Prev: Fine pitch M30x2.0 nut source?
Next: day shot to hell
From: whit3rd on 20 Nov 2009 17:14
On Nov 20, 1:39 am, David Chapman <d...(a)minda.co.uk> wrote:
>    As part of a larger system, I need to design and build an audio VCO
> which will produce tones ranging from around 50Hz to 4KHz or so when the
> applied DC input voltage changes from 0.5volts to 2.5volts.

>    I'm considering using the CMOS 4046 PLL IC,

The thresholds in a '4046 (CMOS) are variable unit-to-unit, some
better precision can be had with a linear design; I'm thinking
of XR2206, LM331, and similar chips. The basic scheme is to
use the voltage input to program tracking current source + sink
elements, onto an integrator-connected amplifier into a
comparator with suitable hysteresis. Analog switches, diode
switches, current mirrors, or transconductance amplifiers are
the key components.
From: Jim Thompson on 20 Nov 2009 17:48
On Fri, 20 Nov 2009 09:39:06 +0000, David Chapman <dave(a)minda.co.uk>
wrote:

>
> As part of a larger system, I need to design and build an audio VCO
>which will produce tones ranging from around 50Hz to 4KHz or so when the
>applied DC input voltage changes from 0.5volts to 2.5volts.
> This will be used simply as a tuning aid for visually impaired users
>so the actual voltage/frequency relationship, and waveform produced, is
>not at all critical. Supply voltage of the VCO can be in the range 3.3v
>- 5v DC.
>
> I'm considering using the CMOS 4046 PLL IC, but wonder if anyone in
>this NG has any better suggestions to offer. FWIW, price is not the most
>important consideration.
>
> Any suggestions will be much appreciated.
>
> TIA - Dave

That 80:1 tuning range is pretty nasty. Do you need that in one swell
foop, or can you use some form of ranging.?

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I once said, "We will bury you," and I got into trouble with it.
Of course we will not bury you with a shovel.
Your own working class will bury you. - Nikita Khrushchev
From: Joerg on 20 Nov 2009 18:10
David Chapman wrote:
>
> As part of a larger system, I need to design and build an audio VCO
> which will produce tones ranging from around 50Hz to 4KHz or so when the
> applied DC input voltage changes from 0.5volts to 2.5volts.
> This will be used simply as a tuning aid for visually impaired users
> so the actual voltage/frequency relationship, and waveform produced, is
> not at all critical. Supply voltage of the VCO can be in the range 3.3v
> - 5v DC.
>
> I'm considering using the CMOS 4046 PLL IC, but wonder if anyone in
> this NG has any better suggestions to offer. FWIW, price is not the most
> important consideration.
>
> Any suggestions will be much appreciated.
>

The LM331 can do that, is nicely linear but you'd have to add the proper
control voltage offset so you get the range you want:

http://www.national.com/ds/LM/LM231.pdf

However, check whether supply voltage and power consumption fit your
requirements. Also, only available in DIP package.

A really slick and precise solution is a micro controller with AD
converter in there. The MSP430F2003 would be a good candidate and for
the basic function you'd need almost no external parts other than a
decoupling capacitor. Feed you control voltage to its built-in AD
converter, digitally offset and scale its output to whatever you need
and let the output set the overflow register of the internal timer. The
timer output gets piped to a port pin and, voila, there is your output
frequency. Even without any external crystal and just using the internal
digitally controlled oscillator (DCO) the precision would be in the
single digit percent. TI has super-cheap development kits for that series.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
From: Spehro Pefhany on 20 Nov 2009 18:13
On Fri, 20 Nov 2009 09:39:06 +0000, the renowned David Chapman
<dave(a)minda.co.uk> wrote:

>
> As part of a larger system, I need to design and build an audio VCO
>which will produce tones ranging from around 50Hz to 4KHz or so when the
>applied DC input voltage changes from 0.5volts to 2.5volts.
> This will be used simply as a tuning aid for visually impaired users
>so the actual voltage/frequency relationship, and waveform produced, is
>not at all critical. Supply voltage of the VCO can be in the range 3.3v
>- 5v DC.
>
> I'm considering using the CMOS 4046 PLL IC, but wonder if anyone in
>this NG has any better suggestions to offer. FWIW, price is not the most
>important consideration.
>
> Any suggestions will be much appreciated.
>
> TIA - Dave

If you don't mind a linear 50mV-4V for 50Hz-4kHz, it's pretty easy to
do this with a couple of opamps (or an op-amp and a comparator) and a
transistor (BJT, MOSFET or analog switch). You set one amplifier up as
a +/- integrator, output goes to a comparator with hysteresis which
controls the +/- switching. You get a triangle wave and a square wave
output.



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff(a)interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
From: Jan Panteltje on 20 Nov 2009 18:24
On a sunny day (Fri, 20 Nov 2009 18:13:51 -0500) it happened Spehro Pefhany
<speffSNIP(a)interlogDOTyou.knowwhat> wrote in
<df8eg5d5i3reaet7sjh6b5jgbh75h7ac3e(a)4ax.com>:

>On Fri, 20 Nov 2009 09:39:06 +0000, the renowned David Chapman
><dave(a)minda.co.uk> wrote:
>
>>
>> As part of a larger system, I need to design and build an audio VCO
>>which will produce tones ranging from around 50Hz to 4KHz or so when the
>>applied DC input voltage changes from 0.5volts to 2.5volts.
>> This will be used simply as a tuning aid for visually impaired users
>>so the actual voltage/frequency relationship, and waveform produced, is
>>not at all critical. Supply voltage of the VCO can be in the range 3.3v
>>- 5v DC.
>>
>> I'm considering using the CMOS 4046 PLL IC, but wonder if anyone in
>>this NG has any better suggestions to offer. FWIW, price is not the most
>>important consideration.
>>
>> Any suggestions will be much appreciated.
>>
>> TIA - Dave
>
>If you don't mind a linear 50mV-4V for 50Hz-4kHz, it's pretty easy to
>do this with a couple of opamps (or an op-amp and a comparator) and a
>transistor (BJT, MOSFET or analog switch). You set one amplifier up as
>a +/- integrator, output goes to a comparator with hysteresis which
>controls the +/- switching. You get a triangle wave and a square wave
>output.
>
>
>
>Best regards,
>Spehro Pefhany

OK, my turn...
X MHz xtal, X + a bit MHz VCO (varicap), dual gate MOSFET mixer, lowpass.
Can make a very wide range.
But I would use the 4046 too.
First  |  Prev  |  Next  |  Last
Pages: 1 2 3 4
Prev: Fine pitch M30x2.0 nut source?
Next: day shot to hell