Need audio vco circuit

[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

 

[Spehro Pefhany]

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

 

[Jamie]

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.

 

[Ken Smith]

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?

 

[royalmp2001]

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

 

[John Popelish]

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. ;-)

 

[Ken Smith]

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?

 

[royalmp2001]

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

 

[Ken Smith]

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.

 

[Mark Jones]

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

 

[Terry Pinnell]

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