THE ELUSVE 1us TC TARGET

[Tinkerer]

Please explain, because I do not understand what you want. = example showing how coils are connected to PCB, here is missing shielding .



and how it is done

For the coil, look at: https://www.geotech1.com/forums/foru...625#post419625
For the preamp schematic and test results look at: https://www.geotech1.com/forums/foru...387#post419387
https://www.geotech1.com/forums/foru...441#post419441

For the TX schematic and TX board

[moodz]

I been using the 5mm and 10mm squares cut from a aluminum beer can. But aluminum thickness and grade will vary from can to can. I had an idea for standardize targets. We could make them using a pcb. Draw up board with multiple geometries and sizes. These could then be cut into separate targets and glued to wands. This would create a standard gerber file that everyone could use. Assuming say 1 oz. copper, people around the world could test and compare results

Excellent idea ... I am at the point where I need a set of standardised targets based on time constant not on detection distance .....

[Detectorist#1]

Hi Tinkerer,

Do you really think that TX end stage with 10 MOS FETs is appropriate for hobby manufacturing of PI MD?

[Tinkerer]

Hi Tinkerer,

What do you need this code to do for starters?

1. TX ‘H’ bridge drive signals. What cycle timing do you require and what FET drivers and FETs are you using so we can work out how much “dead time” is required.
2. Internal 12bit ADC sampling sync to TX timing. What sample rate do you require?
3. How do you want to monitor the digital signal processing?
4. ??

Jeff

Hi Jeff,
I have just revisited the AMX Thead: https://www.geotech1.com/forums/foru...concept-design where we got lost in squabbling.
One year has passed and the project has been stagnant.
I have worked a little on the RX :https://www.geotech1.com/forums/foru...387#post419387 For the testing of the frontend I used my own well tested TX board that is a bit more complex for the timing because it is synchronous. (Mooz's TX uses the internal diodes of the Mosfets). The use of the Nucleo STM 32F446 is definitely not ideal. This seems to be where we are.
I think the consensus for the micro processor was a STM 32?? I will have to take a closer look at the thread to see if an actual microprocessor has been decided on.

I should have answers to your questions soon.

[Tinkerer]

Hi Tinkerer,

Do you really think that TX end stage with 10 MOS FETs is appropriate for hobby manufacturing of PI MD?

Detectorist#, thank you for the feedback.
I think it is 8 Mosfets or did I post a wrong schematic? Right, I just checked, it is a different schematic with 2 additional Mosfets. I will look for the right one.
2 high voltage Mosfets about US$ 10 each
6 Cheap low voltage Mosfets.

I would appreciate if you would tell me in more detail what your concerns are. Cost? Assembly? Timing?

[Detectorist#1]

Hi Tinkerer,

My concerns are for all mentioned. The cost, assembly difficult and not at the end - the timing - osc is not present in mass hobby detectorist!

[Detectorist#1]

Hi Tinkerer,
Maybe some of active writers in this forum are former engineers in military area - in this area no limits for cost and complexity - but hobby area is different!

[Tinkerer]

Hi Tinkerer,
Maybe some of active writers in this forum are former engineers in military area - in this area no limits for cost and complexity - but hobby area is different!

Detectorist#, thank you for your feedback.

[Carl-NC]

Do you really think that TX end stage with 10 MOS FETs is appropriate for hobby manufacturing of PI MD?

Take a look at some Minelab patents and you will TX designs with even more FETs. Tinkerer's circuit looks intimidating because he used big devices where small devices could have been used, most could be SOT23. The AMX transmitter is a similar design, there are two big FETs, the rest are SOT23s. The layout includes 5 package options for the 2 big FETs (in this photo I'm using TO220s) which makes the layout much larger than needed. In the end, this TX design can be small and cheap, depending on the choice of the 2 big FETs.

[Detectorist#1]

Hi Carl,
I'm not against top designs, but I'm not sure that many hobby detectorists will repeat this relatively complex solution.

[Carl-NC]

There are a lot of simpler projects posted on Geotech for those who want simpler, but we also explore new concepts that might be a bit more complex. Different strokes...

[Detectorist#1]

Hi Carl,

Yes, you are right - this forum have to be useful for very new hobbyists and for serious designers!

[Detectorist#1]

Hi Carl,

My idea is that designs of Surf Pi, HH and Barracuda have to rest for very new detectorists, but more complex designs have to be well balanced between these designs and too complex designs. Yes, I know, this is not simple task!

[moodz]

Hi Jeff,
I have just revisited the AMX Thead: https://www.geotech1.com/forums/foru...concept-design where we got lost in squabbling.
One year has passed and the project has been stagnant.
I have worked a little on the RX :https://www.geotech1.com/forums/foru...387#post419387 For the testing of the frontend I used my own well tested TX board that is a bit more complex for the timing because it is synchronous. (Mooz's TX uses the internal diodes of the Mosfets). The use of the Nucleo STM 32F446 is definitely not ideal. This seems to be where we are.
I think the consensus for the micro processor was a STM 32?? I will have to take a closer look at the thread to see if an actual microprocessor has been decided on.

I should have answers to your questions soon.

Slight correction the circuit is not a H bridge but more correctly a switch buffered H bridge as there are only two switching elements connected to the coil ( unlike 4 in a "conventional" H bridge )

Also the two high voltage Mosfets should be used with a parallel shottky diode to minimise body diode losses like so below ... I dont use the body diode.

[Tinkerer]

Slight correction the circuit is not a H bridge but more correctly a switch buffered H bridge as there are only two switching elements connected to the coil ( unlike 4 in a "conventional" H bridge )

Also the two high voltage Mosfets should be used with a parallel shottky diode to minimise body diode losses like so below ... I dont use the body diode.

Discrete Silicon Carbide (SiC) Schottky Diodes | Wolfspeed

CoolSiC™ Schottky Diodes - Infineon Technologies


Choices of Silicon Schottky diodes.

The Moodz TX stands out for its elegant simplicity. It is a pity that we do not have yet an RX Preamp test available with it.