Relationship between Series LC and Parallel LC

1) At so low frequencies as 300kHz or 3MHz an antenna of less than 1 meter, is only a capacitor. The antenna inductance is pratically neglectable. Finally, player's hand adds a capacitance of about 0.001 pF to 1 pF.

2) Our voltage is 30 volts peak to peak, not so different from that of an Etherwave, but since we use a 10 times higher frequency, it is like if we are using a voltage of 300 volts (transmitters that disturb, decrease their power proportionally to the frequency). So our 30 Volts at 3 MHz are similar to 300 Volt at 300 KHz.

In addition the band from 2 to 3 MHz is absolutely more interference-free than the "Long Waves", where are present extra powerful transmitters. 

3) There are about 1000 Theremino modules in use (500 Master, 250 CapSensors and 250 Servo) and in two years, zero units have returned. An incredible performance for an electronic production. Based on this results, we are sure that our CapSensor circuit doesn't have any ESD problem at all. A more technical response is: ESD events are blocked by the first very little capacitor (only 18 pF), by the grounded inductor, by another little capacitor (only 10 pF) and finally grounded by the two large gate capacitors, typical of Colpitts circuits. Someone has suggested that 10 pF SMD capacitors, are rated for 200 volts only. This is true but not real. We use SMD capacitors, with the same volume, and same X5R ceramic, in our "Photomultiplier Tube Adapters" and "Geiger Adapters" and they are 10 nF at 2000 Volt, in the same volume!!! So, because the X5R ceramic is the same, for the two components, a little calulation (2000 Volt * 10 nF / 10 pF), leads to a incredible 2 Million Volts. Naturally this is not true, mainly because of the limited spacing between SMD 0805 terminals, but today, I have tested them, with the 1800 Volts, coming from our PmtAdapter, and they does not leaks any measurable current.   

4) Phase offsets indicate that temperature has some influence... it is very difficult to simulate those things... But a Colpitts FET oscillator is absolutely more stable than a two transistor oscillator. All the radio VFO oscillators are Colpitts! And all the more stable VFO are with FETs, not transistors.

"1) At so low frequencies as 300kHz or 3MHz an antenna of less than 1 meter, is only a capacitor. The antenna inductance is pratically neglectable. Finally, player's hand adds a capacitance of about 0.001 pF to 1 pF."  - livio

Yes.

"2) Our voltage is 30 volts peak to peak, not so different from that of an Etherwave, but since we use a 10 times higher frequency, it is like if we are using a voltage of 300 volts (transmitters that disturb, decrease their power proportionally to the frequency). So our 30 Volts at 3 MHz are similar to 300 Volt at 300 KHz."

I'm sorry, but I don't follow your line of reasoning here.  Are you talking about photon energy?

"3) There are about 1000 Theremino modules in use (500 Master, 250 CapSensors and 250 Servo) and in two years, zero units have returned. An incredible performance for an electronic production. Based on this results, we are sure that our CapSensor circuit doesn't have any ESD problem at all. A more technical response is: ESD events are blocked by the first very little capacitor (only 18 pF), by the grounded inductor, by another little capacitor (only 10 pF) and finally grounded by the two large gate capacitors, typical of Colpitts circuits."

A lack of returns is generally a good sign, but hypothetically some units may have failed and the owners just didn't bother to return them.  Have you tried zapping one repeatedly to see what happens?

Seems that the DIY electronics community and manufacturers targeting this community are at least 15 years behind industry when it comes to ESD protection. I have now seen videos of well designed / constructed SMD digital theremin modules being constructed with absolutely no regard for even the most rudimentry protection, and statements like " we are sure that our CapSensor circuit doesn't have any ESD problem at all. A more technical response is: ESD events are blocked by the first very little capacitor (only 18 pF),"

Understand this! From an ESD perspective that "very little capacitor" simply doesnt exist! - it provides absolutely NO protection - its effectively a short circuit (or fuze) with a voltage (dielectric) rating of probably not more than 100V - 10kV WILL just ignore it and damage this capacitor as it ignores it! - If a small capacitance provided protection, ESD wouldnt be much of a problem - Discharges occur across insulators when the capacitance between source and ground is far lower than 18pF - its the dielectric breakdown voltage which is more significant!

