Moodz' Awesome Gold Pulse Induction Version 3 - MAGPI V3 Project

[moodz]

Very well done !

[Gunghouk]

Very well done !

Thank you. It was an enjoyable learning experience using Diptrace.

[moodz]

The Magpi has been fitted with NMOS TX parts and autodamping. Should be able to do 2 amps transmit @ 600volts peak.
Autodamping means the CPU no longer controls the active damping - faster recovery and tracking ... possibly be able to do iron discrim also.
Pix below for 1 amp 350 volts. 8.33 Khz TX. Traces show no target, IRON and COPPER. No amplification ... ( ie straight off the autodamp frontend ).

[Gunghouk]

Looks like a great addition/mod. Could this be an add on TX daughter board to the thru hole Magpi?

Is the new firmware firm or still setting?

[moodz]

With all this talk of new detectors with discrimination .. A few changes and we have autodamping with discrimination.
Here is a video showing the result.

Auto damper with full iron / non iron discrim with high signal to noise.

https://youtu.be/DoSXoeZ13pA?si=FpIjg1S2vmZTLotP

[ivconic]

Did I hear correctly; no amplification? Does that mean there is no RX front end or is the first amp with zero gain?
That is, the oscilloscope is connected directly to the RX coil?
In case the oscilloscope is connected directly to the RX coil; what are the predictions when the full RX frontend is present?
The iron signal will be significantly increased.

[moodz]

Did I hear correctly; no amplification? Does that mean there is no RX front end or is the first amp with zero gain?
That is, the oscilloscope is connected directly to the RX coil?
In case the oscilloscope is connected directly to the RX coil; what are the predictions when the full RX frontend is present?
The iron signal will be significantly increased.

Yes you did hear correctly ..the auto damping function damps the coil and prevents high voltage hitting the front end amplifier but there is no amplifier present ... so we are looking at the coil through the damping circuit. If you noticed that iron causes the signal to rise. Non iron causes the signal to fall. So discrim is very obvious and easy to do.

[moodz]

Pictures tell it all ... cant be more obvious ...PI discrim is done. Are you familiar with fourier transform of unit pulse ?

Pliers and aluminium heat sink. Blue is no sig. Orange is pliers. Green is heatsink.

[ivconic]

Yes you did hear correctly ..the auto damping function damps the coil and prevents high voltage hitting the front end amplifier but there is no amplifier present ... so we are looking at the coil through the damping circuit. If you noticed that iron causes the signal to rise. Non iron causes the signal to fall. So discrim is very obvious and easy to do.

Cool! (and I mean it)
So far so good.

But you didn't answer the second part of my question; "...what are the predictions when the full RX frontend is present?..."
See, you're waving "huge" objects very close to the coil surface.
It is clear that there is no amplification.
(I was just wondering if it was directly from the coil or if it was going through an amp with no gain)
The idea/goal, I hope, is that such detector successfully detects small targets with as short a TC as possible.
So later you will add an RX frontend, probably two-stage, the first one will have a very low gain to prevent saturation, and the second one will have a higher gain,
so that the detector will still have good sensitivity to short TC targets.
In that sense, I am interested in "...what are the predictions when the full RX frontend is present?..."
...
"..Are you familiar with fourier transform of unit pulse ?..."
Don't worry, that's my middle name!

[moodz]

Cool! (and I mean it)
So far so good.

But you didn't answer the second part of my question; "...what are the predictions when the full RX frontend is present?..."
See, you're waving "huge" objects very close to the coil surface.
It is clear that there is no amplification.
(I was just wondering if it was directly from the coil or if it was going through an amp with no gain)
The idea/goal, I hope, is that such detector successfully detects small targets with as short a TC as possible.
So later you will add an RX frontend, probably two-stage, the first one will have a very low gain to prevent saturation, and the second one will have a higher gain,
so that the detector will still have good sensitivity to short TC targets.
In that sense, I am interested in "...what are the predictions when the full RX frontend is present?..."
...
"..Are you familiar with fourier transform of unit pulse ?..."
Don't worry, that's my middle name!

The discrimination problem for PI is like peeling an onion layer by layer ... you solve one problem and then there is another layer and it brings tears to your eyes.

This particular problem cant be modelled easily but involves stabilising a DC operating point with microvolt stability and still resolving the targets. So yes on the bench we can discrim targets but when conditions are not stable ( like waving detector around ) there is another story. So I will build a new piece of hardware to test this.

[ivconic]

My not so extensive experience with better PI detectors is enough to realize that this is not their strong point.
And I fundamentally do not expect good discrimination from PI detectors.
It is much more important that it has a good GEB. And of course, to be sensitive to targets with short TC.
I would like to build a MAGPI V3 and then I looked at the BOM.
And just like by the Murphy's Law...I can't find almost anything from chips in stores!
A story that repeats itself with a large number of interesting projects so far.

[moodz]

Solved the DC operating point issue .. another layer of the onion is gone. I can now resolve a copper coin from a steel washer and will be able to get an actual VDI reading on a PI. The V3 Magpi only has a single channel ... I now realise I need a target channel and a VDI channel. Its just like VLF only PI. MAGPI V4.

I will try to use 555 and mosfet semis only.

[moodz]

MAGPI V4 discrim on smaller targets.

https://www.youtube.com/watch?v=t00RdBtrHQ4

[ivconic]

Solved the DC operating point issue .. another layer of the onion is gone. I can now resolve a copper coin from a steel washer and will be able to get an actual VDI reading on a PI. The V3 Magpi only has a single channel ... I now realise I need a target channel and a VDI channel. Its just like VLF only PI. MAGPI V4.

I will try to use 555 and mosfet semis only.

Would be nice to port the code to some AVR.
I can't obtain INA, DG.... you name it! Hell!
...
You opened Pandora's box now, you will be tempted to move forward step by step.
But that's good. Eventually at the end you may end up with comercial design.

[Orbit]

MAGPI V4 discrim on smaller targets.

https://www.youtube.com/watch?v=t00RdBtrHQ4

Greetings Moodz!
You did everything right, but something is wrong I think you should share the complete project herebecause I think it's still less money for a mono coil
I think that Ivica will do yours first and then Altra'she has a strong witness so he is not kidding,you know with an oscilloscope it's not very smart, not everyone knows how to use it and what some hieroglyphs show.I love it when I do nothing and win Bingo!