Tachometer

Hello,

I'm fairly new to electronics, no formal education but i have a basic understaning of most devices. But I'm looking for a schematic to help me out I'm going to need to modify it for placements. I'm looking for a Tachometer that uses 7 segment leds roughly 1 inch would be ok for a read out. The ability for dual input sensors would be great but i can dup the circuit. but it seems that all i can find has ranges of 100 rpm or faster is there not a way to have between 15 to i'm estimating it's 120 rpms it's slow enough that i can keep up with a blade with my eyes but i get dizzy really fast If anyone knows what pic or mc i sould try to use or if there is a schmatic floating around that i could not google. The option to build it my self is a top priority due to space and design constraints of project. thank you

Forgot to metion Would perfer touchless sensor but it is capable of going either way. and dual outputs instead of a single array. i'm thinking this might be way out of my skill but nothing ventured nothing gained