With 1000 boards in customers hands there is absolutely no basis for confidence - Some % of these boards could have failed through some catastrophic ESD event, but the users not bothered to return them because in the DIY field people often dont, thinking they have got things wrong - they just give up.  Whatever that number is, ten times as many boards will have suffered non-catastrophic failure and be either operating below standard or have a "time bomb" which will cause failure in the future.

So, from a DIY-Market manufacturers perspective, it could be argued that their neglect of basic known established ESD risk is "understandable" - they wont get many returns, simply because of the nature of the market and its customers.

IMO, it is a DISGRACE! - for the want of an extra 10p of components and a little extra expenditure on the assembly line, customers are being supplied with unreliable boards.

Its a bit like global warming - Everyone KNOWS its happening, some just choose to ignore it, some choose to ignore it by argueing that it isnt happening.... With ESD (as IMO with global warning) there is NO doubt about the damage ESD causes..

But, unlike global warming, ESD protection is CHEAP and SIMPLE!

Fred.

Some facts:

HBM (Human Body Model) ESD voltages are standardised at 12kV (although higer voltages are possible). Using 12kV, and the breakdown voltage of air (1200 to 2800 V/mm) it can be seen that an ESD discharge can occur when the hand is as far as 10mm from the antenna! - a 6kV charge can jump 5mm. Hand-antenna capacitance at these distances is far less than 10pF.

Putting a plastic film over the antenna can greatly reduce ESD risk:

Material:          Breakdown (V/mm):      Required min thickness:

ABS                           16kV                     0.8

Acrylic                        13kV                     0.9

Polycarbonate              16kV                    0.8

PET (Mylar)  Polymide (Clapton)   280kV                  0.04

Standard ceramic capacitors (as generally used in theremins) have a specified breakdown voltage of either 50 or 100 volts - this is the voltage across them that they can tolerate before they break down .. so if one side is at say +50V and the other is, due to ESD, taken to even 1kV (let alone 12kV) they will be more than 9* overvoltage - would you plug something designed for a 9V battery into a 90V supply and expect it to survive? Yeah? then how about if you plugged it into a 900V supply? ;-)

Ok - the above is a bit biased and unfair, because the time that this excessive voltage across the part is extremely short - otherwise every ESD would be highly destructive not only to equipment but also fatal to people... But even the briefest of over-voltage events can damage, if not kill, an electronic component.. and not just solid state components, ANY component whose votage (and/or current) specification is exceeded through an ESD event.

Unfortunately I have not found heat shrink sleeving with good properties (about 400V/mm to 1kV/mm is standard) - a snug ABS pipe with the antenna inside this is the best easily available condom for a pitch antenna that I have found ... But IMO, the circuit board is where the protection should be!   (forget condoms, give it a vasectomy!  ;-)

We do not have ESD problems but, if necessary, there is a simple and perfect solution: antennas can be made from a thick plastic tube, maybe thick nylon or other hi-voltage resistent plastic, with a little copper wire inside.

Complete and absolute protection from ESD events, guaranteed!

In response to dewster
--------------------------------------------------------------------------------------------------------------------
1) Yes.
2) 'm sorry, but I don't follow your line of reasoning here.  Are you talking about photon energy?
3) lack of returns is generally a good sign, but hypothetically some units may have failed...
--------------------------------------------------------------------------------------------------------------------

1) Sorry, I confused your questions on the impedance, to the impedance of the antenna. I'm glad we agree on this point.

2) No, not photon energy. I'm talking about the power needed to compete against atmospheric interferences and against high power broadcast emissions.

Short Waves - about 3 to 30MHz - Broadcast transmitters power is about 1kW to 10kW

Medium Waves - about 500KHz to 2MHz - powers in the range of 10 kW to 100kW

Long Waves - about 50 to 500KHz - powers of 100kW and up

Therefore, the power required to work undisturbed around 3 MHz is about ten times less, than that necessary at 300KHz.

3) Regardind ESD events, we do not only have feedback from the users. We have used these circuits as "physical intefaces" for many years, back when we did not know already, that they could be useful for building a Theremin. Dozens of prototypes were mistreated in many ways, with no respect for the rules on how electronic components, "should" be handled. None of us has ever used precautions, sometimes we weld directly on live circuits and we do not use electrostatic bracelets. Some of these prototypes have been in use in museums for many years. The artists Ennio Bertrand and Piero Gilardi, use them regularly in their art installations and some are working since years, eight CapSensors at the mercy of the public, outdoors. 

