How to make a Voltage Controlled Oscillator - Page 7

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Re: How to make a Voltage Controlled Oscillator
Quoted text here. Click to load it

No need. I've got a bunch already that cover almost all of the screw
heads that come into the house - slotted, Philips, Pozidrive and the
weird three-lobed thing that drives the self-tapping screws that hold
the leaf-blower together.

In any event the "tools" that Jim was talking about were software -
things like PSpice and Hi-Lo, to confine the discussion to the ones
that you might have heard about.

--
Bill Sloman, Nijmegen

Re: How to make a Voltage Controlled Oscillator
Quoted text here. Click to load it
e.net> wrote:
Quoted text here. Click to load it

But since you don't seem to be as familiar with anything more modern,
you judge it to be the "right" choice in a lot of cases where less
biassed designers would come up with something different, better, and
sometimes even cheaper.

Quoted text here. Click to load it

That was your interpretation. The 4046 is distinctly more modern in
the sense that it was designed to handle a specific job, where the 555
is a timing element tied to a switching transistor - a jack of all
trades and a master of none.

Quoted text here. Click to load it

You do have your obvious prejudices.

Quoted text here. Click to load it

Exactly right - though the 555 is more like the Chinese version of the
Swiss army knife, made with soft steel that barely cuts butter.

Quoted text here. Click to load it

He'd like to be doing assembly and test, which is why he asked us for
a design. Sadly, the designs we can give are never going to exactly
adapted to solve his particular problem, so he is stuck with at least
a measure of design and development.

Quoted text here. Click to load it

To solve the problem as Jim understands it. Nobody who posts a problem
here gives enough background detail to let anybody design a solution
that is going to be perfectly adapted to solving the problem that OP
actually needs solved. As you should know, most customers don't
appreciate the exact nature of the problem they are facing, and what
they want is rarely exaclty what they actually need.

Quoted text here. Click to load it

Not a problem. I've contemplated doing it a couple of times, but the
motivating circumstances changed before I'd got around to spending the
money. I've now got a Farnell account - that I've never actually used
- from one of those episodes.

But there is a price attached to buying the tools and investing the
effort to get them to do what you want.

--
Bill Sloman, Nijmegen


Re: How to make a Voltage Controlled Oscillator
On Wed, 27 Oct 2010 05:55:58 -0500, John Fields

Quoted text here. Click to load it
[snip]
Quoted text here. Click to load it

Slowman probably has never heard of the MC4024 (and its descendants),
that I designed ~45 years ago.
        
                                        ...Jim Thompson
--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
We've slightly trimmed the long signature. Click to see the full one.
Re: How to make a Voltage Controlled Oscillator
On Oct 27, 7:39A0%pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:
Quoted text here. Click to load it

Jim should remember that I not only knew about it but got it to work
in a system I put togehter back in 1972. I didn't think much of the
MC4024 or the MC4044 by the time I'd managed to get them to do what I
wanted - the bipolar process that Jim was stuck with didn't do him any
favours - but I certainly know about those chips, and have mentioned
this here from time to time.

--
Bill Sloman, Nijmegen

Re: How to make a Voltage Controlled Oscillator

Quoted text here. Click to load it

Like this...

http://analog-innovations.com/SED/LM555-VCO.pdf

Add OpAmps to the current mirror turn-arounds to improve headroom and
get more tuning range.

Square-wave?  Run twice as fast, then divide-by-2 with a D-Flop.
        
                                        ...Jim Thompson
--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
We've slightly trimmed the long signature. Click to see the full one.
Re: How to make a Voltage Controlled Oscillator
On 26 Oct 2010 02:16:16 GMT, the renowned Cem Uzunoglu

Quoted text here. Click to load it

http://www.national.com/ds/LM/LM124.pdf

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"
snipped-for-privacy@interlog.com             Info for manufacturers: http://www.trexon.com
We've slightly trimmed the long signature. Click to see the full one.
Re: How to make a Voltage Controlled Oscillator

Quoted text here. Click to load it

If you need a linear sweep from 20 Hz to 20 kHz, the traditional
approach would be to use a 100 kHz crystal oscillator and a VCO with a
tuning range of 100.020 kHz to 120.000 kHz and mix those two
frequencies down and do some low pass filtering.

A more modern approach would be to use a simple processor (PIC etc.)
with 32768 Hz interrupt rate (watch crystal) and using the NCO
principle, generate any frequency between 0 and 16 kHz.


Re: How to make a Voltage Controlled Oscillator

Quoted text here. Click to load it

What is special about that interrupt rate?


Re: How to make a Voltage Controlled Oscillator
Cem Uzunoglu:

Quoted text here. Click to load it

The crystal is cheap and covers the audible frequency just enough.

Google  "numerically controlled oscillator".

With NCO you will also be able, using much more of the otherwise unused
computational resources of the processor and a D/A, to approximate a
sinusoid or any arbitrary waveform (the higher the frequency, the lower the
resolution).

Re: How to make a Voltage Controlled Oscillator
Quoted text here. Click to load it
"The Journey is the reward"
Quoted text here. Click to load it

I was going to suggest this type of circuit, but it seemed to
complicated.  One 'gotcha' to look out for is the supply reference
that Spehro mentioned.  Variation in the supply voltage causes a
variation in the frequency.  (I was biten by that.)

George H.

Site Timeline