“LED filaments are thin, stick like LEDs. They are used in many Edison bulb look-a-like LED bulbs.Each of those thin sticks contain many - 20 to 30 LEDs connected in series. So they are quite bright and energy efficient, however typically require over 70V to turn on.I wanted to make a small, battery operated lamp using those LED filaments. After trying out many circuits, I discovered a very simple circuit to light a filament LED with only one, 1.5V battery.”