Our staff and users have submitted our modules, to every possible torture, reversing the power supply wires, using the serial line instead of the signals of the pins, failing to mount components while assembling themselves into DIY... anything you can imagine.

In all these years no one has ever seen a broken FET or other components failures.

Please note that the modules are produced by independent firms. We, in the Theremino System, do not sell anything, just explain how to do. Theremino System is "Didactical", "Nonprofit" and " Open Source". I'm telling you this just because I'm proud of the good design we made.

I'm so sure of what I'm saying, that I will fix myself for free each module that accidentally should break. I have repeatedly written this, even in our blog. We have received thousands of emails and posts about all sorts of problems, but no one has ever written anything about broken or defective hardware, you can check here:

www.theremino.com/en/blog/master-and-slaves/

www.theremino.com/en/blog/the-hal/

www.theremino.com/en/blog/multimedia/

www.theremino.com/en/blog/robotics-and-cnc/

www.theremino.com/en/blog/biometry/

www.theremino.com/en/blog/geigers-and-ionchambers/

www.theremino.com/en/blog/gamma-spectrometry/

www.theremino.com/en/blog/standalone-applicatons/

www.theremino.com/en/blog/tips-and-tricks/

www.theremino.com/en/blog/usercomments/

Why is there such total resistance to implementing a reliable solution? Why the complete refusal to even think about putting a 90V neon on the board or a better slightly more expensive ($0.25) low capacitance discharge tube specifically designed for purpose of protection, on the board?

These parts are fitted as standard on telephone equipment, and ESD protection is included in all Cap-sense products I know, together with detailed instructions about the dielectrics / insulation thicknesses etc required for capacitive sensing applications, and details about adding protection diodes on the board when these requirements cannot be met.

The theremin is one of the most susceptable applications I can think of - So you have your antenna in a tube - there is still an ESD route when the antenna is unplugged..

And even with protection, stating "Complete and absolute protection" is always utter folly - there is no such thing as "Complete and absolute protection" particularly while any component can be accessed.

Also, manufacturers cannot know the situation their products may find themselves in - All may appear fine in their lab, but not be so fine when the product is used in a dry environment an some hotel in the Middle East for example.

But not to worry - After all, its only hobbyist DIY bods who buy this stuff, and they have plenty of time and havent spent that much money that they will take action.. And even Bob never bothered on his quite expensive EW products, so why should anyone else ? - Most products will fail after their warranty has expired, even if the damage was done during assembly, and no one is going to go to the effort of determining cause or time of initial failure, even if it was possible to do so...

Fred.

"None of us has ever used precautions, sometimes we weld directly on live circuits and we do not use electrostatic bracelets."

So the whole electronics industry are a bunch of fools - companies employing knowledgable engineers and physicists merely spend millions on ESD "clean rooms" for fun, and to waste money (their profits).. The time and expense of training staff in ESD safe practices is entirely pointless.. Intel and TI and Cypress and AMD and Phillips and Siemens and IBM and EVERY other large electronics manufacturer dont have a clue... !

I dont think so!

I certainly would never buy any assembled product from a company boasting about their stupidity!

And sorry - but that is exactly what you are doing.. boasting about stupidity and carelessness.

Its no wonder that some countries in the EU are sometimes scorned by more advanced technical nations..

Fred.

It is not for the expense but for the project elegance. We do not like unnecessary components. In addition I think that neon bulbs, and similar solutions, would not increase the ESD resistance.

Theremino Modules do not fail after the warranty has expired! I will repair personally, free of charge, any broken Theremino Module, for the rest of my life (about another 20 to 40 years, I hope).

I would be very happy to see some broken Theremino Modules, I've never seen one.

"...I dont think so!
I certainly would never buy any assembled product from a company boasting about their stupidity!
And sorry - but that is exactly what you are doing.. boasting about stupidity and carelessness.
Its no wonder that some countries in the EU are sometimes scorned by more advanced technical nations..
Fred..."

This is not true, but if you think so, no problem...

