New Bipolar Boost TX and Front End

[Mdtoday]

More progress on the enclosure.

The 3d printer has been busy this last week with 2 main enclosures and sub parts completed.

Still some clean up to do on the parts but all screws, PCB and sundry components fit together well.



There is a slight difference between the first and second printed enclosures (bottom right).
Originally, I had allowed for a 1.5 mm soft form gasket to be placed between both halves of the main enclosure but decided it was better to remove this as the enclosure will rarely need to come apart.
The other changes were related to the top screw holes, shaft clamp area, connector bays and internal sub-enclosure mounting ribs. There was not much material above the top assembly holes and I wanted to strengthen that area , therefore I added another 2 mm on the top of the enclosure and put a slight draft on the front and rear side.
The gasket area is taken care of by printing one with same profile as the enclosure joint edge and using that as the infill, it fits well. It is required for first print only.
A fine bead of silicone sealant between the 2 halves during assembly is enough to keep dust out.
The gap between bottom shaft mount clamp area was reduced to 3mm.
Next, a single 6mm hole was added to the rear of each connector bay to facilitate fitment of a 3.5 mm audio jack. If not used A Heyco type plug can be fitted.
Final change was to trim the internal side ribs where the sub-enclosure slides into as it was too tight, so I relaxed the tolerance.
As a final measure, the whole assemble can be sprayed with polyurethane clear paint to protect the PLA and give a nice finish but for prototypes, this particular material will be fine.

As I had already started the print, I was not going to waste it so the above changes are on the second unit only.

These units will be on their way to you soon JL.

cheers

Mdtoday

[KingJL]

The 3d printer has been busy this last week with 2 main enclosures and sub parts completed.

Indeed!!

I am afraid that I have not been quite that productive. I gave my brain a rest and tackled a couple of electronic gate control issues at our subdivision entry gate. Will be back at the code next week.

[Mdtoday]

Indeed!!

I gave my brain a rest and tackled a couple of electronic gate control issues at our subdivision entry gate. Will be back at the code next week.

Yes, it is a good thing to step away from heavy brain work for sure, my release will be in a few days time painting some ceilings.

[6666]

More progress on the enclosure.

Nice work

[Mdtoday]

Nice work

thanks 6666, we are getting there

[Mdtoday]

This is the push button I have used and recommend as the replacement for original Pin Point switch which is no longer manufactured.

https://lcsc.com/product-detail/Elec...K_C237038.html

IP67 rated and good quality and available from other suppliers.

It is slightly smaller in diameter but a thin O ring is placed in mid section of threaded area and the whole switch pushed into the enclosure hole.
The section of switch body above threaded section is a press fit into the hole and the fitted O ring acts as the seal and firmly holds the push button in place.

The nut and washer supplied with the switch are not required.

[liudengyuan]

Why can't I open the pdf file and zip file inside, and for a long time, no one posted the video file, what effect did it make when it was made? Stability, ground balance, detection sensitivity, who can tell me, thank you all

[Mdtoday]

Why can't I open the pdf file and zip file inside, and for a long time, no one posted the video file, what effect did it make when it was made? Stability, ground balance, detection sensitivity, who can tell me, thank you all

liudengyuan, this design was started by KingJL and is still in progress and done as time allows. It is not physically, a working detector at this stage but the design is well advanced.

KingJL has posted all files which are readable but you will need to read from the beginning of the thread to understand what is required in the way of software to open and read some of those files.

Schematics and board design were done in Kicad which you can download for free.
To open the FPGA project files requires a program called Vivado which is also available free to download.
KingJL has also posted PDF and TXT files relating to the FPGA design so those folk who don't have Vivado or just wish to browse the project, can read them too.

The enclosure design is a side project part which will allow us to test the design in the field when it gets to that stage.

Which PDF file can't you open btw?

Hope this helps

cheers

Mdtoday

[Mdtoday]

Finally got to sit down and load the TX board up to the stage where I could test the supply lines with 99% of parts installed.

No surprises JL, looks great. Maybe a tweek of the 13.8v output which is sitting at 13.6 but not a problem.
The reference is fully adjustable up from 1.25 to to 20v.
The 5v line is adjustable with a good range but I must check the full extents again as I forgot to take notes on that one.
No shorts or loading down on supplies, all looks good on the DSO.
I will spend some more time tomorrow looking more closely with the scope and do some current tests and power up down sequences but looks good JL.

[KingJL]

Finally got to sit down and load the TX board up to the stage where I could test the supply lines with 99% of parts installed.
[ATTACH]48237[/ATTACH]
No surprises JL, looks great. Maybe a tweek of the 13.8v output which is sitting at 13.6 but not a problem.
The reference is fully adjustable up from 1.25 to to 20v.
The 5v line is adjustable with a good range but I must check the full extents again as I forgot to take notes on that one.
No shorts or loading down on supplies, all looks good on the DSO.
I will spend some more time tomorrow looking more closely with the scope and do some current tests and power up down sequences but looks good JL.

Looking good!!!

[KingJL]

Finally got to sit down and load the TX board up to the stage where I could test the supply lines with 99% of parts installed.
[ATTACH]48237[/ATTACH]
No surprises JL, looks great. Maybe a tweek of the 13.8v output which is sitting at 13.6 but not a problem.

The 13.8V isn't critical... 13.6V should be fine.

The reference is fully adjustable up from 1.25 to to 20v.
The 5v line is adjustable with a good range but I must check the full extents again as I forgot to take notes on that one.
No shorts or loading down on supplies, all looks good on the DSO.
I will spend some more time tomorrow looking more closely with the scope and do some current tests and power up down sequences but looks good JL.

