About Positive and negative edge triggering

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qwertyqwq

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Hi all. I want to make a positive and negative edge trigger circuit. May you guys help me...
First of all the goal is to trigger clock pin of a d flip flop (cd4013). The project is just about to learn something interesting.
Incıming signal is variable square wave %50 duty cycled. I want to generate a clock signal from that square wave. Every changing edges (rising & falling) the circuit will generate a pulse for clock pin of the flip flop. It will not change by input frequency. By the way bedore i wrote here , i also tried to do some but it wasnt desired one. The scheme is here ;

This circuit is working on high freq about 200hz-25 khz. But on less is not working well. I have also changed caps and resistor different type of values but the result didnt changed. In theory it was working. And also tried with ltspice. All things working as i desired. But in pratic ...
Some of the websites also mentioned sometihng like that;

But this time in simulation softwares the time width is too small then i wanted to generate.
So i thought you guys may help me about that. If you have any spesific diagram for that , i can take it gladly

Edit: The reason why im not using D Latch is all i want to do generate edge trigger.
 
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perhaps your trigger problems are due to logic family impedance. Rather than slow 4xxx series (assumption) Use 74ALC' or 74HC' series The pulse width can be very short <20ns which limits your maximum frequency but has no effect on minimum frequency when going into an edge trigger circuit.
 
Hi steward thanks for reply all.
I dont think the reason about slow cd4013. Cause when i look at output of the XOR gate with scope , some of edge signals are missing. Sometimes it can detect edge espesially at high frequency , but sometimes not at lower frequemcy that i mentioned before.
Thanks.
Edit: xor gate is 74hc series.
 
What are you feeding the XOR gate circuit with?

That must be a logic level signal with a fast edge for the R-C delay to function properly.
If it's a slow signal you could feed it through a schmitt gate such as a 4093 or 40106?
 
Thanks
Actually yes i though that before so you are right the signal is rising and falling slowly. After i saw that i put a buffer after it. The buffer is Nxp’s HEF4050bp. Now it looks like sharo enough. What do you think ? Should i change the buffer against two 74hc14 schmitts cause i dont have 4093 or 40106 ics .
 

hello,

if your using your custom edge trigger circuit to clock a CD4013, it won’t clock on a negative edge. The CD4013 clock input has a built-in positive edge trigger. So it will only clock on a positive edge.

eT
 
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