Sequential shift light
 

Ok, so I had my gauge cluster out for the tach mod and was poking around for a place to tap in for a shift light. Well I found the wire I need, but the tach is a frequency based signal like I had thought. Can someone point me towards a DIY freq based LED bar draph driver? I'm trying to build a F1 style sequential shift light but the schematic I was basing it off of was voltage based.... Back to the drawing board.... TIA
--Alex