I have a main board with microcontroller and two long distance panel boards with standard 5mm red LEDs with 3.3k resistors. I supply panel boards with 24V over 20m cable. Whole system power is supplied with Meanwell SMPS. I use ULN2003 open collector transistor array for switching LEDs with my microcontroller. So, I draw ULN2003 like switch in schematic. Panel boards is in a plastic box.
My original schematic:
The problem: My LEDs in panel boards, fail after a few months. Mostly, not in same time for two panels. I think some ESD occurs and breaks my LEDs. I searched and find this kind of protections.
First one, TVS:
And diode solutions:
simulate this circuit – Schematic created using CircuitLab
Red rectange is my main board. I show my power supply and reverse voltage protection. Switches are ULN2003 outputs.
Finally, which is the best choice for protecting LEDs from ESD events?
Edit: LED Datasheet
Best Answer