ARMD (ARMRADIO based Metal Detector) VLF IB PROJECT

[pito]

And here is TC4420 in action, for now just ferrous/non ferrous, more discrimination in the future.

https://www.youtube.com/shorts/rSO9MA7j4f8

[ivconic]

[moodz]

The output impedance of the TC4420 is too high at 2.5 ohms.

The mosfets are in the test circuits are a few milliohms and of course they can be in one package. .... they are drawn separately for ltspice modelling.

[pito]

then you use this circuit, for low impedance, and
2 milliohms IPD100N04S402ATMA1

[moodz]

then you use this circuit, for low impedance, and
2 milliohms IPD100N04S402ATMA1

What you suggest will work no problem but it does not improve the performance ( identical ) and adds an additional part type to the BOM. If the PCB layout is easier it can be considered.

[Carl-NC]

@Carl-NC

Thanks, I see this design is not new, but there is no video of how it is performing, interesting is the very low voltage.

I'm not sure what you would want a video of. moodz shows real results in posts 41 & 42. Here is a version I built, also with real results, but it does not have the sine option:

https://www.geotech1.com/forums/foru...x-test-results

[pito]

I mean working detector using such design.

[Carl-NC]

A lot of what gets posted here are ideas and subcircuits, many of them quite useful for designing a detector. Getting a final design is a much bigger challenge that takes a lot of time. As an example, my AMX project is based on a transmitter moodz posted, plus some ideas of my own. But it stalled because I just don't have the time to do it right now. But everything is posted for someone else to take it on.

[pito]

When i look at some schematic the first thing is - how to make it simpler, https://www.geotech1.com/forums/foru...ge5#post236615 post #70 ( ( That was on video post # 61), when I saw the filters in the post # 52 they scared me.
Maybe there are some advantages but I don't see them for IB detectors, and I working mostly on them.

[moodz]

When i look at some schematic the first thing is - how to make it simpler, https://www.geotech1.com/forums/foru...ge5#post236615 post #70 ( ( That was on video post # 61), when I saw the filters in the post # 52 they scared me.
Maybe there are some advantages but I don't see them for IB detectors, and I working mostly on them.

This is a development project not a finished project. So that means all sorts of proposals are put up but the useful ideas move forward and some dont. The main part of this project is a MCU based DSP system ( STM32 ) thats why its called ARMD. The TX could be a conventional low power oscillator or something else like the CCPI.
The CCPI is a hybrid pulse / sine generator that is just one of the options for the TX.
Since the project is now going to support VLF and Pulse Induction using the same coil ... this is a useful idea. Saves me carrying two metal detectors.
There are plenty of projects around that reinvent the wheel ... the aim here is to move to the bleeding edge a bit. ( DSP and hi power VLF and PI )
As far as I know , high power VLFs are not the industry standard in hand held detectors and even though there are some patents around .. a hybrid VLF / PI is rare as well. ( Dave Emery patent ?? ).

Currrently working on a log response non demodulating signal recovery for the front end RX. ( there are log amplifiers but distort the sine wave )

moodz

[pito]

VLF and Pulse Induction using the same coil ... this is a useful idea. Saves me carrying two metal detectors. = now you have my attention. Start with PI, once it works properly, adding VLF will be an easy task.
the same coil = concentric coil, not a Minelab double DD

high power VLFs = years ago I build Tx Rx detector, power consumption was 15V/350mA, detector was able to respond to sewing needle from distance 60 cm, so there was no needs for more power.
but distort the sine wave = use MAX7400 or MSFS5

[ivconic]

From a start I have the problem of obtaining a suitable driver, plus the inability to work with small SMD components.
And that is the first and foremost deterrent factor from trying to do anything on this subject.
So every now and then I find something interesting on the net and try to think...
I used the totem-pole emitter follower often in my works to drive either loudspeakers or piezo transducers directly from MCU.
It has perfect isolation to the MCU side, amplifies the current and generally proved to be a good and simple solution with a minimal number of components.
This configuration performed very well at/up to 10kHz.
Although so far I've only used it up to 1kHz.
It would be good to do the analysis for 25kHz.
"Shut through" or "dead time" will first depend on the code in the processor. But the on/off delay should also be taken into account.
Opinions?

[pito]

The problem is with software, this one doesn't need it.


https://www.homemade-circuits.com/in...-for-labs-and/

[moodz]

From a start I have the problem of obtaining a suitable driver, plus the inability to work with small SMD components.
And that is the first and foremost deterrent factor from trying to do anything on this subject.
So every now and then I find something interesting on the net and try to think...
I used the totem-pole emitter follower often in my works to drive either loudspeakers or piezo transducers directly from MCU.
It has perfect isolation to the MCU side, amplifies the current and generally proved to be a good and simple solution with a minimal number of components.
This configuration performed very well at/up to 10kHz.
Although so far I've only used it up to 1kHz.
It would be good to do the analysis for 25kHz.
"Shut through" or "dead time" will first depend on the code in the processor. But the on/off delay should also be taken into account.
Opinions?

You are over analyzing the circuit Ivica .. there is no shoot thru ( or if there its not a problem ).

Just use a TC4428A chip to drive both sides of the bridge. Its available in DIP no smd. The worry about your driver is making me ill.

moodz

[moodz]

[/QUOTE]

You are over analyzing the circuit Ivica .. there is no shoot thru ( or if there its not a problem ).

Just use a TC4428A chip to drive both sides of the bridge. Its available in DIP no smd. The worry about your driver is making me ill.

moodz