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[on:]

I have this sensor:

http://www.miniinthebox.com/smart-car-to-avoid-the-obstacle-sensor-infrared-sensor-photoelectric-switch-201211270080034_p480362.html

I want to measure the RPM of a diesel engine in range 200..3000 RPM
I have connected the signal line of the sensor to pin 2 (interrupt 0) on the UNO.
With a simple sketch i'm able to read the pulses, but, here's the problem:

A pulse can trigger anything from 1 up to 9 interrupts!
So I presume the signal is not clean (i don't have an oscilloscope to check)
I have tried some software debouncing tactics, but with no luck (or the deboucing is too slow)

Can i clean up the signal with a schmitt trigger circuit?
Will it be fast enough?

Will a simple solution with a 4093 NAND schmitt trigger IC work, like here? :

http://yogibotics.blogspot.com.au/

..or do I also need "analog smoothing" first, and if so, can someone give me a link to such a
circuit, cause i'm not a real electronics expert..
Thanks

[Reply #1 on:]

Can you post a picture of how you have installed that sensor to a diesel engine to get RPMs? In my opinion it's the wrong sensor for that task.

A pulse can trigger anything from 1 up to 9 interrupts!

How do you know that one pulse generates multiple interrupts without a scope? How do you check that?