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This question already has an answer here:

I need to design an edge detection circuit to detect when a square wave signal goes from Low to High (rising edge) and when it goes from High to Low (falling edge). The circuit should preferably use simple logic control such as 74LS series logic. I know people are gonna suggest using an arduino with interrupts but in my application this needs to be done in hardware rather than software.

Edit: The output is expected to be a short digital pulse, used as a trigger.

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marked as duplicate by Ale..chenski, brhans, Marcus Müller, Dave Tweed Jul 3 '18 at 11:47

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • \$\begingroup\$ A resistor, a capacitor, and an xor gate should do the trick. \$\endgroup\$ – brhans Jul 3 '18 at 0:34
  • \$\begingroup\$ Did you ever bother to google for {edge detection with logic} ? Or Stack Exchange at least? electronics.stackexchange.com/q/270894/117785 I know it is not nice, but really? \$\endgroup\$ – Ale..chenski Jul 3 '18 at 0:35
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    \$\begingroup\$ @AliChen, no, it is actually a second attempt to ask the same question electronics.stackexchange.com/questions/382104 \$\endgroup\$ – Maple Jul 3 '18 at 1:07
  • \$\begingroup\$ @Maple, this is the second attempt by OP, true. But exactly this question was asked years ago and has perfect answers. \$\endgroup\$ – Ale..chenski Jul 3 '18 at 4:10
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A simple differentiator circuit should do what you ask(the pulse will be fairly short but enough to trigger a bistable multivibrator or something). Read more at https://www.electronics-tutorials.ws/opamp/opamp_7.html: enter image description here

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    \$\begingroup\$ Your circuit produces negative spike on falling edge. I suspect it is not what OP wants even though he refuses to tell what he's connecting edge detecting circuit to. \$\endgroup\$ – Maple Jul 3 '18 at 1:15
  • \$\begingroup\$ Wouldn't the negative spike be on the rising edge? \$\endgroup\$ – atomSmasher Jul 3 '18 at 3:14
  • \$\begingroup\$ He can add a diode if he doesn't want the negative edge. \$\endgroup\$ – user1949350 Jul 3 '18 at 7:39
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How about this

schematic

simulate this circuit – Schematic created using CircuitLab

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