William Chops" Westfield" wrote:
> I dunno.  Asking for help on a Freq to Voltage converter that is part
> of a PROJECT to run a motor at constant speed seems to me to be a LOT
> different than having a homework problem that says "design a Freq to
> Voltage converter without magic chips" and posting that exact question
> to the net.  It's the difference between asking for help and asking
> for just the answer...

I didn't get the feeling that he was asking for the solution on a silver
platter, but I did think it was important to establish whether this was some
kind of assignment where the purpose was to learn about the solution.  Since
it is, hopefully nobody here will just tell him the answer or design a
circuit for him.  I have no problem leading him in the right direction,
however, and giving him general ideas how to solve the problem.

As for the solution, I see that a bunch of people gave the standard knee
jerk answer of low pass filtering a one-shot output.  While that is a valid
approach, it is a bit cumbersome to do just in analog electronics as his
assignment apparently dictates.  Then there is the issue of response time
versus ripple, which we don't have enough information to decide about, but
it will most likely need to be carefully considered.

I think there are easier ways to do this in analog considering a one-shot
chip is not allowed.  Think of creating a signal proportional to the time
between pulses instead of duty cycle.  No, I'm not going to spell out the
answer.  But if the OP comes back, answers the questions asked whether he
thinks they matter or not, and shows he's done some thinking I'm willing to
continue to give him clues to prod him into coming up with the idea himself.


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