How to make a Voltage Controlled Oscillator

Does the uC not have an internal timer/oscillator circuit? It's the best way to go:

Heheh, I recorded this song from an 8MHz uC, but the song file was written for 4MHz. Sounds a little strange, overclocked. The correctly formatted song file plays in tune at a reasonable tempo, of course.

I have the AVR code used for this player, if that's any help.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

They're upset because the government is increasing the legal retirement age by two years. Quite understandable, in my opinion. Widespread strikes upset the distribution of goods, especially fuel, around the country. The situation seems to be gradually returning to normal now.

Jeroen Belleman

Most healthy adults can hear upto at least 12kHz pure sinewave. Some younger children can hear nearly 20kHz. As a youngster I recall hearing an annoying whistle from the line flyback transformer on some TVs (presumably the ones with something loose). That is around 15k6Hz. I can still just about hear pipestrelle bats calls - though presumably only sidebands off their chirp since the fundamental is ~45kHz.

I had the opportunity to to test a moderate sized audience with a pure sine wave pulsed and the kiddies hands started going up at 18kHz last year. I could hear it at 14kHz and most adults were around 10-12kHz. A few elderly folk still couldn't hear 5kHz but by then it was getting annoyingly loud for the rest.

C8 is just the pianos highest note. Nothing special about that and most people can easily hear it. It won't sound much like a piano note though unless you include at least the third harmonic. There is something seriously wrong with your hearing if you cannot hear 4kHz.

I set my Theremin up to do 50Hz-10kHz which covers the range most useful for its ethereal style weird music. Linearising hand movement for logarithmic frequency control was a nightmare. The Dr Who theme is harder to play than it sounds as is Good Vibrations.

People may not hear higher frequencies distinctly, but that doesn't prevent other parts of the ear detecting the sharper rise time. You can squeeze intelligible speach over a very limited bandwidth, but it actually takes skill to get broadcast quality high fidelity audio right. UK DAB radio has failed in this respect at least for classical music.

Regards, Martin Brown

ote:

Do pay attention. The original poster - Cem Uzunoglu - asked for "the simplest VCO that can be done with off-the-shelf components". I went for the VCO in the 4046 - and mentioned the AD654 which is simpler, but less easily available (though Farnell still stocks it).

Rich Grise, being an idiot, suggested the 555, which can be made to work as a sort of VCO. When it was suggested that he had done this just to annoy me, his response clearly refers to the original request. Why Rich should think that getting a 555 to work as a VCO is "simple" escapes me - one can only imagine that he (like John Fields) finds it difficult to get to grips with new devices and finds it easier to get a familiar device to do what he wants as opposed to identifying a more suitable modern device and working out how to use that.

Jim Thompson's circuit for getting a 555 to act as a VCO calls for rather more external components than are required to get an AD654 to work.

-- Bill Sloman, Nijmegen

-- Bill Sloman, Nijmegen

Martin Brown:

Exactly. What is the frequency of the third armonic of C8?

16744 Hz, that, according to you, lies outside the range of most adults and is anyway rather near the Nyquist frequency of a CD.

--
Saluti

Page 13. You can use a faster single supply dual op-amp if you like.

With minor changes you can do this with 5 parts and it will cost less than 25 cents in moderate quantity:

1 dual op-amp 2 4- resistor networks (use two resistors in parallel for R/2) 1 2N7002 or similar 1 capacitor

If it's not obvious, the reference is the (single) power supply voltage.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Jeroen Belleman:

Is your opinion based on data you have about the number of people getting benefits and the number of people paying for it, and does this data takes in account that baby-boomers are about to retire?

Now that their President passed the law despite this senseless strike? :D

Could be a linguistic thing here but in English the second harmonic is

2f and the third is 3f or around 12k5Hz which is borderline for many adults and probably why the piano keyboard stops where it does.

According to you the alias from 16744Hz sampled at 44k01 for CD at

5376Hz is still above the range of human hearing. This is obvious nonsense unless you were a roadie for loud heavy metal rock bands or work in a boiler making shop.

