This is only necessary if you want the light to come on when movement is seen on both sides of the obstacle. If you have to go around a corner or through a door way or some other obstacle to see the other switch, then you may want to buy (2) SINGLE-POLE motion sensor switches.

Buy a blank cover plate to put on the wall where the other switch used to be, as you'll remove it to avoid confusion. While standing next to one of the switches, can you see the other one from across the room? If so, (1) single-pole motion sensor switch will be sufficient. Some of the responses above are over-complicating this very simple project. Images and links are for illustration only, not an endorsement of goods or sources There are three way switches that are illuminated when off, such as this one. UPDATE: If you can't see both switches at the same time, you cannot know the motion controlled device is ready (ON) unless you set up some sort of pilot light. How do you know if the motion sensor controlled device is ready to go? If you can see both three way switches at the same time, a practical way to do this is to set up the switches so that they are on when both are up or down and off when they are not in the same position.

However, for three ways, up on a given switch an be on or off depending on the orientation of the other switch. Regular switches (single pole, one way) are on when up and off when down. The problem is that it will be difficult to determine when the light is primed to go on. The motion detector (which controls power after the switches) then either turns the light on or off based on motion. The switches determine if there is power to the light socket. The motion sensor limits the controlled light, if it is set to go on, only when it senses motion.Įffectively, the three way switches prime the light to go on and the motion triggers it. The three way just allows two switches to turn a light on and off.

Three way motion sensor light switch