Keep your computer awake with Mouse Jiggler or Caffeine

Mouse Jiggler simulates a mouse movement at a regular interval to prevent your Windows PC from going to sleep.

Caffeine simulates a keypress at a regular interval to accomplish the same.

I prefer Mouse Jiggler, as Caffeine's default keypress of F15 inserts a ~ character in my ssh sessions.  I read this thread about fixing it, but switching to Mouse Jiggler is simpler.