Android: How to disable sleep mode on a device

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Applicable To Android Devices Sleep Timeout

Configure the Sleep timeout in the Display settings.
The Maximum time the display can remain on the battery is 30 minutes.
Go to Apps.
Select Settings.
Select Display.
Select Sleep or Screen Timeout.
Select (15 seconds - 30 minutes).

On AC or external battery power

(This will only be active when the device is connected to an external Power source, not while running on battery only).
You can enable the Stay Awake option, dim the display but prevent the device from sleeping.
To enable this setting, the Developer mode needs to be enabled.

NOTE: When the expansion back Power Pack accessory is connected, it is seen as an external power source.

To enable Developer mode and Stay Awake
Go to Apps.
Select Settings.
Select About Phone.
Tap on the Build number repeatedly until the "You Are now a Developer" message is displayed.
Go back to one menu.
Select Developer Options or "System," then "Advanced," then "Developer Options."
Toggle Stay Awake to enabled.