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

Well, I flipped one of the internal antenna inductors around and it might have made things marginally better.  What's confounding things a bit is the recompile with the new center frequency - all of the PLL static design parameters are now derived mathematically in the code, and I think a higher center frequency is giving a higher frequency farther from the antenna, which exacerbates SNR, and which is more audible at higher frequencies.  Oh well, no worries, I'll stick to putting the inductors on the breadboard for now.  Tried the UHF right angle adapter on the antenna and this lowers the null frequency to around 57kHz, seems a bit less sensitive, but still works fine.  I may forgo the angled adapter and simply mount the antenna vertically on whatever enclosure I end up using.

[EDIT] Hmm.  Mixing it up: the antenna with internal inductors combined with the UHF right angle adapter gives a 71kHz null.  I have a fluorescent desk lamp two feet away and it seems fairly stable.

Lol - Sorry Dewster - I thought I was keeping up... But when you talk about UHF RA adaptors in the context of 71kHz "RF" signals, I get lost - ... Actually, I am quite lost when it comes to what you are doing - particularly on the digital side - but, alas, not only there!

At least I can see that you know what you are doing, and everything of yours which I have fully understood has made complete sense! - so its down to my comprehension .. I much prefer this situation to the other, which is that one cannot understand because what you are trying to understand is BS.

Perhaps the reason I am having particular difficulties with your latest stuff is that I have my head deeply into 1930's analogue technology at the moment - I feel like ive aged about 20 years, and even with that am still young compared to the age those whose designs I am exploring would be today! LOL..

I could, actually, quite happily go back to that age - Tubes and early transistors.. I was lucky enough to just live a little of it before it got washed away in the tide.. If I was a youngster now, there is no way I would be interested in the boring electronics industry! 

"...when you talk about UHF RA adaptors in the context of 71kHz "RF" signals, I get lost..."  - FredM

Oh, nothing RF about it at all, just the added bulk capacitance of the adapter lowering the frequency.  This is why I really kind of want the inductors in the antenna, the coaxial antenna mount and right angle adapter add capacitance, and if they add it on the tank side it seems to not impact sensitivity so much.

UHF connectors make terrific quick-disconnect / sturdily mounted Theremin antennas.  The poor man's plumbing on the EW looks like total crap in comparison.

"If I was a youngster now, there is no way I would be interested in the boring electronics industry!"

Digital, particularly when you absolutely control your creations down to the last gate and flip flop in an FPGA, is the cleanest, most interesting, and creative electrical environment I've ever worked in.  For that I'm super happy to be living now (and before our super intelligent robot children take over and decide they don't want us around, even as pets!).

"and before our super intelligent robot children take over and decide they don't want us around, even as pets!" - Dewster

 LOL ;-) .. Perhaps its that kind of paranoia which puts me off modern electronics ;-)

ok.. off on one of my rants .. completely ot and reading it makes me kringe and think "is this really what ive become !? - A rambling ol fart !? .. LOL ..

But no - I think its the more cerebral nature of electronics which would put me off if I was a youngster.. Back in my day (LOL) as a kid I could go down the weekly market to Joe's stall where there were mountains of wrecked electronic junk - everything from tube 'scopes to communication recievers to tube based analogue computers for projectile computation (most was ex military) - And there were a few transistor circuits - mostly cards from mainframes which had about 20 transistors forming 10 bistables.. It was fun - going home with another box of junk, and messing with a soldering iron more often than with a slide rule.

These days, if you want to make anything that you cannot go out and buy for a fraction of the cost of making it, you need to do a lot of studying - you need to be serious and studious - - In those days, you could build a transistor radio cheaper than you could buy one! - And put a Hi-Fi system together which was better than what you could buy, for a fraction of the price of an inferior system.. A synthesiser (Arp or Moog) was an economic impossibility for me - but I made one mostly from scraps for probably the equivalent of todays £50.

So as a youngster, I probably wouldnt be interested in electronics today - would probably study law, become a divorce barister, and fight for equal rights for males with regard to parenting and access, as a woman, even if abusive and a proven irresposible individual, will be more likely to get custody of children than a responsible caring father.

