Digital Tachometer

I am looking for a method of converting a digital pulse (created by a LED and a photo-sensative diode) into a revs per minute value that can be displayed on several 7 segment displays. I am completly unsure where to start with this, any suggestions would be great!

digi tach

hi,

try google search "digital tachometer circuit diagram" or if you want the basics of this stuff try, **broken link removed**