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I have a set of Christmas lights (the LEDs are red, green, blue and yellow) that I unplugged last night, and in the morning the bulbs continued to glow dimly but noticeably.

It seems like it's been too long a time for the smoothing capacitor to still be holding charge. So I'm stuck wondering: why do they remain on?

To clarify once more, the plug has been removed from the outlet and there is a high impedance air gap.

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  • \$\begingroup\$ Well then, these LED colors do not use phosphorus so it's probably the power supply. \$\endgroup\$
    – StarCat
    Jan 6, 2023 at 7:18
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    \$\begingroup\$ Capacitive coupling with nearby power lines? See if this ledwatcher.com/stop-led-lights-glowing-when-off has useful advice for your case. \$\endgroup\$ Jan 6, 2023 at 8:08
  • \$\begingroup\$ I've had LEDs lit by capacitors for days. Depends on the capacitance and LED. If it's just a very dull glow, the current draw will be extreamly low, so I am not that surprised. Give it a week or two. \$\endgroup\$
    – Puffafish
    Jan 6, 2023 at 8:28
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    \$\begingroup\$ Maybe you live near a radio station or power transmission line. \$\endgroup\$ Jan 6, 2023 at 10:09

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Ok, I figured out the source of the light. The Christmas tree had a set of battery powered lights as well as the wall powered ones, the lights were dim due to the batteries being low. Guess I didn't look close enough to realize half the lights were off. HaHa, guess we all make mistakes here and there.

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It is most likely the capacitor, I have had a 470uf capacitor glow an led, dimly, but noticeably for 3 days. It was still glowing but I unplugged it. The led, if it isn't using phosphor is pulling ua, max from the cap. If it is using phosphor, the LED die underneath the phosphor would still be glowing, just not enough to excite it. The internal leakage of the cap is probably more than what the led is drawing.

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I had the same thing this year. The LED lights at my bar were unplugged and they remained glowing for days. After trial and error what I found is that my gas filled bar light was the source of the power. even though unplugged it was still drawing from that light. Proved it several times to my friends.

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Don”t worry, you have not found perpetual motion.

They will go out eventually. The power supply was generic based on price not designed for that use specifically.

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