If I understand what you’re asking, this should be very simple as long as you have the right DTH.
If you use the one in the community FAQ with is both A switch and a sensor, you should be able to set up the switch part of it with the regular power allowance feature of smartlighting so that it always turns itself off after the time you specify.
Did that not work for you?
FAQ: Can I trigger an Echo Action without Speaking to It?
Or are you looking for something more complicated? If so, you should still be able to do it using Webcore. 