Re: Frequency sensor cct for a power line...

On Thu, 01 Oct 2009 03:19:57 -0500, chulanga wrote:

On Wed, 30 Sep 2009 17:28:40 -0500, chulanga wrote:

Hi guys,
I want to find a Frequency detecting cct or a chip for 300V power
line. It is to be measured small fluctuations around 50Hz Domestic
Hope there are people to help me.. :)

There are approximately one bazzilion different ways to do this. Even
when you throw out the 99.44% of them that are pointless, that still
leaves you with a bazzilion different good ways to solve this problem.

Tell us what you really need, and maybe someone can help. High
precision? Quick acquisition? Low cost? Easily understood? Uses no
processor resources? Minimizes external components through clever use

processor resources? Sensitive to fast variations of frequency?
Insensitive to short-term changes? What?


Thanks for the reply ..
Ya,, followings are the specifications :- 1) sense 49.5Hz
2) Will be used in a 230V Electric power line 3) Quick response- within
abt 100mS.
4) low cost
5) It will be used in portable device 6) Simple
If you knw something similar to our requirements, pls be kind to
forword.. :)

I don't think you're going to find what you want, if for no other reason
than because it is both too easy and too hard. The too easy part is
actually figuring out the frequency of a sine wave; the too hard part is
going from your 220V line to a nice clean sine wave.

I _suspect_ that after you figure out a good way to sample the voltage of
the line across whatever galvanic barriers are between the line and your
device (this would be fairly easy if you are using a power transformer,
even an AC-out wall-wart) you should be thinking along the lines of a low-
pass filter to clean up the worst transients, a comparator, and the built-
in timer circuitry in the microprocessor that I hope you're using.