93 lines
3.7 KiB
Markdown
93 lines
3.7 KiB
Markdown
# FireFly Solar / 日輪蛍
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**Nichirin Hotaru**
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*A small solar-powered Morse firefly for the outdoors.*
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**太陽を宿し、夜にモールスを灯す蛍。**
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*Taiyō o yadoshi, yoru ni Mōrusu o tomosu hotaru.*
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*A firefly carrying the sun, lighting Morse in the night.*
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## Overview
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FireFly Solar is a small outdoor LED blinker inspired by the idea of an LED throwie, but powered by sunlight instead of a disposable coin cell.
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During the day, the solar cell charges the energy storage.
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At night, the circuit wakes up and sends a simple Morse-style light signal.
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## About this Project
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FireFly Solar is my **technology playground**. It is a small garden object, but its real purpose is to learn by building something complete. With it I learn about:
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- **Circuit design at the edge**: in this case, as low power as possible
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- **PCB design**
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- **Weatherproof casing**
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- **ATtiny programming**
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Possible next technology step: everything about DIY SMD design and soldering.
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## Project Goals
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- Build a solar-powered outdoor Morse blinker
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- Keep the hardware simple and robust
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- Improve practical low-power design skills
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- Test mechanical concepts for outdoor 3D-printed parts
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- Learn what is needed to turn a small electronics project into a possible DIY kit
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## Software
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The firmware runs on an **ATtiny85** at 1 MHz (internal clock, ATTinyCore: `clock=1internal`, `millis=disabled`). The LED itself is used as the light sensor. When it is dark, the firefly sends a short Morse text ("TGO 26") about once a minute.
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### Current Firmware version: v0.4 (2026-11-08)
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Goal: lowest possible average current.
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Changes vs v0.3:
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- No `delay()` / `millis()`; Timer0 and Timer1 are gated off in PRR.
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- The watchdog (interrupt mode) is the only timebase: Morse units (~96 ms), the sensing window and the 8 s sleeps. The CPU sleeps in power-down in between.
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- Darkness sensing: the CPU sleeps in 16 ms steps while the LED junction discharges, instead of a busy `digitalRead()` loop. Bright light exits after the first step. `darknessThreshold` is replaced by `darkSteps`.
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- The ADC is disabled before it is gated off in PRR; pins are set up before PRR.
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- After a power-on or external reset, no blinking for `RECOVER_CYCLES` (about 16 min), so the supercap can recharge.
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- `DEBUG_TEST` switch for bench testing: 8 s cycle, no recovery wait, short flash when the sketch decides "bright". Set it to 0 for the field.
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- Optional `BOD_FUSE_ENABLED` (BOD off during sleep); unused with the BOD fuse off.
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Tested: compiles with ATTinyCore and runs on hardware. Current draw is not yet measured.
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## PCB
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- Finished: a batch of 10 is assembled, tested and working.
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- Latest adjustment: fine-tuned the resistors for the LED, and the 3.9 V Zener diode is confirmed safe avoid overcharging 4V supercap.
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- Next version: the PCB should be a little shorter. The wiring space is a bit too tight now.
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## Casing
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Works basically as intended. Lessons for the next version:
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- Better locking of the solar modules.
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- The rope structure works, but building it is too complicated and takes a lot of nerves.
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- Using material tension to secure the modules via rope was basically a good idea.
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## Naming
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The English project name remains:
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**FireFly Solar**
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For blog posts, documentation, and presentation, the project also uses the Japanese name:
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**日輪蛍 / Nichirin Hotaru**
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The name roughly means **sun-disc firefly**. It keeps the solar theme, adds a slightly mythic tone, and still fits a small piece of outdoor hardware.
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---
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## Contributing
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PRs and issues welcome. Keep it simple.
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Photos of your build you send me go in `Documentation/gallery/` with a short caption and license notice.
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---
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## License
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Default license: [CC-BY-NC-4.0](https://creativecommons.org/licenses/by-nc/4.0/) |