New Bipolar Boost TX and Front End

[Mdtoday]

Looking great!!

Thanks JL, it was at the stage where I needed to take a break and physically see the overall design full size, so I can review placements.

3D CAD is brilliant with close tolerances and is repeatable and reliable but a 3D printed part this size and shape can shrink in unexpected places, therefore I wanted to allow for that in the final run home and using the production filament.
The green used on the draft prints wont be the final colour

[Mdtoday]

First draft prints of the main enclosure.

Left side was printed with .4mm outer shell so it's very rough, right side has .8mm shell much better but final prints will be 1.6mm shell.

Already, I see some necessary changes but generally, I am happy with it. Print time was around 15 hours for each side.
Mounting screw hole positions will be moved a little to give more material around them and a few other bits and pieces to tidy up.

Coil and probe connector housing areas will be modified to one standard fit with a vertical split down the centre of each to form left and right "covers", more on that later.








Current total weight is 200g

cheers

Mdtoday

[6666]

Wow Mdtoday you have been busy

[Mdtoday]

Wow Mdtoday you have been busy

Hi 6666, yes a few things on the go.

Could you PM me your postal address please and Ill send one of those PCB coils for you to play with..no charge.
They were designed for RX only hence the high inductance but you can tap off anywhere.

cheers

Mdtoday

[6666]

Hi 6666, yes a few things on the go.

Could you PM me your postal address please and Ill send one of those PCB coils for you to play with..no charge.
They were designed for RX only hence the high inductance but you can tap off anywhere.

cheers

Mdtoday

Hi Mdtoday, thank you thats extremely generous of you, much appreciated, cheers.

[Mdtoday]

Hi Mdtoday, thank you thats extremely generous of you, much appreciated, cheers.

Your welcome 6666, PM me with your postal address and I'll get them to you in the next few days

cheers

[Mdtoday]

More progress on power supply board.

All works fine, much quieter layout.

The only small issue is the output voltage connector pin assignments.
I should have placed the GND alongside the 20v output instead of the 5v line, no big deal but would have been better option.

Just have to be careful when testing.. I might add a transzorb on top side between 5v track and ground, this won't require a new board and will protect the 5v line from over-voltage

[Mdtoday]

On to the Coil/Probe connector bay mods to main enclosure.

Screw on covers which will also enable easy add-on in place of the dome shaped cover if required



This mod also enables better access and assembly and fixes another issue I noticed with the actual printed part...the push button position and handle length were designed to present a comfortable height for pressing with the thumb but when adding the original coil connector housings, they were positioned too high on the base which meant an uncomfortable bend of the thumb and a loosened grip on the detector....not a good thing.
I lowered the connector housings by 15 mm which fixed the issue.
It may be a small thing but it's at a stage when we can get it right and when one swings a detector for hours on end, comfort is high on the agenda.

[KingJL]

... It may be a small thing but it's at a stage when we can get it right and when one swings a detector for hours on end, comfort is high on the agenda...

Great work!! I have been out of pocket for a few days... will be heading back to Tennessee Thursday.

[KingJL]

FPGA hardware definition complete!!

... I have been out of pocket for a few days... will be heading back to Tennessee Thursday...

Well, back home and added the last FPGA hardware definition module... the audio interface. The Audio_IF module produces a 1 MHz based Pulse Density Modulated (PDM) signal whose filtered output audio frequency is controlled by the value of a Frequency Control Word (PCW). The FCW value is determined by the formula FCW = F/CLK*(2**ACCUM_LEN) where F = desired audio frequency, CLK = 100 MHz, and ACCUM_LEN = 29. I have included a spreadsheet (FCW Calculator.xlsm), that will calculate the FCW for a given audio frequency, in the Audio_IF sub directory of the project archive. Originally, I was using the 100 MHz clock to cock the PDM output, but decided to reduce the clock to 1 MHz as 100 MHz was above the practical limits for driving the VCMOS33 outputs of the FPGA. Using 1 MHz the unwanted spectrum of the PDM output should still be easily filtered out using a simple RC low-pass filter with a cutoff frequency of ~ 13 KHz.

The current Bipolar_PI block desgn:


The current change log:
Change Log.txt

The current project archive is Vivado_Bipolar_PI(9-26-2019).zip


Except for correcting any errors in the hardware design, the focus from this point forward will be the software to control and process the outputs of the Bipolar PI hardware definition. The initial software development will be the Bipolar initializing sequence (TX/RX parameters, pre-amp offset calibration, damp start timing, S1, S2 and S3 no-target (TX coil decay) determination, S1, S2, and S3 ground (coil decay + ground signal) determination, S1 vs. ground ratio and S2 vs. ground ratio calculation). A lot of this has already been done while developing the verification code for the various FPGA hardware modules. Next will be the completion of the menu system, making all menus interrupt driven (only in the menu processing code in response to an interrupt so as to not interfere with normal signal processing when in the menu system). And finally the code to effect the RX target signal processing.

[Mdtoday]

Well, back home and added the last FPGA hardware definition module... the audio interface.
........


