Email: Password: Remember Me | Create Account (Free)

Back to Subject List

Old thread has been locked -- no new posts accepted in this thread
???
02/25/09 16:11
Read: times


 		 #162825 - Yes, 3.3V is right and works correctly
Responding to: ???'s previous message
Kai Klaas said:

1. In the scheme, is this 3.3V at the supply of 74LS02?



Yes, this 74LS02 uses 3.3V for the Rail

Kai Klaas said:


2. The speedometer is (very probably) always connected to the battery and the battery is only removed from the vehiclce when the vehicle isn't driving, so when no speed is to be measured at all. Maybe you can free this INT input somehow then?

Kai


No, the sensor toggles between 12V and GND, but the interrupt is set to edge trigger to watch for the negative signal transistion so I'm not stuck in a continual ISR routine. This is the hardware as it stands, no room or ability to change it.


One method I found is that using the 5Khz fixed reference, a log function is created as frequency of the signal drops, if I can find a way for the 8051 to use linear interpolation on that function, I might be able to keep everything as is, and have a working reliable solution.....

If anyone has a tip on how to do this, that would be very helpful.

As it stands, my testing in simulation shows this for counts.....if I could linearize this, it would be a done deal, here is the testing using the INT toggle at fixed frequencies and the next pulse count from the fixed 5KHz reference.

1MPH = 1344h
5MPH = 380h
10MPH = 1C0h
30MPH = 96h
60MPH = 4Ah
120MPH = 26h
150MPH = 1Dh
200MPH = 16h

Does anyone think that linear interpolation will solve this? Looks like a simple log to linear conversion, but is there a way to have the 8051 do this and then use the function result to a lookup table for fast conversion?

Any pointers would be great........and by the way, thanks to all thus far for taking the time to help me. This is a great learning part for me.

Regards,
Chris


List of 49 messages in thread
TopicAuthorDate
Tip for Speed sensor via External Interrupt            01/01/70 00:00      
   Fresh thoughts.            01/01/70 00:00      
      Try measuring time instead of count for slow pulse trains            01/01/70 00:00      
         The highest frequency would be            01/01/70 00:00      
            Once more - think time instead of frequency            01/01/70 00:00      
            Rough estimation...            01/01/70 00:00      
         On the teatering edge......            01/01/70 00:00      
            Is that not good enough?            01/01/70 00:00      
               I was having issues with that.....            01/01/70 00:00      
                  Did you read this post?            01/01/70 00:00      
                     I think that's the bullseye, I was forgetting....            01/01/70 00:00      
                     Yes, and your solution is in my code...perfect!            01/01/70 00:00      
                        Happy that it works            01/01/70 00:00      
                           I'm using this model.....at least            01/01/70 00:00      
                           I'm using this model.....at least            01/01/70 00:00      
                           Looks like I was blind to the obvious.            01/01/70 00:00      
                              All depends on the input scale            01/01/70 00:00      
                                 That will be the next step.......            01/01/70 00:00      
                                 Per,            01/01/70 00:00      
                                    Would this work for a Random() Seeding?            01/01/70 00:00      
                                       Thermal noise from a diode            01/01/70 00:00      
                        Bisection.            01/01/70 00:00      
                           I was a bit hasty ...            01/01/70 00:00      
   PLL ?            01/01/70 00:00      
      Stability            01/01/70 00:00      
         Yes, for a car            01/01/70 00:00      
            Are you sure?            01/01/70 00:00      
               your math is correct            01/01/70 00:00      
                  Ok, can you please explain...            01/01/70 00:00      
                     Should be minute not seconds, typo            01/01/70 00:00      
                        Two questions...            01/01/70 00:00      
                           Yes, 3.3V is right and works correctly            01/01/70 00:00      
                              Have you read...            01/01/70 00:00      
                                 In more detail...            01/01/70 00:00      
                                 It would take forever to go through all the combos            01/01/70 00:00      
                                    This is no log function, ...            01/01/70 00:00      
                                       This is my solution, and almost there            01/01/70 00:00      
                              do you read datasheets???            01/01/70 00:00      
                                 Yes/No            01/01/70 00:00      
                                    better perfomance if ...            01/01/70 00:00      
         The PLL approach isn't that hopeless...            01/01/70 00:00      
   period measurement            01/01/70 00:00      
      Here is an image of what I think you mean?            01/01/70 00:00      
         what derivative do you use?            01/01/70 00:00      
            I'm using the NXP LPC936            01/01/70 00:00      
         Your drawing is still in the frequency domain            01/01/70 00:00      
            Yes, you're correct, and I undestand, connecting...            01/01/70 00:00      
            Where I'm at and software recap            01/01/70 00:00      
               more step-by-step            01/01/70 00:00      

Back to Subject List