You can manage this through either the web interface or the Tether app - Click Read More below for the full solution.
This is the most reliable way to access the full range of system tools.
Connect to the Extender: Ensure your device is connected to the extender's network (via Wi-Fi or Ethernet).
Log In: Open a web browser and go to http://tplinkrepeater.net. Log in with your admin password.
Navigate to Settings: Go to the Settings tab at the top of the page.
Find Night Mode: On the left-hand sidebar, click on System Tools and then select LED Control.
Enable Night Mode:
Toggle the Night Mode switch to On.
Set the LED Off Time (e.g., from 22:00 to 07:00).
Click Save.
If you prefer using your smartphone, the Tether app provides a more modern interface for these adjustments.
Open Tether: Launch the app and select your TL-WA850RE from the device list.
Access Tools: Tap on the Tools icon at the bottom right of the screen.
LED Control: Select LED Control from the menu.
Configure: * You can toggle the LEDs off immediately using the LED Status switch.
Alternatively, tap Night Mode to schedule a specific time for the lights to deactivate automatically each evening.
Time Settings: If Night Mode doesn't trigger at the correct hour, go to System Tools > Time Settings in the web interface to ensure the extender is synced to the correct time zone.
Manual Button: Note that the physical button on the device is typically for WPS/Reset; there is usually no physical button to toggle the LEDs, so software control is essential.
Firmware: If you don't see the "LED Control" option, you may need to update your firmware under System Tools > Firmware Upgrade.