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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.

Build

Notes

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.

Construction

First testing the circiut on a breadboard:

Breadboard

Schematic

SingleShotTrigger_bb_build

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).

SingleShotTrigger_module

Performance

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

scope_debounce

The outputs from the CD4049 on a trigger pulse:

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

scope_output

Credits and References

About LEAP#565 Breadboard Bling555 TimerCD4049
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 my personal collection of electronics projects, 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 (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.