Android Tablet keeps going dark !

[#1]

My un-named android tablet screen goes into sleep mode if I don`t do something for about 10 seconds... most annoying... is there any way of keeping the screen " active " under settings  ? ? ?  ...while I think about my next thing to do ?  It  happens even if it is plugged into the mains and charging...
it does come back after about 6 seconds, from moving the mouse...  but it means I have to keep shoving the mouse about to keep the screen active...

[#2]

What version of Android?
On my phone I have Settings|Display|Sleep available...

[#3]

Ah.. OK>.. been to settings and the sleep was set at 1 minute... ( but it seemed to be much shorter than that...) ..... have now changed it to 10 minutes.... if that isn`t long enough I also have 30 minutes or Never available...
Thanks.