of wire, 1mm of 26AWG wire weighs .000143 Grams

[Nupi]

********** Rectification ********

The smallest chain link from the small chain of the video does not weigh 0.07 grams but only 0.007 grams. and detected at 0.5 centimeters.(air test)

[chemelec]

Data of the Pinpointer nupi.

Coins Don't mean Much?

Our Older Penny were Copper.
Our Newer Pennys are Copper Plated SOMETHING?
And NOW there are NO Pennies in Canada, DISCONTINUED.

Prior to 1967,Quarters and Dimes were Silver.
After that Older Quarters, Dimes and Nickels Were Nickel.
In Some Years they were Stainless Steel and other metals.

These Newer ones now are Only Heaven Knows metal.

[Thomas]

Nupi Sweep?

[Nupi]

Designation		Frequency	Wavelength
ELF	extremely low frequency	3Hz to 30Hz	100'000km to 10'000 km
SLF	superlow frequency	30Hz to 300Hz	10'000km to 1'000km
ULF	ultralow frequency	300Hz to 3000Hz	1'000km to 100km
VLF	very low frequency	3kHz to 30kHz	100km to 10km
LF	low frequency	30kHz to 300kHz	10km to 1km
MF	medium frequency	300kHz to 3000kHz	1km to 100m
HF	high frequency	3MHz to 30MHz	100m to 10m
VHF	very high frequency	30MHz to 300MHz	10m to 1m
UHF	ultrahigh frequency	300MHz to 3000MHz	1m to 10cm
SHF	superhigh frequency	3GHz to 30GHz	10cm to 1cm
EHF	extremely high frequency	30GHz to 300GHz	1cm to 1mm

However, to simplify things about VLF a good idea would be to use term audio frequency range. Imagine doing a project covering 20 Hz to 20 kHz, it would be annoying to write ELF/SLF/ULF/VLF all the time. But again it would not be correct if you just write VLF because there is much more in that range. Right? Instead, simply use term 'audio frequency range'. As I said in the beginning there are already dozens of articles with wrong frequency designations and a good thing would be to correct and minimize mistakes.

Imagine doing a project covering 3 Hz to 26 kHz.
How would you call it????

[Waikiki_Sweep]

It is a great pinpointer and very nice documented project. I think also it needs a notes with explanation how electronic part works to let users to understand it better and fix it more easy if problems occurs. Thanks!

[Davor]

It is very nice!