Backlight ON with a PC OFF

SYMPTOMS

You turn off the PC but the buttons or screen abcklight stays ON.

EXPLANATION

Our devices don't have the ON/OFF switch. We try to detect if the PC is ON or OFF and shutdown the display / buttons accordingly.

For the display we use a signal from the LCD driver board and for the buttons we use the USB signal. However some PCs give USB signal/power on some of the ports even when the PC is powered off and therefore there is no way for us to detect if the PC is OFF. It also often happens with externally powered USB hubs. 

SOLUTION

• Try using a different USB port.
• Check your BIOS settings and disable power on USB ports when the PC is off.