"UHF connectors make terrific quick-disconnect / sturdily mounted Theremin antennas.  The poor man's plumbing on the EW looks like total crap in comparison."

Do you have any particular connectors you would recomend ?

"Do you have any particular connectors you would recomend ?"  - FredM

I'm using RS stuff at the moment:

http://www.radioshack.com/product/index.jsp?productId=2103295

http://www.radioshack.com/product/index.jsp?productId=2103402

I ordered the elbows off of ebay and in the future I'll probably order more connectors from that outfit.

3/8" PEX plastic plumbing fits in the connector nicely, a little epoxy and it's permanent.  Some aluminum tape, heat shrink over that, a 3/8" vinyl vacuum cap on top, and you've got yourself a slick looking "rubber duckie" Theremin pitch rod!

Hi Dewster -

Ive just been going over the threads, sorting wheat from the chaff so to speak, and copying the really useful stuff to .pdf's..

In this process, and going over the TW Theremin threads, I noticed that the entire TW theremin project has almost been "hijacked" because (primarily, I think) of Uncle Howie's "It should be like a RCA" intervention..

I believe this has led to some really exciting discoveries and possibilities - but one sad aspect of this perhaps is that we have not even looked at possible digital implementation (as in, the sort of design ideas you are talking about on this thread) of a simple theremin - and we havent even explored mixed-signal (as in quasi-digital) implementations.

I may well be a causitive mechanism for some of the above, being analogue focussed, and jumping so wholeheartedly into the RCA .. But reviewing the postings, particularly with reference to your CMOS oscillator, I feel that there is probably a place for a parallel path for the TW "project" - one which was not "digital-phobic" LOL ;-)

For me, most of your digital implementation is now beyond my grasp at this time - I could understand it IF I was willing to devote the time required to get my head back into that "mode".. At present, I an reluctant to do so ...

But I think there are probably many here who are more competent in digital than they are in analogue -

I would really like to see another, completely different TW Theremin being worked on simultaneously to the analogue one..

I also wish to apologise to you - I have been somewhat dismissive of the digital direction, and have failed to register the validity of many of your arguments.. I know that digital  implementations are the inevitable future of theremins - perhaps I have been trying to delay this "judgement day" LOL ;-) Perhaps it has arived, and you are the prophet , not an antique theremin shaman.. ;-)

Fred.

Ditto everything Fred said.

My coffee pot has a microprocessor, why not a theremin?

My software skills are basically nonexistent so I'm just gonna nod and smile....

"I also wish to apologise to you - I have been somewhat dismissive of the digital direction, and have failed to register the validity of many of your arguments.." - FredM

Gosh, no apologies necessary!  You've been quite even handed when it comes to my ramblings.  I apologize for being something of a negative vibe merchant regarding the Lev oscillator and analog Theremins in general.  You're on an analog roll and I shouldn't be impeding it with my rudimentary intuitions and borderline pot shots.

Ok - This calls for some sort of argument / fight/ barney - What was it they did in England when there was an "honor" issue between "gentlemen"  - Set the time and place (usually morning) and it was pistols at dawn - LOL.

Its the oscillator wars Mk 2 - ;-)

Seriously though - I think both of us clearly have our "passions" and defend these, well, passionately ;-).

"rudimentary intuitions and borderline pot shots" is the stuff which drives the synergy we have been seeing here - and the " negative vibe merchant s" (which I am when it comes to digital, and you are when it comes to analogue) are essential to keep "enthusiasm" or "passion" from morphing into pure sillyness.

So no apologies required either way, it would seem - And I certainly dont want you to go quiet.. Hell, I need a sanity checker - my built-in sanity evaluator is unreliable!

;-)

Fred.

It's an incredible honor to be able to chat and swap ideas with some of the world's most knowledgeable Theremin designers, builders, and players here at TW.

"And I certainly dont want you to go quiet"  - FredM

No chance of that - which probably kind of sucks for those (to?) whom (which?) I've worn out my welcome!

"Its the oscillator wars Mk 2"

I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhauser gate.