Falling and Rasing Edge Detector

Question

I will use a motor adapter in my design.This motor adapter doesn't have a spice model. Therofore I will design inside structure of this adapter. In this motor adapter has a delay and xor gate part.I think this part makes edge detection.By using below reference desing from this website rising edge (0 to1)and falling edge(1 to 0) detector circuit for flipflops? I built a edge detector circuit in LTSpice by using 74HCT04 inverters. But 74HCT04 gives only inverse of input, it doesn't give any delay. How 74hct04 can give delay and how I can obtain an positive edge detector by using delay and xor gate?

Answer 1

Here's the general idea about edge detectors: -

Three examples all of which use an RC to slightly delay one input to the gate (schmitt input type gate of course).

But 74HCT04 gives only inverse of input, it doesn't give any delay.

Oh yes it does, read the data sheet (it tells you that the propagation delay is about 7 ns on a 5V supply) and, if you want more delay add more inverters: -

Or this: -

If you just want a positive edge detector use the 2nd circuit in your question with an odd number of gates.

Answer 2

This is from an LT spice manual I searched for on line;

You should set the TD paramater on your 7404 device to something other than 0.