Just to remind you, we are not a company, I'm not here to try to sell you anything, the only purpose for my posts, was to try to help. I am only a Theremin lover as you are...

" In addition I think that neon bulbs, and similar solutions, would not increase the ESD resistance."

I am now even more puzzled - Do you have reason for this "feeling"? I agree that discharge tubes, when fitted correctly, only reduce the ESD EMF down from the initial thousands of volts  to their breakdown voltage (usually 70V or more depending on part selected) and that this voltage is still able to cause damage if no other protective measures are taken..

But it is easy to add this extra protection if required, and often sufficient protection to deal with a 90V transient is built in to semiconductor parts if preceded with a few hundred ohms or (as in the case of some tough logic) has all the required components on-chip..

But as I see it, there is no possible way that adding a discharge tube in the right place wont improve reliability and increase ESD immunity - I would be most interested in hearing your reasoning on this matter..

Well, no - Im not really interested to be honest.. Its simply a nonsence statement with no possible theoretical or practical truth in it.. just as your statement about the 18pF capacitor was nonsence - its ok - its an easy mistake to make ;-) I spent 6 months working for an engineer who had a doctorate in electrostatics and ESD in particular, I may have been just as ignorant if I hadnt had this expierience! I have no wish to engage in further inane argument about this matter - I have said my piece, and you have not seen any failures - lets leave it at that with regard to the theremino boards.

I accept your position "Just to remind you, we are not a company, I'm not here to try to sell you anything, the only purpose for my posts, was to try to help. I am only a Theremin lover as you are..." and understand that in a hobbyist environment neglect for theoretical risks is common - I also understand how easy it is when one has a working prototype, to simply put this into production without going through the expensive verification stages almost all manufacturers must comply with..

(The following is a more general OT rant about some possible legal issues:)

I also accept that if we were all subjected to compliance (and in Europe, technically we all are - but it seems one can get away with non-compliance in the DIY sector and if one stays below the "radar") there would be far fewer theremin products on the market - As even through the self certification route, one needs at least one visit to a test lab (unless one owns the required equipment and facilities) to verify things such as EMC and ESD before one can legally sell an electronic product... In fact, even to have 16 theremins on display for the public to use for one week, I was forced to have each unit checked for safety, and basic EMC and ESD tests were performed by the customers engineer, before use of the equipment was permitted.

I think different EU Nations enforce compliance to differing degrees - It seems to me that the UK is far tougher on its manufacturers (or at least forces compliance with the directives) than some other EU nations are on their manufacturers - I have seem stuff from EU nations having a CE mark but failing on almost every important directive (and when I find outrageous ones, I report them ;-).

(my biggest problem with compliance is the RoHS directive - I simply cannot use the awful lead-free solder, so will be forced to have boards built by contractors - I will however keep all active components socketed, so I can fit these myself - but if I ever go into production the first units I produce will be compliant on everything except RoHS - but in theory my selling any newly built electronic equipment which does not comply with RoHS is an offence that could result in a hefty fine. - The same applies to product which has not undergone EMC / ESD testing - but its easier to detect lead than it is to detect lack of testing.)

AFAICS there is no mandatory ESD immunity compliance requirement on general electronic products anywhere in the world except the EU (I am sure though that other countries will have adopted and enforce similar standards) - So Moog for example probably do not face possible penalty. Standards are certainly enforced on products for critical applications, or where UL certification is required.

To be honest, I dont know what the EU rules are on importing non-compliant products from other nations - I understood that all products imported required CE certification, and if this is true then the sale of some theremins in Europe is technically illegal.

Personally I applaud the EU position. Manufacturers should be forced to comply with good practice if they wish to sell into Europe IMO! - For all its faults, I strongly hope that our stupid government and the masses of brainwashed morons in this country dont manage to pull the UK out of the EU!

Fred.

"The European Union’s EMC Directive mandates ESD immunity testing for virtually all electrical and/or electronic products as a condition for obtaining the CE Mark before shipping to a member state of the European Union. "

http://www.technick.net/public/code/cp_dpage.php?aiocp_dp=guide_esd_006

http://snebulos.mit.edu/projects/reference/NASA-Generic/ANSI-ESD-S20-20.pdf

http://cds.linear.com/docs/en/quality/esdprotection.pdf