Why Cheap LED Lights Keep Glowing
Why Electrical Engineering Stack Exchange recommends it
Electronics Stack Exchange users link it when asking or answering why a mains LED lamp or LED indicator glows dimly while switched off, as a demonstration of stray capacitive coupling and a way to bleed it off with a load resistor.
Recommended by 1 people across 1 different months, 2022 to 2023.
What it is
Mehdi Sadaghdar of ElectroBOOM explains why some cheap LED lights keep glowing faintly after being switched off, tracing it to the small capacitance between wires and the capacitor-based, rectifier-fed driver circuits inside cheap lamps. It is a short demo-and-explanation video that pairs with a companion video by Steve Mould and shows a resistor-based fix.
What people said
Recommends DrakeJest · 2022-02 · Electrical Engineering Stack Exchange · on “How to fix LED fixture not turning off completely when the switch is off”
I have LED ceiling lights that are not completely turning off even when the switch is off. [LINK] Sometimes the brightness of the glow is just to much for me and finally decided to do something about it. This video by steeve mould [LINK] tried to explain what is going on but did not offer a solution on how to fix the issue. The PCB on 8:11 [LINK] looked really similar to what mine uses. The solution to the problem though is on another video by Electroboom [this video] saying to place a 470 kohm resistor on the output of the rectifier. [LINK] The circuit that electroboom is using is not the exact same circuit as I have. So will it still work? And how do I calculate the value of the resistor for my
Cites mo FEAR · 2022-01 · Electrical Engineering Stack Exchange · on “Why does a mains LED lamp attached to an inverter glow dimly despite being switched off?”
I have 220V AC LED lamps (bought from eBay) connected to a 1000W pure sine wave inverter, which itself is connected to a car battery. There is a ususal on/off switch between the lamp and inverter on the "hot" wire (called L or phase). Strangely and unexpectedly, the lamp glows dimly (at about 10%) even when off. The LED lamp has a ceramic capacitor in it, along with another unidentified component (that looks like an IC or transistor.) I assume the capacitor (and other component) is to smoothen "flutter" due to mains frequency, but my assumption is that no non-negligible current can flow through it as long as one of the wires (be it phase or neutral,) is disconnected. I know parasitic capacit
Cites micropyre · 2023-05 · Electrical Engineering Stack Exchange · on “Why does my TS101 soldering iron turn on LEDs upon contact?”
These LEDs are sensitive to electric fields in the air that even a small amount of current can pass through it and generate light if an AC voltage potential is applied on one end. The other open-end behaves like a capacitor sending the electric current into the nearest ground potential through air. Here's an exciting video by Electroboom demonstrating this effect: [this video] Update: To answer your additional queries Why does my supposedly grounded iron tip, powered by a switching AC/DC supply, carry an AC voltage? Your soldering iron should be powered by AC, so the AC circuit is probably electrically connected to the heating element of your tip and thus carries an AC voltage potential that can
Critical mo FEAR · 2022-01 · Electrical Engineering Stack Exchange · on “Why does a mains LED lamp attached to an inverter glow dimly despite being switched off?”
thx for the reference to ElectroBoom. I checked out the video: [this video] honestly, it doesn't seem satisfying, since he also comes to the conclusion of "capacitance somewhere in the wires" even though the only thing changing in my case is the power source, moreover, any filter capacitor of any other device would already supposed to provide enough capacitance to make this effect always happen, but it doesn't. Moreover, the light intensity I'm seeing is a bit stronger than in the video.