[sdiy] (Low) frequency to voltage conversion

[Steve Lenham]

On 26/03/2014 18:44, Justin Owen wrote:
> Has anyone got any experience with using off the shelf F/V chips like
> LM2907/LM2917/AD650/ADVFC32 with frequencies between approx. 1Hz and
> 0.001Hz?

0.001Hz? One cycle every 16.7 minutes?

Methinks any analogue solution is going to need some jolly large caps! 
And the ripple on the output will be fearsome.

I know not everyone has the skills/desire to do so, but (especially 
since you are only dealing with 50/50 squarewaves) a tiny 
microcontroller is surely the best solution. All it has to do is count 
clock cycles (appropriately divided down) while the input squarewave is 
high, then calculate/look up an appropriate output value based on the 
count it reaches. That value can be DAC'd or whatever, and the droop 
between updates will be zero.

Cheers,

Steve L.