I need to design a frequency to voltage converter and I found this circuit on internet:
I removed the resistor R6 and the capacitor C5 because what I need is the PWM output it gives on the 555 timer. I have run a simulation and it seems to work pretty nice, where the output gives a PWM with 50% of the duty cycle on the lower frequency and almost 100% of duty cycle on the higher frequency of the input range. However, it is configured to work in a range if frequencies different from the one I need, and I don't know exactly what should I change because I have never seen such a 555 timer configuration. I guess it has to be related with R4, R5, C2 or C4 but I'm not really sure because the configuration I used before was with the pin 2 connected to pin 7, not 6.
I hope anyone can help me with changing the range of input frequencies that this circuit can measure. More precisely, what I need is a range that goes from 1Hz to 2Hz on the input, to get 50% to 100% of duty cycle on the output. If anyone knows any other circuit or alternative to do such conversion from frequency to voltage I would appreciate it too!