Bipolar PI MD with GB and DD Coil

[Detectorist#1]

I propose bipolar PI MD design with GB and ready manufactured DD coil (15" x 12" SEF coil from DETECH company). This project is based on bipolar MD with GB from ITMD3 book, but have more aggressive timings with hope to be useful for smaller nuggets.

[Op04]

Amazing! Thanks Detectorist#1

[Detectorist#1]

I think, this project is convenient with possibility to be used many ready DD coils for PI detectors.

[eduardo1979]

Hello Detectorist 1.
This is a project worth doing. I really like the idea, and I assume this detector discriminates between Fe and Non-Fe metals.
If so, I'd love to make this detector.
Congratulations!

[Detectorist#1]

Yes, thanks to DD coil, this detector made very good discrimination Fe/non-Fe.

[GeoMax]

Hi Detectorist#1

can you recommend a ready made DD coil for that project?

[eduardo1979]

Hello Detectorist #1.
Analyzing your schematic, I see that your detector is a Bipolar PI, just like Carl's.
The only differences are that your TX isn't a full H-bridge and that you've configured the RX to use a DD coil. At first, I thought it was a Hybrid metal detector. I notice you've chosen to use differential integrators, but as you well know, these types of integrators are a bit more delicate, since all the capacitors must match within 1% for these integrators to work properly. Could practical integrators be used in your project? I'd like you to tell us a little more about your detector. Do you have any videos of it in operation? Why did you choose to use the LM393?

[Detectorist#1]

Hi GeoMax,

https://www.detech-metaldetectors.com/contacts.html
https://www.detech-metaldetectors.com/products/coils/52-15-x-12q-sef-search-coil.html

[Detectorist#1]

Hi eduardo1979,
1. Yes, this detector use bipolar pulses, as mentioned in the title.
2. The TX channel uses half-bridge. This gives possibility to use standard DD coils with screens connected to the GND ends of TX and RX coils. Also, half-bridge haves less additional capacitances in comparison with full-bridge. This allows to be used shorter first delay for more good sensitivity to smaller nuggets.
3. I think, this is not hybrid detector. My opinion is that some detector is hybrid only when two different technologies are used - like pulse and sinus (or parts of sinus) signals are used in the same design.
4. Yes, in differential integrators the capacitors must match within 1% in pairs, but this give more freedom for design of previous stages. Single integrators needs using of inverter stage and this stage haves some delay for signals and the two paths for signals (inverting and non-inverting) will be different. This difference have to be have in mind when we want to work with minimal first delay.
5. The using of LM393 is selected for easy "OR"-ing of the output signals (they have open collector outputs).
Now, this detector is still assembling from me. I hope, very soon the detector will be ready for real tests on the ground.

[AhmatAhmatov1959]

Hi eduardo1979,
1. Yes, this detector use bipolar pulses, as mentioned in the title.
2. The TX channel uses half-bridge. This gives possibility to use standard DD coils with screens connected to the GND ends of TX and RX coils. Also, half-bridge haves less additional capacitances in comparison with full-bridge. This allows to be used shorter first delay for more good sensitivity to smaller nuggets.
3. I think, this is not hybrid detector. My opinion is that some detector is hybrid only when two different technologies are used - like pulse and sinus (or parts of sinus) signals are used in the same design.
4. Yes, in differential integrators the capacitors must match within 1% in pairs, but this give more freedom for design of previous stages. Single integrators needs using of inverter stage and this stage haves some delay for signals and the two paths for signals (inverting and non-inverting) will be different. This difference have to be have in mind when we want to work with minimal first delay.
5. The using of LM393 is selected for easy "OR"-ing of the output signals (they have open collector outputs).
Now, this detector is still assembling from me. I hope, very soon the detector will be ready for real tests on the ground.

What chip can replace TLV271IP Thank you

[Detectorist#1]

The requirements for this chip are:
1. Supply voltage more than 10V
2. Low input current (1pA)
3. Rail to rail output voltage