PCB kit [Re: Welcome!]

[Bionerd42]

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Ok, some more questions. 

When I look at the Gerber files, the PCB is a proper analog circuit design, with two internal ground/power planes in addition to the top and bottom routing layers. 
Do we need the non-free version of Eagle to tinker with it? 

Places like elecrow seem to be pretty good and fast at not only fabricating PCBs (and they actually seem to work with Eagle), but also at populating them. 
Are you planning to order the empty PCBs or fully populated ones? 
If the former, why?
It's nice to solder your own boards, but elecrow et al. have the better equipment and are faster, more reliable, and maybe even cheaper, because they have quick access to really cheap standard components.

42

-------- Original Message --------

Subject: Re: Welcome!

Local Time: January 2, 2018 12:05 PM

UTC Time: January 2, 2018 11:05 AM

From: openbiomed...@googlegroups.com

To: openbiomed...@googlegroups.com

Hi there,

I'd like to make a PCB order in January or February, probably at Seeed [1] or Elecrow [2], 5 to 20 units depending on the price and minimum order, so I have some spares just in case I break something, and also, if any of you wants some. Also, I'll need at least one stencil, and it will be my first time ordering one, so lets see if I don't screw it up :)

About Octopart, on the right of the "Preferred Distributors" column, there's an 'edit' button. There you can choose your preferred distributors. Can't see Reichelt but you can find other european distributors I've used before as Farnell/Element14, Mouser or RS. Also, some tweaking might be needed on the BOM, so more common versions of the products are listed, and then, more distributors can be chosen to buy that options.

PS: If you use Eurocircuits to create your PCBs, just remember the name is kind of a trick: some of the PCB fabrication facilities are out of europe, and depending on the process you choose, it'll be fabricated in India, Germany, Hungary or other places I cannot remember now. [3]

Cheers!

[1] - https://www.seeedstudio.com/fusion_pcb.html

[2] - https://www.elecrow.com/pcb-manufacturing.html

[3] -https://www.eurocircuits.com/eurocircuits-production-units-quality-labels/

On 01/02/2018 10:44 AM, 'Bionerd42' via OpenBiomedicalImaging wrote:

Happy New Year, 

and thanks, Alvaro, for the import of the BOM into Octopart.

A few questions:

Is the PCB immediately available, or are you planning a collective order of the PCB, preferrably in Europe?

Do you know how to include European distributors (e.g., Reichelt) into Octopart?

thanks

42

[Jean Rintoul]

I recommend assembly due to the BGA part which is impossible to assemble by hand. 

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[Jean Rintoul]

Also, I have the cheapest paid version of Eagle to export the Gerbers for the 4 layer board. It's 4 layer to try to maximize the possible SNR. 

I believe you can view and tinker but not export with the completely free version of Eagle. If you are associated with an academic institution there are discounts but you should look on Eagle website for details. 

For next revision I am considering moving to a better tool for analog design but using the free open version(Altium CircuitMaker) for this project. It's free and can do 4 layer boards including Gerber export.  

Jean 

On Tue, Jan 2, 2018 at 6:03 AM, Jean Rintoul <jean.r...@gmail.com> wrote:

I recommend assembly due to the BGA part which is impossible to assemble by hand. 

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[Bionerd42]

Do you have any strong reason _not_ to use KiCAD?
It's free and can do at least 16 layers with no PCB size restrictions I'm aware of. 
Ground/supply planes and flood fills work.
42

[Jean Rintoul]

no reason not to use KiCAD. If you'd like to move the board to KiCAD that would be great. 

Eagle seems to be going out of style for Open Projects so good to move to something else. Thinking behind the free Altium CircuitMaker tool was it has ability to 3D render the board into an .STL file and other fancy routing options that are also used in industry. Maybe KiCAD can do this too though - I just think it should eventually move from Eagle. 

[Albertas Mickėnas]

Hi all,

I have some experience migrating eagle to KiCad.

Nightly builds provide tons of new functionality - eagle import, 3d visualization and step file export. I am busy next couple weeks, but later could work on this.

Jean, do you have a plan for the next release ready?

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[Arne]

As far as I know with the Freecad Plugin "StepUp"
https://sourceforge.net/projects/kicadstepup/
you can generate a 3D-Step Model of your Kicad-PCB.

A little pain in the ass is the kicad part library. If you want to build a "professional" board, you should use atomic parts for being able to generate BOMs the manufacturer can use. This is in Kicad a lot of work, especially at the beginning. I wrote a tool which makes this a lot easier:
https://github.com/pioupus/kicadLibCreator

Last Year I had a big project using Kicad. It was a lot of work establishing workflows and a library but at the end it worked out pretty well. So I think it is possible to work with kicad even on projects with "professional" standards.

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[Bionerd42]

Sounds great!

Do you think it's worth installing the most up-to date version of KiCAD directly instead of version 4.0.2 or some such that comes with ubuntu apt-get? 

As for a next release ... I don't know ... probably the existing board is quite well tested and characterized (Jean?),
so it probably makes sense just to build some of them without modification.

As a warm-up for KiCAD, it might be feasible to start with an add-on PCB that galvanically separates all supplies and wired signals, in case a CR2032 battery and Bluetooth turn out to be inadequate for extensive testing of electrodes and test volume geometries. 

42

[Jean Rintoul]

Yes, part of the reason to move away from Eagle is the workflow is terrible and allows for mistakes to sneak in unless you are incredibly careful. Parts/BOM management is also not well done. So if you change the design just a little, it takes a while(read lots of manual work) to regenerate gerbers. Ideally a new PCB tool should be an advantage over Eagle. 

I'm working on another project until friday, so might be a bit quiet until I have got that out the way. 

Goodluck with your discussions! 

Jean 

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[Albertas Mickėnas]

Well, I am running nightly builds for 3 years. Sometimes they break it
for a day or two, but mostly it is surprisingly stable and the most
feature rich. Also you get the privilege to get the most annoying bugs
fixed first.

Now it currently has all the features people talk about - step files for
3d models, step export, improvements to import from different formats,
improvements to schematics tool, etc. Also the standard library
available via package is becoming very mature - all the main symbols
have footprints and 3d models.

There is a culprit with using the nightly recent build though - they
have broken the backwards compatibility for schematics files, so if we
move to the nightly version, it will be possible to open schematics only
with the nightly version, till the version 5 comes out officially (which
is bound to happen fairly "soon").

If you want to try it under Linux, you can add this ppa:
deb http://ppa.launchpad.net/js-reynaud/ppa-kicad/ubuntu xenial main

https://code.launchpad.net/~js-reynaud/+archive/ubuntu/ppa-kicad

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Albertas Mickėnas

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http://wemakethings.net
https://www.tindie.com/stores/miceuz/

[Bionerd42]

The dominant (within analog design accuracy, the only) problem to make all sorts of medical imaging techniques happen are not technical, but entry barriers.
 
On the one hand, you want to use free software tools whenever you can, 
on the other hand, you want to concentrate on your design and not your toolchain. 
So, I would consider backwards compatibility to stable tool versions a must, even though as an expert, you can make good use of the nightly build features. 

Turns out, though, that the entry barrier for firmware development may be MUCH higher. 

42 

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