Regards, Martin Brown

Martin Brown:

Right, I said "harmonic" and calculated the octave.

The point is that Cem would like to build a Moog-style synthesizer, and there is little reason to complicate the VCO in order to produce notes that are outside a piano keyboard. All the further shaping of the fundamental note he's going to produce is very likely to be useless, at such high frequiencies.

I'm not sure I understood what you mean.

--
Since you're pretty much 555 illiterate, that's certainly no surprise.

Clue: Pin 5

On a sunny day (Wed, 27 Oct 2010 11:58:16 +0200) it happened "F. Bertolazzi" wrote in :

One point of view on this is that if you payed taxes all your life for a guaranteed gov pension at say age X, and the gov than decides that it will only pay at X+n and you have to work n more years, that sounds like a breach of contract to me. Now we all know politicians promise, and that is their main business, but I can imagine the anger of some those people on the streets,

Of course this is only the beginning. After the devaluation of the US dollar, the subsequent decrease of exports to the US, more unrest will come. This is actually what the US wants, the destabilisation of Europe. So they can then sell more weapons. Of course US will also destabilise in the process, already the deficit is so big that it cannot be payed back, traders are buying bonds at 105%, betting on an interest raise... Gold is way up... War is coming.

Jan Panteltje:

guaranteed gov pension at say age X,

more years,

If a contract cannot be honoured because of "act of God", then the contract is void. The "act of God", in this case, is the doubling or tripling or even more of the life expectancy while retired.

the US, more unrest will come.

Most definitely, but not (only) because of a weak dollar.

Right. While Europeans are actively destabilizing Africa for selling their weapons.

It's a sad and miserable world the one in which paranoid live.

big that it cannot

raise...

Probably, but not because some Goldfinger decided it.

It's an inevitable outcome of keeping the unemployment rate at artificially low levels. Our politicians (pushed by us voters) did it, and now we have to pay it back. Or else.

Funny, when they did the exact same thing in the US, no one said a word of protest... Sad, isn't it!

PeterD:

Yes, it's sad that Europeans behave that stupidly, without taking example from the more responsible and sensible US citizens.

--- You say that facetiously, but it wasn't us that started two world wars.

Moreover, we've been the United States of America for 230 years or so and our system, in that scant time, has allowed us to become the most powerful nation on Earth.

Strange, but now that you've finally gotten around to following our example and are becoming the United States of Europe, you seem to think it's something you thought up and aren't following anyone's example!

--- JF

John Fields:

By no means.

Exactly.

Well, on this I have to disagree. When the US was formed the population was relatively homogeneous, no history, one language and one money. It's rather different from putting together different people with different historie.

Our model is more the USSR, and it shows.

--
Saluti

On a sunny day (Wed, 27 Oct 2010 14:26:03 +0200) it happened "F. Bertolazzi" wrote in :

Na, if you call GWBush and his clan of murders 'resposible' and 'sensible', then anything goes :-)

Unfamilar as I am with the 555 (along with steam engines and horse- driven wood-turning machinery), I relied on Jim Thompson's example of the 555 as a VCO. You haven't yet described him as an idiot vis-a-vis the 555 ....

Jim Thompson has claimed that it is the CMOS version of his diabolical biploar 4024/4044 VCO and phase detector (which I got to work back in

1972). It is certainly more modern (by a few years and an integrated circuit manufacturing technology) than the 555.

But it was explicitly designed for the job, and too specialised to be manufactured in large enough numbers to make it really cheap. Cem Uzunologlu doesn't seem to want to go into large scale production with his device, so it might make sense for him to spend more money on a specialised part which requires minimal design and development input.

Why?

But - as you have pointed out in other contexts - you've got to work out how to program the =B5C you've selected, which isn't always that simple.

-- Bill Sloman, Nijmegen

Sorry for the bad quoting

John Fields:

By no means.