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

A Tale Of Two Antenna Plates (& Woe)

Yesterday I printed out a full-sized version of the proposed antenna plate.  Today I modified it a bit and printed it again:

First one is on the left, today's is on the right.  Not a ton of difference, but significant.  For today's I went with 2 top and bottom layers and 3 side layers, which seems better suited for the threads, and hopefully no one will ever see the backside of this thing (don't look! ;-).  Jacked up the print speed to 75mm/s so the print only took ~6.5 hours.  The threaded stud is now M12 x 2, which comes out kinda skanky when printed at low Z resolution, but likely still usable.  The face went from 4mm thick to 5mm, which seems more rigid.  The sides are flimsier with larger cutout holes and side thickness at 1.2mm.  The box corner radii are larger, and because of that I think I will dispense with any significant back face to outer box chamfer.  The countersunk screw hole geometry was messed up, and that got fixed.  Next step is to design simple adapters for my current PVC coils and stick them in there with the AFEs.  Production (god willing) will use printed coil forms.  Moral: you can learn more than you can possibly imagine from a single print.

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The ribbon cable & connectors & tool arrived yesterday, and I unfortunately had to send the latter two back to Amazon (I never return anything, particularly if I can fix it, so you know it was F'ed up).  Connectors were fine, but the tool was so far out of parallel it basically destroyed anything I put in it:

Above is a view into the back of the tool.  For it to work correctly one might be able to tolerate a degree or two, but this is an order of magnitude above and beyond working.  I did get a bit of satisfaction by using two of the 16 pin connectors on my D-Lev cabling and crimping them with a C-clamp, but that was after almost ruining my soldered on cabling with this shitty tool, so I think we're even.  Bad tools bad tools, whatcha gonna do...  (is there anything worse?)

The good news is the main LCD / FPGA PWB Roger sent me + encoders are working 100% and looking quite sharp in their printed doghouse.  So yay.

http://www.thereminworld.com/forums/T/28554?post=213258#213258

OMG, oldtemecula you old dog!  You didn't tell us that Touchless and you were an item back in 2018!  You must have made a good impression because he speaks very highly of you:

"I have met who you speak of, an unselfish contributor who helps theremin enthusiasts build things that work."  - Touchless

But then he goes on to disparage me, oddly almost exactly like you always do:

"... trying not to be a cheap digital whistle..."

I think you two must be hanging around too much, you're rubbing off on him.  How's he doing?  Wife and kids and store in Tombstone OK?  Seems like a multi-faceted kinda fella.  He hasn't posted lately, but for some reason I still feel his presence here at TW.

Thierry said on that page "Dewster, your self-adulation is ridiculous. You never made an attempt to get your design approved by at least one of the well known professional thereminists, like Carolina Eyck, Lydia Kavina, Thorwald Jorgensen, or Peter Pringle. AFAIK, none of them played your instrument in a public concert up to now. All your (arrogant sounding) statements like "could mop the floor with the EW-Pro" are only based on... your personal experience as a professional musician? Did I miss your last concert and CD recording with the New York Philharmonics? "

dew I have never put down any theremin design as I know how difficult she can be. I put down a sound that misses the mark. Thierry can be overly cocky with his nicotine stained fingers. You have a rude awakening coming as your sound leaves a lot to be desired after so many years. I will have new samples coming soon, judge not least ye be judged. Like me you need to take the risk and send your design as a gift to a reputable professional to demonstrate what you hope to achieve.

Until then how can you be so nasty about everyone else's design?

Christopher

"Until then how can you be so nasty about everyone else's design?"  - oldtemecula

Whatever.  So when's the last time you and Touchless got together?  You guys have so much in common, it must be like meeting your soul mate.  He talks about you a lot, why don't you ever talk about him?

Plate Progress

I've disassembled my old P1 plate antennas, and printed out some supports for the PVC coils that were in them for P3:

Above you can see the volume (left) and pitch (right) plates face down.  The volume coil support is disassembled so you can see the printed support details.  The AFE's are mounted on the foil support walls, and obviously I haven't installed the foil yet.  The foil will form a U on the pitch plate, covering the left, bottom, and right sides.  On the volume plate the foil will cover the left, bottom, and far sides - which will keep the volume plate area away from the body.

I kind of like having separate PVC coils as I can heat shrink them without fear of them melting, but they are more massive than I would like or need.  Is there a much thinner-walled & lighter weight alternative, perhaps PVC, ABS, or phenolic (od = ~50mm)?  I wonder if a printed PETG coil form could withstand heat shrinking? 

The separate coil & support also lets you easily orient the coil leads: just screw on the bottom support, position the coil, and screw on the top support while holding the coil stationary.

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Been working on the librarian too. Roger requested a way to dump all the presets - it works well and is something I should have incorporated long ago.  Been polishing on that as well as some other portions of the code today.  I'd like the librarian to be as open source as possible so that it will run on any OS, and if people run into trouble with it they can fix it themselves, but I don't know what that entails exactly - do it in Python / TKinter?  Cross-compiles are definitely on my not-to-do list.

What a steady movement towards the goal!

Great!

Live Nude Girls Editing

Tuesday morning I was laying in bed thinking about how relatively useless the editing function was on the librarian F1 EDITOR screen.  It lets you change any values in a preset, but with no audible feedback, so I mainly use the F1 screen to examine presets, not edit them.  I looked at the D-Lev SW for a while and then implemented a way to change the encoder values via the serial port.  Basically you write the desired byte value to the target encoder memory location, then set a flag by writing to another (fixed) byte location in memory, and this initiates a mass update of either the system or the user encoders, and finally updates the LCD.  Then I added a feature to the librarian code so that it sends the new encoder value over the serial port whenever the librarian screen knob value is changed.  Except for the new flag, these mechanisms are already in the SW for when loading a preset, and all of it isn't exactly a technical miracle or anything, but it is a bit eerie to see the LCD values change with librarian knob changes, kinda ghost-in-the-machine-ish.

