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Mahmood Elnasser
02/29/12 14:45
Read: 981 times
Sacramento
USA


 
#186300 - answers
Responding to: Richard Erlacher's previous message
Richard Erlacher said:

What, exactly, is it that you find boring about using a simple, though long-established method for solving this relatively trivial problem? A PLL with wide capture range can easily deal with this problem, and, as others have already stated, it only takes a coupld of IC's and a few cheap passives requiring perhaps 3 square centimeters of PCB space. It can even be done with one CMOS IC, e.g. one of the MC14515x or 14517x series frequency synthesizers.

You are right, Maybe that is the classical approach, but it is interesting doing it with MCU. I did it in a simple way to use a timer with 16x prescale to count input frequency, once finished this value is transferred to 1x prescale timer to count down, this way I get o/p frequency 16* input frequency.

I previously mentioned rate multipliers, e.g. 7497 or 74167, or CD4089. If they are too costly (the CD4089 costs $0.52US, IIRC) you can probably replicate all their functions in firmware, since you're operating at a snail's pace frequency.
will look into that.

You haven't really stated what your ultimate goal is. Do you wish to control/adjust the operating speed of the motor, or just display its rate?

no it is just for monitoring rpm of engine.
Mahmood





List of 52 messages in thread
TopicAuthorDate
frequency multiplier x 10      Mahmood Elnasser      02/20/12 14:29      
   You need some specs first.      Michael Karas      02/20/12 19:56      
      and even more questions for your tutor        Jim Granville      02/21/12 12:42      
   Analog solution...      Kai Klaas      02/21/12 05:49      
      Input wave form      Per Westermark      02/21/12 06:09      
      Too Bad...      Michael Karas      02/21/12 06:16      
   have you considered a "rate multiplier"?      Richard Erlacher      02/21/12 08:18      
   PCA?      Erik Malund      02/21/12 12:51      
      PCA Yes      Michael Karas      02/21/12 15:38      
   Update      Mahmood Elnasser      02/22/12 00:43      
      2 i.c.s plus 6 R, C      David Prentice      02/22/12 03:03      
      4046 / 7490      Michael Karas      02/22/12 03:36      
      I put my bet in the digital solution      Daniel Contarino      02/22/12 13:33      
         digital solution      Mahmood Elnasser      02/22/12 13:46      
            MCU / CPLD      Michael Karas      02/22/12 13:57      
            Simple digital solution...      Kai Klaas      02/23/12 05:59      
               Engine too fast      Mahmood Elnasser      02/23/12 06:48      
                  it could be made simpler        Jim Granville      02/29/12 19:22      
                     cute      Erik Malund      03/01/12 08:07      
               OR      Erik Malund      02/23/12 06:52      
   Frequency Multipiler      Satish S Munot      02/29/12 10:06      
      Motivation?      Per Westermark      02/29/12 10:14      
         Motivation ?????????      Satish S Munot      02/29/12 10:55      
            Motives      Per Westermark      02/29/12 11:24      
               OK      Satish S Munot      02/29/12 12:40      
                  motivation guess      Maarten Brock      03/02/12 01:14      
                     I had the same feeling...      Kai Klaas      03/02/12 08:25      
                        and if you looked at any of his previous posts ...      Richard Erlacher      03/02/12 20:02      
   A number of thins concern me ...      Richard Erlacher      02/29/12 12:31      
      answers      Mahmood Elnasser      02/29/12 14:45      
      Boring...      Kai Klaas      02/29/12 16:05      
         And in this case...      Daniel Contarino      02/29/12 18:11      
            Yes ... but ...      Richard Erlacher      02/29/12 20:12      
               Making what you need, from what you can get..      Jim Granville      02/29/12 22:14      
                  slogans      Satish S Munot      02/29/12 23:59      
                  Is that what the display needs?      Richard Erlacher      03/01/12 06:38      
                     10-700 Hz is expected output frequency - not input frequency      Per Westermark      03/01/12 06:57      
                        I did make one mistake      Richard Erlacher      03/01/12 07:18      
                           old rpm analog (or digital) display is what they have      Jim Granville      03/01/12 12:01      
                              bursts...      Kai Klaas      03/01/12 13:19      
                                 See LM2917 for ancient tacho examples      Jim Granville      03/01/12 13:40      
   PLL      Mahmood Elnasser      03/18/12 06:57      
   More detail?      Richard Erlacher      03/18/12 12:30      
      Yes, more details, please...      Kai Klaas      03/18/12 12:43      
         Details      Mahmood Elnasser      03/31/12 00:24      
            This can have to do ...      Kai Klaas      03/31/12 09:25      
               sharp edges      Mahmood Elnasser      04/01/12 03:59      
                  Which phase-detector?      Richard Erlacher      04/01/12 08:21      
               re: this can have      Andy Peters      04/02/12 10:49      
                  What I would do...        Kai Klaas      04/03/12 07:40      
                     Very Low Frequency      Mahmood Elnasser      04/19/12 15:30      
                        Give it a try...      Kai Klaas      04/19/12 17:14      

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