How Theremins Really Work

"Someone lost their vibrator?"

Now there's a phrase I've heard before...

It was spoken by a burly builder arriving at a site where they were laying concrete. I was a teenager, just old enough to have some idea what a vibrator was. But I was not prepared for what he produced from the back of his van; a concrete vibrator, similar in form to the personal sort but made of steel, three feet long and powered by a two stroke diesel engine!

Back in the old days, a vibrator was not an uncommon component to find in circuits..

These were usually in metal cans, and looked similar to the large canned capacitors of the time.. They contained an electromagnet configured with contacts much like a relay.. a "closed when electromagnet not energised" contactor was in series with the electromagnet - so when power was applied, this contact broke the circuit, causing the whole entity to 'vibrate' - an independent contact provided a nasty square type waveform if connected to a suitable circuit.. or some just used the current flow through the unit to generate a waveform.

Horrible nasty parts - contacts would burn out or wear out.. These parts were certainly not designed to give pleasure to anyone! ;-) ... But they might have been a basis upon which lator "vibrators" were created. (In fact, I worked with someone who left his electronics design job and started an exclusive business making high-end vibrators using precious metals and embedded with jewels etc - These sold [and were custom designed sometimes] to wealthy celebs etc.. The names he dropped when showing me some of his products... Not to mention the prices.. ) This is the same person who got me to design a synthesiser into a toaster for a wealthy shiek..

Sorry - im doing it again! ... Getting "real" in the middle of a jokey fantasy .. ;-(

'Sorry - im doing it again! ... Getting "real" in the middle of a jokey fantasy .. ;-(   ' - Fred

:-)

Fred, I'm sure that the normal run of the jokey fantasy thread will be resumed without a problem so have no fears!
Of course it's not going to be by me since I'm all innocent like...

Oh I loved your post to the Floyd track by the way:-)

Fred, this kind of relay vibrators could even be used as RF oscillators. They were the poor man's version of the spark gap transmitter. When I was about 10 years old, I spent my time disturbing all AM radios in the neighborhood with that. I added a ferrite antenna in series with the sparkling contact which greatly increased the effect...

"When I was about 10 years old, I spent my time disturbing all AM radios in the neighborhood with that" - Thierry

LOL ;-) .. So did I ! - Those were the days ;-) .. Bags of surplus 'junk' one could pick up for peanuts as the world became transistorised and siliconised.. I still have a small box of parts I kept from those days, a couple of valves, some germaniums - but no vibrator )-:

We had a small taste of those days when loads of parts went cheap due to RoHS - but it wasnt nearly as exciting, and certainly never compensated for the major pain-in-the-but that RoHS caused.

ps - I cannot remember the frequency these things actually switched at - but I think, as you suggest, RF was more a function of sparking and switch-bounce than that the frequency was actually RF..  I never owned a 'scope till I was 14, and by then I had gone off vibrators and was venturing into more exciting territory..... ;-)

But, back to the topic! (Deviation or hijacking of threads in no longer tolerated! ;-)

Makes me wonder about how one gets the above theremin CE certified!  ;-) (and im not sure about bats and RoHS - also, the solder blobs composition is not specified, but looking carefully at how they work, I suspect they need to be a mix of lead, tin and plutonium)

The vibrator alone will be a major problem getting past EMC regs  - Particularly with the length of wire required to connect its BLH quadrant! - I hate to think what this wires impedance will be - As for modelling it, lord! what a nightmare! what with the electrosphere and magnetosphere and all.. and thats before weve gone past lunar orbit ! - Wavelength ?? ;-) - 

This wire would certainly need a "Shlev antenna" construction due to the elliptical nature of the rotation of the earthing point WRT this  wires connection point.. (Hey, there is a use for the Shlev antenna after all! ;-) - A spring antenna construction for this wire might seem improbable, but realize that its astronomical length will need to change as the distance of earth from the sun changes.. given its length, the elastic function is required to be distributed evenly, and a thick, high tensile spring is not a daft idea (or at least not as daft as the idea behind the original Shlev antenna ;-)  But how did they solve the rotation of the earthing point WRT E-W WRT this wire ? Is this what the compass is for ?

ps - I see it now! Silly me! I completely misunderstood the schematic symbol (LH-BQ) to which this wire connects! - Its a hemespherical track arround the earth at the equator with a network of theremin venues spread out from this track at which the theremin can pause for a brief period for performances! Real clever!..

The only limitation is that only daytime performances can be achieved (as close to noon as possible - Please Note! I sayed NOON NOT MOON!  - See my next posting!) , as otherwise this high tensile Shlev "wire" is likely to chop through mountains and  demolish cities as the sun sinks on the horizon, or slice through the earth, shorting to ground as it does - such a mishap could be worse than Armaggedon and, sadly, as an engineer who has extensive expierience with safety critical design, I am not happy about this possibility..

"Oh I loved your post to the Floyd track by the way:-)" - Roy

Glad you did! - Any excuse to put some good music up, and I jump at it ;-) .. The moment I saw that wire, I knew I had to find that track!

(in fact, if I hadnt seen that wire, I wouldnt have had nearly as much fun, or as much to say! ;-) .. Perhaps the reason it appealed to me was because I had to do some preliminary analysis for a mega-rich nutty client, who wanted to have a wire to the electrosphere to collect power - Fortunately NASA had an evaluation of a space-elevator which I used to get the data to show that, although rich, this project was outside his budget! ;-) .. Should just say that I never actually met this client - I have an "agent" with these clients, and occasionally he passes work to me... I doubt that his client ever knows the job is being passed to a solo engineer with a tiny lab, LOL ;-) He probably thinks MIT is doing the work...

Life is even crazier than that schematic!

Beware!

The theremin will need to be moved during solar eclipses, to a position where the moon is not obscured by the sun.. or did I get that the wrong way 'round ?

If this is not done, there are several possible serious outcomes:

1.) The "Shlev antenna" will twang the moon into a different orbit.

2.) The "Shlev antenna" will gouge into the moon causing the sea of tranquility to, well, lose all tranquility.. (dont be too surprised if the legs / base of a LEM crash lands in your back yard... Or a spring-loaded American flag impales you).. Hey - Just wondering about the springs they used in those flags .. An Armstrong antenna to go with the Armstrong oscillator ?? ;-)

3.) the theremin and anyone in its vicinity will be twanged into deep space, where theremin loving Vogons await so you can accompany them musically as they recite their poetry. (this will usher in a intergalactic dark age of purile debate about which is worse - Vogon "poetry" or theremin "music" which will only end after a bloody war and victorious Vogons re-writing history so that they invented the theremin)

4.) We will all learn that there is no dark side of the moon really - as a matter of fact, its all dark!

In the light of the high probability that the moon / its orbit, will be affected, whatever of the above scenarios occurred, its a good idea if you live by the coast to sell up and move to the Alps or Tibet or anywhere REALLY high above sea level... This is probably a prudent action anyway, if one thinks about global warming..

In fact, the only thing any of the above disasters might make happy would be the bat, who could fly away, free!

There .. A happy, fairytale ending! ;-)

There's nothing at all inside a theremin. It's just a magic box. You wave your hands around & beautiful music appears.