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Project Notes

#062 SR Latch Flipper

Set/Reset latch with BJTs, controlled and monitored by an Arduino.

Here’s a quick video of the circuit in action:

SRLatchFlipper demo


This is a classic Set-Reset latch under Arduino control.

See the LEAP#061 SRLatch project for the implementation details and design notes on the flip-flop. SRLatch uses manual switch entry to control the flip-flop.

This version of the circuit uses an Arduino to drive the set/reset inputs, and monitor the output state. For simplicity, the circuit is powered from the Arduino’s 5V regulated pin. Output state is read with analog ports, and the data sent to the serial port for plotting with LEAP#090 PlotNValues (a simple Processing sketch).

The processing trace below demonstrates the behaviour using 4 traces. From bottom to top:

  • Lower plot: SET input
  • Lower-middle plot: RESET input
  • Upper-middle: Out1 output state Q
  • Upper plot: Out2 inverted output state -Q

processing trace

The plot demonstrates:

  • how repeated triggers have no effect on the output
  • SET sends Out1/Q high
  • RESET sends Out1/Q low
  • Out2/-Q is always the inverse of Out1/Q


The Breadboard

The Schematic

The Build

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.