help needed...

guys i need to built a circuit such tat if ther is no speed it should give 5v or logic 1 signal and even for slight variation in speed the output should be logic 0.........

i built a circuit usin reed switch,frequency to voltage converter circuit, and voltage limiter but it gives voltage corresponding to reed switch how to modify this circuit to get above results

You really aren't providing much information. Can you please post the circuit and then in detail what you are trying to do? I am guessing a reed switch used as a speed pickup feeding a frequency to voltage converter? How many pulses per revolution of your motor? Post a circuit please.

Ron