Frequenzy to voltage converter

I want to build this

https://www.circuitstoday.com/wp-content/uploads/2009/09/frequency-to-voltage-converter-circuit.png

Sometimes people in here have been against the circuits I have found and build so this time Im gonna ask before I build. Does this seem possible and to work?

Thanks

and 100 quistions will come later on

What is the range of input frequencies? What is your expected output? What is the purpose of the RC circuit on pin 7?

I dont know about pin 7

Input frequenze could be in quite a wide range sinse I can gear the motor down. But I would guess 200 - 800 rpm. That would be 3 hz - 13hz. I would be able to make those higher easily.
My output should be 0-5v

thanks in advance

Hi!!!

I have recently or should I say currently been working with a Frequency to Voltage convertor for a car tachometer project of mine...

I must recommend the LM2917 IC made by National Semiconductor.

The IC is designed for the purpose of F-V and will give you far better results than a 555 IC.

The datasheet has information on how to configure it based on a simple formula.

I recommend looking into it!!!

Enjoy!

use the LM2917, like suggested above. The price is cheap as well.

Hi Simon,

Your circuit implements a PWM which is controlled by the input frequency. The pulse width is detected by the output network (hence, mcneary's question about the output network) It can make a pretty good F/v converter, but you should understand how the pulse width is determined and how it is affected by the input frequency. You can look up the equations for a 555 based one-shot to understand the core circuit, and get simple equations for the pulse duration. There is lots and lots of good info online. It should be fairly easy to determine the optimum design for your frequency of interest. Basically, I think the period of the one-shot should be 50% of the frequency being measured. That period is set by R5 and C4. If you do the homework to understand the circuit, you'll learn alot. Good luck!

Ediot: Mcneary asked about the input network, not the output network. My bad. Anyway, you should make a good effort to understand the networks on both pin 7 and pin 3.

Agree,
this circuit can make a reasonable F/V converter. However, you must understand how it works and its limitations. For instance the R6*C5 time constant will dictate both the output ripple and the settling time.

Seems to me that there was an LM2917 F-V converter on the back of every U.S.-made 5-1/4" disk drive. You should be able to find all kinds of freebies.

The reason I asked about the purpose of R5 and C4 on pin 7 is because they do nothing.