The LED with the “OVL” marking show you a thermal overload of the CONTROLLINO PLC.
At the CONTROLLINO MINI there are 2 temperature sensors integrated. They are placed on the Relays-Board and on the Control-Board. If the temperature goes over 80°C the red “OVL” LED will go on and shows you a thermal overload.
At the CONTROLLINO MAXI it is the same but the overload signal will also be available at the microcontroller PE7 (Arduino Pin 9). Therefore, you can use this signal in your user program.
At the CONTROLLINO MEGA additional to the thermal control, the „Half-Bridge“ Driver also has a FAULT signal which is also connected to the Controllino general overload signal. Internal protection functions are provided for undervoltage, charge pump faults, overcurrent, short circuits, and overtemperature.