displaying speed of wheels by using a LCD and a IR-photosensitive resistor

[waleedkk]

i've not been able for the appropriate alogrithim to calculate the speed of my wheels of my micromouse. i've actually had the idea of pasting a black tape on my white wheel and using a photo resistor to detect between the black and white and make it count.....
BUT i can't get the algorithim set in my mind ...
please some one help me.....

 

[BradtheRad]

One way is to time one revolution and take the reciprocal. I never figured out a feasible way to do this.

I ended up painting black stripes all around a cassette flywheel to gauge its speed variations.

The straightforward way is to count revolutions during a one second window. This will give you a usable value.

Reset the counter every second.

Or paint two stripes. Or use a 1/2 second window. Etc.
So that you get a usable figure.

You can count digitally.
Or you can use a charge bucket circuit whose output voltage is proportional to the frequency.

 

[andre_luis]

Precision can be increased painting multiple marks.

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