Led Overheating in Fluorescent Microscope - melting PLA, and Solder

I have purchased the LEDs that were used in the initial design of the fluorescent microscope:


I have the LED plugged into the Rasberry pi correctly as per the instructions- red is in the 4th peg and black is in the 6th - with the red being soldered onto spot 6 and the black is soldered into spot 1.

That bring said within seconds of plugging the LED in it gets very hot, and just under a minute it gets so hot it melts the PLA to the led then melts the solder off and so the LED stops working,

I have a power supply where I can alter the voltage and the current, and the lowest voltage I can put it on without dimming the LED was 3.3 volts- but still on this voltage it overheats.
I did the math to calculate if I needed resistance, but the value came out to be .5 resistance- which should be pretty much irrelevant.
I was thinking I could buy a heat sink, but I really shouldn’t need one according to the LED’s stats.

Did other people struggle with this? What can I do to keep it from over heating?

Welcome @Eaoke3. The star LEDs are quite high power, the one that you have linked is specified up to 1A current. This has two things that need to be taken care of. The first is that it is best to power through a separate power supply - if you have a motorised microscope use the motor power supply. Pulling 1A from the Pi itself is a lot of current. The second is that 1A at nearly 4V is 4W, which can make things hot. I have not used the fluorescent version, but I think it is not designed to need a heatsink. However, if you have not regulated the current in any way, you are likely to be delivering much more than 1A and then that means a lot more heat. If you have the variable power supply that can regulate the current, then operate in the current regulated mode, and try lower current. You probably don’t need the LED at full power to see what you need to.

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Yes we’re still trying to work out the best way to power the star LED. At the moment a variable power supply with constant current mode is our recommended solution.

There’s a few tips in this thread: Delta v.1 Build Questions

For example for the blue LED at 3.3V, I set the current at around 0.1A for fluorescence imaging. It still will get hot, but I find a heat sink (the ones for Raspberry Pi fit nicely) does improve matters, and not leaving it on for long periods.


Thank you so much, dropping the current solved the problem. I am new too engineering, (especially electric) so the detailed response is very appreciated.

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