Tuesday, July 29, 2014

Fireflys in a jar

New! Webinterface

A toy webinterface for a similar jar can be found here:
Note that it is the real deal and the jar, standing next to my window, will actually start flashing if you click any of the buttons


  • A large jam jar (Ikea)
  • Mini USB Nano V3.0 ATmega328 5V Microcontroller Board (eBay)
  • FTDI serial cable for flashing (eBay)
  • Solar cell, 5.5 V, 50 mA or larger (eBay)
  • Lipo - battery cell, 100 mAh - 600 mAh (eBay / old laptop / old cellphone, etc.)
  • 12 x tiny LEDs, different colors, the smaller the better, with ~80 - 200 Ohm series resistors, depending on how bright you want it (kit from eBay)
  • Very thin magnet wire from the coil of a miniature relais
  • SMD resistors with 1 % tolerance: 2 x 560 kOhm,  2 x 160 kOhm. For two voltage dividers to sample the solar cell and battery voltage
  • SMD ceramic capacitors, 2 x 100 nF, to stabilize the analog inputs of the AVR
  • Some circuit board, glue, prototyping wires, sticky tape 
The making-of after the click ...