I don't know if I mentioned previously, but the design was baselined with a 500uH / 1.5 ohm mono coil, 5 Volt supply adjusted to 1 A coil current (measured at R9). I felt that we could experiment with coils up to about 750uH / 2.0 ohm. I also plan on creating a 500uH(24awgTX)/500uH(32awgRX) double D. I know some people prefer a positive ratio RX vs TX of the doubleD windings, but I prefer a balance RX/TX for better noise/gnd capacitance cancellation. I already have a 500uH 1.5 ohm (24awgTX) concentric ( I don't readily recall what I wound the RX at... will measure). I also planned on tweaking the gain (via FB resistor R21) of U10 ( OPA828 ). The 500K as in the design, I feel is quite optimistic... will probably end up around 150K to 220K to maintain short TC response.

[Mdtoday]

The 13.8V isn't critical... 13.6V should be fine.
I don't know if I mentioned previously, but the design was baselined with a 500uH / 1.5 ohm mono coil, 5 Volt supply adjusted to 1 A coil current (measured at R9). I felt that we could experiment with coils up to about 750uH / 2.0 ohm. I also plan on creating a 500uH(24awgTX)/500uH(32awgRX) double D. I know some people prefer a positive ratio RX vs TX of the doubleD windings, but I prefer a balance RX/TX for better noise/gnd capacitance cancellation. I already have a 500uH 1.5 ohm (24awgTX) concentric ( I don't readily recall what I wound the RX at... will measure). I also planned on tweaking the gain (via FB resistor R21) of U10 ( OPA828 ). The 500K as in the design, I feel is quite optimistic... will probably end up around 150K to 220K to maintain short TC response.

Thanks JL, I thought the 13.6v would be ok, I measured again this morning with my bench top meter and it's actually 13.69v , so pretty close to the mark anyway and as you say, not critical.

On the coils, thanks for the information, I have a few different coils but with a max of 450uH RX and 320uH TX concentrics. I planned on building some more to suit this project so it is good to have the baseline info.
If you can let me know what size coil you test with , I'll build one to match so we can compare notes when it gets to that stage.
It will be interesting to see what gain is arrived at for the OPA828, a balancing act for sure.

In my designs I use a firmware controlled analog switch to select one of 3 resistors in series with a high stability panel mount pot to vary the gain. I find it allows for more flexibility with coils and detector stability on different soils.
The gain pot has an 'O' ring between panel and knob which greatly reduces accidental movement of the gain position.

On another note, I have a hand drawn layout of the proposed internal power supply to main board wiring which I'll put into CAD and post. Will do in Kicad so you can amend as required.

[KingJL]

On the coils, thanks for the information, I have a few different coils but with a max of 450uH RX and 320uH TX concentrics. I planned on building some more to suit this project so it is good to have the baseline info.

You can try the ~320uH TX, but preliminary experimentation seems to indicate that < 500uH starts to lose to much boost. I am hoping to see the opposite effect of > 500uH with a good compromise of speed and exceptional boost being in the range of 750uH... we'll see.

It will be interesting to see what gain is arrived at for the OPA828, a balancing act for sure.

I really don't expect any real gains in sensitivity with the current preamp/ADC configuration (mainly due to the minimum sensitivity granularity limitation of the 12 bit ADC). This design is mainly to prove and exploit the benefits of FPGA concurrency and upc interrupt driven processing to achieve all desired DSP. The next step after this is proven is to use 2 opa828's configured as a low gain ( <= 10 ) differential input 2 op-amp instrumentation amplifier (with pseudo log limiting) feeding an LTC2380-24 ADC circuit. There is enough room on the I/F board for the 2380 and reference circuit by getting rid of J3 and J6 (which are currently unused and not needed). I would expect this configuration to have significant performance/dynamic range benefits. There is not much change to the FPGA HDL and software design as I have already allowed for a 24 bit Rx. But that version will have to wait until after the next spring household move to the Florida panhandle gulf coast.

[Mdtoday]

You can try the ~320uH TX, but preliminary experimentation seems to indicate that < 500uH starts to lose to much boost. I am hoping to see the opposite effect of > 500uH with a good compromise of speed and exceptional boost being in the range of 750uH... we'll see.I really don't expect any real gains in sensitivity with the current preamp/ADC configuration (mainly due to the minimum sensitivity granularity limitation of the 12 bit ADC). This design is mainly to prove and exploit the benefits of FPGA concurrency and upc interrupt driven processing to achieve all desired DSP. The next step after this is proven is to use 2 opa828's configured as a low gain ( <= 10 ) differential input 2 op-amp instrumentation amplifier (with pseudo log limiting) feeding an LTC2380-24 ADC circuit. There is enough room on the I/F board for the 2380 and reference circuit by getting rid of J3 and J6 (which are currently unused and not needed). I would expect this configuration to have significant performance/dynamic range benefits. There is not much change to the FPGA HDL and software design as I have already allowed for a 24 bit Rx. But that version will have to wait until after the next spring household move to the Florida panhandle gulf coast.

Sounds like a great plan and the LTC2380 is a good device.
I will try the 320uH coils at some stage but wind a new coil to suit your baseline design.

KingJL_Bipolar_TX_Internal Wiring_A.pdf
Here is a draft view of the internal power wiring, need to add probe board and then a sanity check, I will post the Kicad file later today.

[Mdtoday]

Bit more work on the internal wiring layout.
It is still in draft form.
KingJL_Bipolar_TX_Wiring.pdf

Kicad File KingJL_Bipolar TX wiring.zip

I will update again soon.

While doing this layout, I did realise a problem with the Probe/coil connector PCB.

It is fine for Mono coil use but requires a track cut between the 2 RX pins on the 5 pin connector for use with DD or concentric.
The zero ohm links were meant to cater for this but I messed up. Still it's an easy fix, just annoying that I missed it.