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design | [?] Audio VCO design


There are 21 messages in this thread.

You are currently looking at messages 1 to 10.

[?] Audio VCO design - David Chapman - 2009-11-20 04:39:00

   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

-- 
David C.Chapman - (d...@minda.co.uk)
--------------------------------------------------------------------------

Re: [?] Audio VCO design - Holloway,Graham (UK) - 2009-11-20 06:34:00

"David Chapman" <d...@minda.co.uk> wrote in message 
news:DDdWWuJ6OmBLFw+u...@chassis.demon.co.uk...
>
>   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
>
> -- 
> David C.Chapman - (d...@minda.co.uk)
> --------------------------------------------------------------------------

David

Don't use the 4046, unles you are prepared to calibrate each one. I found 
3:1 variations between parts from different suppliers, i.e. frequency vs. 
volts.

regards
Graham H 



Re: [?] Audio VCO design - John Fields - 2009-11-20 09:11:00

On Fri, 20 Nov 2009 09:39:06 +0000, David Chapman <d...@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

---
View in courier:
.                                VCC
.                                 |
.                     +-----------|---------+  
.                     |           |8        |  
.                    [Rt]    +----+----+    |
.VC>--------+         |      |_  Vcc   |    |
.           |         +---7-O|D      VC|    | 
.         [LED]-->  [LDR]    |        _|    |
.           |         +----6-|TH      R|O-4-+ 
.           |         |      |__       |                   
.           |         +---2-O|TR    OUT|-3----->OUT       
.          [R]        |      |   GND   |                     
.           |        [Ct]    +----+----+   
.           |         |      7555 |1     
.GND>-------+---------+-----------+

or:


.                     +--------[Ct]--------+
.                     |                    |
.                     |   | \  HC04  | \   |
.Vc>---[R]--+         +---|  >O--+--O|  >--+-->OUT
.           |         |   | /    |   | /
.         [LED]---> [LDR]        |      
.           |         |          |
.GND>-------+         +---[R]----+


The LED/LDR combo or an incandescent/LDR combo is available as a single
device called a "Vactrol":


http://www.google.com/search?q=Vactrol&btnG=Search&hl=en&rlz=1T4GFRC_en&sa=2

JF 

Re: [?] Audio VCO design - Phil Hobbs - 2009-11-20 09:13:00

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.
>
> TIA - Dave
>

The old metal gate 4046 has a much wider VCO range than the HC version, 
which craps out at low control voltages, so that's good.  The frequency 
tolerance is around +-50%, however, so you might wind up with 75 Hz to 6 
kHz or 25 Hz to 2 kHz, which might matter to you.

I'd either nudge the frequency specs up a bit to accommodate that 
tolerance, or if I wanted something more accurate, use a BJT diff pair 
to provide a charging current to a cap and a little comparator with 
well-defined hysteresis to reset it.  That way you get a nearly 
exponential tuning curve, which is a good match to human hearing, and a 
much more dependable frequency range.  If you're feeling posh, you could 
use an LM13700 and a few Rs and Cs for the whole job.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

Re: [?] Audio VCO design - John Larkin - 2009-11-20 11:38:00

On Fri, 20 Nov 2009 09:39:06 +0000, David Chapman <d...@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


http://www.analog.com/en/analog-to-digital-converters/voltage-to-frequency-converters/products/index.html

http://focus.ti.com/lit/ds/sbvs023/sbvs023.pdf

If you want a nicer sound than a square wave, you can generate a
multiple of the desired frequency and run it through some sort of
simple sine shaper.

John


Re: [?] Audio VCO design - Rich Grise - 2009-11-20 16:25:00

On Fri, 20 Nov 2009 09:39:06 +0000, 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.
> 
I'll probably get pilloried for this, but it sounds like the app cries
out for a 555 or 7555. :-)

You might have to scale the tuning voltage a bit.

Good Luck!
Rich


Re: Audio VCO design - whit3rd - 2009-11-20 17:14:00

On Nov 20, 1:39 am, David Chapman <d...@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.

Re: [?] Audio VCO design - Jim Thompson - 2009-11-20 17:48:00

On Fri, 20 Nov 2009 09:39:06 +0000, David Chapman <d...@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

Re: [?] Audio VCO design - Joerg - 2009-11-20 18:10:00

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.

Re: [?] Audio VCO design - Spehro Pefhany - 2009-11-20 18:13:00

On Fri, 20 Nov 2009 09:39:06 +0000, the renowned David Chapman
<d...@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"
s...@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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