LM331 Ic frequency to voltage conversion problem

[anumwasim]

I made the circuit of LM331 for frequency to voltage conversion as mentioned in the data sheet. But the voltage doesn't change with frequency. Please help.

 

[Audioguru]

Your schematic drawing software creates a nightmare of wires all over the place! Also the grid lines are distracting.

You do not show an input frequency range.
Your 5V power supply is much less than the 15V shown in the datasheet.

 

[anumwasim]

Sorry about the wires. I tried this circuit at 15v but it won't work, however on the first page of the data sheet it says that it works on 5v. I basically have to apply variable frequency from 1hz to 10khz. which I did but the voltage won't change.

 

[Audioguru]

The circuit on the first page of the datasheet with the 5V supply is the opposite to your circuit. It is a voltage to frequency variable oscillator.
Look at your value for C1 at 100pF. It is 10,000 times too low and should be 1uF (use a plastic film type).

 

[anumwasim]

I did change the capacitance but it resulted in no result. I am not getting an output.
Please read the highlighted part. It says it works on a single 5v supply..

 

[Audioguru]

The sheet says it works with a 5V supply (when it is a voltage to frequency oscillator like the first schematic) but your circuit is the one that shows a 15V supply.
What is the output voltage that does not change? Does your voltmeter have a high input resistance?

 

[FvM]

Are you reporting a Proteus simulation or real circuit measurements? In the former case, how do you know that the Proteus model is working as f/V converter?

 

[anumwasim]

At 5 volts supply i get 3 volt and no ouput at 15 volt supply. i am measuring it on an oscilloscope in Proteus so its not a problem.

 

[anumwasim]

I am reporting Proteus simulation measurements. On Proteus it is not working like a frequency to voltage converter because the output should be DC but it is not. I copied this circuit from the datasheet of Lm331 so it should be right, right?

 

[Audioguru]

You showed a simulation which probably knows nothing about an LM331 IC.
You also did not show the frequency, amplitude and duration of the tone that you used. It should be shown on one of the 'scope channels.

Your "oscilloscope" does not show a line for 0V, does not show its voltage per division and does not show its timebase.

 

[anumwasim]

oh it edited out the voltage per division part...the frequency is 10k hz..amp 1 volt.. 50% duty cycle.. I can send you the circuit file of Proteus..

 

[anumwasim]

I really appreciate all your help. Thanks alot.

 

[jay1691]

hello all,
Can anyone give me spice model for LM331 ?
Thank you in advance.