Reclaimed wood was used to replace the stair treads in this stairwell but the knot holes were coming out. Broken glass and epoxy was used to fill the knot holes, a bunch of LED were added to let the knot holes light up. A motion sensor is used to light the stairs for 9 seconds which is just enough time to enjoy the look of the cool knot holes as you walk up the stairs.
Via: Stair Lighting Blog
“Foot lights on our stairway are epoxy pools of glass in the knot holes. They are triggered by a light motion sensor modified to drive a solid state relay which in turn switches a Dell power supply driving 11.5 V to approximately 35 LED lights.”