Let's Design and Build a (mostly) Digital Theremin!

Posted: 6/28/2021 9:52:47 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Roger's P3 Write-up and Video

Roger did a super nice write-up of his P3: https://technitoys.com/another-d-lev-digital-theremin-build-project/ - check out his other projects too while you're there, he picks interesting projects and is a great documenter & writer, and his blog is a thing of beauty!

There's a super nice video he did there too: https://www.youtube.com/watch?v=vVgT8tT-UI0 - excellent work all around Roger!  You got the lilting vocal inflections and everything!  Great production values, I like the tuner view, your muting of it at the end, and the librarian preset view!

[EDIT] Roger, I am extremely impressed with your playing ability - I didn't cringe once! ;-)  And I see from the preset librarian view that you aren't using the internal pitch correction either - giant kudos!

Jason or Thierry: Roger's posts are ending up in Theremin World MODERATION purgatory - can anyone here help him out?

Posted: 6/29/2021 3:31:24 AM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Main Board Layout

Spent the day learning how to use vias (tiny plated through holes that connect one copper plane to another) in KiCad:

Saved this board for last as I figured it would be the most challenging (it was!) and wanted to be at least a little past the dangerous noob stage.  The FPGA demo board, LCD, encoders, LED tuner, and everything else plugs into it, so all the interconnect, and as well as the logistics of how to handle the extra stuff like UART, SPDIF, MIDI, mute and ACAL, and mute LED I/O had to be worked out.  Roger blazed this trail and I'm not deviating from it substantially as it makes a lot of sense.  I guess it's a little dangerous (in terms of plugging the wrong thing into the wrong socket) but I decided to break that I/O into two reused 8 pin connectors used for the AFE's and tuner.

This is just a two layer board, so you have to get creative when wiring things together as the layers are already spoken for by ground and +5V.  I split the +5V layer at the top into a +3.3 V layer and stuck the EEPROM up there with the LCD, as they are both 3.3V devices.  Then I kept the paths horizontal on the front and vertical on the back.  Laying resistors down on the board gave some copper room underneath, and bunching the traces together helped too.  Adjusting the copper fill keep out clearances to 0.254mm minimum allowed it to snake between the 2.54mm pins and connect otherwise stranded regions.

I've seen others do this a lot at work, and I've laid out my own hand wired vector boards, so it's nothing all that shockingly new.  And KiCad is really pretty nice - can't complain about the price!  A new improved version is due out quite soon, which is exciting.  Open software is the only way to go IMO, particularly when you're putting a lot of effort into creating lots of files.  I bow to the KiCad developers, and very much appreciate their efforts.  They are genuinely making the world a better place.

I had absolutely no intention to take on board layout, particularly at this point - it was just a one-thing-led-to-another and whoops! before you know it here-I-am kind of thing.  Mostly I'm following Roger's physical layouts, which is 90% of the work IMO, and I deeply appreciate all the time and effort he put into it.

Posted: 6/29/2021 9:48:45 AM
Buggins

From: Theremin Motherland

Joined: 3/16/2017

PCB looks nice.

Why are you still using DIP and THT components?
What about migration to SMD / SO packages?

Posted: 6/29/2021 10:22:02 AM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"Why are you still using DIP and THT components?"  - Buggins

One-off manufacturability?  I don't have a reflow oven handy.  How are you handling SMD?

Posted: 6/29/2021 1:49:17 PM
Buggins

From: Theremin Motherland

Joined: 3/16/2017


How are you handling SMD?


I'm just soldering them manually, with soldering iron.

Posted: 6/29/2021 9:33:49 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

P-Vox

I copied Roger's Patsy Cline preset from the settings in his video, and it was so nice that I had to play it for a while: [MP3].

Two of the formants drop with volume, and two rise / one drops with pitch.  I added some resonator, pitch correction, and a little outboard reverb (couldn't help myself).

Posted: 6/30/2021 1:12:00 AM
tnewbie

Joined: 5/21/2021

Beautiful!

Posted: 6/30/2021 1:17:41 AM
tnewbie

Joined: 5/21/2021

@dewster some PCA shops will make up 5 units inexpensively so using SMD is not too big an issue.

Posted: 6/30/2021 12:30:07 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"...some PCA shops will make up 5 units inexpensively so using SMD is not too big an issue."  - tnewbie

I guess I'm aiming for future repairability too.  Though through hole everything will probably disappear at some point.

Posted: 6/30/2021 8:26:07 PM
Mr_Dham

From: Occitanie

Joined: 3/4/2012

Just out of curiosity, do you have a quick manual for D-lib.exe ?


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