LED dimming over 24hr period

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RichH
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LED dimming over 24hr period

Hi all. Apologies for posting this again, I put it in the LED spotlight section and haven’t found the cause.

I bought a few of these things. They’re lensed with a thick round lens with a colour filter and led sat on a star shaped board behind. Runs off a USB plug, not much to go wrong.

https://www.amazon.co.uk/Jooayou-Projection-Rotation-Romantic-Birthday/d…(link is external)

I left one of the rainbow ones on overnight and it didn’t seem as bright the next day. I switched it off to cool down and turned it back on, it definitely wasn’t running as bright so I sent it back.

As an experiment I left one of the sunset colours on and one off for 24 hrs. This is what happened. Anyone know why this is happening? It’s a simple circuit, running low wattage and voltage. I’m powering them through a couple of old iPhone USB chargers. Here’s a pic of one left on overnight and one switched off. The dimming is permanent

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Rockenrooster
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Cheap LEDs looks like.
Maybe permanent damage from overheating??? That’s hard to believe though since they are USB powered.
How much power do they draw?

ggf31416
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Defective heatsinking most likely, like the MCPCB separating from the heatsink, that can easily kill even high power LEDs.

RichH
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Rockenrooster wrote:
Cheap LEDs looks like. Maybe permanent damage from overheating??? That’s hard to believe though since they are USB powered. How much power do they draw?

Hard to say, typical Amazon non description says 6 watts, but I’m assuming that’s the output as that’s what the average lightbulb buyer needs to know. I’m plugging in to an old iPhone plug so it’s not able to draw much.

Did get kind of warm at the back where the plastic is close to the board, so it might be that. It’s a pity they’re sealed units or I’d get to work with some thermo paste and a couple of decent leds.

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Rockenrooster
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RichH wrote:
Rockenrooster wrote:
Cheap LEDs looks like. Maybe permanent damage from overheating??? That’s hard to believe though since they are USB powered. How much power do they draw?

Hard to say, typical Amazon non description says 6 watts, but I’m assuming that’s the output as that’s what the average lightbulb buyer needs to know. I’m plugging in to an old iPhone plug so it’s not able to draw much.

Did get kind of warm at the back where the plastic is close to the board, so it might be that. It’s a pity they’re sealed units or I’d get to work with some thermo paste and a couple of decent leds.

Hmmm 5v 1amp power bricks?
If it indeed draws 6 watts then that would be over the 5 watt rating of the power bricks.
Try a 5v 2 or 2.1amp USB plug and see if anything changes.

All my old 5v 1amp ones make a buzzing noise now when I plug in my 2021 phone into them lol.

If that doesn change anything then I suspect heat damage/poor quality leds

Hank33
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Someone mentioned heat and just wanted to mention that yeah I find these led bulbs don’t have good heat dissipation at all. I mean it’s all sealed and everything. Kinda like being in a sauna too long lol. Plus they don’t really last that long. I know, it’s a bulb so a heat sink is kinda hard so I guess it’s a necessary evil for now. Evil

RichH
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Rockenrooster wrote:
RichH wrote:
Rockenrooster wrote:
Cheap LEDs looks like. Maybe permanent damage from overheating??? That’s hard to believe though since they are USB powered. How much power do they draw?

Hard to say, typical Amazon non description says 6 watts, but I’m assuming that’s the output as that’s what the average lightbulb buyer needs to know. I’m plugging in to an old iPhone plug so it’s not able to draw much.

Did get kind of warm at the back where the plastic is close to the board, so it might be that. It’s a pity they’re sealed units or I’d get to work with some thermo paste and a couple of decent leds.

Hmmm 5v 1amp power bricks?
If it indeed draws 6 watts then that would be over the 5 watt rating of the power bricks.
Try a 5v 2 or 2.1amp USB plug and see if anything changes.

All my old 5v 1amp ones make a buzzing noise now when I plug in my 2021 phone into them lol.

If that doesn change anything then I suspect heat damage/poor quality leds

I tried a 2amp plug, same thing happened, dimmed after a few hours so I sacrificed one lamp. Basically we have a really decent quality product completely let down by a simple circuit. I bought 5 of these, have returned 3, and will return the one I haven’t broken open too. LED has gone brown, red wire is burnt.

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NeutralFan
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Looks like the LED board is sitting on a hollow plastic shelf. No where for the heat to go and it’s enclosed.

It appears there is too much current/brightness for these lights and the LEDs are overheating.

I’d rather use my flashlight around the house than turn on the lights.

RichH
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NeutralFan wrote:
Looks like the LED board is sitting on a hollow plastic shelf. No where for the heat to go and it’s enclosed.

It appears there is too much current/brightness for these lights and the LEDs are overheating.

I think that’s exactly it. Pity, as the lens is glass and not plastic, the colour filter is thick and hard plastic which is much better than the thin film ones, the lamp base is nice and heavy, and the ball joint and adjustable stem are decent too.

All let down by the wrong driver or led and lack of heat sinking.

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