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Project Notes

#552 Freeform Popsicle Airways

aka Aircraft Navigation Lights!

Demonstrating a simple aircraft navigation beacon sequence implemented with a couple of 555 timers.


Here’s a quick demo..



I came across this Aircraft Navigation Beacon circuit and thought it was an interesting trick to achieve with some 555 timers. It runs white LED beacons that flash twice then delay 2 seconds before repeating.

These apparently simulate anti-collision strobe lights for aircraft.

After a few tweaks found the circuit works reasonably well, however it is very touchy and component values need to be carefully selected in order to get the timing right.

To show the circuit off a little better, I fashioned a little aeroplane model from some popsicle sticks that sits proudly atop a 9V battery.


The circuit uses two 555 timers running as astable oscillators.

The first 555 timer provides the basic on/off cycle, with a very low duty cycle since D1 diode steering selects a different resistor for charge/discharge:

The second 555 timer provides the oscillator for the LEDs.

  • frequency is governed by R3/C2 (1MΩ, 220nF) nominally 3.2Hz
  • is only enabled (vai pin 4) when the first 555 timer output is high



Testing on a breadboard:


In order to ensure two LED flashes each cycle, the on time of the first timer must be just right for the frequency of the second timer. I fiddled around with component values a bit to get it “close”. Still not perfect; here’s a scope trace showing how my “on time” is just a little bit too short to get two equal flashes each cycle:

  • CH1 (Yellow) - timer 1 output
  • CH2 (Blue) - timer 2 output


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.