Experimenting with Half Bridge Bi-Polar Transmitters

[Tinkerer]

Sounds good

Ha, where is the "start new thread" button gone to?

[6666]

top left corner" Post new thread" in Tech forum page

[eclipse]

Thanks Carl for your response also Tinkerer. I can't wait what your ideas.
I've done a lot of experiments with your Tinkerer project (different coils, preamps and coil nulling)
its very nice to build a non-traditional PI also very hard to go outside comfort zone (whatever mono coil, sample at x us, beep a signal).

[Altra]

I made some good progress over the weekend. I built a complete front-end with Tx, pre-amp and demodulator. Unfortunately it can only take two samples/phase. This really needs four to six samples to exploit all the possible signals. I was able to balance a coil with little problem. The other day I had problems nulling a coil due to a sloppy setup. The coil is not optimized, I used magnet wire. Will redo with pvc stranded this week sometime.



See video for target responses. The sample during THS set to ground balance for various ferrites and some hot rocks. The second sample is taken after the flyback and is combined with the first in a differential demodulator. Ferrous objects give positive or negative, depending on orientation. Non-ferrous always the same. Lots of possibilities.

Coil tx 540uH, rx 400uH. Tx pw=100us, samples 10us. Power supply current about 160ma.

https://www.youtube.com/watch?v=M4tSrN7QcU4

[Mdtoday]

I made some good progress over the weekend. I built a complete front-end with Tx, pre-amp and demodulator. Unfortunately it can only take two samples/phase. This really needs four to six samples to exploit all the possible signals. I was able to balance a coil with little problem. The other day I had problems nulling a coil due to a sloppy setup. The coil is not optimized, I used magnet wire. Will redo with pvc stranded this week sometime.

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See video for target responses. The sample during THS set to ground balance for various ferrites and some hot rocks. The second sample is taken after the flyback and is combined with the first in a differential demodulator. Ferrous objects give positive or negative, depending on orientation. Non-ferrous always the same. Lots of possibilities.

Coil tx 540uH, rx 400uH. Tx pw=100us, samples 10us. Power supply current about 160ma.

https://www.youtube.com/watch?v=M4tSrN7QcU4

Nice work and great progress Altra, thanks for sharing.

[Altra]

Nice work and great progress Altra, thanks for sharing.

Thanks! What's going on are you making anything these days?

[Mdtoday]

Thanks! What's going on are you making anything these days?

I have been working with KingJL on his Bipolar TX design and we are moving at a reduced pace due to KingJL moving house and my work commitments and home renovation over the last couple of months or so.
The power supply board is designed and I sent those off for manufacture, received them a week or so ago, now just waiting on some parts from Digikey then I'll load some, test and send some to KingJL.
Once the PS board is loaded and tested I'll post the schematic and board files.
KingJL has been busy with finishing off the main board as there were some possible changes to the ADC and reference, I'll let KingJL update on this but it is looking very nice.

[Altra]

I have been working with KingJL on his Bipolar TX design and we are moving at a reduced pace due to KingJL moving house and my work commitments and home renovation over the last couple of months or so.
The power supply board is designed and I sent those off for manufacture, received them a week or so ago, now just waiting on some parts from Digikey then I'll load some, test and send some to KingJL.
Once the PS board is loaded and tested I'll post the schematic and board files.
KingJL has been busy with finishing off the main board as there were some possible changes to the ADC and reference, I'll let KingJL update on this but it is looking very nice.

[ATTACH]50909[/ATTACH]

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Great, I glad to hear KingJL and you are going ahead with the project. Keep us posted

[Mdtoday]

Great, I glad to hear KingJL and you are going ahead with the project. Keep us posted

Will do Altra.

While I'm waiting for parts to arrive, I have been working on a project in Kicad based on your THS schematic.
It will use SMD parts mostly as that is all I have these days, except for the high voltage caps. I'm interested to see what can be done with it.
Will post progress.

cheers

Mdtoday

[Sean_Goddard]

If anyone remember that French PI which claimed to discriminate but in reality had depth SO BAD it didn't have any at all (thus technically it DID discriminate, just EVERYTHING)!!

The Manta is made by the SAME guy. Tried his website and it says access forbidden (sound like the wife during Covid lockdown )!

[eclipse]

What's the name of the PI if you can recall?

[SaltyDog]

Hey Guys, Great thread ..

Can you folk that talk in code (acronyms) please explain TEM, THS etc ..

Thanks

[eclipse]

For THS search for whites patent thread for Truncated Half Sine Pulse Induction and for TEM read the Tinkerer's project in the forum section.

[SaltyDog]

Hey Guys,

It's always puzzled me why the signal is first throttled (back-to-back diodes) then amplified massively increasing noise.
I would like to try using the 1/2 bridge, but will use LED's to keep the signal +-3V approx. Then place that straight into a differential 18Bit ADC with input range scaled to +-2.5V, the resolution would then be approx LSB 20uV. Thinking of using the ADS8691 .. what do you think?

Cheers

[Qiaozhi]

Hey Guys,

It's always puzzled me why the signal is first throttled (back-to-back diodes) then amplified massively increasing noise.

Cheers

The diodes are there to limit the high flyback voltage from the coil and hence prevent it from destroying the opamp. You have to wait for the final portion of the decay before sampling, otherwise the target signal will be swamped by the remnants of the flyback. The signal may only be a few uV for deep or miniscule targets.