Except for correcting any errors in the hardware design, the focus from this point forward will be the software to control and process the outputs of the Bipolar PI hardware definition.

Welcome back JL and great work, It's looking very good, I really like where this is heading, thanks for sharing.

I've been offline for a few days myself but back on deck last night, did a bit more on the enclosure and discovered problem with the probe 5 pin connector PCB... The footprint is not quite right for the connector I purchased. Must have had a brain fade on that one as the pin spacing on 2 pins were incorrect. When I did the model based on the actual manufacturer part I did symmetrical spacing on all 5 pins.. they are out by enough that the solder bucket pins don't fit through PCB. Fix is to redo the board but to use what we have we need to solder tin copper wire leads to the connector first then fit to pcb which is an acceptable solution. I will redo the PCB at a later stage.

My to do list is to load some more power supply and probe boards and get some off to you in the next few days, rewind some inductors, finish loading the TX boards and look at positions on front panel for power switch and think about position of audio jack.. I have a thought for the latter being in one of the connector bays or at the end of the shaft but I'm thinking that depends on sensitivity of RX, proximity to etc. Either position simple enough.

On the enclosure, I designed an arm rest just in case.. there is a lot of strength in this one and weighs in at 110 grams.
also the colour of the parts is very close to what I use but let me know your preference.

[KingJL]

...Fix is to redo the board but to use what we have we need to solder tin copper wire leads to the connector first then fit to pcb which is an acceptable solution...

I agree... a very acceptable solution. A point while we are discussing the 5 pin coil connector... a reminder that the TX (and RX if used for IB) are "floating"... meaning that neither end of the coil can be connected to actual GND. If an actual grounded shielding is desired, it will require a cable with a 3rd (or 5th for IB) conductor for the ground, which could be connected to pin 3 of the connector (and case ground).

... look at positions on front panel for power switch and think about position of audio jack.. I have a thought for the latter being in one of the connector bays or at the end of the shaft but I'm thinking that depends on sensitivity of RX, proximity to etc. Either position simple enough.

I think we can include the RC low-pass filter for the audio PDM signal right on the audio connector (PMOD J4, pin9 to a 330 ohm to tip of audio connector with a 56n capacitor between audio connector tip and sleeve). Your thoughts? Forgot to mention that the audio output is high impedance (600 ohm or greater)... should work well feeding a bluetooth TX!

On the enclosure, I designed an arm rest just in case.. [ATTACH]47638[/ATTACH] [ATTACH]47639[/ATTACH] there is a lot of strength in this one and weighs in at 110 grams.
also the colour of the parts is very close to what I use but let me know your preference.

I cannot open the attachments... I get the following message ..."Invalid Attachment specified. If you followed a valid link, please notify the administrator".

[KingJL]

I cannot open the attachments... I get the following message ..."Invalid Attachment specified. If you followed a valid link, please notify the administrator".

Links are working now. Arm rest looks great!

[Mdtoday]

I agree... a very acceptable solution. A point while we are discussing the 5 pin coil connector... a reminder that the TX (and RX if used for IB) are "floating"... meaning that neither end of the coil can be connected to actual GND. If an actual grounded shielding is desired, it will require a cable with a 3rd (or 5th for IB) conductor for the ground, which could be connected to pin 3 of the connector (and case ground). I think we can include the RC low-pass filter for the audio PDM signal right on the audio connector (PMOD J4, pin9 to a 330 ohm to tip of audio connector with a 56n capacitor between audio connector tip and sleeve). Your thoughts? Forgot to mention that the audio output is high impedance (600 ohm or greater)... should work well feeding a bluetooth TX!I cannot open the attachments... I get the following message ..."Invalid Attachment specified. If you followed a valid link, please notify the administrator".

Sorry about that, I was editing the post as the image on one was black for some reason, so probably why it was invalid.

Yes, I think the RC low-pass filter components will be fine in the suggested position.
I was thinking of Bluetooth as that is what I use, just makes operating the detector so much easier, I will work on ideas along that line.

The ground plane on the connector board is isolated and can be wire linked to connector housing , so yes just used as screen if required .
The probe/coil switch board TX/RX circuit is floating I added a ground plane to pin 3 so we had some wiggle room to solder a screen wire from the connector board if required.

The other 4 x solder pads around the edges of both boards are also isolated and are included with the intention to add tinned copper wire legs for stability, again if required.

[KingJL]

... I was thinking of Bluetooth as that is what I use, just makes operating the detector so much easier, I will work on ideas along that line...

I have been using this paired with over-the-ear bone conductor BT 5.0 headphones... for me, it is multi-functional... I use it for my entertainment center and for my metal detectors. I have a patch of velcro on the BT TX and on each of the units that I use it with and use a short 3.5mm audio jumper cable to connect between the device and the BT TX. I have found it to be a most satisfactory BT solution. The key is to make sure that what ever you use, make sure the BT TX is using BT 5.0 for low latency (same goes for whatever headphone you use).