On Jul 29, 2020, at 12:46 PM, Arno Luijten <arno.luijten@...> wrote:

Hi David,

The problem is that the blue lights are switched via resistors. Blue LEDs are by their nature very sensitive to overvoltage. You should supply LEDs ideally with a current source instead of a voltage source. A current source supplies a certain current and regulates the voltage to get to that current.
Using resistors is (especially) for blue LEDs a poor choice as your supply voltage can be anything from 24 to 29 volt. For a blue LED this means that when you pick a resistor suitable for 29 Volt, the thing will hardly light up at 24 volt. Picking a resistor for 24 Volt will fry the LED at 29 volt. This is why these switch panel lights die.

What I've did is count the number of LEDs (pairs) you need, multiply this with the optimal current for each pair of LEDs. The pairs are set in series on the PCB so the optimal current for one LED is the same as for the pair. I'm not sure anymore but I think I got to 500 mA for the lot. Then I bought a converter similar to this one from Amazon: https://www.amazon.com/Power-Supplies-25-2W-15-50V-500mA/dp/B00HKJAW20/ref=sr_1_63?crid=3YQWWEX2UH14&dchild=1&keywords=constant+current+led+driver&qid=1596040540&sprefix=constant+current+%2Caps%2C266&sr=8-63
This is a constant current supply to feed all the leds (in pairs). This has been working excellent for some time now. Each individual LED is fed their optimal current. I can't find the LEDs anymore that I bought from Amazon at the time, but I bought them in small bulk similar to these https://www.amazon.com/100pcs-Ultra-Bright-Emitting-Diffused/dp/B01GE4WEGI/ref=sr_1_8?dchild=1&keywords=blue+LED+5mm&qid=1596041080&sr=8-8

Hope this helps,

Arno Luijten
SV Luna,
A54-121