If you own the model Samsung Galaxy A5,in the model year 2017, then you have already made use of the always on display. This can remain permanently activated and displays new notifications in addition to the time or calendar.
If you do not see any notifications on the Always On Display then you can enable the option as follows:
Allow notifications on the Samsung Galaxy A5 Always On Display:
1. From the Samsung Galaxy A5 home screen, open the App menu and there the settings
2. Now select "Device Security" and continue to "Always On Display"
3. Under "Content to display" select an option with "Information" It should now be possible for you to see the notifications on the Always On Display.