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Electronics => Electronics => Topic started by: jorj on August 20, 2009, 08:47:18 PM

Title: Frequency
Post by: jorj on August 20, 2009, 08:47:18 PM

I have in the input of the system 60 HZ
and I want that the output of the system will be 25 HZ
How can I do this ?

Title: Re: Frequency
Post by: chelmi on August 21, 2009, 09:27:24 AM

not enough details...

What kind of signal are you talking about ? AC? DC? analog? digital?

Title: Re: Frequency
Post by: benji on August 21, 2009, 01:32:12 PM

a frequency converter,, still the question isnt clear

Title: Re: Frequency
Post by: jorj on August 21, 2009, 01:50:08 PM

AC + analog

Title: Re: Frequency
Post by: Soeren on August 21, 2009, 03:45:22 PM

Hi,

Quote from: jorj on August 20, 2009, 08:47:18 PM

I have in the input of the system 60 HZ
and I want that the output of the system will be 25 HZ
How can I do this ?

If it's signal levels, the usual way is with a Phase Locked Loop (PLL) and a couple of dividers (which may be part of the PLL chip). you simply divide the input signal (the 60 Hz) by 12 to get 5 Hz and divide the output of an oscillator (controlled by the PLL's error magnitude) by 5.
Both these signals is compared in the PLL and when the two are equal, the output of the oscillator will be 25 Hz. Any deviation will adjust the oscillator up or down, keeping the output 5/12th of the input frequency.

That said, if you just need 25 Hz out, why bother with the 60 Hz at all?
An oscillator controlled by a X-tal divided down will be very precise.
Btw. What precision is needed?