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Per Westermark
03/01/12 06:57
Read: 1003 times
Sweden


 
#186326 - 10-700 Hz is expected output frequency - not input frequency
Responding to: Richard Erlacher's previous message
Richard. You have now several posts where you talk about 10-700Hz as input frequency. It isn't. It's the intended output frequency.

Anyway - unless there are extreme needs (which does not seem to be the case), the problem can be solved quite easily in a large number of ways in software. Both based on the input signal as digital pulses and the input signal as a sine wave with ability to pick up phase of signal using an 8-bit ADC input.

A software-based solution can have all parameters modified almost instantly. A hardware-based solution requires changes to component values.

In the end, it's just a question of how fast the output frequency should change for a change of the input frequency, and how exact it should match a 10-times frequency increase. And if an integration over say 10 minutes should show exactly 10 times the number of pulses, requiring the algorithm to keep an error component accumulating the difference between nominal and actual behaviour and trying to zero that error component.

If the design allows a 1 second delay between input and output, the problem suddenly became trivial. Count number of pulses during second n. Emit 10 times as many pulses during second n+1. Almost no code at all involved. With a sine wave input to an ADC, very trivial code can manage almost perfect behaviour with maybe 0.2-0.3 second response lag. The lag mainly caused by a need for a low-pass filtering of the input to make sure noise on the signal don't fool the system into making a huge jump in output frequency.

By the way - a diesel engine can change RPM quite fast. It's more a question of what kind of diesel engine. It makes a big difference if it's an engine for a truck or for a premium car.

"yet I don't see the 10x multiplier"

But you don't agree with the information in the original post? That the sensor produces a frequency that is 0.1 times the frequency the RPM meter expects? For such a condition, there are basically just three options. Frequency-scale the signal. Get a different tachometer. Or get a different RPM meter. Keeping tachometer and RPM display, that 10x multiplier is very much visible in the signal chain.

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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