Stop Raspberry Pi Going to sleep

I used simple steps and it perfectly worked for me:

1. Open a root terminal in raspberry Pi. Now you need to edit your script that's starting X. In the default build with lightdm.
2. Open "lightdm.conf" file located in,
   /etc/lightdm/lightdm.conf
3. Add below line in to SeatDefault section.
   [SeatDefaults]
   xserver-command=X -s 0 -dpms
4. Restart your Raspberry Pi.

Now issue should be solved.

Source link: http://chamaras.blogspot.com/2013/03/how-to-deactivate-monitor-sleep-in.html