Three timers, one little flame

LogiFlame began with a simple question: could a few 555 timers create a convincing LED flame effect without an Arduino? It became a hands-on journey through oscillators, analog mixing, feedback, PCB design and tiny SMD soldering.

Designed and built by Sergio Veneziani, the manufactured PCB worked on its first power-up on 27 October 2026. The finished unit fits in a custom translucent enclosure with a rechargeable battery, a separate USB-C charging/power module and a switch.

HOW IT WORKS

Three NE555 astable oscillators run at nominal frequencies of approximately 0.69, 2.08 and 6.87 Hz. Resistors mix their outputs with different weights and an RC network smooths the transitions. One amplifier section of an LM324 drives a D882 NPN transistor using emitter-current feedback to vary the brightness of an external LED bulb.

The combination produces an apparently irregular flicker. It is not a true random generator. There is no microcontroller, software or firmware.

FROM BREADBOARD TO SMD

The original breadboard was the place to learn and troubleshoot. The final two-layer PCB uses SOIC timers and op-amp, a SOT-89 transistor and mostly 0402 passive components. The gallery shows the breadboard, assembled board, internal packaging and finished light.

POWER AND COMPONENT NOTES

The flame-driver PCB is designed for regulated 5 V. The builder observed a varying input current around 50 mA; average consumption and battery runtime have not been characterized. The external bulb is nominally 3 V / 200 mA and is operated at a lower, varying current.

The charger and battery-power module are separate from this PCB. Their exact model and wiring still need documentation. Follow the hardware notes in the repository and verify the supply output, D882 pinout and actual sense-resistor power rating before reproducing the build. The enclosure is not specified as waterproof.

FILES AND DOCUMENTATION

https://github.com/SVeneziani/LogiFlame

The repository contains editable KiCad files, the schematic, extracted BOM, original ordered Gerbers, enclosure Fusion/STEP/STL files, build photographs and Italian/English documentation. Read the hardware notes before ordering or modifying the design. CAD print settings and the battery subsystem remain to be fully documented.

A FIRST SMD PROJECT

This was my first PCB assembled at this scale. Getting from a crowded breadboard to a working little light was as rewarding as the finished effect. I hope the project helps others explore analog electronics, one measurement at a time.

Design, layout, soldering, enclosure and bench testing: Sergio Veneziani. Development and troubleshooting assistance: OpenAI ChatGPT/Codex.

LICENSE

Original hardware and enclosure design contributions: CC BY-NC-SA 4.0. Attribution to Sergio Veneziani, noncommercial use and ShareAlike apply. Commercial use requires separate permission. Third-party materials retain their own licenses. See the repository LICENSE.md for scope.

IN ITALIANO

LogiFlame nasce dagli esperimenti con tre NE555: i segnali vengono miscelati e filtrati, poi LM324 e D882 regolano la corrente del LED. Nessun programma da caricare: solo elettronica analogica. Il PCB SMD ha funzionato alla prima accensione ed è stato montato in un contenitore traslucido con batteria e modulo USB-C separato. Sul repository trovate anche la documentazione in italiano.