AMX TX

[Tinkerer]

I added a coupling command, Tx to Rx with my spice circuit. Big change, tilt doesn't work. Removed Rx damping resistor, tilt worked but oscillates. Wanted to learn something, see I have a lot to learn.

The amount of permissible static tilt depends on the RX circuit.
Any tilt in the TX, is transferred to the RX and amplified there unless measures are taken to compensate for it.
If you use AC coupling to remove the offset in the RX signal, the tilt in the RX is only limited by the headroom of the amplifier.
For example:
With a preamp running on 3V supply there is much less headroom than with +/- 5V supply.
Another point to observe is the voltage swing of the opamp. Like the AD797 has a voltage swing of only +/-2.5V with a +/- 5 V supply and 600 Ohm load.

The dynamic tilt is a bigger problem.
A loss of TX current caused by a large target or ground has a cumulative effect. Like a loss of only 1mA ads up to many mA after many cycles. It adds up until a new balance between the loss and the regenerating TX voltage has been reached.

[Tinkerer]

No that is completely wrong .... if I have a flyback of say 500.0 volts in the TX coil .. that circuit will not give a reading of 500.0 volts .... The RX coil responds to changes in magnetic field ( from anywhere ) ... how can it measure the peak flyback voltage in the TX coil ????

You are right, a 500V Flyback will not give a direct reading of 500v on the RX.
The circuit measures the changes in the Flyback voltage.
Try it.
You can omit the filters for the try.

[moodz]

I'm not entirely sure if I understand what you're saying, but series resistance within the coil does affect tilt. During the transition, the currents that convert the coil's magnetic field energy to electric field energy flow through the coil's series resistance, and that causes a real power loss. It happens again within the same transition as the electric field energy converts back to magnetic field energy. So the magnetic field energy coming out of the transition always has to be less than it was going in. Yes, more series resistance will reduce peak current, but for the same peak current it will also increase tilt.

Transitional energy loss also has to increase with eddy targets or viscous ground, same as with any other TX circuit.

Addendum: A parallel resistor across the coil becomes a series coil resistance during the transition, when the isolation FETs are off. So if you put in a 1k resistor you will see a massive amount of tilt. A series R also affects the tilt, but you have to look more closely.

True ... but the point is that a change in series resistance will cause a much larger change in peak coil amplitude than tilt. So if you vary the series resistance you will modulate the peak current much more than any impact on the tilt ... and this would not be good unless your signal chain was somehow using the modulation of peak current to do something.
Tilt will vary much more with changes in parallel loading losses versus series losses in the coil.

[Tinkerer]

... I reckon your DSP algorithm is broken ... come to Australia and try the ground signals here

We all would love to go to Australia but the flights are booked out.
Maybe you could explain your ground signals for us?

Many years ago somebody told me that his detector saw the worst ground in Australia like a steel bottle top at 8cm from the coil.
Is this an accurate description?

How would YOU describe the ground signal?

[moodz]

True ... but the point is that a change in series resistance will cause a much larger change in peak coil amplitude than tilt. So if you vary the series resistance you will modulate the peak current much more than any impact on the tilt ... and this would not be good unless your signal chain was somehow using the modulation of peak current to do something.
Tilt will vary much more with changes in parallel loading losses versus series losses in the coil.

case in point ... the tilt is "worse" on the circuit with the lower series resistance ( but the peak current is higher ).

First circuit green trace is fitted with 10 ohms the second circuit blue trace is zero ohms additional resistance.

[moodz]

We all would love to go to Australia but the flights are booked out.
Maybe you could explain your ground signals for us?

Many years ago somebody told me that his detector saw the worst ground in Australia like a steel bottle top at 8cm from the coil.
Is this an accurate description?

How would YOU describe the ground signal?

In alot of the gold places that is true ... you put a magnet on the ground and the nearly all of the ground sticks to your magnet.

[Tinkerer]

In alot of the gold places that is true ... you put a magnet on the ground and the nearly all of the ground sticks to your magnet.

Does the Flyback voltage go up or down at such places?

I seem to remember (many years ago) using a concentric induction balanced coil, to see the flyback voltage increase when turning the steel bottle top vertical and the flyback voltage diminish with the bottle top flat.

[Teleno]

I'm curious about Carl's comment on that...
...
"...TC4428 mosfet driver chip that produces the inverting gate drive..."
Is it relevant at all? Inverting or not?
I just checked with the local suppliers, the IR2103 is currently the only driver that can be found, albeit at a ridiculous price.
It has high and low sides. In this case, the low side would be used.
But I wonder; why use of driver?
Can't logic level fet be used without driver?
IRLZ44NN comes to mind, I have those...
I worked with them and made constant current regulators and powered them with a signal directly from the Atmega...

