Need audio vco circuit

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I need a simple and cheap circuit for a voltage controlled oscillator
that will drive a small speaker with an audible tone.  The voltage
range will be 0-1V from across a 1K resistor in another circuit.
Thanks



Re: Need audio vco circuit


On 7 Mar 2005 08:08:23 -0800, the renowned "royalmp2001"

>I need a simple and cheap circuit for a voltage controlled oscillator
>that will drive a small speaker with an audible tone.  The voltage
>range will be 0-1V from across a 1K resistor in another circuit.
>Thanks

Assuming square wave or triangle will do you, check out the VCO
circuit on the LM324 datasheet. Can't get much cheaper/easier. If the
speaker is low impedance you'll need a buffer on the output, or if you
just need "audible", use a series resistor to knock the output current
down to single-digit mA.


Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
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Re: Need audio vco circuit



> I need a simple and cheap circuit for a voltage controlled oscillator
> that will drive a small speaker with an audible tone.  The voltage
> range will be 0-1V from across a 1K resistor in another circuit.
> Thanks
>
http://www.ee.washington.edu/stores/DataSheets/linear/lm566.pdf

that chip has been around all over.
check it out.



Re: Need audio vco circuit


>I need a simple and cheap circuit for a voltage controlled oscillator
>that will drive a small speaker with an audible tone.  The voltage
>range will be 0-1V from across a 1K resistor in another circuit.
>Thanks

How about a CD4046?


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Re: Need audio vco circuit


Sounds good, Ken...where can I find such a circuit?



Re: Need audio vco circuit


>
> Sounds good, Ken...where can I find such a circuit?

You design it.  The 555 has quite a bit if what you need, inside. It
has the threshold sensor and the discharge switch.  You add a flip
flop to the pulse output to get a square wave.  And you have to come
up with a variable current source to charge the capacitor that is
controlled by a second 555 oscillator to do the sweep.  Hence the name
of this group.  ;-)

--
John Popelish


Re: Need audio vco circuit


>Sounds good, Ken...where can I find such a circuit?
>

Please explain "find such a circuit" in this context.  Do you mean find a
CD4046?  Do you mean find an existing application?  Do you mean find a
schematic with part values?


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Re: Need audio vco circuit


sorry, Ken
I mean what does the schematic look like. I'm no designer.
Thanks



Re: Need audio vco circuit


>sorry, Ken
>I mean what does the schematic look like. I'm no designer.
>Thanks

Get a copy of the data sheet and app-notes for the CD4046 and read them,
ignoring the stuff about the phase detector and looking carefully at the
VCO section.
 

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Re: Need audio vco circuit


>
>>sorry, Ken
>>I mean what does the schematic look like. I'm no designer.
>>Thanks
>
>
> Get a copy of the data sheet and app-notes for the CD4046 and read them,
> ignoring the stuff about the phase detector and looking carefully at the
> VCO section.
>  
>

 See a photo of an interactive spreadsheet calculator for the 4046:
 
http://groups.yahoo.com/group/jallist/files/heliosstudios/4046CalcRevA0.4.png

 Perhaps I could make a Win32 executable equivalent with MASM32. Uggh, another
project. :)


-- "Rightousness is found within one's self, not in the demoralization or
subjigation of others." MCJ 200411


Re: Need audio vco circuit



>sorry, Ken
>I mean what does the schematic look like. I'm no designer.
>Thanks

Here's a practical circuit to get you started:
http://www.terrypin.dial.pipex.com/Images/4046VCO.gif

--
Terry Pinnell
Hobbyist, West Sussex, UK



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