voltage controlled

Thread Starter

enjoykilian

Joined May 15, 2021
79
hello i am wondering how that i can make this circuit below voltage controlled
1663695870758.png
the potentiometer controls the frequency
 

Alec_t

Joined Sep 17, 2013
13,153
The circuit you show probably isn't the best starting point for a VCO.
What frequency range are you hoping to get?
Is a linear relationship between control-voltage and frequency important? If so, what is the linearity tolerance?
What supply voltage?
 

DickCappels

Joined Aug 21, 2008
9,319
Just a note, the LM124 is similar to the LM324 but intended for a different market. For the most part they are interchangeable. The LM358 is a dual opamp of the same design and the LM324.

I think the circuit to which bertus linked is a pretty nice circuit up through audio frequencies, and beyond for faster opamps, and is nearly fool-proof.

The choice of transistor is not critical. 2N3904, 2N4401, 2N2222 -quite flexible.
 

WBahn

Joined Mar 31, 2012
27,411
Questions of whether your circuit is the best place to start or not aside, the potentiometer in that circuit doesn't control anything. The wiper is unconnected, which means that the resistance between the two connected leads is a fixed 100kΩ regardless of where the wiper is positioned.
 
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Alec_t

Joined Sep 17, 2013
13,153
i already have a schematic
If it's the one in post #1 then you could replace the pot with a CdS cell and illuminate the cell with a LED driven by a variable control voltage. It's sluggish, not an ideal approach and won't give a linear voltage-v-frequency response (I don't know if that's what you want, because you haven't answered the questions in post #3
Why are you reluctant to use the post #2 (or #7) circuit?
 
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Thread Starter

enjoykilian

Joined May 15, 2021
79
The circuit you show probably isn't the best starting point for a VCO.
What frequency range are you hoping to get?
Is a linear relationship between control-voltage and frequency important? If so, what is the linearity tolerance?
What supply voltage?
around 20-20kHz +-15V no its not important
 
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