I want to measure RPM of a motor. For this, I am planning to put an assembly where an IR LED facing with IR sensor under line of sight. With every rotation, the line will be cut once - and hence the IR sensor LED.
Where I am stuck at is that once I get pulse of the signal, how do I count these pulses to make the Frequency (i.e. rpm) estimate? Is there a simple way to do it? I can use Oscilloscope - but I don't have easy to access to one. I have seen that most entry level multimeters don't have frequency measurement.
Also, unlike this question, I would also refrain from involving microprocessor based counting on this. [Basically this is a simple hobby project for high school student]
So is there a good and easy way to do it? Is there any completely alternative way to do this?
PS: The motor speed will typically be between 0-500 rpm not beyond. EDIT2: I want this to use a tool for physics experiments - so I need it as a quick indicator of rpm.