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Project Notes

#565 Single-Shot Trigger

A debounced single-shot pulse generator with inverted amd non-inverted output designed for use on a breadboard.



This little module is for those breadboard occassions where when one needs a debounced pulse - or possibly an inverted pulse for active low logic.

It uses a 555 timer in monostable mode to debounced a pushbutton, emitting a pulse of trigger a pulse of at least 22ms (R1=20k and C1=1uF).

A CD4049 is used to buffer and invert the outputs (inverted amd non-inverted) so that it can match any required load.


First testing the circiut on a breadboard:




Making it a “Breadboard Bling” Module

I went for dead-bug stlye on a small piece of protoboard in order to keep the module small (I don’t have SMD versions of these chips on hand).



A scope trace of the pushbutton (CH2 - Blue) and the triggered and debounced 555 output (CH1 - Yellow):


The outputs from the CD4049 on a trigger pulse:

  • CH1 - Yellow: non-inverted output
  • CH2 - Blue: inverted output (offset -3.5V)


Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.