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Hi all, need some help here, as i'm new to uc i have a few problems of how to use it properly, i'm capturing speed sensor signal using uc C167, the signal operates between 0 to 135Hz max, how i can set the prescaler of the uc to match the capture signal so that i could take the measurement? the signal is a digital pulse (50-50 duty cycle), and what algorithm i need to convert the measurements to mph?? thanks to all.....
I don't know where you have your sensor, but if it generates one pulse for each wheel revolution, then each pulse represents a traveled distance wich follows from the circumference of the wheel.
And speed is the amount of traveled distance in a specific time space.
That means that your speed is a constant multiplied by the number of pulses you get every second. Your initial formula may contain a number of constants - one for wheel diameter or wheel radius or wheel circumference. Another for number of pulses/second. Yet another to convert from speed/second to speed/hour. But all these constants can be combined.
Your job is to calibrate your system by finding out how the value of that constant. The next step is to express this in a way your processor can handle. It will be trivial if you can afford to use floating point numbers. But it can be solved just as well (or normally better as in smaller and faster) with integer arithmetic.
yer the speed sensor is attached to the rear wheel, the wheel size is 10inch. I measured its operating frequency which is 0 to 135Hz representing 0 to 60mph. I think I'm getting closer just to work out the basic maths
The sentence "Another for number of pulses/second." should have been "Another for the number of pulses/wheel rotation".
ok....so i can also obtain the rpm as well as speed, i just checked the speed sensor results i had obtained. It seems to be depending on frequency rather than number of pulses. It generates a duty cycle and from that, 10Hz may represent 4mph....along that line..
Obviously, you can't get anywhere until you understand precisely what the output from your sensor actually means!
What does its Datasheet say?
Number of pulses = Distance. Number of pulses/second = Frequency = Speed
Number of pulses/second => RPM of wheel, not RPM of engine