INC / DEC of encoder values on the F1 screen with the hilite enabled has changed to CTRL + arrows (was the +/- keys).  As before, you can zero out an entire UI page by hiliting the page name and entering a zero.  Not sure how useful live editing will be without stimulus (it's hard to do pitch & volume hand input while sitting at a PC and editing) but it might cut down on dialing for dollars all over the place during the editing process.  Keyboard editors have this issue too, and they often have a soft screen keyboard for stimulus.

The command to dump the presets to slot numbered files is now "  stopn " (slots to preset numbered files) and you have to specify both start and end slots.  This makes it more generic to use, and I think this also makes it a little safer to not inadvertently trigger and have it poop files all over your directory.

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"What a steady movement towards the goal!"  - Martel

Thanks!  Steady, but slooooow - hope it's not been too boring!

P3 Guts Operational

Just got the third prototype guts all together and up and running:

Above: The volume plate (left) and pitch plate (right) with aluminum foil and all wired up.  AFEs interface via short DuPonts plugged into to a 2x4 pin header, the other side of which is soldered to the ribbon cable.  The other end of the ribbon is identical, but will be replaced by proper connectors once they arrive on Sunday. Electrical contact with the plates is by simply pinching some bare wire wrap wire under the coil holders.  I definitely want to use some heavier foil for the real deal, this cheesy store foil is way too thin to stand up to much man handling during manly prototyping sessions performed by real men.

Above: All connected up and operational!  I briefly fumbled through "Lara's Theme" and "Ave Maria" - a horizontal pitch plate is a tough thing to get used to - it will be more vertical once mounted in the yet-to-be-build P3 enclosure.

[EDIT] There's a bunch of steel right under the plastic desk top, and still it works fine with barely any adjustment - try that with your analog Theremin! :-)

For some reason as I was following along I thought these cubes were tiny, like a couple inches across, until I saw the boards and coils inside. What are you planning to do with the cubes - enclose them as standalone modules on swivels or put them into a single cabinet?  I'm guessing from the screw holes that they go into something...

As an aside, I think it's interesting that I don't think either of us would normally have any great interest in learning 3D modeling, but when it's for your own projects it just sort of happens without any real pain.  If I had to do it for work I would have hated it.  Somehow the paycheck was never sufficient motivation to get interested in it, but a home project is. 

You'll have to report how the pitch side works like that.  The constant pitch contours are going to transition from roughly spherical surfaces at a distance to surfaces approaching the shape of the element at close range, increasing sensitivity to the vertical component of hand movements when compared with a rod antenna.  Because of that it's going to have a different feel and require at least some change in playing style IF a player is used to a rod antenna (unless they use primarily in-and-out hand and arm movements)  It might be a minor difference that the player can adapt to within a short time, or it may take longer.  What is the possible benefit of this shape that would attract an experienced player to it knowing that it might require a change in playing style?  Or is this just testing the concept of electronics inside of antenna elements?

"For some reason as I was following along I thought these cubes were tiny, like a couple inches across, until I saw the boards and coils inside."  - pitts8rh

I initially did a 1/2 size proof of concept, that's maybe what you're thinking of?  I hate wasting plastic, and little models can tell you a little.

"What are you planning to do with the cubes - enclose them as standalone modules on swivels or put them into a single cabinet?  I'm guessing from the screw holes that they go into something..."

The current plan is for the tuner, pitch plate, and main control to go in a single cabinet, the volume plate may or may not be articulated off of that.

"As an aside, I think it's interesting that I don't think either of us would normally have any great interest in learning 3D modeling, but when it's for your own projects it just sort of happens without any real pain.  If I had to do it for work I would have hated it.  Somehow the paycheck was never sufficient motivation to get interested in it, but a home project is."

Yes, it's oddly quite painless when there's an immediate goal.  And money seems to often be more confounding than helpful where creativity is involved.

"You'll have to report how the pitch side works like that."

I assume it will be highly similar to P1, which has highly similar plate geometry.  I'm hoping so anyway.

"The constant pitch contours are going to transition from roughly spherical surfaces at a distance to surfaces approaching the shape of the element at close range, increasing sensitivity to the vertical component of hand movements when compared with a rod antenna."

True, and what I was anticipating.  I find vertical pretty easy to hit, but horizontal needs some slop (hence the perpendicular sides, which should also help with far-field sensitivity), particularly when the tuner is located somewhat away from the pitch antenna.  P3 will have these much more co-located.

"Because of that it's going to have a different feel and require at least some change in playing style IF a player is used to a rod antenna (unless they use primarily in-and-out hand and arm movements)  It might be a minor difference that the player can adapt to within a short time, or it may take longer.  What is the possible benefit of this shape that would attract an experienced player to it knowing that it might require a change in playing style?  Or is this just testing the concept of electronics inside of antenna elements?"

I do get that - and i really get it now that I'm playing P2 with the outboard paddle antennas - which I'm very slowly warming up to but still don't like as much as P1 (not that it was perfect or anything).  Some configurations will feel uncomfortable due to previous training / experience, some configurations will be inherently uncomfortable regardless.  I've been trying to remain a child raised by the tribe in a cave so I can hopefully tell the difference, but maybe there's been too much water under the bridge with P1 and ~P2.