How hot is too hot for LEDs?

[primuspaul]

I made a custom LED lamp using a small aluminum heat sink, some paste, power converter, and a cheap 12V LED chip. After running it for a few minutes, the heat sink got so hot I couldn't hold my finger to it for more than 2 seconds (I hope I didn't damage the LED in those few minutes). I then tried a 9V power supply. Still too hot. Now I'm trying an 8.4V, hoping that it will be enough to keep the heat down.

How hot is an LED supposed to get without cutting its life too short?

The 8.4 is keeping it a bit lower. After a few minutes, I can hold my finger to it for about 10 seconds, so it's not terribly hot.

 

[davenn]

I made a custom LED lamp using a small aluminum heat sink, some paste, power converter, and a cheap 12V LED chip. After running it for a few minutes, the heat sink got so hot I couldn't hold my finger to it for more than 2 seconds (I hope I didn't damage the LED in those few minutes). I then tried a 9V power supply. Still too hot. Now I'm trying an 8.4V, hoping that it will be enough to keep the heat down.

How hot is an LED supposed to get without cutting its life too short?

The 8.4 is keeping it a bit lower. After a few minutes, I can hold my finger to it for about 10 seconds, so it's not terribly hot.

You have told us nothing about the type of LED, their ratings or how big the heatsink is ??
You didn't even show a photo of your construction
as a result, it's really difficult for anyone to give you a decent answer

Dave

 

[(*steve*)]

But, yes, that's too hot.

What sorry of current control are you using?

You so realise that driving them from a voltage source is a great way to destroy LEDs, right?

Go into the resource section and look for out resource showing how to use LEDs if you're not sure about anything.

 

[primuspaul]

LED chips: https://www.ebay.com/itm/10pcs-High...lb-Chip-DIY-10W-20W-50W-100W-12V/272389345999

10W 12V rated.

Heat sink: https://www.ebay.com/itm/332498749254

I realize it's a small heat sink and that the power supply is a voltage-driven one, which is the opposite of what is recommended for LEDs (current-driven). The reason for the usage of these parts is mostly that I have them and/or they are readily available and very cheap. If my understanding is correct, as long as the temperature is not too high, the LED's life should not suffer significantly. This is why I am trying to figure out the right temperature.

I've read on various forums that people complain their brand-name LEDs get very hot, too, and was wondering what's OK.

 

[primuspaul]

I dipped a thermocouple in thermal paste and touched it to the heat sink. Looks like it tops out at 123 degrees F after running for about 20 minutes. No idea if it's accurate. It's a K-type thermocouple that came with the Klein CL800 I have. I couldn't find a way to calibrate it (nothing in the manual) so I assume it's a feature that doesn't require calibration. Meter is almost new.

 

[primuspaul]

This lists the temp:

https://www.lifx.com/blogs/the-latest/19032975-how-hot-are-led-light-bulbs

In development and testing, we found that the heatsink of a fully lit LED bulb was around 60°C-100°C (140°F-212°F) depending on the make and model of the LED bulb, room temperature, and airflow.

So I'd say my set-up should provide a good LED life, right? I can obviously get the temperature significantly lower by using a bigger heat sink, but those are expensive.

 

[kellys_eye]

The manufacturers will give data re the temperature and lifespan (possibly) but cooler is always better.
If you have expectations for a given life span for the LED then cool it as per the manufacturers recommendations or it WILL fail prematurely.
Is the extra cost of a larger heatsink more than the cost of a replacement LED (and fitting it)?

Choice is yours.

 

[primuspaul]

The manufacturers will give data re the temperature and lifespan (possibly) but cooler is always better.
If you have expectations for a given life span for the LED then cool it as per the manufacturers recommendations or it WILL fail prematurely.
Is the extra cost of a larger heatsink more than the cost of a replacement LED (and fitting it)?

Choice is yours.

They say this:

11. Working Temperature: -20 centigrade to 60 centigrade

Which is 140 F. That's less than the 123 F I measured, but I measured at the heat sink. I don't know if that's what they mean, since how can you even measure the actual LED? It's inside the chip.

 

[(*steve*)]

It sounds like perfectly acceptable Chinese engineering. Just be sure not to provide a warranty.

 

[primuspaul]

It sounds like perfectly acceptable Chinese engineering. Just be sure not to provide a warranty.

At about a quarter a cell, it's kind of hard to beat warranty or no warranty. Anyway, I'll use it. What's the worst that can happen? It's $0.30 / pc.