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I need an edge-detector to put out a single high pulse on the rising edge of a signal (which will then remain high for an indeterminate amount of time). The purpose of the pulse is to trigger the set on an RS latch, which will then be reset at some point later. Resetting the latch will indirectly cause the signal going into the edge detector to return to a low state. I found several designs, none of which were exactly what I need. I would like to create the edge detector completely out of 74xx series ICs. Any help with this would be appreciated.

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    \$\begingroup\$ If it's just an RS that you are already required to use, placing a series capacitor to the set-side input can be made to be enough to achieve the goal. No added 74xx at all. But it is "analog" and it's design and ability to operate will depend on circuit details. \$\endgroup\$ – jonk Feb 23 '18 at 23:22
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I need an edge-detector to put out a single high pulse on the rising edge of a signal (which will then remain high for an indeterminate amount of time). The purpose of the pulse is to trigger the set on an RS latch, which will then be reset at some point later.

How about this: use a D flop like HC74, feed your input signal into its clock input, and set the D input to 1.

When the edge comes, the flop will register the D input which is 1, and output 1.

When you want to reset it, simply use the reset input, and the output will go back to 0.

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  • \$\begingroup\$ This is perfect! I tested it, and it is exactly what I need. \$\endgroup\$ – Eli Lorden Feb 23 '18 at 23:19
  • \$\begingroup\$ An alternative method would be to use a differentiator to turn the leading edge into a trigger pulse. \$\endgroup\$ – Norm Feb 23 '18 at 23:22
  • \$\begingroup\$ actually, this is very much what's inside a D flip-flop (edge detector followed by RS) \$\endgroup\$ – bobflux Feb 23 '18 at 23:38

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