On 03/04/2011 06:55, geetansh arora wrote:
> i m trying to measure speed of objects using LDR/photodiode connected to
> interupt pin n a light beam is focussed on it. when a object passes d lig=
ht
> beam,d voltage at that pin will change but only for some milli seconds n =
i
> want to calculate that time.
> plz help.
> i think this time i m more clear abt my problem n u guys will be able to
> help me.
> thank you

If it is milliseconds (last time it was microseconds?) then it's a=20
little easier. The advice is pretty much the same though, check out the=20
CCP peripheral in the datasheet, this is probably the simplest way.=20
Alternatives are things like using the timers, or counting cycles in a=20
loop. All basically involve detecting a change of voltage on a pin, then=20
counting until it changes again.
I would give it a try and see how you go, then if you run into problems=20
post your code and we can help more.

--=20
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