Each time a previously-connected device connects to your TP-Link network, a record of the connection will be kept in a Google Drive spreadsheet.
If
Device Connects
This trigger fires every time a previously-connected device connects to your TP-Link router.
Then
Add row to spreadsheet
This action will add a single row to the bottom of the first worksheet of a spreadsheet you specify. Note: a new spreadsheet is created after 2000 rows.
Explore more great ways to automate Google Sheets and TP-Link Router