The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

The New Hotness

  • Discrete LM3909: Green LED at 1.15 V

    The green-LED discrete LM3909 is still flashing, even with its AA NiMH cells burned down to 1.15 V:

    LM3909 green LED - 1.15 V NiMH
    LM3909 green LED – 1.15 V NiMH

    If the truth be known, one of the cells is now reverse-charged to 200 mV, so that’s a bit beyond as low as it can go.

    The flash period has stretched to 8.7 s:

    LM3909 green LED - 1.17 V - 8.7s period
    LM3909 green LED – 1.17 V – 8.7s period

    The circuit boosts the battery by 800 mV to put 1.94 V across the green LED at the start of each flash:

    LM3909 green LED - 1.15 V - V LED
    LM3909 green LED – 1.15 V – V LED

    Admittedly, the LED isn’t particularly bright at 2.8 mA:

    LM3909 green LED - 1.15 V - LED current
    LM3909 green LED – 1.15 V – LED current

    But it’s still flashing!

    Swapping the cells into the LM3909 with a blue LED doesn’t produce any blinking, which is about what the earlier tests showed.