You need drivers to switch the MOSFETs fast. The gate capacitance is in the orfer of 1nF and you need hundreds of mA to charge/discharge it in nanoseconds time. The Atmega ports can barely handle 20 mA.

[ivconic]

You need drivers to switch the MOSFETs fast. The gate capacitance is in the orfer of 1nF and you need hundreds of mA to charge/discharge it in nanoseconds time. The Atmega ports can barely handle 20 mA.

Truth is; I never had a work like that. Mostly I used Atmega to switch logic level fets slower, much slower than that.

[ivconic]

I see lot of confusion and missunderstandings beween people here, about the "tilt".
Well... that's what you get; when you overplay with different simulators!

[Tinkerer]

I see lot of confusion and missunderstandings beween people here, about the "tilt".
Well... that's what you get; when you overplay with different simulators!

Maybe one day when you get older, you will understand what it means to work in a team.

To work in a team, means each team member brings his knowledge and experience to the table. The whole team learns from that. Sharing and comparing the knowledge and experience of each team member, adds to the total knowledge and experience of the team.

This is how a team becomes so much stronger that an individual.

Of course, there is always an eel in every team. What is an eel?
Google it. "What is an eel in a team"? or "do we have an eel in our team"?

[moodz]

Maybe one day when you get older, you will understand what it means to work in a team.

To work in a team, means each team member brings his knowledge and experience to the table. The whole team learns from that. Sharing and comparing the knowledge and experience of each team member, adds to the total knowledge and experience of the team.

This is how a team becomes so much stronger that an individual.

Of course, there is always an eel in every team. What is an eel?
Google it. "What is an eel in a team"? or "do we have an eel in our team"?

I spent 40 years working in teams and I reckon half of that was explaining what needed to be done ...

There is no "I" in team ... but there is a ME.

https://lohdownonscience.com/eel-team-six/

[ivconic]

Maybe one day when you get older, you will understand what it means to work in a team.

To work in a team, means each team member brings his knowledge and experience to the table. The whole team learns from that. Sharing and comparing the knowledge and experience of each team member, adds to the total knowledge and experience of the team.

This is how a team becomes so much stronger that an individual.

Of course, there is always an eel in every team. What is an eel?
Google it. "What is an eel in a team"? or "do we have an eel in our team"?

For God's sake Tony! 1992-94. On Creta island; I swam and dived among the eels.
Of course I know what eel is.
Compare me to anything you want, even eel, I don't find it particularly bad.
I just get the impression that most of the decisions here are made based on what is seen in the simulator.
As far as I have been able to understand so far; Paul is the only one here who has actually built something, has a physical device, TX at least, and some experience with it.
And the others try to simulate and predict the behavior of that circuit in simulators.
I guess not everyone uses the same simulators, and if they do; then they don't use them with the same settings and component definitions.
Hence the confusion.
I am not an expert in using LTspice type simulators. The Proteus simulator is much easier for me, and I rarely use it either.
I am even less expert in this type of electronics.
And when it comes to modern technology, new components that are very difficult to get from abroad... the situation is even worse for me.
What do I have left? To try to learn, something, figure something out along the way and see what others are doing.
Sometimes I ask what I don't understand to be explained, etc.
It is difficult to join a team and be an equal member of that team with the handicaps I have described.
If that is the definition of an "eel" in a team; then I agree, so be it.
The only constant for me is my love for detectors and great interest in everything new.
Everything that possibly slightly pushes the limits in detecting; is something I will always be very interested in.
And I have to underline this; I am always more interested in the practical side of detectors than the technical side.
I would rather not even know how it works, but to have it and be able to take it with me to the field and check how it works there.
Because at the end of the day, only that counts is only what the detector shows on the real site.

[ivconic]

Ah yes, I forgot this; you see:
I wouldn't worry too much about pre-solving the various "tilts" and similar artifacts that will (or won't) eventually appear due to the imperfection of the frontends.
I would assign another "channel" for such occurrences. Which doesn't have to be heard in the speaker, doesn't even have to be shown on the LCD.
Eventually, a short "alert" can be heard in the speaker or some small graphic symbol can be displayed on the LCD.
Because we cannot predict in advance what the battery will be like, of what quality, how successfully it will hold the current and capacity, etc.
Nor is the coil cable damaged in the meantime, maybe the connector is not inserted properly, maybe the pins on the connector have excessively
oxidized and reduced the area for current flow...etc.
I would first like to "roughly" make a detector and start the testing process.
And then that any possible irregularity is corrected on the fly through subsequent revisions.
And of course; The "update" option for the firmware is something that the detector must have. For that, you have to write software for Win, Lin, IoS and Andr.
If the frontends are done well; everything else happens in the code. So you should think about this most seriously.

[Teleno]

Truth is; I never had a work like that. Mostly I used Atmega to switch logic level fets slower, much slower than that.

Sure, not all applications require that speed but a PI detector does if you're after fast decaying targets.