[SpHEAR-devel] Creating a SpHEAR

[Fernando Lopez-Lezcano]

On 02/23/2018 01:02 PM, Tim Maloney wrote:
>
> On Feb 23, 2018, at 12:00 PM, an Rios <ian.rios1a at gmail.com> wrote:
>
>> I was looking to create one of the TinySpHEAR zapnsparks and was wondering
>> if there was a specific file somewhere that listed all the parts I would
>> need to print, as the gitlab hosts many files that might not be what I
>> want, such as the octothingy and such
>
> Hi, Ian!  I built the TinySpHEAR recently, so maybe I can help.  Mine works great, but I’m hung up on the calibration phase (looking for a proper space to do it in right now).
>
> The zapnspark parts list is what you want to start with.  It even has all the mouser numbers.  Getting the mic elements is a bit tougher.  The recommended EM182s or EM200s are only available in bulk from the manufacturer, so you have to put some cash down.  I was researching other possible elements to use, many of which are far cheaper, but they also have a signal-to-noise ratio that could be problematic.  Especially when you’re combining the signal from four sources!
>
> I trust you’ve worked out which .scad files work for printing the case and all that.

Take a look at:
https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/blob/master/doc/building.md

There is a lot of information there.

For building a four capsule microphone you need to load into OpenSCAD 
either this file:
https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/blob/master/TinySpHEAR_EM200.scad
(for 14mm capsules)
or:
https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/blob/master/TinySpHEAR_EM182.scad
(for 10mm capsules)

If you try to render as-is you will see nothing. You have to "uncomment" 
the lines that start with "*", each one renders one of the parts of the 
microphone. Check them out one by one to see which is which. There are 
also lines that render the whole assembly so you can see what it looks like.

> After that, I sent the kicad file for the zapnspark out to get the boards printed.  The only issues I found were that when the boards came back the silkscreened symbol for the transistors was REVERSED for polarity.  Not sure if that’s fixed in the kicad file yet - you should check the dates and if it’s late 2017 or 2018 then they should be right!

That has been fixed (hopefully) in current git but I have not tried 
ordering them online yet. I had to edit the kicad file and change the 
layer in which the traces were laid out (beginner's mistake on my part 
to begin with). The 3D view in Kicad now shows the components, traces 
and silk screen in the right place.

Good luck!
-- Fernando


> Everything else built great for me.  Sending the board out was cheap (I went through https://oshpark.com and ended up with a couple extra boards while I was at it.  These proved useful in another project, seeing as how the board design is good and clean.
>
> I keep meaning to write this up on my own site.  Push me if you’re interested; because I’ve got pictures, too.
>
> Tim Maloney
> Professor, Department of Cinema and Television Arts
> California State University, Fullerton
> 657.278.2923  CP650-22