Antenna in a box ?

Invisiblejelly I still have hope for you as you seem to think outside the ego driven mind of the engineering box. The box antenna idea is silly because this photo is real with perfect linearity. The antenna is in the bamboo stock. The theremin board is below the glass dolphin, you can see the pitch knob. Why engineer minds are shut down to this simple approach is a mystery in itself.

This flawed perception here in our midst forces me to believe the Higgs-boson theory is most likely flawed!

Christopher

To Invisiblejelly:

I'm a Newbie to Theremins, and not an engineer. But I have used the Lev antenna on my Theremax/SewerPipe build and it works. I never did any documented empirical data testing on it, but to my "arm" and "fingers" the linearity is there. I feel the improvement was so drastic that I am using it on my present build -- A one-of-a-Kind highbred special Theremin, which I might unveil here at TW in a few weeks. And Christopher, it will include a sound byte! A door spring just doesn't look right ------ But it Works!!!(It is easy to hide/cover up)

IHS ---- Dana  

"but you couldn't play it like the Ondes Martenot ie sitting at a keyboard...or could you?" - IJ

Oh yes, you could! - Its simply about how the antenna is shaped.. The drawings I posted show total capacitance for the arm + hand, and the antenna shape would need to account for this.. But one could design the antenna shape to give a linear response for just a moving hand - effectively the angle and curve of the antenna would need to be steeper.

Remember, there are two primary 'variables' when it comes to capacitance between two conductors - one is area, the other is distance. My diagrams show the area of the arm being included - But if one makes the area constant (as in, the overlap between the hand and the antenna) one can play with the distance alone - in fact, this should be easier.

I simply knocked this idea together as a quick and easily implemented solution to my possible problem. It is possible to make a much more accurate 'keyboard' arrangement by using more than one shaped "antenna" and looking at the capacitive difference between these to determine the hands position - This is what I did on my "Epsilon" pitch antenna.. But it is much more complex than what I have prsented here.

"That is if the antenna is a thin metal strip the capacitive sensing would be directional therefore you may be able to sit next to your box and slide you hand side to side over the keyboard" - IJ

For this sort of construction, I found that self adhesive aluminium tape is a great material to work with, one can stick this onto flexible plastic sheet (in fact, I once used a 1m plastic rule which was perfect, as it flexed easily and was easy to bend to an exponential shape).. Most of my experiments (and prototype "products") however did not use bent antenna - I shaped the antenna by cutting the tape into the required shape so that it could be stuck onto a flat surface -

On Epsilon there were 4 antenna formed with a quite complex pattern (to distribute the sensing evenly) etched onto PCB. The thinness of the tape / PCB means that you dont have to worry overmuch about horizontally induced capacitance - although, on the scheme I drew here, this will probably need to be taken into account if one does a "keyboard" version, as the players body will be sensed by the antenna due to the angular capacitive components - It may not work well (or at all! ;-)

Fred.

Instead of a Theremin, the first musical capacitance instrument I pondered building was similar to this.  A truly easy to play capacitance plate keyboard, where the X axis would be pitch, Z axis volume (and perhaps Y axis as another performance parameter).  Rather than one large antenna, each key would be a separate element, with interpolation between them (FPGAs have zillions of pins and I was working on simple capacitance sensing before getting sucked into the digital Theremin project).  Make the keyboard plate out of plexiglas, route depressions in the top at each key for tactile feedback, put LEDs behind it for snazz factor.  A piezo element or two coupled to the top would excite the digital waveguide based synthesis.  If the plate were excited with the audio signal and you shaped the feedback you might be able to play it like a violin.

"Instead of a Theremin, the first musical capacitance instrument I pondered building was similar to this.  A truly easy to play capacitance plate keyboard, where the X axis would be pitch, Z axis volume (and perhaps Y axis as another performance parameter)." - Dewster.

I have just placed a copy of my Epsilon "advert" (LOL) on Epsilon on element 14 .. This was my target specification, but I never got close to realizing everything specified - I had the basic system running and had bought in some analogue synth modules..

But when I put it all together and actually started to play it, I realized I had made a big error in investing in the idea - and abandoned it before I wasted more money.

Seeing your "Truly easy to play" sent a humerous chill through me - Hell, at times we seem so alike! - That is exactly what I felt about the idea, and the shock I got when I realised that playing a theremin was EASY by comparison to this instrument, nearly knocked me over!

Fred.

"Seeing your "Truly easy to play" sent a humerous chill through me - Hell, at times we seem so alike!"  - FredM

Ha ha!  This town ain't big enough for the both of us, Sheriff!

Actually, I was thinking more along the lines of having to touch the top plate in order to play it (exciting the waveguide with the noise of touching it) - more of a percussive instrument.  Grooves routed into the top would give tactile feedback of one's location.  Separate sensors for each key would keep the whole thing from floating around, perhaps one long routed groove connecting all the key grooves for Theremin-esque slides.  I believe something like that would be much easier to play than a Theremin, though I haven't investigated this beyond my 100% reliable thought experiments (yea right!).

"Ha ha!  This town ain't big enough for the both of us, Sheriff!" - Dewster

I know that the above is entirely joking Dewster - But it is a sad factor in business - Some of the people one has the most in common with, and who could be best friends, are your competitors.

I had an early bitter expierience of this with a theremin designer / manufacturer with whom I shared many of my ideas and with whom a design / manufacturing partnership was discussed.

Things went quiet for a while and I started getting vague communications from him - I had been getting daily emails with questions and offers to make circuit boards for me, etc .. - then he publicly announced "his" new theremin - which had some of my circuitry in it..

If he had informed me of his plans, I would have happily given him permision to use the stuff (but would have advised him against doing so, as by that time I had discovered serious problems with these circuits).. Real sad - I dont have many friends I can talk to on a technical level, and losing a potential friend / partner because of something stupid like greed, well, it hurts.

ps - I am not talking about anyone active at TW, and will not give any hints about who this person is.. It was years ago, and we all make big mistakes and can be a bit dishonest at times. If anyone asks me "was it 'X' " I will say No - Even if this means lying!

Fred.

"Are you seriously thinking about flying to Alpha Centauri?" - ILYA

No, sorry - not planning to go there anytime soon.. You'l need to find someone else if you want to cadge a lift home!

;-)

RS Theremin said"This flawed perception here in our midst makes me believe the Higgs-boson theory is most likely flawed!"

Invisiblejelly says"Your Lev antenna is brilliant RS Theremin and so is Fred's antenna in a box..The above picture has your spring in a log (well if bamboo is a log) and Fred's is in a box..both are woody and brilliant emitting Higgs-Boson particles, that's where your basic brilliance comes from..I enjoy basking and getting sun burned in all the brilliance here at TW.

SewerPipe said"A one-of-a-Kind highbred special Theremin, which I might unveil here at TW in a few weeks."

Invisiblejelly says"Lovely..but if it's an 'highbred ' is it only for kings and queens and princes and princesses? 

"I had an early bitter expierience of this with a theremin designer / manufacturer with whom I shared many of my ideas..."  -FredM

Very sorry to hear about that Fred - you have so many good Theremin ideas it's hard not to find oneself incorporating a few, and imitation is the sincerest form of flattery and all - though of course blatant unattributed ripoff is an entirely separate category.

I'm using your "coil in the base of the antenna" idea for my DT prototype and it works very well - I would certainly request your permission to use it and credit you if it ends up going anywhere commercially.  In many ways I'm rather relieved that I'm not designing an analog Theremin as I'd be exceedingly hard pressed to come up with as many interesting and useful innovations in that department as you have.