How to schedule automatic backup of a site collection?

To Schedule automatic backup of the site, you need to have your powershell script ready which we will schedule as below. You can have the script from here:-
http://sharepointfamily.blogspot.com/2015/03/how-to-backup-site-collection-in.html

1) Copy your ps1 file in some directory where you want to take backup every night.
2) Go to Windows Task Scheduler and create a new JOB in it.ex- SiteBackup
3) Under Task properties, you can set job to run for a given time under Triggers.
4) Under Actions, select Start a Program and under programs\cripts, we need to put path to powershell. Foe ex:- C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe. And under "Add arguments" put " -WindowStyle Hidden & 'c:\Backup\Backupsite.ps1' " () Path to the saved PS1 (powershell script for doing site backup).

5) Then you need to give a username and password to run this task in thw windows scduler based on your time.
  Once done, Click OK and you are good to go. Site will be created everyday with datetime stamp.