Hi,dear engineer fellas. Here is my query : We are team of students who compete in international FSAE competition-that is,we are making a racing car if you will.The engine is motorcycle engine. Our team is responsible of the different circuitry . Funny stuff is,we are all mechanical engineers :) . Anyways: I have to design device ,that reads the data from onboard ECU (engine control unit) tachometer.The output from the drive circuit is a square wave with a 30% “on” (Vbat) and 70% “off” (0v) duty cycle.Every pulse means one revolution (that is changable with ECU service program ,anyway,that's what we agreed on). What circuit can I use to decifer the RPM?The circuit we agreed on will have 9 Leds,each led simbolizes range of 1000 RPM. http://imageshack.us/f/7/vm4s.jpg/ Anyway,being in distant past practical electronics engineer,I will try my hardest to understand what you will throw at me :) . Thanks in advance.